Fenton Oxidation Treatment Research Articles

Fenton's oxidative treatment of municipal landfill leachate as an alternative to biological process

The aim of our work was to compare Fenton's oxidation with existing biological SBR (sequencing batch reactor) reactor employed for treatment of the leachate, generated in local municipal landfill (35,000 inhabitants). Efficiencies of both procedures were monitored by chemical analyses and by acute toxicity studies with Vibrio fischeri and measurement of inhibition of oxygen consumption by activated sludge. Leachate was very toxic to V. fischeri and activated sludge and toxicity was not significantly reduced as well as effluent limits were not met during treatment in existing biological treatment plant. Fenton's oxidation, accomplished at different molar ratios of reagents (M(Fe2+)/M(H2O2) was 1/1; 1/3.3; 1/6.6 and 1/13.3) and various temperatures (20–45°C), assured good removal of organic compounds (80% as COD) as well as other pollutants and slightly reduced toxicity, but effluent limits were not always met. Furthermore, additional oxidation experiments with biologically treated leachate confirmed, that Fenton's oxidation is not appropriate for polishing already treated leachate in SBR, because it degraded persistent organics into more biodegradable, still toxic ones, which could affect oxygen regime in a receiving stream. Fenton's process could not replace SBR treatment plant, but it could be a viable option for pretreatment of landfill leachate.

Fenton oxidation treatment of tannery wastewater and tanning agents: synthetic tannin and nonylphenol ethoxylate based degreasing agent

In the present experimental work, the degradation and detoxification of two commercially important products being widely used in the tannery industry as synthetic tannin (ST) and degreasing agent (EP) containing 0.1% of nonylphenol ethoxylate (NPE) as well as degreasing wastewater from re-tanning was investigated using Fenton (FO) and Photo-Fenton (PFC) oxidation processes. FO and PFC oxidation experiments were performed in batch reactors for 30 min at pH 3 ± 0.2 and 40–45°C, considering the actual temperature and pH values of retanning bath effluents. For the FO experiments the effect of varying Fe2+ and H2O2 concentrations and UV-C light irradiation on oxidation measured by the parameters COD, UV254 and UV280 absorbancies was studied. Toxicity of untreated and FO, PFC-treated synthetic solutions to the freshwater cladoceran Daphnia magna was also tested. PFC provided appreciably high COD (>80%) and UV254 and UV280 (>90%) removals for ST. The toxicity could be drastically reduced in the PFC-treated ST sa...

Amoxicillin degradation at ppb levels by Fenton's oxidation using design of experiments

A central composite factorial design methodology was employed to optimise the amoxicillin degradation using the Fenton's oxidation treatment. In this study, the variables considered for the process optimisation were the hydrogen peroxide and ferrous ion initial concentrations and the temperature, for an antibiotic concentration of 450 μg L − 1 at pH = 3.5. This methodology also allowed assessing and identifying the effects of the different factors studied and their interactions in the process response. An appropriate quadratic model was developed in order to plot the response surface and contour curves, which was used to perform the process optimisation. From this study, it was concluded that ferrous ion concentration and temperature were the variables that most influenced the response. Under the optimal conditions (hydrogen peroxide concentration = 3.50–4.28 mg L − 1 , ferrous ion concentration = 254–350 μg L − 1 and temperature = 20–30 °C), it was possible to achieve total amoxicillin degradation after 30 min of reaction.

Optimization of a Photo‐assisted Fenton Oxidation Process: A Statistical Model for MDF Effluent Treatment

AbstractIn the present study, the effects of initial COD (chemical oxygen demand), initial pH, Fe2+/H2O2 molar ratio and UV contact time on COD removal from medium density fiberboard (MDF) wastewater using photo‐assisted Fenton oxidation treatment were investigated. In order to optimize the removal efficiency, batch operations were carried out. The influence of the aforementioned parameters on COD removal efficiency was studied using response surface methodology (RSM). The optimal conditions for maximum COD removal efficiency from MDF wastewater under experimental conditions were obtained at initial COD of 4000 mg/L, Fe2+/H2O2 molar ratio of 0.11, initial solution pH of 6.5 and UV contact time of 70 min. The obtained results for maximum COD removal efficiency of 96% revealed that photo‐assisted Fenton oxidation is very effective for treating MDF wastewater.

