“A Study on Immobilization of Copper, Cadmium and Lead in Polluted Soil Using Nanoparticles”

Abstract

Abstract: Copper Cu, Cadmium Cd and Lead Pb pollution of soils is a serious environmental and agricultural issue, posing a threat to crop production, environmental quality, food safety, and human health. Therefore, immobilization of Copper Cu, Cadmium Cd and Lead Pb in soils is crucial. Biochar-based materials are receiving significant attention as Copper Cu, Cadmium Cd and Lead Pb immobilizers, due to their multifunctional surface properties. The remediation/immobilization mechanisms involved are, mainly, surface complexation, chemical reduction, precipitation, ion exchange, π–π interactions, hydrogen bonding, and adsorption. These mechanisms are mostly dependent on biochar surface pore size, oxygen-containing functional groups, pyrolysis temperature used in biochar preparation, biochar feedstock, and soil characteristics. So far, various pristine and modified biochar substrates have been used to remediate heavy metal-contaminated soils. Therefore, in this review paper, we briefly summarize the chemical forms, release sources, and maximum permissible limits of Copper Cu, Cadmium Cd and Lead Pb in soil. We also summarize recent scientific findings on the performance of biochar substrates in Copper Cu, Cadmium Cd and Lead Pb -contaminated soils to minimize Copper Cu, Cadmium Cd and Lead Pb mobility, bioavailability, and potential accumulation in crops. Finally, we identify challenges associated with the use of biochar and suggest areas for future research. The review presents an overview of the knowledge of biochar as a promising amendment for the decontamination of Copper Cu, Cadmium Cd and Lead Pb -polluted soils. Sediment and soil contamination with toxic heavy metals, including cadmium (Cd2+) and lead (Pb2+), represents a major long-term remediation challenge. Resuspension of contaminated sediments into the water column, or the uptake of toxic metals from top soil, can lead to exposure of aquatic or terrestrial organisms, followed by bioconcentration, bioaccumulation and biomagnification, which may pose a threat to public health. We have developed a novel nanoscale engineered material, namely ligand-coated dense nanoparticles (Ligand DNPs), which contain a dense WO3 nanoparticle core and a shell functionalized with a metal-binding organic ligand (EDTA), to effectively sequester heavy metal ions deeper into the soil and sediments. We demonstrate that one application of Ligand DNPs can remove from 60% to almost 80% of the Cd and Pb in two different soil matrices, driving these metal ions deeper into the sediment or soil column via gravity, and making them less bioavailable. Ligand DNPs can provide a relatively fast, convenient, and efficient insitu approach for the remediation of sediments and soils contaminated with heavy metals.