Abstract
Water treatment residuals (WTRs), obtained from a groundwater treatment plant for biological iron and manganese removal, were investigated and used as adsorbents for arsenic removal. The surface morphology and structural features of the WTRs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauner–Emmett–Teller analysis (BET). Laboratory experiments were also carried out to test the adsorption capability and adaptability of WTRs on both As (III) and As (V) removal from the water. The results showed that the WTRs were mainly amorphous and had a large specific surface area of 253.152 m2/g. The maximum adsorption capacities, evaluated using the Langmuir isotherm equation, were 36.53 mg/g and 40.37 mg/g for As (III) and As (V), respectively. The pseudo-second-order model fitted the kinetic data better, with R2 more than 0.99 for both As (III) and As (V). The removal of As (V) decreased with the increase in pH, especially when the pH was above 9, whereas for As (III), the removal effectiveness almost remained constant at both acidic and neutral pHs. H2PO4− and SiO32− could strongly inhibit arsenic adsorption onto the WTRs, and the effect of other ions was little.
Highlights
Arsenic pollution in water is a global concern due to its toxicity and chronic effects on human health
This study aimed to examine the adsorption behaviors of Water Treatment Residuals (WTRs) from waterworks for iron and waste requires chemical pretreatment, due to the presence of heavy metals
WTRs, andplant batchfor experiments manganese removal using the aeration-biofiltration process, which was under steady operation for were conducted to investigate the kinetics and isotherm characteristics of As (III) and As (V) adsorption many years since its successful startup
Summary
Arsenic pollution in water is a global concern due to its toxicity and chronic effects on human health. Agency (USEPA), the Ministry of Health of People’s Republic of China (MHPRC), and the Bureau of Indian Standards (BIS) have decreased the maximum contaminant level (MCL) of arsenic in drinking water from 50 to 10 ug/L [2], creating a strong demand for economical and efficient treatment methods. Various arsenic-removal techniques have been developed, including precipitation, coagulation, membrane separation, ion exchange, lime softening and adsorption. Among these methods, adsorption and coagulation are the most promising and are widely used in the developing world [3], but the application of the coagulation method is limited, due to the requirement of skilled operators in small communities and at household levels.
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