CHITOSAN-ASSISTED SOIL WASHING: INFLUENCE OF CONCENTRATION AND LIQUID-TO-SOLID RATIO ON HEAVY METAL REMOVAL

Abstract

The process of mining has led to metal contamination of soils, which is an environmental concern in Romania, and especially in the Apuseni Mountains region, where considerable extractive activity has been conducted that has left behind large amounts of tailings and waste materials. The purpose of this study was to investigate the effect of chitosan-based washing solutions on the removal of copper (Cu) and lead (Pb) from contaminated soil collected from the Larga de Sus mining site (Alba County, Romania). Soil washing was conducted using chitosan solutions with various chitosan content (0%, 2% and 5% w/v) and at a liquid-to-solid ratios (mL:g) of 5:1 and 8:1. The washing process was done using a mechanical stirrer for up to 40 hours, and the concentration of metals was measured by Atomic Absorption Spectrometry (AAS). Results demonstrated that both chitosan concentration and washing solution volume strongly influenced metal removal efficiency. The maximum rate of metal removal was obtained using the 2% chitosan solution and an 8:1 liquid-to-solid ratio, resulting in the removal of Cu and Pb by 74.5% and 79.6%, respectively. Copper concentration after soil washing dropped below the Romanian regulatory intervention limit while Pb concentration remained slightly over that limit. Overall, the results indicate that chitosan is a natural, green, and effective chelating agent for soil remediation, with a potential for large scale and field applications to remediate heavy metal contaminated sites.