Solar photo-Fenton Process Research Articles

Tertiary treatment of pulp mill wastewater by solar photo-Fenton

This work reports on pulp mill wastewater (PMW) tertiary treatment by Fenton (Fe2+/H2O2) and solar photo-Fenton (Fe2+/H2O2/UV) processes in a pilot plant based on compound parabolic collectors (CPCs). Solar photo-Fenton reaction is much more efficient than the respective dark reaction under identical experimental conditions. It leads to DOC mineralisation, COD and total polyphenols (TP) removal higher than 90%. The solar photo-Fenton experiment with 5mgFeL−1 reaches 90% of DOC mineralisation with 31kJL−1 of UV energy and 50mM of H2O2. The initial non-biodegradability of PMW, as shown by respirometry assays and BOD5/COD ratio, can be changed after a solar photo-Fenton treatment. Experiments with 20 and 50mgFeL−1 revealed that solar photo-Fenton can reach the same DOC degradation (90%), however, consuming less H2O2 and time. Diluting the initial organic load to 50% also diminishes the dosage of H2O2 and the necessary reaction time to achieve high DOC removals. Accordingly, solar photo-Fenton can be considered an alternative or complementary process to improve the performance of a biologic treatment and, subsequently, achieve legal limits on discharge into natural waters.

Photocatalytic treatment of an industrial effluent using artificial and solar UV radiation: An operational cost study on a pilot plant scale

The aim of this work was to study the operation costs of treating a real effluent from an integrated gasification combined cycle (IGCC) power station located in Spain. The study compares different homogeneous photocatalytic processes on a pilot plant scale using different types of radiation (artificial UV or solar UV with a compound parabolic collector). The efficiency of the processes was evaluated by an analysis of the total organic carbon (TOC) removed. The following processes were considered in the study: (i) a photo-Fenton process at an artificial UV pilot plant (with the initial addition of H(2)O(2)), (ii) a modified photo-Fenton process with continuous addition of H(2)O(2) and O(2) to the system and (iii) a ferrioxalate-assisted solar photo-Fenton process at a compound parabolic collector (CPC) pilot plant. The efficiency of these processes in degrading pollutants has been studied previously, and the results obtained in each of those studies have been published elsewhere. The operational costs due to the consumption of electrical energy, reagents and catalysts were calculated from the optimal conditions of each process. The results showed that the solar photo-Fenton system was economically feasible, being able to achieve up to 75% mineralization with a total cost of 6 €/m(3), which can be reduced to 3.6 €/m(3) by subtracting the electrical costs because the IGCC plant is self-sufficient in terms of energy.

Treatment of Color Filter Wastewater by Fresnel Lens Enhanced Solar Photo-Fenton Process

Treatment of color filter wastewater using solar photo-Fenton process enhanced by high-concentrating Fresnel lens was investigated in this paper. Optimal reaction conditions based on response surface methodology (RSM) were established as under an initial pH of 5, a [H2O2]0/COD0ratio of 1~1.35 and a [H2O2]0/[Fe2+]0ratio of 15 for a reaction time of 60 min, which could reach a readily biodegradable level, that is, the biodegradability (BOD5/COD) of wastewater was more than 0.3. With the assistance of Fresnel lens, the solar photo-Fenton process increased the COD degradation rate and mineralization rate by a factor of 4.5 and 6.5, respectively. In addition, the microtoxicity (TU50) of wastewater was almost diminished after a 60 min of treatment, whereas the microtoxicity of treated wastewater without the assistance of Fresnel lens remained a TU50value of 1.166. This could be mainly due to the concentrating effect of Fresnel lens for solar energy, resulting in an increase of 2~3 times of solar light intensity and a raising heat irradiation in terms of 15~30 °C of wastewater temperature. These results revealed that solar energy could be concentrated effectively by using Fresnel lens and showed a significant promoting effect on the photo-Fenton reaction for treating color filter wastewater.

