Lignin-based hierarchical porous carbon with high specific surface area and preparation method and application thereof

Abstract

The present invention discloses a lignin-based hierarchical porous carbon with high specific surface area and preparation method and application thereof. The present invention employs maleic anhydride, acrylic acid, and hypophosphorous acid to modify a lignin, then performs a cross-linking reaction with a glutaraldehyde-triethanolamine condensate to prepare a lignin graft-copolymerized by phosphino carboxylic acid copolymer, and then dropwise adding a soluble calcium salt solution and a soluble carbonate solution into the lignin graft-copolymerized by phosphino carboxylic acid copolymer dispersion successively, co-precipitates to prepare a lignin/nano CaCO.sub.3 complex, finally obtains a lignin-based hierarchical porous carbon with high specific surface area through carbonizing at a high temperature. The preparation method of the present invention may enable nano CaCO.sub.3 to be uniformly and stably dispersed in a three-dimensional network structure of the lignin graft-copolymerized by phosphino carboxylic acid copolymer, realizing full and uniform complexation of the lignin with nano CaCO.sub.3.

Claims

1. A preparation method for a lignin-based hierarchical porous carbon with a specific surface area of 2200-3000 m.sup.2/g, comprising the following steps: (1) stirring and mixing aqueous solutions of triethanolamine and glutaraldehyde at 50 to 80° C., and reacting for 1 to 6 h, to obtain a solution of triethanolamine-glutaraldehyde condensate; (2) formulating a lignin into an aqueous solution having a mass concentration of 50 to 300 g/L, then adding maleic anhydride, acrylic acid and hypophosphorous acid thereinto, stirring evenly at 60 to 80° C., then dropwise adding an initiator solution having a predetermined mass concentration, reacting for 2 to 4 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 1 to 6 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer; (3) adding an aqueous solution of a soluble calcium salt into the solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer obtained in the step (2) at a predetermined volumetric flowrate, continuing to stir and mix for 30 min to 2 h after a completion of the adding, then adding an aqueous solution of a soluble carbonate thereinto at a predetermined volumetric flowrate, continuing to stir and mix for 1 to 3 h after completion of the adding, standing still and aging for 3 to 6 h, filtering and separating out a precipitate, and drying the precipitate, to obtain a lignin/nano CaCO.sub.3 complex; and (4) carbonizing the lignin/nano CaCO.sub.3 complex obtained in the step (3) in an inert atmosphere, then washing with an acid, washing with water, filtering, and drying, to obtain a lignin-based hierarchical porous carbon; in terms of parts by weight, a formula for quantities of respective reactants is as follows: TABLE-US-00004 lignin 100 parts, triethanolamine 5 to 20 parts, glutaraldehyde 5 to 20 parts, maleic anhydride 2 to 20 parts, acrylic acid 2 to 20 parts, hypophosphorous acid 1 to 10 parts, initiator 2 to 20 parts, soluble calcium salt 50 to 100 parts, and soluble carbonate 50 to 100 parts, the lignin in the step (2) is at least one selected from the group consisting of sodium lignosulfonate in a red liquor from acid pulping, calcium lignosulphonate in the red liquor from acid pulping, magnesium lignosulfonate in the red liquor from acid pulping, a sulfonated product of alkali lignin in a black liquor from alkaline pulping or a sulfonated product of enzymatic lignin from a biorefinery process.

2. The preparation method for the lignin-based hierarchical porous carbon according to claim 1, wherein, in the step (3), the soluble calcium salt is at least one of calcium chloride, calcium nitrate and calcium acetate; and the soluble carbonate is at least one of potassium carbonate, sodium carbonate and ammonium carbonate.

3. The preparation method for the lignin-based hierarchical porous carbon according to claim 1, wherein, mass concentrations of the soluble calcium salt solution and the soluble carbonate solution in the step (3) are 50 to 200 g/L, and the volumetric flowrates for the adding are both 50 to 100 mL/min.

4. The preparation method for the lignin-based hierarchical porous carbon according to claim 1, wherein, a temperature for the carbonizing in the step (4) is 650 to 950° C., and a time for the carbonizing is 1 to 4 h.

5. The preparation method for the lignin-based hierarchical porous carbon according to claim 4, wherein, the temperature for the carbonizing in the step (4) is 750 to 850° C., and the time for the carbonizing is 2 to 3 h.

