Abstract
Heavy metal wastes generated from mining activities are a major concern in developing countries such as Iran. Increasing concentrations of these metals in the soil make up a severe health hazard due to their non-degradability and toxicity. In this study, batch washing experiments were conducted in order to investigate the removal efficiency of zinc by biodegradable chelates, tartaric acid. For this purpose, soil samples were collected from the zinc contaminated soil in the region of the Angouran, Zanjan, Iran. Hence, optimization of batch washing conditions followed using a three-level central composite design approach based on the response surface methodology. The results demonstrated that the effects of pH, tartaric acid concentration, and interaction between selective factors on the zinc removal efficiency were all positive and significant (P < 0.05). An optimum zinc removal efficiency of 89.35 ±2.12% was achieved at tartaric acid concentration of 200 mM l−1, pH of 4.46, and incubation time of 120 min as the optimal conditions. Accordingly, response surface methodology is appropriately capable to determine and optimize chemical soil washing process to remediate heavy metal polluted soil.
Highlights
Toxic heavy metal contamination of soil is a major environmental problem throughout the world because of their long residual time, strong concealment, toxicity, and other characteristics (Wei et al, 2019)
The removal of Zn becomes more by increasing the concentration of tartaric acid (TA) from 10 to 200 mM, and this range is chosen as the range of TA concentration for central composite design (CCD) design based on response surface methodology (RSM)
200 mM, the removal efficiency is constant and does not vary considerably. This can be expressed by the existence of other heavy metals in soil such as lead, cadmium, and arsenic, that they compete with Zn to wash with TA (Wang et al, 2015)
Summary
Toxic heavy metal contamination of soil is a major environmental problem throughout the world because of their long residual time, strong concealment, toxicity, and other characteristics (Wei et al, 2019). A variety of in situ and ex situ remediation techniques have been developed to contain, clean up, or restore heavy metal-contaminated soils, such as soil flushing, surface capping, solidification, electrokinetic extraction, phytoremediation, and vitrification. These techniques can be classified into five categories: physical, chemical, electrical, thermal, and biological remediation or three divisions: transformation-based (e.g. stabilization/ immobilization), containment-based (e.g. capping/encapsulation), and transport-based (e.g. extraction/removal) methods (Liu et al, 2018)
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