Application of Fenton and Solar Photo-Fenton Processes to the Treatment of a Sanitary Landfill Leachate in a Pilot Plant with CPCs

AbstractThis paper reports on landfill leachate treatment by Fenton (Fe

Significant decrease of THMs generated during chlorination of river water by previous photo-Fenton treatment at near neutral pH

► THMs generation decrease by reducing NOM concentration prior to the chlorination step. ► Photo-Fenton process at neutral pH is effective system for the NOM degradation. ► Solar photo-Fenton process can be used to obtain at low cost drinking water safe. An important issue in chlorine drinking water disinfection is the generation from natural organic matter (NOM) of disinfection by-products (DBPs), especially trihalomethanes (THMs). The THMs generation can be limited by reducing the levels of NOM prior to the chlorination step. Herein, photo-Fenton system under solar simulator degraded humic acid solutions (as NOM model compounds), as well as NOM contained in river water (Pance River, Cali-Colombia), and dramatically reduced THMs formation during the subsequent chlorination step. In both cases the initial pH of treated water was near to 7. In no pre-treated river water 100–160 μg/L of THMs are formed during chlorination while values of 20–60 μg/L were reached in water previously treated for 4 h by neutral photo-Fenton under solar simulator. The decrease in the generated THMs/total organic carbon ratio suggests that mainly the NOM fraction sensitive to THMs formation was photo-degraded. Therefore, the neutral photo-Fenton reagent could be implemented as a technological option for NOM removal for limiting THMs formation during a subsequent chlorination step.

Ferrioxalate-induced solar photo-Fenton system for the treatment of winery wastewaters

In this study, the mineralization of wastewater from an actual winery using a ferrioxalate-induced solar photo-Fenton process was analyzed. Their main characterization parameters were: Total Organic Carbon: 2674mgL−1; total solids: 12.06mgL−1; sedimentable solids: 0.80mlL−1 and pH: 12.40. First, a physico-chemical pre-treatment of the raw wastewater was conducted, using either coagulation–flocculation or precipitation methods. Next, a photochemical reaction was carried out in a pilot plant consisting of a compound parabolic collector (CPC) solar reactor to remove the Total Organic Carbon (TOC) content of the wastewater. An optimization study was performed combining a multivariate experimental design and Neuronal Networks that included the following variables: the initial concentrations of H2O2, Fe(II) and oxalic acid (H2C2O4), temperature and solar power. Under optimal conditions, 61% TOC removal from the treated water was achieved in 360min. Temperature and the initial concentrations of H2O2 and oxalic acid were the most significant factors affecting the wastewater mineralization. A detailed analysis of the reaction was performed. The correlation between consumed hydrogen peroxide and removed TOC was found to remain constant. Thus the addition of H2O2 can be used to control the degree of mineralization for this type of wastewater. OH radicals were the main oxidative intermediate species in the process, although hydroperoxyl (HO2), singlet oxygen (1O2), triplet oxygen (O23) and the superoxide radical anion (O2−) also played a role. Photocatalytically degraded wastewater, containing significant residual organic content, can be treated at a later stage by a biological process, thus reducing the cost of its total mineralization using just photochemical oxidation methods.

Kinetic degradation of the pollutant guaiacol by dark Fenton and solar photo-Fenton processes

This work is first intended to optimize the experimental conditions for the maximum degradation of guaiacol (2-methoxyphenol) by Fenton's reagent, and second, to improve the process efficiency through the use of solar radiation. Guaiacol is considered as a model compound of pulp and paper mill effluent. The experiments were carried out in a laboratory-scale reactor subjected or not to solar radiation. Hydrogen peroxide solution was continuously introduced into the reactor at a constant flow rate. The kinetics of organic matter decay was evaluated by means of the chemical oxygen demand (COD) and the absorbance measurements. The experimental results showed that the Fenton and solar photo-Fenton systems lead successfully to 90% elimination of COD and absorbance at 604 nm from a guaiacol solution under particular experimental conditions. The COD removal always obeyed a pseudo-first-order kinetics. The effect of pH, temperature, H(2)O(2) dosing rate, initial concentration of Fe(2+), and initial COD was investigated using the Fenton process. The solar photo-Fenton system needed less time and consequently less quantity of H(2)O(2). Under the optimum experimental conditions, the solar photo-Fenton process needs a dose of H(2)O(2) 40% lower than that used in the Fenton process to remove 90% of COD.

