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−, Fe2+ and Mn2+ 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−, Fe2+ and Mn2+ 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 Fe2+, and 5 mg/L Mn2+ (pH of 6, reaction temperature of 35 °C, and time of 150 min), the removal rates of F−, Fe2+, and Mn2+ were 94.3%, 99.0%, 98.9%, respectively. The adsorption of F−, Fe2+ and Mn2+ 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. HIGHLIGHTS Microscopic characterization of calcined serpentine was carried out.; Calcined serpentine can achieve the synchronous removal of high fluoride, iron and manganese concentrations in groundwater.; The adsorption isothermal model and adsorption kinetic equation of calcined serpentine were established.; The mechanism for the simultaneous removal of fluoride, iron and manganese by calcined serpentine was analysed.;

Keywords

• calcined modification
• fluoride
• iron
• manganese
• removal mechanism
• serpentine