Acid rock drainage treatment by clinoptilolite with slurry bubble column: Sustainable zinc removal with regeneration of clinoptilolite

Clinoptilolite is shown to be capable of removing zinc from ARD, while the zinc in loaded clinoptilolite is displaced by NaCl as regenerant. Repeated capture–regeneration cycles were tested, showing the evolution of uptake capacity over multiple cycles. Fresh and reused NaCl as regenerant were compared to explore a possible means of minimizing the waste volume. The results prove that uptake/removal cycles can be repeated several times while maintaining reasonable uptake and removal capacities. Three removal-only cycles after 10 full cycles continuously decreased the accumulated zinc in clinoptilolite, allowing the uptake capacity for further upcoming cycles to be recovered. When 10 full cycles were tested after the three removal stages, results were similar to those for the first 10 cycles. By reusing NaCl as regenerant, only one-quarter of the regenerant volume was required to achieve a similar total zinc uptake from ARD compared with fresh NaCl.