Photodegradation of steroid-hormone micropollutants in a flow-through membrane reactor coated with Pd(II)-porphyrin

Abstract The efficient degradation of steroid-hormone micropollutants is demonstrated in a single-pass, continuous operation of the photocatalytic membrane reactor (PMR) holding a visible-light excited Pd(II)-porphyrin-coated poly(vinylidene fluoride) microfiltration membrane. The PMR operated at a water flux of 600 L m-2 h-1 exhibited a residence time of 0.6.s and significant removal of 17s-estradiol and estrone at environmentally relevant (ng.L-1) concentrations, when treated either individually (R = 85 ± 5%) or as a mixture of estrone, 17s-estradiol, testosterone and progesterone. At alkaline pH, the photodegradation process was inhibited by the repulsion between the ionized 17s-estradiol molecules and the membrane surface. An increase of a water flux through the PMR decreased the removal, but favoured the rate of disappearance. The rate constant for reactions of singlet oxygen with 17s-estradiol (7·108.M-1.s-1) at ng.L-1 concentrations was close to the diffusion limit. This study provides the new insights into solar-driven photocatalytic water treatment technologies for effective removal of micropollutants.