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Abstract:Reverse osmosis (RO) concentrate from wastewater reuse facilities contains concentrated emerging pollutants, such as pharmaceuticals. In this research, a paper-like composite sheet consisting of titanium dioxide (TiO 2 ) and zeolite was synthesized, and removal of the antipruritic agent crotamiton from RO concentrate was studied using the TiO 2 /zeolite composite sheet. The RO concentrate was obtained from a pilot-scale municipal secondary effluent reclamation plant. Effective immobilization of the two powders in the sheet made it easy to handle and to separate the photocatalyst and adsorbent from purified water. The TiO 2 /zeolite composite sheet showed excellent performance for crotamiton adsorption without obvious inhibition by other components in the RO concentrate. With ultraviolet irradiation, crotamiton was simultaneously removed through adsorption and photocatalysis. The photocatalytic decomposition of crotamiton in the RO concentrate was significantly inhibited by the water matrix at high initial crotamiton concentrations, whereas rapid decomposition was achieved at low initial crotamiton concentrations. The major degradation intermediates were also adsorbed by the composite sheet. This result provides a promising method of mitigating secondary pollution caused by the harmful intermediates produced during advanced oxidation processes. The cyclic use of the HSZ-385/P25 composite sheet indicated the feasibility of continuously removing crotamiton from RO concentrate.

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A novel rotating advanced oxidation contactor (RAOC) equipped with a composite titanium dioxide–zeolite sheet was used to remove the antipruritic agent crotamiton from reverse osmosis concentrate with coagulation as a pretreatment. Coagulation was more efficient at pH 5 in terms of reducing total organic carbon and light absorbance, and the efficiency of coagulation improved with an increase in polymeric aluminum dosage from 0 to 6 mmol/L Al3+. The RAOC performed well in adsorbing crotamiton without obvious inhibition by other components in the reverse osmosis concentrate, and a majority of the crotamiton was removed after 6 h, resulting in the purification of the treated solution. With ultraviolet irradiation, crotamiton was simultaneously removed through adsorption and photocatalysis by the RAOC. The behavior of the main degradation intermediates of crotamiton during treatment showed that the degradation intermediates were also captured by the composite sheet. Coagulation followed by treatment with the RAOC was effective in the removal of organic matter in the RO concentrate and in the photocatalytic degradation of crotamiton.

Crotamiton, a scabicide and antipruritic agent persistent during biological treatment processes, is frequently detected in secondary effluent. In this study, titanium dioxide (TiO) and high-silica zeolite (HSZ-385) composites were synthesized and applied for the treatment of crotamiton in secondary effluent. Crotamiton was rapidly adsorbed by HSZ-385, and the adsorption performance of crotamiton in the secondary effluent was quite close to that in the test using ultrapure water. Even though the TiO-zeolite composites showed lower adsorption rates than that of HSZ-385, similar crotamiton adsorption capacities were revealed using both test materials. The photocatalytic decomposition of crotamiton was significantly inhibited by the water matrix at low initial concentrations. The TiO-zeolite composites rapidly adsorbed crotamiton from secondary effluent, and then the crotamiton was gradually decomposed under ultraviolet irradiation. Importantly, when using TiO-zeolite composites, coexisting material in the secondary effluent did not markedly inhibit crotamiton removal at low initial crotamiton concentration. The behaviors of the main intermediates during treatment demonstrated that the main degradation intermediates of crotamiton were also captured by the composites.