Treatment of a sanitary landfill leachate using combined solar photo-Fenton and biological immobilized biomass reactor at a pilot scale

A solar photo-Fenton process combined with a biological nitrification and denitrification system is proposed for the decontamination of a landfill leachate in a pilot plant using photocatalytic (4.16 m 2 of Compound Parabolic Collectors – CPCs) and biological systems (immobilized biomass reactor). The optimum iron concentration for the photo-Fenton reaction of the leachate is 60 mg Fe 2+ L −1. The organic carbon degradation follows a first-order reaction kinetics ( k = 0.020 L kJ UV −1, r 0 = 12.5 mg kJ UV −1) with a H 2O 2 consumption rate of 3.0 mmol H 2O 2 kJ UV −1. Complete removal of ammonium, nitrates and nitrites of the photo-pre-treated leachate was achieved by biological denitrification and nitrification, after previous neutralization/sedimentation of iron sludge (40 mL of iron sludge per liter of photo-treated leachate after 3 h of sedimentation). The optimum C/N ratio obtained for the denitrification reaction was 2.8 mg CH 3OH per mg N–NO 3 −, consuming 7.9 g/8.2 mL of commercial methanol per liter of leachate. The maximum nitrification rate obtained was 68 mg N–NH 4 + per day, consuming 33 mmol (1.3 g) of NaOH per liter during nitrification and 27.5 mmol of H 2SO 4 per liter during denitrification. The optimal phototreatment energy estimated to reach a biodegradable effluent, considering Zahn–Wellens, respirometry and biological oxidation tests, at pilot plant scale, is 29.2 kJ UV L −1 (3.3 h of photo-Fenton at a constant solar UV power of 30 W m −2), consuming 90 mM of H 2O 2 when used in excess, which means almost 57% mineralization of the leachate, 57% reduction of polyphenols concentration and 86% reduction of aromatic content.

Life cycle assessment of solar photo-Fenton and solar photoelectro-Fenton processes used for the degradation of aqueous α-methylphenylglycine

A comparative Life Cycle Assessment (LCA) of solar photo-Fenton and solar photoelectro-Fenton, two solar-driven advanced oxidation processes (AOPs) devoted to the removal of non-biodegradable pollutants in water, is performed. The study is based on the removal, at laboratory scale, of the amino acid α-methylphenylglycine, a good example of soluble and non-biodegradable target pollutant. The system under study includes chemicals, electricity, transport of all raw materials to the plant site, and the generation of emissions, but it does not take into account the impact of the infrastructure needed to build a hypothetical solar plant. Nine environmental impact categories are included in the LCA: global warming potential, ozone depletion potential, aquatic eutrophication potential, acidification potential, human toxicity potential, photochemical ozone formation potential, fresh water aquatic ecotoxicity potential, marine aquatic ecotoxicity potential, and terrestrial ecotoxicity potential and abiotic resource depletion potential. Although previous experimental results show that both AOPs are able to efficiently degrade the pollutant, the LCA indicates that solar-driven photo-Fenton is the most environmentally friendly alternative, mainly because the use of electricity in solar photoelectro-Fenton experiments involves high environmental impacts.

Economic evaluation of the photo-Fenton process. Mineralization level and reaction time: The keys for increasing plant efficiency

The use of the solar photo-Fenton process is proposed to degrade Paracetamol in water in order to form biodegradable reaction intermediates which can be finally removed with a downstream biological treatment. Firstly, biodegradability enhancement with photo-Fenton treatment time has been evaluated; the minimum mineralization level should be at least 18.6% where Paracetamol has been degraded and biodegradability efficiency is higher than 40%. 20mgL−1 of Fe2+ and 200mgL−1 of H2O2 were selected in a lab-scale study looking at Paracetamol's degradation rate and organic carbon mineralization rate. As a result of scaling up the process at a pilot plant, 157.5mgL−1 of Paracetamol (∼1mM) was treated in 25min of photo-Fenton treatment achieving the desired biodegradability. A further economic evaluation shows how the proposed treatment strategy markedly increases plant efficiency, resulting in an 83.33% reduction in reagent cost and a 79.11% reduction in costs associated with reaction time. Total cost is reduced from 3.4502€/m3 to 0.7392€/m3.

