Method and reactor for separating and removing heavy metals from wastewater using sulfhydryl-modified nano-magnetized activated carbon

Abstract

A method and reactor are disclosed for separating and removing heavy metals from wastewater using a sulfhydryl-modified nano-magnetized activated carbon. The method includes the steps of preparing a sulfhydryl-modified nano-magnetized activated carbon first; introducing heavy-metal-containing wastewater into a reactor which is equipped with a stirrer and keeping stirring, and then adding the sulfhydryl-modified nano-magnetized activated carbon, continuously stirring for a reaction; after reacting for a period, precipitating under a magnetic field generated by a magnet separator, discharging the resulting supernate, and then discharging the precipitated sludge.

Claims

1. A method for separating and removing heavy metals from wastewater using a sulfhydryl-modified nano-magnetized activated carbon, comprising step 1, preparing a sulfhydryl-modified nano-magnetized activated carbon: adding an activated carbon into a mixed solution of FeCl.sub.2 and FeCl.sub.3 for a reduction reaction at a pH value of 10-11, and a temperature of 70-80° C. for 60 min, and then aging at ambient temperature for 24 h, to form Fe.sub.3O.sub.4 on the activated carbon, obtaining a nano-magnetized activated carbon, wherein a mass ratio of the activated carbon to Fe.sub.3O.sub.4 formed is 1:1, 1:2 or 1:3; subjecting the nano-magnetized activated carbon to a sulfhydryl modification, to obtain a sulfhydryl-modified nano-magnetized activated carbon; step 2, introducing wastewater: introducing heavy-metal-containing wastewater into a batch reactor via a water inlet pipe; step 3, stirring: turning a stirring device inside the batch reactor on for stirring; step 4, adding the sulfhydryl-modified nano-magnetized activated carbon obtained in step 1 into the batch reactor; step 5, performing an adsorption reaction while stirring in the batch reactor, to adsorb heavy metals in the wastewater by the sulfhydryl-modified nano-magnetized activated carbon; step 6, separating: after the adsorption reaction, precipitating the sulfhydryl-modified nano-magnetized activated carbon under a magnetic field generated by a magnetic separator, obtaining a precipitated sulfhydryl-modified nano-magnetized activated carbon and a supernate; step 7, opening a water outlet pipe after the separating, to discharge the supernate; and step 8, opening a sludge outlet at the bottom of the batch reactor, to discharge the precipitated sulfhydryl-modified nano-magnetized activated carbon, thereby completing a treatment cycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to illustrate the embodiments of the present disclosure or the technical solutions in the prior art more clearly, the drawings used in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present disclosure, and other drawings could be obtained according to these drawings for those of ordinary skill in the art without paying creative labor.

(2) FIG. 1 is a structural schematic diagram according to an embodiment of the present disclosure.

(3) In the drawing: 1 represents an adsorption reaction cell; 2 represents a sulfhydryl-modified nano-magnetized activated carbon; 3 represents a thermostatic stirring device; 4 represents a magnet separator; 5 represents a water inlet; 6 represents a water outlet; 7 represents a self-priming pump; 8 represents a sludge outlet.

DETAILED DESCRIPTION

(4) It should be noted that the features in different embodiments of the present disclosure could be combined with each other without conflict. The present disclosure will be described in detail with reference to the drawings and embodiments.

(5) In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely with reference to the drawings according to the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, but not all of them. The following description of at least one exemplary embodiment is merely illustrative in nature and in no way serves as any limitation on the disclosure and its application or use. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative labor shall fall within the protection scope of the present disclosure.

(6) It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present disclosure. As used herein, unless the context explicitly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the term “comprising” and/or “including” is used in this specification, it indicates the presence of features, steps, operations, devices, components and/or combinations thereof.

