MECHANISMS AND PROCESSES OF METAL BINDING BY BIOCHAR MATERIALS IN SOILS

Abstract

Heavy metals in the environment pose health risks to living things. Once in the environment, the metals persist for a long time and when in mobile forms, they may be taken-up by plants or leached to the underground water resources. Biochars have capacity of adsorbing heavy metals   and render them immobile. The mechanisms involved in the adsorption of metals by biochars are fragmented in different literature. It is therefore important to review these mechanisms to increase our understanding of the mechanisms involved in metal adsorption by biochars in order to use the information to enhance the quality and efficiency of the materials to immobilize heavy metals in the soil environment. The study reviewed about 200 publications. Out of these, about 66 were relevant and were used in this article. Literature shows that biochars are diverse as they are derived from different plant material sources and are processed at different temperatures and at varied processing duration. This makes biochars have different physico-chemical properties leading to different capacities of adsorbing metals. Due to differences in the sources and processing temperatures that lead to differences in chemical composition and chemical properties, biochars exhibit different mechanisms of binding heavy metals in the soils.

Keywords: Heavy metals, adsorption, pollution, contamination, plants