Metal Recovery and Catalyst Reuse from the Photocatalytic Oxidation of Copper-Ethylenediaminetetraacetic Acid

Photocatalytic oxidation (PCO) is an advanced oxidation process that has recently been shown to be effective in the treatment of recalcitrant metal complexes, such as Cu(II)-ethylenediaminetetraacetic acid (EDTA). The PCO of Cu(II)-EDTA was studied to determine copper recovery and the reusability of the titanium dioxide $\left({\mathrm{TiO}}_2\right)$ photocatalyst. Aqueous solutions of Cu(II)-EDTA $\left({10}^{-4} M\right)$ were treated using illuminated ${\mathrm{TiO}}_2\text{.}$ After PCO treatment, ${\mathrm{TiO}}_2$ was filtered and extracted with $H_2{\mathrm{SO}}_4$ (0.1, 0.5, 1 N) to remove adsorbed copper. The recovered ${\mathrm{TiO}}_2$ catalyst was then reused in subsequent experiments. The recovered copper was concentrated in the extraction solution by a factor of 14.7 over that of the initial copper concentration. An additional experiment was performed using the same ${\mathrm{TiO}}_2$ without copper removal for eight consecutive PCO treatments. In both experiments, the initial rate of photocatalysis did not change significantly with reuse and was similar to that obtained from virgin ${\mathrm{TiO}}_2$ (5.6 μM/min). It is suggested that Cu(II)-EDTA could be effectively treated using an integrated cyclic procedure of PCO, catalyst recovery, and acid extraction for Cu recovery.