Lead immobilisation in mining contaminated soil using biochar and ash from sugarcane

Abstract

Immobilisation of lead (Pb) and toxic elements in contaminated soils is of importance due to their persis-tence in the environment. Herein, we investigated the effects of sugarcane filter cake biochar (SFCB) and sugarcane bagasse ash (SBA) on the extractability of Pb and some toxic and potentially toxic elements (As, Cd, Cu, and Zn) in polluted mine soil samples from Lower Klity Creek, Thailand. The soil was equilibrated with the SFCB and SBA at the respective rates of 0, 1, and 5% (w/w) for 120 days at field capacity. The results revealed that both SFCB and SBA materials significantly (P < 0.05) decreased Pb extractability in the studied soil, and it stabilised after 56 days of incubation. At 120 days, the SFCB and SBA application at the rates of 5% SFCB, 5% SBA, 1% SFCB, and 1% SBA decreased the extractable Pb contents by 50.35, 40.81, 29.42, and 19.27%, respectively, compared to unamended soil. The SFCB and SBA materials also improved soil chemical properties by increasing the soil pH, available phosphorus, and extractable sulfur. At 5%, SFCB decreased As extractability and increased organic carbon in the studied soil. The Zn availability in the studied soil was also improved by SFCB and SBA addition. This study highlights the potential use of biochar and ash from the sugarcane industry to stabilise Pb and As in contaminated soils.