Hybrid sorbent

Abstract

Hybrid sorbent on the base of anion-exchange polymeric matrix with HFO for selective sorption of arsenic characterized in that, HFO exists in matrix as particles, which at most are amorphous ferrihydrite, fraction of which is not less than 80%, preferably more than 90% from total mass of HFO. The object of the invention and the technical result achieved with the use of the invention is to develop new hybrid sorbent with HFO with increased sorption kinetics of two arsenic forms As(III) and As(V) simultaneously.

Claims

1. Hybrid sorbent comprising: a base of anion exchange polymeric matrix; and an HFO for selective sorption of arsenic characterized in that, the HFO exists in said matrix as particles comprising primarily amorphous ferrihydrite, a fraction of said amorphous ferrihydrite being more than 90% from a total mass of the HFO.

2. Hybrid sorbent according to claim 1, characterized in that the HFO particles have a microporous structure and their size varies from 5 to 500 nm.

3. Hybrid sorbent according to claim 1, characterized in that the anion exchange polymeric matrix comprises macroporous fiber.

4. Hybrid sorbent according to claim 1, characterized in that an anion exchange content in the anion exchange polymeric matrix is not less than 6.0 mmol/g.

5. Hybrid sorbent according to claim 1, characterized in that the anion exchange polymeric matrix comprises a granulated material.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1. Electronic microphotography of the initial anoinexchange polymeric fiber (1a). Electronic microphotography of the hybrid sorbent on the base of anoinexchange PAN-fiber with HFO (1).

(2) FIG. 2. Mossbauer spectrum of the sample of hybrid sorbent on the base of anoinexchange PAN-fiber with HFO, described in example 1.

(3) FIG. 3. Mossbauer spectrum of the sample of hybrid sorbent of U.S. Pat. No. 7,291,578.

(4) FIG. 4. Sorption kinetic diagram of arsenic As(III) by hybrid sorbent with HFO on the base of PAN-fiber, described in example 1, sorption kinetic diagram of arsenic As(III) by hybrid sorbent with HFO on the base of PAN fiber and ionexchange resin, described in the example 3 and sorption kinetic of arsenic As(III) by hybrid sorbent of a U.S. Pat. No. 7,291,578 (trade name FO36), chosen by the applicant as the closest analogue.

(5) FIG. 5. Sorption kinetic diagram of arsenic As(V) by hybrid sorbent with HFO on the base of PAN-fiber, described in example 1, sorption kinetic diagram of arsenic As(V) by hybrid sorbent with HFO on the base of PAN fiber and ionexchange resin, described in the example 3 and sorption kinetic of arsenic As(V) by hybrid sorbent FO36 of a U.S. Pat. No. 7,291,578, chosen by the applicant as the closest analogue.

(6) The claimed hybrid sorbent is anoinexchange polymeric matrix with HFO fixed in it. At the same time HFO on hybrid sorbent consists of at least 90% of amorphous ferrihydrite and less than 10% of iron-containing impurities, forming complex of HFO compounds. HFO is microporous particles with size from 5 to 500 nm, formed and fixed directly inside of micropoures of anionexchange material after changeable iron (III) complexes are destructed when treated with alkali metal.

(7) Fibrous or granulated material or their mixture can be used as an anioinexchange material.

(8) So the anoinexchange polymeric matrix may be granulated anioinexchange resin with secondary or tertiary amine groups or anionexchange polymeric fibers with secondary or tertiary amine groups, and/or mixture of resin and fibers, and anoinexchange group content in polymeric matrix is not less than 6.0 mmol/g.

(9) Complex salt can be complex iron salt, where ligands are oxalate, salicylate, citrate or tartrate. Sodium or potassium hydroxide maybe used as alkali hydroxide.

(10) Production method of hybrid sorbent with HFO is the following. The solution of complex salt, where central ion is the cation of iron (III) and anions of carbon salts are ligands is prepared. The derived solution is added to the anionexchange polymeric matrix for sorption of complex anions on the matrix. After that the derived provisional structure is treated with alkali hydroxide solution till hybrid sorbent is formed, which then is rinsed with water.

(11) The provisional structure is derived during reaction between anionexchange groups of polymeric matrix with anion of complex salt. When provisional structure is treated with alkali hydroxide the unstable complex—amorphous ferrihydrite—in the phase of anionexchange polymeric matrix is formed with its further degrading. As the formation and degrading of the complex takes place in the solution, the degrading is slow, that helps HFO to form on different, parts of polymeric matrix separated from each other, so the HFO particles are finer. In such conditions during alkali hydroxide removal FIFO structure consolidates more slowly, providing big amount of micropores in HFO particles. Sorption properties of HFO particles, as well as their composition depend on their size and porosity. The smaller is the size of the particles and higher is their porosity, the bigger is the contact area of the sorbing compound with HFO surface, and so the bigger is the sorption capacity. The bigger is the sorption capacity, the less amount of sorbent is required to purify the given volume of water, that widens the opportunities of sorbents practical use.