6. The preparation method for the lignin-based hierarchical porous carbon according to claim 1, wherein, in the mixed solution of triethanolamine and glutaraldehyde of the step (1), the mass concentrations of triethanolamine and glutaraldehyde are both 20 to 200 g/L; and the initiator in the step (2) is sodium persulfate; a volumetric flowrate for dropwise adding the initiator solution is 2 to 15 mL/min, and a mass concentration of the initiator solution is 20 to 100 g/L.

7. The preparation method for the lignin-based hierarchical porous carbon according to claim 1, wherein, the washing with the acid in the step (4) comprises placing the carbonized product in a solution of the acid of 0.5 to 2 mol/L and soaking for 3 to 12 h; and the solution of the acid is at least one of a solution of hydrochloric acid, a solution of sulfuric acid, and a solution of nitric acid.

8. A lignin-based hierarchical porous carbon prepared according to the method of claim 1.

9. An application of the lignin-based hierarchical porous carbon according to claim 8, comprising using the lignin-based hierarchical porous carbon in an adsorbing material for treating antibiotic-contaminated wastewater.

10. A preparation method for a lignin-based hierarchical porous carbon according to claim 1, wherein the inert atmosphere is nitrogen gas.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a SEM photograph of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention.

(2) FIG. 2 is a TEM photograph of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention.

(3) FIG. 3 is an adsorption-desorption curve for nitrogen gas and a pore diameter distribution graph of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention.

(4) FIG. 4 is a relationship curve of adsorption capacity with adsorbing time for an antibiotic-contaminated solution of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention.

(5) FIG. 5 is an adsorbing isotherm for an antibiotic-contaminated solution of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) The present invention will be further described below in detail in combination with Examples and the drawings, but embodiments of the present invention are not limited thereto.

(7) In Examples of the present invention, where particular conditions are not noted, it is carried out in accordance with conventional conditions or conditions recommended by the manufacturer. The raw materials and reagents, etc., which are not specified by the manufacturer, are all conventional products that can be commercially purchased from the market.

(8) Example 1

(9) The following steps are performed:

(10) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 150 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 150 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde at 80° C. for 4 h, to obtain a solution of triethanolamine-glutaraldehyde condensate;

(11) (2) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, then adding 20 g maleic anhydride, 20 g acrylic acid and 10 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 300 mL of a sodium persulfate solution having a concentration of 50 g/L thereinto at a velocity of 10 mL/min, reacting for 3 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 4 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(12) (3) adding 500 mL of an aqueous solution of calcium chloride having a mass concentration of 200 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 100 mL/min, continuing to stir and mix for 2 h after a completion of the adding, then adding 500 mL of a patassium carbonate solution having a mass concentration of 200 g/L thereinto at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(13) (4) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based hierarchical porous carbon.

(14) Example 2

(15) The following steps are performed:

(16) (1) dissolving 5 g triethanolamine in water to formulate a solution having a concentration of 20 g/L, dissolving 5 g glutaraldehyde in water to formulate a solution having a concentration of 20 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde for 1 h at 50° C., to obtain a solution of triethanolamine-glutaraldehyde condensate;

(17) (2) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 50 g/L, then adding 2 g maleic anhydride, 2 g acrylic acid and 1 g hypophosphorous acid thereinto, stirring evenly at 60° C., then adding 100 mL of a sodium persulfate solution having a concentration of 20 g/L thereinto at a velocity of 2 mL/min, reacting for 2 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 1 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(18) (3) adding 1000 mL of an aqueous solution of calcium chloride having a mass concentration of 50 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 50 mL/min, continuing to stir and mix for 30 min after a completion of the adding, then adding 1000 mL of a patassium carbonate solution having a mass concentration of 50 g/L thereinto at a velocity of 50 mL/min, continuing to stir and mix for 1 h after a completion of the adding, standing still and aging for 3 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(19) (4) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 650° C. at a raising-temperature rate of 15° C./min and maintaining for 1 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 0.5 mol/L for 3 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based hierarchical porous carbon.

(20) Example 3

(21) The following steps are performed:

(22) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 200 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 200 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde for 6 h at 80° C., to obtain a solution of triethanolamine-glutaraldehyde condensate;

(23) (2) dissolving 100 g calcium lignosulphonate in water to formulate a solution having a concentration of 300 g/L, then adding 20 g maleic anhydride, 20 g acrylic acid and 10 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 200 mL of a sodium persulfate solution having a concentration of 100 g/L thereinto at a velocity of 15 mL/min, reacting for 4 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 6 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(24) (3) adding 500 mL of an aqueous solution of calcium chloride having a mass concentration of 200 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 100 mL/min, continuing to stir and mix for 2 h after a completion of the adding, then adding 500 mL of a patassium carbonate solution having a mass concentration of 200 g/L thereinto at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(25) (4) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 950° C. at a raising-temperature rate of 15° C./min and maintaining for 4 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 2 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based hierarchical porous carbon.

