Removal of cobalt ions (II) from simulated radioactive effluent by electrosorption on potassium hydroxide modified activated carbon fiber felt

In this study, the electrosorption property of potassium hydroxide modified activated carbon fiber felt (ACFF-KOH) to Co2+ in simulated radioactive effluent was evaluated. Factors influencing the electrosorption such as applied voltage, initial concentration, pH, cyclic flow rate, competitive ions and cycle numbers on Co2+ removal rate were investigated. Kinetic models and isotherm models were used to evaluate the electrosorption performance of ACFF-KOH. The results showed that the voltage enhanced the removal capacity of Co2+, which raised from 5.92 to 14.80 mg·g−1 when the applied voltage increased from 0 to 1.6 V. Higher initial concentration of the solution induced larger electrosorption capacity. In addition, the optimal adsorption pH of the electrosorption was around 5. When competing ions exist, the removal rate of Co2+ decreased. Furthermore, ACFF-KOH had excellent cycling performance, and the removal rate remained above 85 % after 6 cycles. The pseudo-first-order (PFO) model fitted the data better than the pseudo-second-order (PSO) model, indicating that physisorption was the rate-limiting step during the eletrosorption process. As the Langmuir isotherm had a higher regression coefficient (0.9983) than the Freundlich isotherm, monolayer adsorption was the main adsorption mechanism for Co2+ on the ACFF-KOH electrode. The BET results showed that KOH modification improved the pore parameters of ACFF. According to the XPS and XRD results, Co(OH)2 precipitates were generated on the electrode surface after electrosorption. The above results indicated that ACFF-KOH had excellent electrosorption and regeneration performance for Co2+ in aqueous solution, thus it has great application value in the treatment of cobalt-containing radioactive effluent.