Highly efficient ZnO photocatalytic foam reactors for micropollutant degradation

The efficient removal of organic micropollutants, pharmaceuticals, pesticides, drugs, and others, remains an unsolved challenge in water treatment. Although photocatalysis has proven highly effective at degrading these substances, its large-scale implementation has been so far hampered by technical and economic concerns. This work describes the development and characterization of novel highly efficient, self-supporting photocatalytic ZnO foams for the degradation of organic micropollutants. A systematic investigation of flow rate, catalyst length and stability under both recirculating and single-pass conditions was conducted using carbamazepine as a UV-recalcitrant model pollutant. Under recirculation, 95 % degradation was achieved with photocatalyst quantum yield of 1.2 × 10−3 and electrical energy per order (EEO) as low as 24 kWh m−3, values outperforming current technology, slurry and immobilised systems. For single-pass tests, complete degradation was achieved in 30 min, with the quantum yield increasing to 6.3 × 10−3, and an EEO of 36 kWh m−3. These values also outperform those for slurries, immobilised and other foam photocatalyst reported in the literature under similar conditions. The low energy consumption of these newly developed photocatalytic foams, combined with their high quantum yield and stability, provides a realistic path towards practical implementation of photocatalytic processes in water treatment, addressing the limitations of existing slurry and immobilised photocatalytic technology.