(26) Example 4

(27) The following steps are performed:

(28) (1) dissolving 10 g triethanolamine in water to formulate a solution having a concentration of 50 g/L, dissolving 10 g glutaraldehyde in water to formulate a solution having a concentration of 50 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde for 3 h at 60° C., to obtain a solution of triethanolamine-glutaraldehyde condensate;

(29) (2) dissolving 100 g magnesium lignosulfonate in water to formulate a solution having a concentration of 100 g/L, then adding 5 g maleic anhydride, 5 g acrylic acid and 2 g hypophosphorous acid thereinto, stirring evenly at 70° C., then adding 125 mL of a sodium persulfate solution having a concentration of 40 g/L thereinto at a velocity of 5 mL/min, reacting for 2 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 2 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(30) (3) adding 600 mL of an aqueous solution of calcium chloride having a mass concentration of 100 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 60 mL/min, continuing to stir and mix for 1 h after a completion of the adding, then adding 600 mL of a patassium carbonate solution having a mass concentration of 100 g/L thereinto at a velocity of 60 mL/min, continuing to stir and mix for 2 h after a completion of the adding, standing still and aging for 4 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(31) (4) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 750° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 6 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based hierarchical porous carbon.

(32) Example 5

(33) The following steps are performed:

(34) (1) dissolving 15 g triethanolamine in water to formulate a solution having a concentration of 100 g/L, dissolving 15 g glutaraldehyde in water to formulate a solution having a concentration of 100 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde for 4 h at 70° C., to obtain a solution of triethanolamine-glutaraldehyde condensate;

(35) (2) dissolving 100 g sulfonated alkali lignin in water to formulate a solution having a concentration of 150 g/L, then adding 10 g maleic anhydride, 10 g acrylic acid and 5 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 200 mL of a sodium persulfate solution having a concentration of 50 g/L thereinto at a velocity of 10 mL/min, reacting for 3 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 3 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(36) (3) adding 400 mL of an aqueous solution of calcium chloride having a mass concentration of 200 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 80 mL/min, continuing to stir and mix for 90 min after a completion of the adding, then adding 400 mL of a patassium carbonate solution having a mass concentration of 200 g/L thereinto at a velocity of 80 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 5 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(37) (4) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 3 h, waiting for its decreasing to a room temperature, soaking a carbonized product in 1.5 mol/L of a solution of hydrochloric acid for 8 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based hierarchical porous carbon.

(38) Example 6

(39) The following steps are performed:

(40) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 150 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 150 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde for 5 h at 80° C., to obtain a solution of triethanolamine-glutaraldehyde condensate;

(41) (2) dissolving 100 g sulfonated enzymatic lignin in water to formulate a solution having a concentration of 200 g/L, then adding 15 g maleic anhydride, 15 g acrylic acid and 8 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 250 mL of a sodium persulfate solution having a concentration of 60 g/L thereinto at a velocity of 15 mL/min, reacting for 4 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 4 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(42) (3) adding 600 mL of an aqueous solution of calcium chloride having a mass concentration of 150 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 100 mL/min, continuing to stir and mix for 2 h after a completion of the adding, then adding 600 mL of a patassium carbonate solution having a mass concentration of 150 g/L thereinto at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(43) (4) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 2 mol/L for 10 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based hierarchical porous carbon.

(44) Comparative Example 1 (without graft-copolymerizing modification on lignin)

(45) The following steps are performed:

(46) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 150 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 150 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde at 80° C. for 4 h, to obtain a solution of triethanolamine-glutaraldehyde condensate;

(47) (2) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 4 h, to obtain a crosslinked lignin solution;

(48) (3) adding 500 mL of an aqueous solution of calcium chloride having a mass concentration of 200 g/L into the above-described crosslinked lignin solution at a velocity of 100 mL/min, continuing to stir and mix for 2 h after a completion of the adding, then adding 500 mL of a patassium carbonate solution having a mass concentration of 200 g/L thereinto at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(49) (4) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based porous carbon.

