Arsenic(Ⅴ) Removal by Granular Adsorbents Made from Backwashing Residuals from Biofilters for Iron and Manganese Removal

Abstract

Granular adsorbents for arsenic removal (GA) made from the backwashing residuals from iron and manganese removal biofilters for groundwater were characterized and examined as an arsenate sorbent. The GA were characterized by SEM-EDS microscopy, X-ray diffraction (XRD), and BET surface area measurement. The results showed that the GA had rough surfaces, developed pores, and were mainly amorphous, with small fractions of crystalline quartz and hematite. The surface area of the GA, which consists of many mesopores, was 43.8 m2·g-1. The kinetic studies revealed that arsenate adsorption on the GA was described by a pseudo-second-order kinetic equation, and the Freundlich isotherm equation fit the arsenate adsorption well (R2=0.994). The maximum adsorption capacity calculated by the Langmuir isotherm equation for As(Ⅴ) was 5.05 mg·g-1. Further studies showed that the GA operated well for As(Ⅴ) removal over a broad range in pH from 1.1 to 9.5. The coexistence of HCO3- and SO42- had no great influence on arsenic adsorption, while the H2PO4- and SiO32- showed negative effects. The GA can be regenerated well, and 82% of the original adsorption capacity was maintained after three regeneration cycles.