Utilizing thiourea-modified biochars to mitigate toxic metal pollution and promote mustard (Brassica campestris) plant growth in contaminated soils

Abstract

This study investigated the potential of using biochars made from sugarcane bagasse, banana peel, and watermelon rind that were modified with 1 % thiourea through pyrolysis at 500 °C to make sugarcane bagasse + thiourea modified biochar (STMB), banana peel + thiourea modified biochar (BTMB), and watermelon rind + thiourea modified biochar (WTMB) to immobilize toxic metals such as Cd, Ni, Cu, Pb, Cr, and Zn in polluted soils from Gadap town and Malir cantonment. The modified biochars were used at different dosages (1.25 %, 2.5 %, and 5 %) and the results showed that they were effective in immobilizing the toxic metals (TMs), with immobilization rates ranging from 43.75 % to 93.98 % with application of with BTMB 2.5 % and BTMB 5 %. The addition of these biochars also led to improved growth of mustard plants, with the highest biomass observed with STMB at a 1.25 % dosage. The study also found that soil pH, SOC, CaCO3, and TOC played key roles in reducing the concentration of toxic metals in the polluted soils. The results suggest that a dosage of 1.25 % can be recommended for better plant growth while 2.5 % and 5 % dosage can be recommended for immobilization of TMs in industrial wastewater-polluted soils.