(50) Comparative Example 2 (without cross-linking modification on lignin)

(51) The following steps are performed:

(52) (1) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, then adding 20 g maleic anhydride, 20 g acrylic acid and 10 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 300 mL of a sodium persulfate solution having a concentration of 50 g/L thereinto at a velocity of 10 mL/min, reacting for 3 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(53) (2) adding 500 mL of an aqueous solution of calcium chloride having a mass concentration of 200 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 100 mL/min, continuing to stir and mix for 2 h after a completion of the dropwise adding, then adding 500 mL of a patassium carbonate solution having a mass concentration of 200 g/L thereinto at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the dropwise adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(54) (3) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based porous carbon.

(55) Comparative Example 3 (without any modification on lignin)

(56) The following steps are performed:

(57) (1) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, adding 500 mL of an aqueous solution of calcium chloride having a mass concentration of 200 g/L into the above-described lignin solution at a velocity of 100 mL/min, continuing to stir and mix for 2 h after a completion of the adding, then adding 500 mL of a patassium carbonate solution having a mass concentration of 200 g/L thereinto at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex; and

(58) (2) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based porous carbon.

(59) Comparative Example 4 (directly using CaCO.sub.3 nano particle as a templating agent)

(60) The following steps are performed:

(61) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 150 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 150 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde at 80° C. for 4 h, to obtain a solution of triethanolamine-glutaraldehyde condensate;

(62) (2) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, then adding 20 g maleic anhydride, 20 g acrylic acid and 10 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 300 mL of a sodium persulfate solution having a concentration of 50 g/L thereinto at a velocity of 10 mL/min, reacting for 3 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 4 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(63) (3) adding 362 mL of a nano CaCO.sub.3 dispersion having a mass concentration of 200 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer upon stirring, continuing to stir and mix for 3 h, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/CaCO.sub.3 complex; and

(64) (4) raising a temperature of the lignin/CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based porous carbon.

(65) Comparative Example 5 (directly using K.sub.2CO.sub.3 as an activator)

(66) The following steps are performed:

(67) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 150 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 150 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde at 80° C. for 4 h, to obtain a solution of triethanolamine-glutaraldehyde condensate;

(68) (2) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, then adding 20 g maleic anhydride, 20 g acrylic acid and 10 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 300 mL of a sodium persulfate solution having a concentration of 50 g/L thereinto at a velocity of 10 mL/min, reacting for 3 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 4 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(69) (3) adding 362 mL of K.sub.2CO.sub.3 aqueous solution having a mass concentration of 200 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the dropwise adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/K.sub.2CO.sub.3 complex; and

(70) (4) raising a temperature of the lignin/K.sub.2CO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based porous carbon.

(71) Comparative Example 6 (directly using KCl as an activator)

(72) The following steps are performed:

(73) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 150 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 150 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde at 80° C. for 4 h, to obtain a solution of triethanolamine-glutaraldehyde condensate;

(74) (2) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, then adding 20 g maleic anhydride, 20 g acrylic acid and 10 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 300 mL of a sodium persulfate solution having a concentration of 50 g/L thereinto at a velocity of 10 mL/min, reacting for 3 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 4 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(75) (3) adding 362 mL of KCl aqueous solution having a mass concentration of 200 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/KCl complex; and

(76) (4) raising a temperature of the lignin/KCl complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based porous carbon.

(77) Comparative Example 7 (directly using CaCl.sub.2 as an activator)

(78) The following steps are performed:

(79) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 150 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 150 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde at 80° C. for 4 h, to obtain a solution of triethanolamine-glutaraldehyde condensate;

(80) (2) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, then adding 20 g maleic anhydride, 20 g acrylic acid and 10 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 300 mL of a sodium persulfate solution having a concentration of 50 g/L thereinto at a velocity of 10 mL/min, reacting for 3 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 4 h, to obtain a solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(81) (3) adding 362 mL CaCl.sub.2 aqueous solution having a mass concentration of 200 g/L into the above-described solution of lignin graft-copolymerized by phosphino carboxylic acid copolymer at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/CaCl.sub.2 complex; and

(82) (4) raising a temperature of the lignin/CaCl.sub.2 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based porous carbon.