(7) Unless defined otherwise, the relative arrangement of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present disclosure. Meanwhile, it should be clear that for convenience of description, the dimensions of each part shown in the drawings are not drawn according to the actual scale relationship. Technologies, methods and equipment known to those of ordinary skill in the related arts may not be discussed in detail, but under appropriate circumstances, the technologies, methods and equipment shall be regarded as part of the authorization specification. In all examples shown and discussed herein, any specific value should be understood as an example only, not as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters indicate similar items in the following drawings, and thus once an item is defined in one drawing, it need not be further discussed in the other drawings.

(8) In the description of the present disclosure, it should be understood that the orientation or positional relationship indicated by orientation terms such as “front”, “back”, “upon”, “below”, “left”, “right”, “horizontal”, “vertical”, “top” and “bottom”, is usually based on the orientation or positional relationship shown in the drawings, which is only for convenience of describing the present disclosure and simplifying the description. Unless otherwise stated, these orientation terms do not indicate or imply that the recited devices or elements must have a specific orientation or be constructed and operated in a specific orientation, and thus they should not be understood as limiting the protection scope of the present disclosure; in addition, the orientation terms “inside” and “outside” refer to the inside and outside relative to the outline of each component itself.

(9) For convenience of description, spatially relative terms, such as “above”, “upon”, “on the upper surface of”, and “on”, could be used herein to describe the spatial positional relationship between one device or feature and other devices or features as shown in the drawings. It should be understood that the spatially relative terms are intended to encompass different orientations of the devices in application or operation in addition to the orientations described in the drawings. For example, if the devices in the drawings are inverted, devices that was described as “above” or “upon” other devices or constructions previously will be positioned as “below” or “under” other devices or constructions. Therefore, the exemplary term “above” may include two orientations, i.e. “above” and “below”. The device could also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative description used herein will be illustrated accordingly.

(10) In addition, it should be noted that the words “first” and “second” are used herein to define parts only for convenience of distinguishing corresponding parts. Unless otherwise stated, the above words have no special meaning, and thus they should not be understood as limiting the protection scope of the present disclosure.

(11) The present disclosure provides a method for separating and removing heavy metals from wastewater using a sulfhydryl-modified nano-magnetized activated carbon, comprising:

(12) step 1, preparing a sulfhydryl-modified nano-magnetized activated carbon: adding an activated carbon into a mixed solution of FeCl.sub.2 and FeCl.sub.3 for a reduction reaction at a pH value of 10-11, and a temperature of 70-80° C. for 60 min, and then aging at ambient temperature for 24 h, to form Fe.sub.3O.sub.4 on the activated carbon, obtaining a nano-magnetized activated carbon, wherein a mass ratio of the activated carbon to Fe.sub.3O.sub.4 formed is 1:1, 1:2 or 1:3; subjecting the nano-magnetized activated carbon to a sulfhydryl modification, to obtain a sulfhydryl-modified nano-magnetized activated carbon;

(13) step 2, introducing wastewater: introducing heavy-metal-containing wastewater into a batch reactor via a water inlet pipe;

(14) step 3, stirring: turning a stirring device inside the batch reactor on for stirring;

(15) step 4, adding the sulfhydryl-modified nano-magnetized activated carbon obtained in step 1 into the batch reactor;

(16) step 5, performing an adsorption reaction while stirring in the batch reactor, to adsorb heavy metals in the wastewater by the sulfhydryl-modified nano-magnetized activated carbon, thereby realizing in-situ reduction and removal of heavy metal from the wastewater;

(17) step 6, separating: after the adsorption reaction, precipitating the sulfhydryl-modified nano-magnetized activated carbon under a magnetic field generated by a magnetic separator, obtaining a precipitated sulfhydryl-modified nano-magnetized activated carbon and a supernate;

(18) step 7, opening a water outlet pipe after the separating, to discharge the supernate; and

(19) step 8, opening a sludge outlet at the bottom of the batch reactor, to discharge the precipitated sulfhydryl-modified nano-magnetized activated carbon, thereby completing a treatment cycle.

