Kinetics, equilibrium modeling, and thermodynamics on removal of Cr(VI) ions from aqueous solution using novel composites with strong base anion exchanger microspheres embedded into chitosan/poly(vinyl amine) cryogels

Contribution of Cross-Linker and Silica Morphology on Cr(VI) Sorption Performances of Organic Anion Exchangers Embedded into Silica Pores

“…In the FTIR spectra of PSi1 and PSi2, presented in Figure S2, these peaks are located at 1088, 817, and 470 cm −1 . Even if the silica main peaks are screening the peaks of the organic ANEX, after loading with Cr(VI) (Figure 1), a new peak is visible at 943 cm −1 , which could be assigned to νCr-O bonds [24,48].…”

“…Synthetic polymeric sorbents [1][2][3][4][5][6] and various biosorbents [7][8][9][10][11][12] are investigated for their performances in the recovery/removal of HMIs. Among the HMIs present in the wastewaters, chromium, especially Cr(VI), is one of the most dangerous contaminants of the surface and ground water, being considered a powerful carcinogenic and teratogenic agent threatening living organisms [1,2,11,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. On the other hand, Chromium(III) is listed as an essential element, as a micronutrient, being involved to maintain the normal metabolism of glucose, cholesterol, and fat in human bodies [1,2], being poisonous only at a high concentration.…”

“…Therefore, to avoid the dangerous impact of Cr(VI) on human health and on the environment, as well as for economic considerations, it is essential to remove/recover Cr(VI) from the wastewaters before disposal [1][2][3]. Various techniques are available for the removal of Cr(VI) such as ion exchange, chemical precipitation, reduction [13,14], reverse osmosis, foam flotation, electrolysis, membrane filtration [15,16], ultrafiltration [17], sorption, and biosorption [18][19][20][21][22][23][24][25][26][27][28][29][30][31]. Some of these techniques have disadvantages of either producing toxic sludge as is the case of chemical precipitation, or asking for high capital costs (reverse osmosis), recovery of value metal being difficult [27,28].…”

“…Therefore, the research interest is lately concentrated more on the sorption methods because they offer high efficiency and selectivity, are easy to handle, the metal can be recovered, the sorption process is reversible, and it is cost-effective. In aqueous environment, at pH > 2.0, Cr(VI) exists as oxyanion, and that is the reason why ligands carrying a positive charge, generated by protonation or quaternization, have been successfully used-sorption by electrostatic attractions being favored [21][22][23][24][25][26][27][28][29][30]. Synthetic sorbents offer the possibility to introduce almost any reactive functionality, which could be involved in the retention of HMIs.…”

“…Thus, Zhang et al have developed a composite sorbent consisting of a weak base anion exchanger having tertiary amine groups (D301) modified by poly(epichlorohydrin-dimethylamine) with a maximum sorption capacity of 194 mg Cr(VI)/g [22]. Macroporous strong base anion exchangers (SBAE) bearing quaternary ammonium salt groups have been synthesized and successfully used by our group in the removal of Cr(VI) either as single anion exchangers [25] or embedded in a composite consisting of chitosan and poly(vinyl amine) as cryobeads [24], their maximum sorption capacity being of 200-320 mg Cr(VI)/g sorbent. A biosorbent consisting of chitosan beads modified with malic acid by Zhang et al have showed a maximum equilibrium sorption capacity of 383.2 mg Cr(VI)/g [29].…”