(83) Comparative Example 8 (with a method for modifying lignin refering to Example 3 in Chinese patent application CN109851813A)

(84) The following steps are performed:

(85) (1) adding 573 mL water into a round-bottom flask, successively adding 111 g hydrochloric acid, 17 g sulfuric acid, 176 g HEDP, 327 g citric acid, 100 g sodium lignosulfonate, 67 g ammonium chlorie and 60 g zinc sulfate heptahydrate thereinto upon stirring, stirring and mixing, raising a temperature to 80° C., slowly adding 288 g formaldehyde thereinto within 1 hour, and refluxing and reacting at 80° C. for 3 h, to obtain a solution of sodium lignosulfonate containing polycarboxyl and polyphosphino;

(86) (2) adding 500 mL of an aqueous solution of calcium chloride having a mass concentration of 200 g/L into the above-described solution of sodium lignosulfonate containing polycarboxyl and polyphosphino at a velocity of 100 mL/min, continuing to stir and mix for 2 h after a completion of the adding, then adding 500 mL of a patassium carbonate solution having a mass concentration of 200 g/L thereinto at a velocity of 100 mL/min, continuing to stir and mix for 3 h after a completion of the adding, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin/nano CaCO.sub.3 complex;

(87) (3) raising a temperature of the lignin/nano CaCO.sub.3 complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based hierarchical porous carbon.

(88) Comparative Example 9 (with an activator used for preparing porous carbon referring to a literature of Chemistry of Materials, 2017, 29 (16): 6900-6907.)

(89) The following steps are performed:

(90) (1) dissolving 20 g triethanolamine in water to formulate a solution having a concentration of 150 g/L, dissolving 20 g glutaraldehyde in water to formulate a solution having a concentration of 150 g/L, mixing and reacting the formulated solutions of triethanolamine and glutaraldehyde at 80° C. for 4 h, to obtain a solution of triethanolamine-glutaraldehyde condensate;

(91) (2) dissolving 100 g sodium lignosulfonate in water to formulate a solution having a concentration of 200 g/L, then adding 20 g maleic anhydride, 20 g acrylic acid and 10 g hypophosphorous acid thereinto, stirring evenly at 80° C., then adding 300 mL of a sodium persulfate solution having a concentration of 50 g/L thereinto at a velocity of 10 mL/min, reacting for 3 h, then adding the solution of condensate of the step (1) thereinto, and continuing to react for 4 h, standing still and aging for 6 h, filtering and separating out a precipitate, and drying the precipitate in a blast oven at 120° C. for 3 h, to obtain a lignin graft-copolymerized by phosphino carboxylic acid copolymer;

(92) (3) fully grinding and mixing the above-described lignin graft-copolymerized by phosphino carboxylic acid copolymer with 100 g potassium oxalate, and then adding 100 g nano particles of calcium carbonate thereinto, and grinding and mixing to obtain a lignin/potassium oxalate/calcium carbonate complex; and

(93) (4) raising a temperature of the lignin/potassium oxalate/calcium carbonate complex to 350° C. at a raising-temperature rate of 10° C./min and maintaining for 60 min, and then raising the temperature to 850° C. at a raising-temperature rate of 15° C./min and maintaining for 2 h, waiting for its decreasing to a room temperature, soaking a carbonized product in a solution of hydrochloric acid of 1 mol/L for 12 h, then washing with water, filtering, moving a filter cake into a blast oven at 120° C., and drying for 1 day, to obtain a lignin-based hierarchical porous carbon.

(94) The prepared lignin-based porous carbons are applied in an adsorbing material for antibiotic-contaminated wastewater, and the material characterization and adsorption performance tests are carried out. The results are shown in Tables 1 to 2 and FIGS. 1 to 5.

(95) A microscopic morphology and a structure of the sample are characterized by a scanning electron microscopy (SEM, Zeiss Merlin, Germany) and a high-resolution field emission transmission electron microscopy (TEM, JEOL JEM-2100F). A specific surface area and the porous structure of the sample are tested by using an automatic analyzer for specific surface and porosity (Micromeritics ASAP 2020 instrument).

