Simulation and optimization of the selenium recovery process using the continuous counter-current decantation ion exchange system

A simulation and optimization process based on the electrical network model is presented to recover selenium from solutions using S 108 resins in a continuous counter-current decantation ion exchange system (CCDS). The system's performance is affected by multiple parameters, including the selenium concentration, inlet flow rate, cycle operating time, desorption solution flow rate, resin mass transferred per cycle, diffluent ratio, and so forth. In a simulation process, normally, 20 to 25 cycles are required for the electrical analogue model to reach the cyclic steady state. The average error between the experimental and modeled outlet selenium concentrations was 1.89%. After optimization, the S 108 resin initially adsorbed 856.19 mg/L Se(VI) and 855.33 mg/L Se(IV), which resulted in selenium concentrations of 27.4 and 21.6 g/L. In addition, recovery rates were 91.45 and 88.06% following the 164 mL/min Se(VI) and 128 mL/min Se(IV) solution treatments, respectively.

► The ion exchange process is presented in series circuit and consists of film diffusion, particle diffusion and chemical reaction.
► The electrical analogue model was used for calculations in the continuous counter-current decantation ion exchange system.
► The use of the CCDS to recover selenium can improve the resin usage rate and increase the product concentration.
► The U-shaped desorption column can increase the concentration through diffluence and second adsorption.