The influence of pH, co-existing ions, ionic strength, and temperature on the adsorption and reduction of hexavalent chromium by undissolved humic acid

Treatment of Contaminated Groundwater via Arsenate Removal Using Chitosan-Coated Bentonite

“…Natural groundwater contains a complex matrix of anions and cations that could lead to the suppressed adsorptive performance of CCB in the uptake of As(V). Decreased adsorption capacity of CCB could be due to the inhibitive effect of existing anions (phosphate (PO 4 3− ), chloride (Cl − ), and sulfate (SO 4 − )) in groundwater that would compete for the available adsorption sites of CCB for the uptake of As(V) [80]. Previous studies have reported that the presence of PO 4 3− at high concentration would hinder the removal of As(V) due to similar behavior towards the binding sites of the adsorbent.…”

Recent advances in hexavalent chromium removal from aqueous solutions by adsorptive methods

“…The synergy in adsorption and reduction during the removal of Cr(VI) by adsorbents has been mentioned by several researchers. 16,29,30,44,162,163 Anionic Cr(VI) could be adsorbed through electrostatic bonding on protonated sites or through anion exchange. The strong oxidant nature of Cr(VI) causes the surface where it was bonded to be oxidized while itself is reduced to Cr(III).…”

“…42 Despite the extensive existence of adsorbents for Cr(VI) removal from aqueous solutions, new adsorbents, and modication of existing adsorbing materials have been recently reported. 3,[43][44][45][46][47][48][49][50] Unlike in previous review articles, [37][38][39][40][41] this work focused on reviewing the major adsorbents reported in the literature (up to the year 2019) mainly for the removal of Cr(VI) from aqueous solutions. The objectives of this review included outlining some of the recent developments in the eld of adsorption, where a trend of utilizing composites, particularly incorporating nanomaterials, has dominated the recent literature.…”

Mechanism and modeling of hexavalent chromium interaction with a typical black soil: the importance of the relationship between adsorption and reduction

“…Because the adsorption process of Cr(VI) by black soil was accompanied by Cr(VI) reduction, the equilibrium state of Cr(VI) adsorption/desorption between aqueous and solid phases was almost impossible to obtained from the continuous variation of Cr(VI) concentration in solution. 34 Considering that the reduced Cr(III) on soil particles cannot participate in the reversible reaction of Cr(VI) adsorption-desorption any more, the adsorption and reduction processes of Cr(VI) should be analyzed separately. Consequently, in order to verify whether the adsorbed Cr(VI) and aqueous Cr(VI) followed certain partition law, correlations were established between the remaining Cr(VI) concentration in solution and adsorbed Cr(VI) content on soil particles under different initial Cr(VI) concentrations and pH conditions (Fig.…”