Adsorptive removal of heavy metals from water using thermally treated laterite: an approach for production of drinking water from rain water

Abstract

Access to clean water is still limited in a number of regions, especially country sides, rural, and mountainous areas in Vietnam. Therefore, studies on clean water production by using sustainable and affordable processes for locals to access to clean water are of great importance. In this research, we produced laterite-based adsorbents by thermal treatment of natural laterite. The produced adsorbents were characterized in terms of morphology, crystallite, chemical composition, surface functional groups, surface charges, and surface area. The adsorption processes of Ni2+ and Cu2+ onto thermally treated laterite were studied. The treated laterite was also deployed to the removal of pollutants from real rain water. Finally, treated laterite was used in a combination system to purify rain water to produce drinking water for households in Hai Dong commune, Hai Hau district, Nam Dinh province. The results showed that the adsorption of Ni2+ and Cu2+ by thermally treated laterite reached equilibrium after 40 min and followed the Langmuir sorption isotherm, with the maximum uptake of 27.6 mg/g for Cu2+ and 17.4 mg/g for Ni2+. The second-order-kinetic model described the best the adsorption of Cu2+ and Ni2+ from aqueous solution, implying chemisorption was predominant mechanism. The treated laterite was suitable for heavy metal removal but less effective for the removal of anions from water. The combination of solar heating system with treated laterite, sand, and activated carbon allowed to safely produce drinking water from rain water, which presented the water quality respecting the Vietnam national standard for drinking water (QCVN 01:09/BYT).