The performance of calcined serpentine to simultaneously remove fluoride, iron and manganese

Abstract

To solve the problem of high fluoride, iron and manganese concentrations in groundwater, serpentine (Srp) was modified by metal salt impregnation, acid–base activation and calcination, and the effects of these three modifications on the removal performance of Srp were compared. Specifically, the effects of the calcined serpentine (Csrp) dose, reaction time, pH, and temperature on the removal performance of F, Fe2þ and Mn2þ on Csrp were analysed. An isothermal adsorption model and adsorption kinetic equation were established and confirmed through SEM, EDS, XRD and FTIR spectroscopy to analyse the mechanism of removing F, Fe2þ and Mn2þ by Csrp. The results show that when 3 g/L Csrp was used to treat water samples with 5 mg/L F, 20 mg/L Fe2þ, and 5 mg/L Mn2þ (pH of 6, reaction temperature of 35 °C, and time of 150 min), the removal rates of F, Fe2þ, and Mn2þ were 94.3%, 99.0%, 98.9%, respectively. The adsorption of F, Fe2þ and Mn2þ on Csrp follows the quasi-second-order kinetic equation and Langmuir isotherm adsorption model. After five cycles of regeneration of Csrp, Csrp can still maintain good properties of fluoride, iron and manganese removal.