An Investigation on the Lead Removal from Soil Contaminated by Mining and Industrial Wastes Using Soapnut in Batch Washing Process

Eco-friendly saponin from soapnut was studied for the remediation of the soils contaminated by lead. This study applied a full factorial design of the experiment with 3-factors in 3-level (3×3 factors) to evaluate the effect and interactions of the washing parameters on the lead removal by soapnut in a batch experiment. The parameters studied include: soil-solution ratio, surfactant concentrations by mass, and pH of the washing solution. Two soil samples representing low lead concentration (C1) and high lead concentration (C2) were investigated. The findings indicate that the removal efficiency obtained, increases along with the soil-solution ratio and surfactant concentration, but decreases with an increase in the pH of washing solution. Polynomial models were developed to predict the experimental response and optimal conditions. The model predicted a maximum of 50.54% and 47.44% lead removal from the contaminated soil C1 and C2, respectively. Multiple washing was investigated using the higher values of the parameters; the responses obtained significantly increased the percentage of lead removed and achieved 79.98% removal for C1 and 77.49% removal for C2. The effective performance of the soil washing process demonstrates the potential usage of soapnut saponin in the remediation of contaminated soil. Saponin from soapnut is cheap and environment-friendly.