(96) In a test method for a static adsorption performance of the sample, firstly, 10 mg of the samples of the prepared lignin-based hierarchical porous carbon or Comparative Example are added into a conical flask of 100 mL filled with 50 mL of an antibiotic solution having an initial concentration of 200 mg/L. Then, it is put in a thermostatic oscillator having a rotation speed of 160 rpm for adsorbing experiment. The samples are taken out after oscillating and adsorbing for 24 h, and filtered by means of a syringe filter. After that, a residual content of sulfamethazine is measured by means of a high performance liquid chromatograph (Shimadzu LC-20A), and adsorption capacity thereof is calculated. During the static adsorbing experiment, sampling is performed at a certain time interval to test residual content thereof, adsorption capacities for different adsorbing time are obtained through calculating, and a curve for adsorbing time on adsorption capacity is drawn. In the static adsorbing experiment, the adsorption of the adsorbents on the antibiotic having different initial concentrations (50 mg/L, 75 mg/L, 100 mg/L, 150 mg/L, 200 mg/L, 250 mg/L, 300 mg/L, and 350 mg/L) is tested to obtain an equilibrium concentration and an equilibrium adsorption capacity, and an adsorbing isotherm is drawn. The antibiotics for tests are sulfamethazine (sulfonamides) and acetyl isovaleryl tartrate tylosin (macrolides), which have respectively a relative molecular mass of 278.33 and 1192.34, and both are slight soluble in water.

(97) Table 1 is a comparison of the lignin-based hierarchical porous carbons with high specific surface area prepared in the above-described Examples 1 to 6 with the lignin-based porous carbons prepared in Comparative Examples 1 to 9 in terms of the specific surface area and the porous structure.

(98) Table 2 is a comparision of the lignin-based hierarchical porous carbons with high specific surface area prepared in the above-described Examples 1 to 6 with the lignin-based porous carbons prepared in Comparative Examples 1 to 9 in terms of the adsorption performance for antibiotics.

(99) TABLE-US-00002 TABLE 1 Specific surface area and porous structure of the lignin-based porous carbon lignin-based Chacateristic parameters for pore structure porous S.sub.BET V.sub.total V.sub.micro/V.sub.total V.sub.mes/V.sub.total carbon carbon (m.sup.2/g) (cm.sup.3/g) (%) (%) yield/% Example 1 2984 1.51 53 45 26 Example 2 2616 1.31 58 39 24 Example 3 2561 1.21 52 45 23 Example 4 2553 1.22 57 40 21 Example 5 2616 1.33 52 47 25 Example 6 2794 1.39 55 42 24 Comparative 1839 0.98 38 56 23 Example 1 Comparative 1963 0.82 35 59 21 Example 2 Comparative 1645 0.86 43 45 24 Example 3 Comparative 1045 0.61 47 45 24 Example 4 Comparative 2348 1.55 64 32 21 Example 5 Comparative 1328 0.50 87 6 23 Example 6 Comparative 602 1.48 8 69 22 Example 7 Comparative 2028 1.34 40 52 15 Example 8 Comparative 2605 1.44 33 61 10 Example 9

(100) TABLE-US-00003 TABLE 2 Adsorption performance for antibiotics of the lignin-based porous carbon adsorption performance for lignin-based adsorption performance acetyl isovaleryl porous for sulfamethazine tartrate tylosin carbon Q.sub.e (mg/g) t.sub.95% Qe (min) Q.sub.e (mg/g) t.sub.95% Qe (min) Example 1 827 20 736 18 Example 2 761 27 694 23 Example 3 772 23 722 20 Example 4 753 27 714 23 Example 5 786 25 745 17 Example 6 746 28 706 22 Comparative 466 50 443 33 Example 1 Comparative 423 47 445 30 Example 2 Comparative 351 55 320 35 Example 3 Comparative 285 60 275 35 Example 4 Comparative 535 80 297 45 Example 5 Comparative 140 210 70 50 Example 6 Comparative 96 55 280 30 Example 7 Comparative 398 55 354 40 Example 8 Comparative 477 40 452 25 Example 9

(101) Explanation for Table 1 to Table 2:

(102) The lignin-based hierarchical porous carbon prepared in Example 1 has a specific surface area of 2984 m.sup.2/g, which has a equilibrium adsorption capacity of 827 mg/g and 736 mg/g for waste water with simulated contamination of sulfamethazine and acetyl isovaleryl tartrate tylosin having an initial concentration of 200 mg/L, respectively, and may both attain 95% of the equilibrium adsorption capacity within 20 min. The lignin-based hierarchical porous carbon prepared in Example 1 has all excellent adsorption performance and adsorption rate for antibiotics of different molecular weights, and has obvious application previllage in a biomass porous carbon.

