Abstract
The influence of salinity on the single and binary sorption of Ni and Zn onto iron oxide- and manganese oxide-coated sand (IOCS and MOCS) was investigated at pH = 5. The single sorption experimental data were fitted to Freundlich, Langmuir, Dubinin–Radushkevich, and Sips models, and a nonlinear sorption isotherm was observed (NF = 0.309–0.567). The higher Brunauer–Emmett–Teller (BET) surface area (ABET) and cation exchange capacity (CEC) of MOCS contributed to the higher maximum sorption capacities (qmL) of Ni and Zn than that of IOCS. The Ni sorption capacities in the single sorption were higher than that in the binary sorption, while the Zn sorption capacities in the single sorption were less than that in the binary sorption. The single and binary sorptions onto both IOCS and MOCS were affected by the salinity, as indicated by the decrease in sorption capacities. Satisfactory predictions were shown by the binary sorption model fitting including P-factor, ideal adsorbed solution theory (IAST)–Freundlich, IAST–Langmuir, and IAST–Sips; among these, the P-factor model showed the best fitting results in predicting the influence of salinity of Ni and Zn in the binary sorption system onto IOCS and MOCS. IOCS and MOCS offer a sustainable reactive media in a permeable reactive barrier (PRB) for removing Ni and Zn in the presence of salinity.
Highlights
Heavy metal-contaminated groundwater has become an important issue in the coastal regions where freshwater resources are limited [1]
Ni and Zn are frequently found heavy metals that are strongly correlated with groundwater toxicity and coastal sediment, posing serious risks to human health and ecosystems at large [2,3]
Tian et al [6] and Liu et al [7] reported the significant contribution of industrialization to the increase in Ni and Zn contaminations in water sources in China and Korea, two heavily industrialized countries where 70–75% of major cities and industries are located in the coastal regions
Summary
Heavy metal-contaminated groundwater has become an important issue in the coastal regions where freshwater resources are limited [1]. Most of the shallow groundwater resources in the crowded urban areas near coastal regions, such as megacities, were heavily contaminated by heavy metals due to anthropogenic activities [2]. Tian et al [6] and Liu et al [7] reported the significant contribution of industrialization to the increase in Ni and Zn contaminations in water sources in China and Korea, two heavily industrialized countries where 70–75% of major cities and industries are located in the coastal regions. Ni and Zn removal from water and wastewater has been reported using various sorbents, such as natural and modified zeolite, bentonite, and vermiculite through adsorption and ion exchange mechanisms [8], their removal from the groundwater near coastal regions through sorption has not been examined
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