Uranium removal from Pyhäsalmi/Finland mine water by batch electrocoagulation and optimization with the response surface methodology

Electrocoagulation was used for uranium removal from Pyhäsalmi, Finland mine water. The effect of the electrode type, current density and reaction time was investigated and the removal efficiency, isotherms and kinetic data were calculated. Finally, the process was optimized with the response surface methodology (RSM) and statistically significant factors, which have an effect on the removal efficiency identified. Isotherm studies illustrated that iron–stainless steel and aluminum–stainless steel anode/cathode combinations are obeying Langmuir and Temkin isotherms, respectively. Kinetic studies showed that the iron–stainless steel and aluminum–stainless steel anode/cathode combinations are obeying first order kinetics. The interactions between current density and reaction time on the uranium removal were statistically significant for both, the aluminum–stainless steel and iron–stainless steel anode/cathode combinations. Current density was shown to be a significant parameter for iron–stainless steel and aluminum–stainless steel anode/cathode combinations. However, the reaction time was only a significant parameter in the quadratic model for the aluminum–stainless steel combination. From the analysis of variances (ANOVA), quadratic models have been employed for uranium removal, showing high coefficients of determination (R²) of 0.890 and 0.903 for iron–stainless steel and aluminum–stainless steel anode/cathode combinations, respectively. The optimum conditions for current density and reaction time are 70 mA/cm² and 120 min, respectively, where 99.7% and 97.7% of uranium removal by iron–stainless steel and aluminum–stainless steel anode/cathode combinations could be obtained.