In the process of bio-filter backwash for biological iron and manganese removal from groundwater

a large quantity of sludge rich in iron and manganese oxides was produced

and was trying to be used as an arsenic removal adsorbent to avoid pollution caused by its direct emission. The sludge was characterized after pretreatment using XRD and TEM

and its adsorption properties and related mechanism were studied through the static adsorption experiments. The results show that the sludge of iron and manganese oxides is non-setting structure with small particle size and large specific surface area. The Langmuir isotherm equation is more in line with the adsorption characteristics of As(Ⅴ) (R2>0.99)

and As (Ⅲ) adsorption behavior cannot be simulated by a single model. The maximum adsorption capacity for As (Ⅲ) and As(Ⅴ) is 36.53 mg/g and 40.37 mg/g respectively

and the adsorption capacity increases with the increase of the temperature. The adsorption of As (Ⅲ) and As(Ⅴ) conforms to the pseudo-second order kinetic model with R2 more than 0.99

and As(Ⅴ) adsorption capacity decreases gradually with the increase of pH

while As (Ⅲ) adsorption capacity experiences a process of decrease and increase and then decrease. H2PO4- and SiO32-has significant inhibition on arsenic adsorption and other ions have little effect on the adsorption process.