(103) The lignin-based hierarchical porous carbons prepared in Examples are compared and analyzed with the lignin-based porous carbons prepared in Comparative Examples, in terms of specific surface area, pore diameter distribution, and adsorption performance etc. The lignin-based hierarchical porous carbons prepared in Examples have all obvious improvement on specific surface area, adsorption capacity, and adsorption rate, reasonably distributed hierarchical porous structure (40% to 48% of mesopore and 50% to 58% of micropore), and excellent adsorption capacity for both micromolecule antibiotic of sulfamethazine and macromolecule antibiotic of acetyl isovaleryl tartrate tylosin, which are obviously distinguished from adsorbents in Comparative Examples and other adsorbents having only adsorption performance for micromolecule antibiotics or macromolecule antibiotics. In addition, all Examples have higher yields of 20% to 30%. The reason for the lignin-based hierarchical porous carbon prepared in the present invention having the above-described excellent performances is analyzed. The lignin modified by graft-copolymerizing with phosphino carboxylic acid copolymer has three-dimensional network structure and abundant Ca.sup.2+ combination sites, is beneficial for uniform dispersing and stabilization of Ca.sup.2+, avoids rapid nucleation and growth of CaCO.sub.3 in the three-dimensional network of the lignin, and obtains nano CaCO.sub.3 particles uniformly and stably distributed in the three-dimensional network structure of the lignin. During carbonizing at a high temperature, mesopores and a portion of macropores can be manufactured with nano CaCO.sub.3 as a hard template, and carbon dioxide released by the pyrolysis of nano CaCO.sub.3 can perform gas-phase exfoliation or etching on the lignin-based porous carbon to generate micropores. The porous structure of the lignin-based porous carbon is fully developed with nano CaCO.sub.3 as the templating agent and the activator simultaneously, to form the lignin-based hierarchical porous carbon with high specific surface area having interlinked pores and channels, and the interlinked structure of micropore/mesopore/macropore hierarchical pores and high specific surface area thereof promote rapid mass transfer and efficient adsorption of antibiotic molecules in the lignin porous structure. Moreover, it has universal applicability for antibiotics of different molecular weights.

(104) However, Comparative Examples 1 to 3 respectively mix the lignins without suffering from graft-copolymerizing modification or/and cross-linking modification with the calcium salt and the precipitant. Due to lack of the complexing effect of phosphino and carboxylic acid functional groups or the spatial confinement effect of stable three-dimensional network structure of the lignin, the obtained CaCO.sub.3 particles easily agglomerate and move during carbonizing, and higher specific surface area and abundant micropore/mesopore structure can't therefore be obtained, thus leading to limited adsorbing ability for antibiotics. Comparative Example 4 directly uses CaCO.sub.3 particles for impregnating and mixing with the lignin during the preparation, which is too big to be better embedded in the three-dimensional network structure of the lignin, and uniform complexation of CaCO.sub.3 with the lignin could not thus be realized. During carbonizing, the porous structure of the lignin-based porous carbon could not be fully developed, and therefore the adsorbing ability for antibiotics thereof is limited. Comparative Example 5 directly uses K.sub.2CO.sub.3 having bigger specific surface area as an activator, but the activating effect of K.sub.2CO.sub.3 on the lignin mainly generates a micropore structure and a portion of mesopore structure. During adsorbing, a portion of micropores can't enable the pollutants to enter due to too small pores, leading to a decrease of availability of the pores. Therefore, it has different adsorption capacities for sulfamethazine and acetyl isovaleryl tartrate tylosin, adsorption for acetyl isovaleryl tartrate tylosin as a macromolecule antibiotic, could not fully utilize pores and channels of the micropores, thus decreasing adsorption capacity. Comparative Example 6 has an adsorption capacity for sulfamethazine 1.5 times of that in Comparative Example 7; and Comparative Example 7 has an adsorption capacity for acetyl isovaleryl tartrate tylosin 4 times that in Comparative Example 6, which correlates with a pore diameter distribution of pores for them two. Comparative Example 6 directly uses KCl as an activator, in which the pore structure is almost all micropores; and Comparative Example 7 directly uses CaCl.sub.2 as an activator, in which the pore structure is almost all mesopores. With regard to micromolecule antibiotics, what contributes to adsorption capacity is mainly micropore structure, because too big diameter of the mesopore results in limited interception effect for micromolecule antibiotics. With regard to macromolecule antibiotics, what contributes to adsorption capacity is mainly mesopore structure, because smaller diameter of the micropore can't enable the macromolecule antibiotics to enter.

