Remediation of heavy metal contaminated soil by biodegradable chelator–induced washing: Efficiencies and mechanisms

Abstract

Biodegradable chelators (BCs) are promising substitutes for conventional washing agents in the remediation of heavy metal contaminated soil with strong complexing ability and less cost. However, great challenges for the applications of BC-assisted washing still exist, such as the assessment of the factor affecting the efficiency of metal removal and the unclear of the metal removal mechanism. Batch washing was therefore explored to evaluate the potential for four BCs for removing Cd, Pb, and Zn from polluted soils. The soil spectroscopic characteristics before and after washing were also investigated. The results demonstrated that iminodisuccinic acid (ISA) and glutamate-N, N-diacetic acid (GLDA) were an appealing alternative to commonly used non-biodegradable ethylenediaminetetraacetic acid, but glucomonocarbonic acid (GCA) and polyaspartic acid (PASP) were less efficient. Optimal parameters of BCs were determined to be a concentration of 50 mmol L −1 , a pH of 5.0, a contact time of 120 min, and a solid/liquid ratio of 1:5, considering metal removal efficiencies and the suitable cost. A single removal washing could be up to 52.39% of Cd, 71.79% of Pb, and 34.13% of Zn from mine soil, and 98.28% of Cd, 91.10% of Pb, and 90.91% of Zn from polluted farmland soil. After washing, the intensity of heavy metal binding to soil colloids increased while the metal mobility reduced because of weakly bound fractions removed by BCs. The BCs-induced soil washing revealed that the possible mechanisms of metal removal included the acid dissolution, ion exchange, and surface complexation. Our findings highlight the potential application of especially ISA and GLDA as efficient washing agents to remove potentially toxic elements from contaminated soils.

Short-Term Soil Flushing with Tannic Acid and Its Effect on Metal Mobilization and Selected Properties of Calcareous Soil

“…Decreasing heavy metal concentrations is a crucial objective for remediation of soil for its future reuse. Much more attention should be paid to the environmental risks posed by the presence of mobile metal fractions [ 61 ]. The advantage of using TA is that it decreases metal mobility (MF), defined as the ratio of the metal concentration in the F1 fraction to the sum of the metal concentrations in the F1, F2, F3, and F4 fractions [ 20 ].…”

Remediation of Metal/Metalloid-Polluted Soils: A Short Review

“…Feng et al [83] used ethylenediamine tetra (methylene phosphonic acid) (EDTMP) and polyacrylic acid (PAA) for soil washing, and tried to optimize operative conditions and reduce ecological risks and toxicity. The same was done by Wang et al [84] who studied four types of acids that are less toxic and more biodegradable than EDTA, namely iminodisuccinic acid (ISA), glutamate-N,N-diacetic acid (GLDA), glucomonocarbonic acid (GCA) and polyaspartic acid (PASP). They demonstrated that these acids are more biodegradable but less effective than EDTA.…”

Optimization of Carboniferous Egyptian Kaolin Treatment for Pharmaceutical Applications

“…In the treatment of contaminated media, the S/L ratio is an important parameter that affects both the overall removal and the extraction of contaminants, as well as the amount of residual wash water [33,53]. Optimization using different S/L ratios was investigated to ensure this treatment's suitability for various contaminated kaolin deposits.…”