Arsenic(V) removal by granular adsorbents made from water treatment residuals materials and chitosan

[Display omitted] A novel granular adsorbent (GA) consisting of spheres with size ranging from 1.6 mm to 1.8 mm, was made of iron-containing backwashing residual sludge. The adsorbent was characterized by SEM (scanning electron microscopy), XRD (X-ray diffraction), and BET (Brunauner–Emmett–Teller analysis). Laboratory experiments including batch and column studies were also carried out to survey the adsorption ability of GA for As(V) removal. The results showed that GA was mainly amorphous with a large specific surface area (110.30m2/g) and rich in iron. Langmuir model gave a better representation than that of Freundlich for As(Ⅴ) adsorption behavior, with the maximum adsorption capacity 14.95 mg/g, outperforming most of reported granular sorbents. Pseudo-first order model and pseudo-second order model were suitable to describe the kinetic curves. The results obtained from the thermodynamic parameters indicated that the adsorption of As(V) by GA was feasible, endothermic and spontaneous. Arsenic adsorbed GA was regenerated by washing 4 times with 1% NaOH, resulting in a decrease of adsorption capacity by about 35%. A fixed bed column study showed that about 210 and 1200 bed volumes of influent with 150 μg/L As(V) were respectively treated before the concentration of effluent reached 10 and 50 μg/L.