Abstract
The influence of pH on the degradation of the pharmaceutical diclofenac (DCF) by the solar/photo-Fenton process was investigated using ammonium iron(III) citrate complex (FecitNH4). Although the degradation efficiency decreased as the pH increased (in the pH range 5 to 8), the DCF concentration was lower than its limit of detection after 45 min irradiation while 77% of the total organic carbon was removed after 150 min irradiation at initial pH 7 (without further adjustment). A pseudo-first-order kinetics of DCF degradation was observed, which kinetic constant increased with the increase of the concentrations of FecitNH4 and H2O2. Lower DCF degradation was observed when present in a sewage treatment plant (STP) effluent sample, mainly due to the high concentration of carbonate and bicarbonate at pH 7. However, after adjusting the pH to 5, the DCF concentration was lower than its detection limit after 75 min irradiation.
Highlights
The human consumption of pharmaceuticals as well as veterinary practices and industrial activities including aquaculture has lead to contamination of surface and groundwater
Taking into consideration the maximum concentration of iron allowed in wastewater according to Brazilian legislation (15 mg L-1 or 0.27 mmol L-1), the experiments were performed at three different initial concentrations of ammonium iron (III) citrate (FecitNH4) (0.05, 0.1 and 0.2 mmol L-1), which are below this limit
The use of in situ generated ferric citrate complex was previously reported by Silva et al.[27] for the degradation of the herbicide tebuthiuron, where the degradation efficiency of the iron citrate complex decreased as the pH increased, tebuthiuron oxidation at pH 6 was higher than that observed in the presence of Fe(NO3)[3] at pH 2.5
Summary
The human consumption of pharmaceuticals as well as veterinary practices and industrial activities including aquaculture has lead to contamination of surface and groundwater.
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