New Insight toward Synergetic Effect for Platinum Recovery Coupling with Fe(III)-Oxalate Complexes Degradation through Photocatalysis

Platinum (Pt) is a nonrenewable mineral with limited reserves and a patchy distribution. Pt demand and consumption are growing year after year. As a result, recovering Pt from the secondary resources is critical. A new strategy for effective Pt recovery employing Fe(III)-oxalate complexes under UV and visible light irradiation is proposed in this paper. This approach can recover 98.9% of Pt in 30 min under the conditions of 365 nm UV irradiation, leaching time = 30 min, C2O42– concentration = 333.33 g/L, and H2O2 addition = 0.60 vol %. More importantly, 95.6% of Pt can also be recovered in 8 h under sunlight. The homogeneous photocatalytic reaction is rapid and efficient, and meanwhile, no strong acid, base, or volatile toxic organic solvent is required. Additionally, the iron utilized in the process may be well-recycled, solving the problem of recovery difficulty of homogeneous photocatalysts and lowering the cost of leaching. Simultaneously, the Pt complex recovered from the waste catalyst is utilized in situ to manufacture 0.1 wt % Pt/ZSM-5 catalyst, which shows the complete conversion of toluene at 200 °C and can remain stable during the long duration reaction of 1200 min. Overall, it can not only provide a new environmentally friendly technique to recycle Pt from spent catalysts but also save manufacturing cost of new catalysts.