(12) According to given invention hybrid sorbent has high sorption properties towards arsenic compounds of two forms As(III) and As(V), in particular towards oxo anions in wide range of pH, arsenate ions and non-dissociated arsenites. At the same time hybrid sorbent is capable for effective sorption of toxic anions of chrome Cr(VI), and also cations and hydroxocations of copper and lead. Hybrid sorbent has high sorption kinetics, that increases linear velocity of water flow in sorption column. That is important for practical use, as it helps to provide the filtration velocity convenient for the user without efficiency loss.

EXAMPLES OF HYBRID SORBENTS ACCORDING TO CLAIMED INVENTION

Example 1

(13) Base—macoporous fiber material—anion exchange on the base ob PAN-fiber with anion exchange groups content 8.6 mml/g.

(14) The ferrihydrate content in hybrid sorbent is 98%.

(15) The particle size of HFO, in particular ferrihydrate is—from 80 to 140 nm.

(16) Iron (III) content in hybrid sorbent—63 mg of iron to 1 g of sorbent.

(17) Sorption capacity of As(V)—32 mg/g (at pH 7).

(18) Sorption capacity of As(III)—30 mg/g (at pH 7).

(19) Sorption kinetics of As(V)—semi-sorption time less then 1 min.

(20) Removal kinetics of As(III)—semi-sorption time 1 min.

(21) Sorption capacity of Cr(VI)—250 mg/g (at pH 7).

(22) Sorption capacity of Cu—240 mg/g.

(23) Sorption capacity of Pb—360 mg/g.

(24) Electronic microphotography of initial anionexchange polymeric fiber (1a), used to produce hybrid sorbent in example 1 is given in the FIG. 1. On the second electronic microphotography (1b) hybrid sorbent on the base of anionexchange polymeric fiber with HFO, produced according to method, described in claimed method is given. On the microphotography (1b) particles HFO are sharply visible on the fiber surface.

Example 2

(25) Base—macoporous granulated material—anionexchange resin.

(26) The ferrihydrate content in hybrid sorbent is 92%.

(27) The particle size of HFO, in particular ferrihydrate—from 50 to 120 nm.

(28) Anionexchange groups content in hybrid—9 mmol/g.

(29) Iron (III) content in hybrid sorbent—72 mg/g.

(30) Sorption capacity of As (V)—44 mg/g (at pH 7).

(31) Sorption capacity of As (III)—34 mg/g (at pH 7).

(32) Removal kinetics of As (V)—semi-sorption time 25 min.

(33) Removal kinetics of As (III)—semi-sorption time 30 min.

(34) Sorption capacity of Cr (VI)—300 mg/g (at pH 7).

(35) Sorption capacity of Cu—270 mg/g.

(36) Sorption capacity of Pb—180 mg/g.

Example 3

(37) Base—mixture of macroporous fiber and granulated material 1:8 respectively.

(38) The ferrihydrate content in hybrid sorbent is 93%.

(39) The particle size of HFO, in particular ferrihydrate—from 50 to 140 nm.

(40) Anion exchange group content in hybrid sorbent—8.95 mmol/g.

(41) Iron (III) content in hybrid sorbent—71 mg/g.

(42) Sorption capacity of As (V)—42 mg/g (at pH 7).

(43) Sorption capacity of As(III)—36 mg/g (at pH 7).

(44) Removal kinetics of As(V)—semi-sorption time 1.5 min.

(45) Removal kinetics of As(III)—semi-sorption time 4 min.

(46) Sorption capacity of Cr (VI)—295 mg/g (at pH 7).

(47) Sorption capacity of Cu—265 mg/g.

(48) Sorption capacity of Pb—200 mg/g.

(49) HFO type in the hybrid sorbent phase, described in examples 1-3 was determined by Mossbauer spectroscopy and is given in the FIG. 2.

(50) Mossbauer spectrum of hybrid sorbent on the base of anionexchange polymeric PAN-fiber with HFO of example 1 is given in the FIG. 2. From the spectrum one can see that HFO in the hybrid sorbent sample of example 1, produced according to the claimed method, has more that 90% of ferrihydrite Fe.sub.2O.sub.3.3FeO(OH).3H.sub.2O.

(51) Also HFO type of hybrid sorbent sample of the U.S. Pat. No. 7,291,578 (the closest analogue) was determined by Mossbauer spectroscopy (FIG. 3). The spectrum shows that HFO consists of magnetic crystalline particles, including 23% wustite FeO, 28% ferrihydrite Fe.sub.2O.sub.3⋅3FeO(OH)⋅3H.sub.2O, 13% hematite α-Fe.sub.2O.sub.3 36% lepidocrocite γ-FeO(OH).

