Correlation between sorbent characteristics and metal sorption capacity of soils around Mumbai: Implications on environmental hazard management

Abstract

The present study involves the characterization of soils on the basis of physical and chemical properties including grain size, surface area, cation exchange capacity (CEC), organic matter, types of clay minerals and point of zero charge, which make them effective as geosorbents and correlation of these sorbent characteristics to their metal sorption capacity. The study on characterization of soils involved four types of soils from a single soil profile, a black cotton soil and a brick making soil collected from Mumbai and its surroundings. Completely mixed batch reactor systems were utilized to obtain isotherms for nickel and cadmium sorption on three geosorbents, i.e. top-most profile soil, bottom-most profile soil and black cotton soil. The experimental protocol consisted of geosorbent characterization, kinetic study of nickel and cadmium sorption to determine the equilibrium time and sorption equilibrium studies. The sorption results indicate that CEC, presence of expandable clay minerals and point of zero charge have significant effect on metal sorption. It is also observed that sorbate specific properties such as ionic charge, ionic radius, electronegativity, etc also affect the extent of sorption.