(20) As shown in FIG. 1, a batch reactor for separating and removing heavy metals from wastewater using a sulfhydryl-modified nano-magnetized activated carbon, comprising: an adsorption reaction cell 1, a thermostatic stirring device 3 and a magnet separator 4;

(21) wherein the adsorption reaction cell 1 is provided with a water inlet 5 at one side, the water inlet 5 is connected with a water inlet pipe, and the water inlet pipe is insert in a heavy-metal-containing wastewater to be treated; the adsorption reaction cell 1 is provided with a water outlet 6 at the other side, the water outlet 6 is connected with a water outlet pipe, and the water outlet pipe is connected with a self-priming pump 7 for discharging water; the adsorption reaction cell 1 is provided with a sludge outlet 8 at its bottom;

(22) a stirring part of the thermostatic stirring device 3 extends into an accommodating cavity of the adsorption reaction cell 1; the magnet separator 4 is arranged at the bottom of the adsorption reaction cell 1, and the sulfhydryl-modified nano-magnetized activated carbon is added into the accommodating cavity of the adsorption reaction cell 1 after introducing the wastewater and turning the thermostatic stirring device 3 on.

(23) Through sulfhydryl modification and magnetization modification, it is possible to enhance the selective adsorption of heavy metals by activated carbon, thus improving the in-situ separation and removal efficiency of heavy metals from wastewater; meanwhile, the loaded magnetic nano-Fe.sub.3O.sub.4 promotes the separation of the activated carbon when using a magnet separator, which is beneficial to the recovery of the adsorbent. By means of the method provided by the present disclosure, the removal rate of heavy metals from wastewater could reach 99% or higher.

EXAMPLE

(24) In the following examples, an activated carbon, a nano-magnetized activated carbon and a sulfhydryl-modified nano-magnetized activated carbon are used to treat target wastewater.

(25) The activated carbon was purchased from Tianda Chemical Reagent Factory, Dongli, Tianjin, China, with a particle size not higher than 0.90 mm-1.80 mm, a specific surface area of 883.7 m.sup.2/g and a total pore volume of 0.58 cm.sup.3/g.

(26) The nano-magnetized activated carbon and the sulfhydryl-modified nano-magnetized activated carbon were prepared from the above activated carbon by the following steps:

(27) (1) 23.25 g of FeCl.sub.3.6H.sub.2O and 12.00 g of FeSO.sub.4.7H.sub.2O were dissolved in 300 mL of degassed distilled water to form a mixed solution of FeCl.sub.3 and FeSO.sub.4; 10 g of the activated carbon was added into the mixed solution, the resulting mixture was heated to 70° C. while stirring in nitrogen atmosphere, and then an aqueous NaOH solution having a concentration of 5 mol/L was dropwise added thereto until the pH value thereof reach 10; the resulting solution was continuously stirred for 1 hour in nitrogen atmosphere, and aged at ambient temperature for 24 hours, to form Fe.sub.3O.sub.4 on the activated carbon, obtaining a solution containing a nano-magnetized activated carbon, wherein a mass ratio of the activated carbon to Fe.sub.3O.sub.4 formed was 1:1; a solid substance was separated from the solution by a magnet, and washed repeatedly with distilled water and absolute ethanol to neutrality, and then dried at 120° C. in vacuum for 3 hours, to obtain the nano-magnetized activated carbon.

(28) (2) 100 mL of absolute ethanol was mixed with 2 mL of deionized water and 5 mL of acetic acid to obtain a mixture, and 5 mL of trimethoxysilylpropanethiol was added, to obtain a solution of trimethoxysilylpropanethiol in the mixture. 10 g of the nano-magnetized activated carbon obtained from above was added into the solution, and soaked for 12 hours at 60° C. to obtain a solution containing a sulfhydryl-modified nano-magnetized activated carbon; the solid substance was separated from the solution under magnetic field generate by a magnet and washed repeatedly with absolute ethanol and deionized water to neutrality, and then dried at 50° C. in vacuum for 3 hours to obtain the sulfhydryl-modified nano-magnetized activated carbon.

