Soil Remediation Using Modified Diatomite: Assessing Chemical Properties, Enzymatic Reactions and Heavy Metal Immobilization

This study investigated the efficacy of chemically modified diatomite as a novel agent in soil remediation, focusing on its impact on chemical properties, enzymatic activities, and heavy metal removal. Natural diatomite was modified by grinding and acid treatment to increase surface area and to decrease the impurities. Surface area and pore volume of the modified diatomite were 67.45 m² g⁻¹ and 0.105 cm³ g⁻¹ respectively, and used to immobilize Pb, Zn and Cu in an urban soil. The modified diatomite was added to soil samples at the rates of 2.5, 5, 7.5 and 10% and the samples incubated for 60 days. The addition of modified diatomite increased SSA of the soil. The SSAs of soils with 2.5, 5.0, 7.5 and 10% modified diatomite were 20.82, 22.02, 23.21 and 24.41 m² g⁻¹ respectively. Increasing the SSAs of the soils by the application of modified diatomite reduced the DTPA extractable concentrations of heavy metals compared with un-amendment control. The concentration of Pb, Zn and Cu were reduced by 91.1%, 82% and 91.1% respectively. Modified diatomite reduced the concentration of Exchangeable (EXCH) and Carbonate bounded species (CAR) of Pb, Zn and Cu, compared with the control. Also significantly increased the concentration of Fe–Mn Oxides (OX) and Organic Matter (OM) bound and Residual fraction (Res). Modified diatomite increased the urease, dehydrogenase, and alkaline phosphatase activity by 52%, 57% and 56.6% respectively. The results demonstrated that modified diatomite significantly improved soil chemical properties and enhanced enzymatic activities, indicating a positive impact on soil health. Furthermore, a substantial reduction in the bioavailability of heavy metals was observed, highlighting the material's potential in immobilizing heavy metals and mitigating environmental risks.