Enhanced adsorption of Cr(VI) under neutral conditions using a novel adsorbent with preorganized diquaternary ammonium structure

Chen, Yong; Zeb, Shah; Peng, Xiujing; Zhao, Yiming; Xu, Chengjin; Li, Ling; Cui, Yu; Sun, Guoxin

doi:10.1016/j.molliq.2020.114905

Cited by 7 publications

(1 citation statement)

References 40 publications

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“…Chromium (Cr) widely exists in the surface and underground water as a common poisonous heavy metal. The Cr in water mainly comes from industrial discharges, such as leather tanning, electroplating, metal plating, and chemical manufacturing [ 1 , 2 , 3 ]. There are two primary species of Cr, trivalent (Cr (III)) and hexavalent (Cr (VI)) ions in the aqueous system [ 4 ], and the toxicity and mobility of Cr are highly dependent on its existing species [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

Mn-Doped Spinel for Removing Cr(VI) from Aqueous Solutions: Adsorption Characteristics and Mechanisms

Zhang

et al. 2023

Materials

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In this study, the manganese (Mn) was doped in the MnFe2O4 crystal by the solid-phase synthesis method. Under the optimum conditions (pH = 3), the max removal rate and adsorption quantity of Cr(VI) on MnFe2O4 adsorbent obtain under pH = 3 were 92.54% and 5.813 mg/g, respectively. The DFT calculation results indicated that the adsorption energy (Eads) between HCrO4− and MnFe2O4 is −215.2 KJ/mol. The Cr(VI) is mainly adsorbed on the Mn atoms via chemical bonds in the form of HCrO4−. The adsorption of Mn on the MnFe2O4 surface belonged to chemisorption and conformed to the Pseudo-second-order equation. The mechanism investigation indicated that the Mn in MnFe2O4 has an excellent enhancement effect on the Cr(VI) removal process. The roles of Mn in the Cr(VI) removal process included two parts, providing adsorbing sites and being reductant. Firstly, the Cr(VI) is adsorbed onto the MnFe2O4 via chemisorption. The Mn in MnFe2O4 can form ionic bonds with the O atoms of HCrO4−/CrO42−, thus providing the firm adsorbing sites for the Cr(VI). Subsequently, the dissolved Mn(II) can reduce Cr(VI) to Cr(III). The disproportionation of oxidized Mn(III) produced Mn(II), causing Mn(II) to continue to participate in the Cr(VI) reduction. Finally, the reduced Cr(III) is deposited on the MnFe2O4 surface in the form of Cr(OH)3 colloids, which can be separated by magnetic separation.

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