Abstract
Due to the inherent nature of saline-sodic soils, rapid decomposition of the processing fluids during electrokinetic remediation (EKR) renders the process unstable. This study investigated the influence of voltage gradient, polarity reversal, initial concentration of heavy metals on the frequency of replenishing processing fluids via refilling or replacing during hybrid electrokinetics-adsorption (HEKA) remediation of contaminated saline-sodic clay soil. Fifteen (15) EKR experiments were conducted according to Box–Behnken design. Each experiment was continuously ran for 21 days. As result of predominant electroosmosis flow toward the cathode, replenishing the anolyte was primarily by refilling rather than replacement following its complete degradation, while vice versa was in case of the catholyte. For the optimization and interpretation of results, mathematical models (
R
2
of 81.67–96.84 %) were developed based on response surface methodology with and insignificant lack of fit. Voltage gradient was found to be the most influential parameter for rapid degradation of the processing fluids with resulting increase in the frequency of replenishing and higher current flow and electrical conductivity. Numerical optimization in conjunction with desirability function analysis were employed for the optimization of five (5) different scenarios from which the most desirable scenario yielded a desirability value of 0.61 at an optimal voltage gradient of 0.34 V/cm. Under this condition, the rate of replacement of the anolyte is approximately 2 as against the maximum rate of 32 that was encountered during the tests. This study demonstrates that an optimal voltage gradient that will ensure stability must be chosen to ensure HEKA remediation of saline-sodic soil effectiveness.