Evaluation de la Contribution des carbonates dans la rétention des polluants métalliques dans les sols

Abstract

Pollution by hexavalent chromium is a serious problem that can affect both human health and the environment. This study aims to evaluate the contribution of carbonates in chromium sorption in soils with varying carbonate concentrations in the carbonate-rich region of Djelfa. The retention study was based on three soils containing different concentrations of total limestone. It began with a physico-chemical analysis of the soils, followed by a sorption study where several sorption parameters were modified: contact time, pH, temperature, agitation speed, initial chromium concentration, and finally, a comparison of chromium retention on the three soils relative to their carbonate content. The results showed that sorption followed a pseudo-second-order kinetics with a high regression coefficient (R² between 0.9984 and 0.997). The activation energies were 12.85 and 16.44 kJ/mol, indicating that the sorption mechanism is physical in nature. The data were compatible with the Freundlich model, but not with the Langmuir and Jovanovic models, suggesting that adsorption occurs on heterogeneous surfaces. Adsorption was spontaneous (∆G0 < 0) (-7.4 / -9.49) and exothermic (∆H0 < 0) (-14.07 / 15.54), meaning it is favored at low temperatures. Our results indicate that using carbonates, such as ground limestone, can help stabilize heavy metals in contaminated soils, reducing their toxicity and improving soil fertility. This method is simple and cost-effective, supporting both agriculture and soil decontamination. It is essential to train farmers on its proper application. While larger-scale studies are needed, testing on polluted lands will help assess the effectiveness and costs of this approach