ABSTRACT
This study on tannery wastewater treatment showed that indirect electrooxidation by chlorine generated at a Ti/SnO2/PdO2/RuO2 (SPR) anode led to full ammonia removal, and a decrease in chemical oxygen demand (COD) of up to 77.0%. A combined process of coagulation + H2O2/UV + electrooxidation allowed us to achieve a decrease in COD of up to 97.5%. Equations describing the kinetics of the decrease in COD, the relationship between the decrease in COD and current, and the relationship between the current efficiency of COD reduction and the initial concentrations of the reagents were established. The changes in the Adsorbable Organically Bound Halogen (AOX) value were determined, and the individual compounds, including chloroorganics, present in raw and treated wastewater were identified by gas chromatography mass spectrometry (GC-MS). Values of AOX increased in the initial phase of electrooxidation, while afterwards they decreased.
Subject(s)
Electrochemical Techniques/methods , Tanning , Wastewater/analysis , Water Pollutants, Chemical/analysis , Water Purification/methods , Ammonia/chemistry , Biological Oxygen Demand Analysis , Chlorine/chemistry , Electrodes , Flocculation , Gas Chromatography-Mass Spectrometry , Hydrogen Peroxide/chemistry , Kinetics , Oxidation-Reduction , Ultraviolet Rays , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/radiation effectsABSTRACT
Advanced Oxidation Processes (AOPs), such as the Fenton, photo-Fenton and H2O2/UV processes, have been investigated for the treatment of cosmetic wastewaters that were previously coagulated by FeCl3. The Photo-Fenton process at pH 3.0 with 1000/100 mg L(-1) H2O2/Fe(2+) was the most effective (74.0% Chemical Oxygen Demand (COD) removal). The Fenton process with 1200/500 mg L(-1) H2O2/Fe(2+) achieved a COD removal of 72.0%, and the H2O2/UV process achieved a COD removal of 47.0%. Spreading the H2O2 doses over time to obtain optimal conditions did not improve COD removal. The kinetics of the Fenton and photo-Fenton processes may be described by the following equation: d[COD]/dt = -a[COD] t(m) (t represents time and a and m are constants). The rate of COD removal by the H2O2/UV process may be described by a second-order reaction equation. Head Space, Solid-Phase MicroExtraction, Gas Chromatography and Mass Spectrometry (HS-SPME-GC-MS) were used to identify 48 substances in precoagulated wastewater. Among these substances, 26 were fragrances. Under optimal AOP conditions, over 99% of the identified substances were removed in 120 min.