(105) With reference to the prior art, Comparative Example 8 and Comparative Example 9 respectively perform polycarboxyl and polyphosphino modification on the lignin or use potassium oxalate and calcium carbonate as a binary activator. The porous carbon prepared in Comparative Example 8 has a production obviously less than that in Examples, due to an obvious decrease of carbon content in the modified lignin. In addition, due to denser distribution of the functional groups in the modified lignin, it has stronger adsorbing effect for Ca.sup.2+, lignin and CaCO.sub.3 could not form uniform and reasonable distribution, and CaCO.sub.3 is mainly distributed on the outer surface of the lignin structure, leading to inhomogeneous activating effect during carbonizing The porous structure of the obtained porous carbon is also inhomogeneous and insufficient, and therefore has an adsorbing effect for antibiotics obviously less than that in Examples. Comparative Example 9 prepares a porous carbon by using potassium oxalate as an activator and nano calcium carbonate as a templating agent through grinding, mixing and carbonizing, whose carbon yield is only 10%. This is because the binary activator excessively activates the lignin-based carbon, and the complexation of lignin with calcium carbonate is by menas of physical complexation of grinding and mixing, so that fully uniform complexation could not be realized between the lignin and calcium carbonate. Therefore, the obtained porous carbons have a more disordered structure, and have both adsorption capacitis for antibiotics much less than those of Examples.

(106) All Examples and Comparative Example have adsorption rates for acetyl isovaleryl tartrate tylosin all greater than the adsorption rates for sulfamethazine. This is because what macromolecule antibiotics mainly utilize are mesopores with better accessibility, and what micromolecule antibiotics mainly utilize are micropores with poorer accessibility.

(107) FIG. 1 is a SEM photograph of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention, it can be seen from the figure that a lignin-based hierarchical porous carbon prepared in the present invention has a loose and open three-dimensional structure with abundant porous structure.

(108) FIG. 2 is a TEM photograph of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention, it can be seen from the figure that an interior porous structure of a lignin-based hierarchical porous carbon prepared in the present invention, is abundant and has better connectivity.

(109) FIG. 3 is an adsorption-desorption curve for nitrogen gas and a pore diameter distribution graph of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention, it can be seen from the figure that the adsorption-desorption curve for the lignin-based hierarchical porous carbon prepared in the present invention belongs to isotherms of type I and type IV and has a hysteresis loop of type H4. In an area of lower relative pressure, adsorption capacity for nitrogen gas rapidly increases, demonstrating that it has micropore structure. However, in an area of higher relative pressure, hysteresis loop appears, and when relative pressure close to 1, the adsorption capacity for nitrogen gas has obvious increase, demonstrating that it has mesopore structure. The lignin-based hierarchical porous carbon has a total BET specific surface area of 2984 m.sup.2/g, and a total volume of pore of 1.51 cm.sup.3/g, wherein a micropore volume is 0.80 cm.sup.3/g, and a mesopore volume is 0.68 cm.sup.3/g. The lignin-based hierarchical porous carbon has a pore diameter intensively distributed in a range of 0.5 to 2 nm for micropores and a range of 2 to 6 nm for mesopores, and has a portion of mesopores and macropores in a range of 40 to 70 nm. Therefore, the lignin-based hierarchical porous carbon has a hierarchical porous structure of micropore/mesopore/macropore. High specific surface area, abundant porous structure and reasonable pore diameter distribution of the lignin-based hierarchical porous carbon are beneficial for realizing rapid mass transfer and high adsorption capacity during adsorbing.

(110) FIG. 4 is a relationship curve of adsorption capacity with adsorbing time for an antibiotic-contaminated solution of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention, it can be seen from the figure that the lignin-based hierarchical porous carbon prepared in the present invention has excellent adsorption performance for sulfamethazine and acetyl isovaleryl tartrate, and 95% of the equilibrium adsorption capacity may all be attained within 20 min, demonstrating that the lignin-based hierarchical porous carbon has faster adsorption rate.

(111) FIG. 5 is an adsorbing isotherm for an antibiotic-contaminated solution of a lignin-based hierarchical porous carbon prepared in Example 1 of the present invention, it can be seen from the figure that a lignin-based hierarchical porous carbon prepared in the present invention has an adsorbing isotherm for antibiotic sulfamethazine fitting Langmuir model, with a theoretical maximium single-layer adsorption capacity of 905 mg/g, slightly less than the maximium adsorption capacity for the experimental value 933 mg/g, and the lignin-based hierarchical porous carbon has very high adsorption capacity for antibiotic sulfamethazine.

(112) The above-described Examples are preferred embodiments of the present invention, but embodiments of the present invention are not limited to the above-described Examples, any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and the principle of the present invention should all be equivalent replacement modes, and all be contained in the protection scope of the present invention.