Deep eutectic solvents for the removal of lead contaminants in mangrove soil

Abstract

The remediation of heavy metal contaminated mangrove soil with proper washing agents is critical for reducing the harmfulness of heavy metal contaminated soil to the environment. This work is aimed to investigate the potential of natural-based deep eutectic solvents as soil washing agents. Choline chloride (ChCl) and two organic acids, lactic acid and levulinic acid, are used as degradable and natural washing agents to remove Pb in the soil. Results verified that ChCl: Lactic Acid (1:2) [ChCl-LacA] and ChCl: Levulinic Acid (1:2) [ChCl-LevA] were found to be suitable for the removal of Pb from the contaminated soils, which significantly lowers the total Pb concentration in the soil. The high distribution ratio from the Conductor-like Screening Model for Real Solvents (COSMO-RS) screening gave an early indication that natural acid DESs are effective soil washing agents. The effect of washing agent concentration, soil to liquid ratio, contact time, and the interaction between acid DESs and metal ions was evaluated. ChCl-LacA and ChCl-LevA remove lead to 97% and 99%, respectively, under optimum conditions. ICP-MS, XRD, and FTIR spectroscopy analysis clarified the interaction between DES and metal ions. As a washing agent, green and natural DESs provide an environmentally sustainable alternative. Employing soil washing to remove heavy metals is a simple, rapid, and cheap remediation technology that could potentially be used in mitigating soil pollution.