Pretreatment by Fenton Oxidation of an Amoxillin Wastewater

Relatively few reported works have dealt with wastewaters arising from amoxillin manufacture. To develop a treatment process for one such wastewater, several physicochemical methods such as coagulation, ultrafiltration, and Fenton oxidation (FO), have been investigated. Among these methods, FO proved effective. Consequently the method was further investigated to identify the appropriate H2 O2 ∕ FeSO4 ratio, FeSO4 and H2 O2 concentrations, and reaction pH and temperature. In relation to the wastewater, a suitable H2 O2 ∕ FeSO4 weight ratio was 5:1 (molar ratio: 22.4:1) with H2 O2 and FeSO4 concentrations at 20 g∕L , 4 g∕L , respectively. The corresponding pH range was 2.0–4.0 while the reaction temperature was 60°C . Given these conditions, wastewater total organic carbon was reduced by 48.8–49.4%. After FO treatment, reverse osmosis (RO) effectively reduced the dissolved salt content. The contribution of FO and RO pretreatment improved the wastewater’s biodegradability thus making a downstream biotreatmen...

Efficient photo-assisted Fenton oxidation treatment of multi-walled carbon nanotubes

In this paper, a new and efficient way to oxidize and functionalize the multi-walled carbon nanotubes (MWNTs) has been developed by using a combination of ultraviolet (UV) irradiation and Fenton oxidation process, namely UV/Fenton oxidation treatment. Comparing with conventionally individual Fenton oxidation treatment of MWNTs, UV/Fenton combined treatment improved the etching rates and efficiencies and hence reduced the time for surface modification of MWNTs, which was proved to be an effective method in etching and functionalizing CNTs. The formation of new functional groups, structural changes and thermal stability during oxidation period were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and could be clarified by thermogravimetric analysis (TGA), which showed that it was under UV irradiation conditions that MWNTs could be rapidly functionalized with hydroxyl, carbonyl and carboxyl groups in the presence of Fenton reagents, originating from the increase in the gross HO· concentration and the existent synergetic effect when using UV irradiation combing with Fenton oxidation process. Introduction of such new oxygen-containing functional groups was attributed to attacks of HO· on defect sites and unsaturated bonds of C=C in the MWNTs sample, which should play an important role in accounting for the FTIR and Raman spectral changes.

Application of Fenton oxidation to cosmetic wastewaters treatment

The removal of organic matter (TOC and COD) from a cosmetic wastewater by Fenton oxidation treatment has been evaluated. The operating conditions (temperature as well as ferrous ion and hydrogen peroxide dosage) have been optimized. Working at an initial pH equal to 3.0, a Fe 2+ concentration of 200 mg/L and a H 2O 2 concentration to COD initial weight ratio corresponding to the theoretical stoichiometric value (2.12), a TOC conversion higher than 45% at 25 °C and 60% at 50 °C was achieved. Application of the Fenton oxidation process allows to reach the COD regional limit for industrial wastewaters discharges to the municipal sewer system. A simple kinetic analysis based on TOC was carried out. A second-order equation describes well the overall kinetics of the process within a wide TOC conversion range covering up to the 80–90% of the maximum achievable conversion.

Effect of hydroxyl radical on the structure of multi-walled carbon nanotubes

In this research, we present the systematic investigation of the effect of hydroxyl radical (HO ) on the structure of multi-walled carbon nanotubes (MWNTs) via Fenton oxidation treatment in given conditions: molar ratio of hydrogen peroxide (H 2O 2) and ferrous ion (Fe 2+) is approximately equal to 10 and pH value is controlled at 3 ± 0.5. Fenton oxidation process was followed and characterized by using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The experimental results showed that the original graphene structure was disordered/destroyed by the newly generated oxygen-containing functional groups including OH, COOH and quinone groups, which were introduced while MWNTs was treated by Fenton reagents (Fe 2+–H 2O 2). Moreover, two attackable routes for possible mechanism of interactions between HO and MWNTs were assumed by spectral changes and properties of reactive species, which were described as follows: (l) a preferred attack on defect sites existing in the purified MWNTs sample (2) a synchronous or succedent attack on unsaturated bonds of C C on the sidewalls of MWNTs by electrophilic addition reaction. The possible mechanism indicated that introduction of those functional groups into the structure of MWNTs could be regarded as the results of attacks of HO with double properties of oxidizability and electrophilic addition on defect sites and unsaturated bonds of C C in the MWNTs sample, which were consistent with spectral changes in infrared spectroscopy and Raman spectroscopy.