(52) From the information given above it is seen that HFO in hybrid sorbent sample consists of 90% of amorphous ferrihydrite. At the same time hybrid sorbent of the closest analogue U.S. Pat. No. 7,291,578 consists of ferrihydrite on 28%. This once more consolidates sorption abilities of invention in comparison to closest analogue.

(53) The soption kinetic diagram of arsenic As (III) by hybrid sorbent on the base of PAN-fiber with HFO, described in example 1, soption kinetic diagram of arsenic As (III) by hybrid sorbent on the bae of mixture of PAN-fiber and ionexchange resin, described in the example 3, and also soption kinetic diagram of arsenic As (III) by hybrid sorbent FO36 U.S. Pat. No. 7,291,578, chosen as the closest analogue are depicted in the in the FIG. 4.

(54) The soption kinetic diagram of arsenic As (V) by hybrid sorbent on the base of PAN-fiber with HFO, described in example 1, soption kinetic diagram of arsenic As (V) by hybrid sorbent on the base of mixture of PAN-fiber and ionexchange resin, described in the example 3, and also soption kinetic diagram of arsenic As (V) by hybrid sorbent FO36 U.S. Pat. No. 7,291,578, chosen as the closest analogue are depicted in the in the FIG. 5.

(55) From the diagrams depicted in the FIGS. 4 and 5 it is obvious that hybrid sorbent with HFO on the base of PAN-fiber, described in the example 1 of the invention has the highest sorption kinetics of arsenic As(III) and As(V), particularly: kinetics of 50-percent sorption of As(III) is 1 minute, kinetics of 50-percent sorption of As(V) is less than 1 minute. Sorption kinetics of As(III) and As(V) of hybrid sorbent on the base of a mixture of PAN-fiber and ionexchange resin, described in example 3 is lower: kinetics of 50-percent sorption of As(III) is 4 minutes and kinetics of 50-percent sorption of As(V) is less 1.5 minutes. At the same time hybrid sorbent of a U.S. Pat. No. 7,291,578, chosen by the applicant as the closest analogue has sorption kinetics less than hybrid sorbent in example 3, particularly 50-percent sorption kinetics of ions As(III)—30 minutes and As(V)—25 minutes.

(56) Comparative analysis of hybrid sorbent of the closest analogue (U.S. Pat. No. 7,291,578) and claimed hybrid sorbent with HFO is given in table 1.

(57) Sorption kinetics of As(III) was determined with sodium meta arsenite NaAsO.sub.2, and sorption capacity of As(V) was determined with 12-aqua sodium orto arsenate Na.sub.3AsO.sub.4.12H.sub.2O.

(58) TABLE-US-00001 TABLE 1 Comparative analysis of hybrid sorbent of the closest analogue (U.S. Pat. No. 7,291,578) and claimed hybrid sorbent with HFO. Closest analogue U.S. Pat. No. Material 7,291,578 Claimed Iron content in hybrid sorbent, 35-60 60-110 mg/g HFO type in sorbent phase 23% wustite >90% ferrihydrate 28% ferrihydrate 13% hematite 35% lepidocrocite crystalline amorphous structure prevails structure Necessity of mechanical grinding — — of HFO units HFO Sorption kinetics of As(V), mg/g 22  32 Sorption capacity of As(III), mg/g 17  30 Kinetics 50% removal 25/30 <1/1 As(V)/As(III), min Sorption capacity of Cr (VI), mg/g — 250 Sorption capacity of Cu, mg/g 250 Sorption capacity of Pb, mg/g 360 Suggested linear velocity of water 30 130 filtration, m/h Minimal height of sorbent layer 1000  100 in column, mm

(59) As can be seen form the data indicated in table 1, sorption capacity of the claimed hybrid sorbent far exceeds the sorption capacity of hybrid sorbent of the closest analogue (U.S. Pat. No. 7,291,578), and also sorbents, described in state of the art. It is explained, that in hybroid sorbent with HFO claimed in the invention, the amorphous ferruhydrate fraction in HFO exceeds 90%. As ferrihydrate functional groups due to its amorphous structure are more available for anions, containing arsenic As(III) and As(V), then structures of crystalline magnetic HFO in hybrid sorbents in the state of the art, they have the highest sorption activity towards As(III) and As(V) ions, as well as to different ions of heavy metals such as Cr(VI), Cu and Pb.

(60) As can be seen from the information indicated above from the complex of compounds of HFO, only amorphous ferrihydrate Fe.sub.2O.sub.3⋅3FeO(OH)⋅3H.sub.2O has the highest activity of sorption to both arsenic ions As(III) and As(V), and hybrid sorbent is additionally capable to sorb different ions of heavy metals. The given comparative analysis prove that claimed hybrid sorbent with HFO, in which HFO contains more than 90% from amorphous ferrihydrite is highly active and stable sorbent towards ions of both arsenic As(III) and As(V).

(61) In the description of the invention the preferable embodiment is given. The invention maybe changed, but within the limits of the present claims. This gives the possibility of its common use.