Dual-function hydrogel composite for post-electroplating cationic and anionic metal removal: A practicality study.

Abstract Metals produced as by-products of the electroplating process pose threats to both human and environmental health, so it is important that they are removed from electroplating effluents. In this study, a dual-function hydrogel composite, prepared from a pair of cationic and anionic hydrogel composites via a facile method, was tested in batch and in a fluidized-bed column to treat a simulated electroplating effluent. For the batch treatment, both adsorption and desorption reached equilibrium within 30 min, showing the dual-function composite's fast adsorption capacity. Additionally, the removal efficiency was found to be pH-independent, and insignificant effect was found in the co-presence of monovalent ions (up to 10 meq L−1). Reusability of the dual-function composite was tested for six cycles, where the treated effluent consistently met discharge standards, and the reused adsorbent was confirmed by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy to be highly stable. The fast settling by gravity of the dual-function composite in batch motivated further studies of the material in a fluidized-bed column. Process variables such as feed flow, airflow, and adsorbent's bed depth were optimized using response surface methodology (RSM). Using an optimal solution, the model predicted a treatable cationic volume of 1045 mL and an anionic volume of 1695 mL; their corresponding experimental values were 1028 and 1680 mL. Therefore, in terms of practicality (fast removal, pH-independence, high stability, and gravity-driven settling), the application of the dual-function composite in a fluidized-bed reactor has shown much promise for the simultaneous removal of post-electroplating cationic and anionic metals.