Improvement of cadmium ion electrochemical removal from dilute aqueous solutions by application of multi-stage electrolysis

Improvement of cadmium ion electrochemical removal from dilute aqueous solutions in a spouted bed reactor was investigated. Enlargement of cathode surface area from 1,000 to 1,500 cm² resulted in a decrease of nearly 30 % in both of the process time and the specific energy consumption. Application of a three-stage electrolysis process for a solution containing initial concentration of 270 ppm cadmium ion, resulted in the removal of 99.9 % cadmium ion in 135 min with the specific energy consumption of 2.29 kWh/kg, 23 % less than the value of a single-stage process. For a solution with cadmium ion initial concentration of 180 ppm, 99.9 % of cadmium ion was removed in 135.5 min by application of a two-stage electrolysis process, while the specific energy consumption was 2.82 kWh/kg, 30 % less than that of a single-stage process. For a solution with cadmium ion initial concentration of 90 ppm, 99.5 % of cadmium ion was removed in 100.2 min with the specific energy consumption of 3.78 kWh/kg in a single-stage electrolysis process.