Recent studies have shown an increase in the presence of antibiotics such as tetracycline (TC) in wastewater treatment plants (WWTPs). However, complete removal of TC using conventional treatment technologies has been found inadequate, due to their high recalcitrant nature. Therefore, advance oxidation process (AOP), using newly developed different phases of copper sulphides nanocrystals, as a photocatalysts for the removal of TC is studied. Solvothermal decomposition of copper(II) dithiocarbamate complex in dodecanthiol (DDT) was used to prepare pure phase djurleite (Cu31S16) and roxbyite (Cu7S4), while oleylamine was employed in the synthesis of CuS (covellite) and Cu9S5 (digenite) phases. Reaction temperature was varied in order to control the crystalline type of the copper sulphide phases. The synthesized photocatalysts were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and absorption spectroscopy. The performance of these catalysts in the removal of TC were investigated under the visible light irradiation varying concentration and pH. Photo-degradation results revealed that the Cu7S4 (250 °C) exhibited the best activity in the reaction system, with the TC degradation rate of up to 99% within 120 min of light exposure, Cu9S5 (220 °C) was 98.5%, CuS(120 °C ) was 88 % while Cu31S16 (120 °C) system was only 46.5% under the same condition. Enhanced photocatalytic activity obtained with the use of Cu7S4 (250 °C) might be due to its high crystallinity and surface area. Pseudo first-order kinetics model described the experimental data satisfactory well with high correlations factor (R2) of 0.999 in all cases. However, application of this catalyst in the removal of other antibiotics will confirm its robustness.

Temperature and solvent controlled synthesis of copper sulphide nanophotocatalyst for the degradation of tetracycline

ACS Spring 2022

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