Dynamic separation of a selection of heavy metals using a dithizone-impregnated polymer resin

Abstract

This investigation focuses on optimising and separating metal ions using a dynamic (column) solid-phase extraction method. In this study, a polymer resin, Amberchrom CG-300, was successfully impregnated with dithizone. The investigation primarily focused on cadmium and nickel metal ions. Chelation was used as an adsorption method to optimise the separation of these metal ions. The study involved the selection and concentration of the eluent, flow rate, and column height of the resin to determine the optimal conditions for separating a copper nickel solution. The recovery of these metal ions was determined using inductively coupled plasma and atomic absorption spectroscopy. This research was inspired by a recommendation from Dr Andre Spies in his 2020 doctoral dissertation. All experimental work was carried out at a pH of 8. Hydrochloric acid was determined to be the most suitable eluent for both metal ion investigations, with a concentration of [HCl] = 0.1 M for cadmium and [HCl] = 0.4 M for nickel. This resulted in percentage recoveries of 41.82 % and 84.61 %, respectively. Flow rate experiments were conducted within the range of 4 – 7 mL/min. It was observed that a flow rate of 7 mL/min resulted in the highest recovery rate during the cadmium study, reaching 24.15 %. In the nickel investigation, a flow rate of 6 mL/min yielded a recovery rate of 73.88 %. In the investigation of column height, it was found that the range studied did not significantly affect the elution of cadmium ions. The highest recovery was achieved with 0.4 g of resin for both studies, resulting in an 18.18 % recovery of cadmium ions and 95.30 % for nickel ions. This study was done within 0.2 g – 0.5 g range. Copper and nickel metal ions in a binary solution were separated successfully at a pH of 8, resulting in a 94.40 % recovery of nickel ions and a mere 39.72 % recovery of copper ions. For this experiment 0.4 M hydrochloric acid was used as an eluent at a flow rate of 6 mL/min.