Continuous recovery of tellurium and cadmium from simulated CdTe leachates using a fixed-bed-column adsorption system

Rare element resource (Te) loss and heavy metal (Cd) pollution, derived from waste photovoltaic CdTe cells, have attracted considerable attention in the cleaner production and environmental protection field. However, there are several technical barriers in conventional adsorption strategies for the continuous recovery Te(IV) and Cd(II) due to single-component recovery, inefficient adsorbent utilization and less automation. Herein, this work presented a fixed-bed-column adsorption system for the continuous adsorption recovery of tellurium and cadmium from a simulated CdTe leachate using functional sludge-based adsorption fillers (LDO/SF and EDTA@LDH/SF) that prepared from water-processing sludge via hydrothermal synthesis, thermal activation and surface modification technologies. Breakthrough curves were analyzed for adsorption columns, considering initial concentration, flow rate, and filler height, with parameters evaluated using the Thomas and BDST models to determine the optimal separation parameters. During the continuous adsorption process, the column adsorption system with the filler layer height of 4 cm and liquid delivery rate of 1 mL/min can be used for continuous separation of more than 1000 mL of a simulated CdTe leachate and exhibits adsorption efficiencies of more than 96% and 82% for Te(IV) and Cd(II), respectively. More importantly, the elution procedure was used to treat the column adsorption system with ion adsorption acceptances of 83% and 90% for Te(IV) and Cd(II), respectively. Meanwhile, the functional sludge-based fillers demonstrated great regeneration and recycling capabilities, thus maximizing the utilization of adsorbents and saving treatment costs. This study has established a robust technical solution for the continuous recovery of tellurium and cadmium from simulated leachates, providing a practical framework for evaluating the efficiency of adsorption filler columns in actual applications.