Soil washing has been increasingly viewed as an appropriate remediation technology for diesel and heavy metal contaminated soils. A 2k-1 fractional factorial design was successfully applied for factor screening analysis of temperature, washing time, pH, flow rate and concentration of surfactants on the response of diesel and heavy metal removal efficiency. Results indicated concentration of surfactant, pH and flow rate as significant factors. This was then subjected for response surface methodology (RSM) based on a central composite design for further analysis on its effects and optimum conditions. Both 2k-1 fractional factorial design and central composite design showed a good fit of data which validates the appropriateness of the experimental design. Optimum conditions based on the statistic function showed 5.02 %v/v surfactant, pH 12.04 and 4.64 mL/min flow rate resulted to diesel removal efficiency of 61.42%. The interaction between the concentration of surfactants and pH or flow rate were significant while the interaction of pH and flow rate were not significant. For heavy metals removal efficiency, the effects of concentration of surfactant are positive and flow rate is negative. As the concentration of surfactants was increased from 0 to 4%v/v, zinc removal efficiency increased from 3% to 10.5% while copper removal efficiency slightly increased. The effecting of pH on the removal of copper is very high at pH 3 while removal of zinc is very high at pH 6. The results obtained from this study can be applied for the field work in the future.Keyword: Soil washing, Ethylene glycol monobutyl ether (EGBE), Diesel, Central composite design, Response surface methodology
