The immobilisation and retention of soluble arsenic, cadmium and zinc by biochar

► The capability of biochar to immobilise and retain arsenic (As), cadmium (Cd) and zinc (Zn) from a multi-element contaminated sediment-derived soil was explored by a column leaching experiment and scanning electron microanalysis (SEM/EDX). We highlight the following results from this study: ► Large surface area and surface sorption of Cd and Zn to biochar reduces the concentrations of these metals in leachates from a contaminated soil 300 and 45-fold respectively. ► Metal retention was not reversible by continued leaching of the sorbant biochar. ► Biochar increased leachate pH and water-soluble carbon but this did not appear to be detrimental to its effects and may aid retention of Cd. ► Although some arsenic was sorbed to biochar, leachate concentrations were not duly reduced. ► Developments in micro-analyses techniques will allow more detailed exploration of the encouraging results seen here with regards to interior surfaces of biochar's vast porous structure.