Photo-Fenton process applied for the treatment of industrial wastewaters containing diclofenac: optimization with low iron ions concentrations and without pH control.

Diclofenac (DCF) can cause several adverse effects in the environment and it should be removed from industrial pharmaceutical wastewaters. Advanced oxidation processes (AOPs) are promising methods for the DCF degradation. But, in many cases, AOPs require acidic pH. However, at this condition, DCF precipitates, which may hinder its oxidation. Thus, in this work, some AOP were studied for the DCF degradation, especially the photo-Fenton process, applying the experimental design technique (Doehlert matrix), operating without and with pH control (between 6.5 and 7.0). As independent variables, the initial ferrous ion concentration ([Fe2+]) and the molar addition rate of H2O2 (FH2O2) were evaluated. Empirical models were proposed and optimized conditions were determined without ([Fe2+] = 0.27 mmol L-1 and FH2O2 = 1.64 mmol min-1) and with pH control ([Fe2+] = 1.0 mmol L-1 and FH2O2 = 1.64 mmol L-1), with the following predicted mineralization percentages: 93% and 68%, respectively. So, photo-Fenton process without pH control presented the best performances. Furthermore, at this condition, iron concentration respects the limit value established by the Brazilian environmental legislation. That is, in this condition, additional processes, in order to remove iron ions, would not be necessary, that is very interesting for applications on an industrial scale.

Degradation of amoxicillin applying photo-Fenton and acid hydrolysis processes with toxicity evaluation via antimicrobial susceptibility tests.

ABSTARCTThe antibiotic amoxicillin (AMX) is a semisynthetic aminopenicillin, classified as an ß-lactam antibiotic. This work aims to evaluate the AMX degradation (190 mg L-1), in aqueous medium, applying photo-Fenton ([TOC]0 = 100 mgC L-1; FH2O2 = 3.27 mmol min-1; [Fe2+] = 0.27 mmol L-1; pH = 3.0; T = 40°C) and acid hydrolysis processes. Along the experiments, samples were withdrawn and analyzed by a total organic carbon (TOC) analyzer and a liquid chromatography system coupled to diode array (HPLC-DAD) and mass spectrometry (HPLC-MS) detectors. The hydrolysis process proved to be less efficient, because AMX removals greater than 80% were observed only after 24 hours of reaction (pH 2). Conversely, the photo-Fenton process removed completely AMX in just 20 minutes, reaching 85% of TOC removal in 2 hours. Finally, the AMX aqueous solutions treated by the studied processes was also evaluated in respect of its toxicity to some microorganisms, applying two antimicrobial susceptibility tests: disk-diffusion and broth microdilution methods. It was observed that the AMX aqueous solutions, pretreated by the photo-Fenton process, for just 7.5 min of reaction time, did not inhibit the microorganisms growth. The obtained results show that the photo-Fenton process was able to degrade AMX, in a relatively short time, and that the generated degradation products did not inhibit the microorganisms growth, when compared to acid hydrolysis process. Thus, it was verified the potential application of the photo-Fenton system as a pretreatment step to conventional biological oxidation processes for the treatment of industrial wastewaters.