Modification of ZnIn2S4 by anthraquinone-2-sulfonate doped polypyrrole as acceptor-donor system for enhanced photocatalytic degradation of tetracycline

Visible-light photocatalytic degradation of tetracycline was investigated by functional modified ZnIn2S4 via anthraquinone-2-sulfonate (AQS) doped polypyrrole (PPy). The best photocatalytic activity of AQS/ PPy-ZnIn2S4 composite photocatalyst was obtained when the weight ratio of AQS/PPy versus ZnIn2S4 was 1.0% and the molar ratio of PPy to AQS was 40. After 3.0 h photocatalytic reaction, more than 98% tetracycline was removed and almost 2.0 times higher of NPOC (non-purgeable organic carbon) removal rate was obtained compared with pure ZnIn2S4. Active species trapping experiments demonstrated that O-center dot(2)- played a major role rather than the (OH)-O-center dot and photogenerated holes. The AQS doped in PPy matrix behaved as electron acceptor-donor mediator which facilitated the formation of O-center dot(2)-. Two kinds of solid phase extraction (SPE) methods were developed before gas chromatography mass spectroscopy (GC-MS) analysis and eight intermediates were detected. The degradation of tetracycline originated from the photogenerated holes via loss of some functional groups and then aromatic ring was destroyed by the oxidation of active species O-center dot(2)- and (OH)-O-center dot via hydroxylation reaction. (C) 2017 Elsevier BY. All rights reserved.