Chelating packed bed adsorption column for selective trace metal recovery from seawater and brine

In this study, we developed a chelating polymer, polythiosemicarbazide (PTSC), which was processed into a powder form to enhance surface area and subsequently packed into a column for adsorption experiments targeting various transition metals such as Ni, Zn, Cu, Ag, Mo, V, and Co. A series of controlled experiments were conducted to evaluate the effects of concentration, flow rate, and pH on the polymer's adsorption performance. The study progressed from synthetic solutions to simulated seawater, actual seawater, and finally seawater brine, after pretreating the seawater via reverse osmosis (RO). Characterization of the polymer was performed using NMR and FTIR to confirm the functional groups, while BET analysis determined the surface area. Breakthrough curves were generated to study the adsorption dynamics. The results demonstrated that the PTSC polymer achieved over 98 % recovery of silver at low concentrations (1 ppm) and 20 % recovery of copper under low pH conditions. Zinc recovery improved from 0 % at low pH to 68 % at alkaline pH, and copper recovery reached 99 % at a low concentration (0.1 ppm) and alkaline pH, compared to 20 % recovery at low pH (1 ppm, 5 ml/min). Zinc recovery also reached 98.7 % under alkaline conditions at a flow rate of 2 ml/min. Seawater adsorption experiments yielded 0.0012 mg of silver collected per liter processed, while seawater brine resulted in the recovery of 0.003 mg of silver per liter. Additionally, the adsorption column was effectively regenerated using 0.1 M thiourea, allowing for the reuse and recycling of the column, which is crucial for large-scale applications. These findings highlight the potential of the PTSC polymer for effective trace metal recovery and demonstrate its value in brine management, offering a sustainable approach to extract valuable metals while addressing environmental challenges associated with brine disposal.