Repeated Reductive and Oxidative Treatments of Granular Activated Carbon

Fenton oxidation and reductive treatment solutions were applied to granular activated carbon (GAC) to chemically regenerate the adsorbent. No adsorbate was present on the GAC so physicochemical effects from chemically aggressive regeneration could be distinguished from the potential effects of accumulation of reaction byproducts. Fifteen sequential oxidation treatments with hydrogen peroxide ( H2 O2 ) and fifteen sequential reduction/oxidation treatments with hydroxylamine and H2 O2 on Fe-amended GAC were evaluated. The GAC Iodine number, N2 Brunauer–Emmett–Teller surface area, microporosity, and total porosity declined with sequential treatments, but meso- and macroporosity essentially remained unchanged. Similar changes in Iodine number, surface area, and pore volume distribution suggest that the effects of treatment are functionally dependent on oxidation and independent of hydroxylamine reduction. An inverse relationship was established between the number of chemical treatments and contaminant (methyl...

Removal of mutagen precursor from wastewater by activated sludge and oxidation treatment

Removal of mutagen precursors from wastewaters was investigated. Removal extent of mutagen precursor was evaluated by the mutagen formation potential (MFP) which is mutagenicity of pollutants capable of forming mutagens when chlorinated under the conditions of water purification processes. 77% of the MFP reduction extent for a wastewater from a university was achieved by activated sludge treatment. However, no significant reduction of the MFP was observed for wastewater from food industry, a landfill leachate and mold extract. The Fenton oxidation treatment and ozone treatment are able to remove mutagen precursors from the mold extract and the wastewater from a university, respectively. 90% of the MFP reduction extent was achieved for the mold extract by the Fenton treatment. 54% of the MFP reduction extent was achieved for a sewage by the ozone treatment. Using the oxidation treatments, biodegradability of mutagen precursors in the mold extract and sewage was improved. From the viewpoint of treatment cost, the oxidation treatments should be oriented to the improvement of biodegradability.

Ammonia recovery from high strength agro industry effluents

The aim of the study was to investigate ammonia recovery from high strength agro industry effluents involving significant amounts of ammonia, by applying magnesium ammonium phosphate (MAP) precipitation technology. Two types of industrial effluents have been tested in the study. The first plant was an opium alkaloid processing industry and the second one was a baker's yeast industry. High chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and unacceptable dark brown color characterized effluents from both industries. Effluents from the biologically treated opium alkaloid and baker's yeast industries were both applied at the stoichiometric ratio (Mg:NH4:PO4 = 1:1:1) and above the stoichiometric ratio (Mg:NH4:PO4 = 1.1:1:1.1) to MAP precipitation. NH4 removals of 61-80% were achieved at the pH of 9.2 at the stoichiometric ratio, whereas 83% NH4 removal was obtained at the pH of 9.2 above the stoichiometric ratio. Experimental studies performed on both anaerobically and/or aerobically treated baker's yeast and opium alkaloid industry effluents have clearly indicated that MAP precipitation was an appropriate treatment option for NH4 removal or struvite recovery from high ammonia content agro industry effluents. Additional ammonia recovery studies were conducted on ozonated and Fenton's oxidation applied effluents and these have also indicated that the amounts of struvite and the quality of MAP precipitate was increased significantly. In this framework, MAP sludge recovered from combined biological and Fenton's oxidation treatment effluents were considered as a more valuable slow release fertilizer for agricultural use.

Decomposition of aqueous tetrachloroethylene by Fenton oxidation treatment

Flask-scale experiments were performed to elucidate the reaction mechanism in which tetrachloroethylene (PCE) in water is decomposed by Fenton oxidation treatment. Concentrations of Cl−, total inorganic carbon, and PCE were measured during a 24-h reaction period in which there occurred a pseudo first-order reaction (k=0.17 h−1) and >95% dechlorination and mineralization. Results indicate that: (i) PCE decomposition due to Fenton oxidation is compensated throughout the experiment by increasing Cl− and CO2, and (ii) mineralization rates derived from the increase in CO2 are nearly the same as dechlorination rates due to the increase in Cl−. GC/MS and GC/ECD analyses of reaction intermediates confirmed the presence of trichloroacetic acid (TCAA) only. That is, organic compounds such as dichloroacetic acid (DCAA), monochloroacetic acid, acetic acid, and formic acid were not detected, having been decomposed by Fenton oxidation although no degradation of TCAA occurred and detected TCAA only explained 1% of decomposed PCE. These findings indicate that dechlorination and mineralization proceed almost simultaneously during PCE decomposition by Fenton oxidation treatment, and not via intermediates such as acetic acid and DCAA.