Example 1

(29) The volume of a target wastewater to be treated for an adsorption reaction was 1000 mL;

(30) the temperature of the target wastewater was 25° C.;

(31) the target wastewater contained a heavy metal, Cu.sup.2+, and an initial concentration of Cu.sup.2+ in the target wastewater was 5 mg/L;

(32) the initial pH value of the target wastewater was 7.0;

(33) the adsorption reaction was performed for 120 min;

(34) the adsorbent (the activated carbon, the nano-magnetized activated carbon and the sulfhydryl-modified nano-magnetized activated carbon as listed in Table 1) used in the adsorption reaction was added in an amount of 0.5-2.5 g/1000 mL.

(35) The wastewater containing Cu.sup.2+ was treated in batches, and the results obtained using various amounts of the adsorbent were shown in Table 1.

(36) TABLE-US-00001 TABLE 1 the removal rate of Cu.sup.2+ from the wastewater adding various amounts of the adsorbent amount of the adsorbent (g/1000 mL) 0.5 1.0 1.5 2.0 2.5 type of the adsorbent removal rate of Cu.sup.2+ (%) activated carbon 38.2 44.5 46.7 47.7 48.9 nano-magnetized 52.7 66.7 85.8 89.8 92.1 activated carbon sulfhydryl-modified 69.6 88.4 92.9 99.5 99.6 nano-magnetized activated carbon

Example 2

(37) The volume of a target wastewater to be treated for an adsorption reaction was 1000 mL;

(38) the temperature of the target wastewater was 25° C.;

(39) the target wastewater contained a heavy metal, Cr.sup.3+, and an initial concentration of Cr.sup.3+ in the target wastewater was 5 mg/L;

(40) the initial pH value of the target wastewater was 2.0;

(41) the adsorption reaction was performed for 240 min;

(42) the adsorbent (activated carbon, nano-magnetized activated carbon and sulfhydryl-modified nano-magnetized activated carbon as listed in Table 2) used in the adsorption reaction was added in an amount of 2 g/1000 mL.

(43) The wastewater containing Cr.sup.3+ was treated in batches, and the results obtained under various adsorption time were shown in Table 2.

(44) TABLE-US-00002 TABLE 2 the removal rate of Cr.sup.3+ from the wastewater under various adsorption time adsorption time (min) 5 15 30 60 120 180 240 type of the adsorbent removal rate of Cr.sup.3+ (%) activated carbon 25.6 32.4 36.8 39.3 45.6 48.7 48.9 nano-magnetized 28.3 41.6 48.2 67.0 82.5 93.6 95.3 activated carbon sulfhydryl-modified 43.7 56.6 68.4 82.5 93.6 99.1 99.0 nano-magnetized activated carbon

(45) It can be seen from the examples that the activated carbon exhibits a certain adsorption and removal performance for heavy metals Cu.sup.2+ and Cr.sup.3+ in wastewater; the nano-magnetized activated carbon exhibits a significantly increased adsorption and removal performance for Cu.sup.2+ and Cr.sup.3+; while the sulfhydryl-modified nano-magnetized activated carbon exhibits a more significantly increased adsorption and removal performance for Cu.sup.2+ and Cr.sup.3+, showing that under a certain condition, the removal rate for Cu.sup.2+ and Cr.sup.3+ by the sulfhydryl-modified nano-magnetized activated carbon could reaches 99% or higher. Moreover, due to its magnetic performance, the sulfhydryl-modified nano-magnetized activated carbon could be well recovered and reused under the action of external magnetism, achieving the effect of efficiently removing heavy metal ions such as Cu.sup.2+ and Cr.sup.3+ in wastewater.

(46) In the present disclosure, the parameters of each device, such as the size and the flow rate, are determined according to the conditions such as the scale of wastewater to be treated. The method according to the present disclosure is operated in batches and has strong adaptability.

(47) Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present disclosure, but not to limit it. Although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that the technical solutions described in the foregoing embodiments could still be modified, or some or all of the technical features could be equivalently replaced, and these modifications or replacements do not make the corresponding technical solutions essentially deviate from the scope of the technical solutions of each embodiment of the present disclosure.