Detail Abstract

Adsorptive removal of heavy metals from water using thermal treated laterite: an approach for purification of rain water

Abstract

Many people presently do not have access to clean water, especially in rural/coastal areas. In such areas in Vietnam, rainwater is partly utilized along with groundwater, which risks of being contaminated by heavy metals, especially arsenic in some areas. Besides, rapid industrialization and urbanization may result in lots of pollutants ended up with rainwater. Therefore, the pollutant must be safely removed from rainwater for living purposes. In this study, we modify natural laterite by thermal process to improve its adsorption capacity and mechanical properties. The modified laterite was used to study the adsorption of heavy metals in water medium and purify rainwater. The treatment process led to removal of impurities and decrease in surface area of laterites. The adsorption of of Cu2+ (10 mg/L) and Ni2+ (10 mg/L) reached equilibrium at 35 min, with removal efficiencies of 99% (for Cu2+) and 95% (for Ni2+). The optimal pH was pH 7.0, being linked with the electrostatic interactions. The maximum uptakes of modified laterite were 0.820 mg/g and 1.027 mg/g for Ni2+ and Cu2+, respectively. Rainwater quality at 100 households in Hai Dong coastal commune, Hai Hau district, Nam Dinh province varied from household to household, mainly respecting the national regulation on domestic water quality (QCVN 02: 2009/BYT), with some exceeding values. Fe2+ and Mn2+ contents in some samples exceeded national regulation due to mixture of rainwater with groundwater. The application of modified laterites combined with sands and biochar significantly improved the water quality that could be used for different domestic purposes.