Abstract

Removal of hexavalent chromium [Cr(VI)] from water was evaluated using a low-cost coated sand adsorbent for potential application in a flow-through filter system using permeable adsorption media. Manganese-aluminum coated sand (MACS) was investigated as a hybrid metal oxide based adsorbent due to the potential efficacy of manganese oxide and aluminum oxide for adsorption of Cr(VI) from water. Adsorbent characterization was performed using XRD, SEM/EDX, XPS and BET. Adsorption experiments were performed to determine adsorption capacity and kinetics. The effect of pH, common co-existing ions found in natural water, and the recyclability of adsorbent were investigated. Adsorbent characterization showed that the MACS sorbent contained aluminum oxide, manganese (III) oxide and manganese (IV) oxide. Adsorption followed the Langmuir and Freundlich adsorption equations, indicating favorable adsorption of Cr(VI) onto the MACS sorbent, while results from the Dubinin–Radushkevich equation were suggestive of physical adsorption of Cr(VI). Cr(VI) adsorption onto the MACS sorbent followed pseudo-second order kinetics. The adsorbent was effective in removing Cr(VI) over a broad pH range from 3 to 9.5, while surface charge analysis confirmed the adsorption of Cr(VI) onto the acidic surface of the MACS sorbent with a pH_PZC of 9.72. The presence of co-existing ions bicarbonate, sulfate and phosphate in water resulted in a decrease in Cr(VI) uptake in the following order: phosphate > bicarbonate > sulfate. The presence of calcium resulted in a slight increase in Cr(VI) uptake. The MACS sorbent is a recyclable sorbent for adsorption and removal of Cr(VI) from water within 30 minutes of contact time.

摘要

使用低成本的覆膜砂吸附剂评估了水中六价铬[Cr（VI）]的去除情况，该吸附剂可潜在地用于使用渗透性吸附介质的流通式过滤器系统中。由于锰和铝氧化物从水中吸附Cr（VI）的潜在功效，因此研究了锰铝涂层砂（MACS）作为基于混合金属氧化物的吸附剂。使用XRD，SEM / EDX，XPS和BET对吸附剂进行表征。进行吸附实验以确定吸附容量和动力学。研究了pH值，天然水中常见的共存离子以及吸附剂的可回收性的影响。吸附剂表征表明，MACS吸附剂包含氧化铝，氧化锰（III）和氧化锰（IV）。吸附遵循Langmuir和Freundlich吸附方程，表明Cr（VI）在MACS吸附剂上有良好的吸附，而Dubinin-Radushkevich方程的结果表明对Cr（VI）的物理吸附。Cr（VI）吸附到MACS吸附剂上的过程遵循拟二级动力学。该吸附剂可在3至9.5的宽pH值范围内有效去除Cr（VI），而表面电荷分析证实Cr（VI）在pH为pH的MACS吸附剂的酸性表面上的吸附_PZC为9.72。水中碳酸氢根，硫酸根和磷酸根共存离子的存在导致Cr（VI）吸收的降低顺序如下：磷酸根>碳酸氢根>硫酸根。钙的存在导致Cr（VI）吸收略有增加。MACS吸附剂是一种可回收的吸附剂，用于在接触时间内30分钟内从水中吸附和去除Cr（VI）。