Solar photo-Fenton as a pre-oxidation step for biological treatment of landfill leachate in a pilot plant with CPCs

A solar photo-Fenton process, without iron addition, is proposed for the decontamination of a landfill leachate in a pilot plant with CPCs, after a preliminary pre-treatment in aerated and non-aerated lagoons. The solar photo-Fenton reaction leads to 60% mineralization (DOC final = 1200 mg L −1) and 90% reduction of aromatic content of the leachate after 5 sunny clear days (165 kJ UV L −1), consuming 275 mM of H 2O 2. Photo-Fenton kinetics comprises a “lag period” after the acidification until approximately 68.7 kJ UV L −1 in which less oxidized compounds are converted into more oxidized ones but without significant CO 2 release, followed by a first-order kinetic behaviour ( k = 0.007 L kJ UV −1, r 0 = 20.2 mg kJ UV −1) until 136 kJ UV L −1, with a H 2O 2 consumption rate in both periods of k H 2 O 2 = 2.1 mmol H 2 O 2 k J UV − 1 . According to activated sludge respirometry and Zahn–Wellens biodegradability tests, BOD 5/COD ratio, polyphenols concentration and COS (carbon oxidation state), the biodegradability of the leachate was enhanced during the photo-Fenton treatment. From the kinetic results, the optimal amount of UV solar energy required for photo-treatment to reach a biodegradable effluent is 100 kJ UV L −1 (10.5 h of photo-Fenton at a constant solar UV power of 30 W m −2), consuming 180 mM of H 2O 2 when used in excess, which means almost 40% mineralization of the leachate, 82% reduction of polyphenols concentration and 83% reduction of aromatic content.

Optimization of the mineralization of a mixture of phenolic pollutants under a ferrioxalate-induced solar photo-Fenton process

The mineralization of solutions containing a mixture of three phenolic compounds, gallic, p-coumaric and protocatechuic acids, in a ferrioxalate-induced solar photo-Fenton process was investigated. The reactions were carried out in a pilot plant consisting of a compound parabolic collector (CPC) solar reactor. An optimization study was performed combining a multivariate experimental design and neuronal networks that included the following variables: pH, temperature, solar power, air flow and initial concentrations of H 2O 2, Fe(II) and oxalic acid. Under optimal conditions, total elimination of the original compounds and 94% TOC removal of the mixture were achieved in 5 and 194 min, respectively. pH and initial concentrations of H 2O 2 and Fe(II) were the most significant factors affecting the mixture mineralization. The molar correlation between consumed hydrogen peroxide and removed TOC was always between 1 and 3. A detailed analysis of the reaction was presented. The values of the pseudo-first-order mineralization kinetic rate constant, k TOC , increased as initial Fe(II) and H 2O 2 concentrations and temperature increased. The optimum pH value also slightly increased with greater Fe(II) and hydrogen peroxide concentrations but decreased when temperature increased. OH and O 2 − radicals were the main oxidative intermediate species in the process, although singlet oxygen ( 1O 2) also played a role in the mineralization reaction.

Degradation of water polluted with used cooking oil by solar photolysis, Fenton and solar photo Fenton

The degradation of used cooking safflower oil aqueous solutions by photolysis, Fenton, and photo Fenton under solar light is reported. The processes were carried out in a photochemical reactor with recirculation. Operating variables such as, pH, oil concentration and molar ratio of [H(2)O(2)]:[oil] were investigated to test their effects on the treatment efficiency of Fenton process. Also the iron catalyzed decomposition of hydrogen peroxide in the solar photo Fenton reaction was studied under different experimental conditions. The degree of oil oxidation was monitored by the measurements of chemical oxygen demand (COD) analyses. It was found that at pH 2.6 and a molar ratio of [H(2)O(2)]:[oil] of 489:1 were more efficient for COD abatement. The experimental results showed that the sole effect of the solar irradiation (photolysis) aided to decrease approximately 65% of COD at neutral pH in a reaction time period of 15 h; whereas a decrease of 47% and approximately 90% of COD was obtained by Fenton and photo Fenton treatment, respectively, after a reaction time of 50 min. It was observed a decrease in the decomposition of H(2)O(2) in the solar photo Fenton process, in subsequent additions of H(2)O(2), and H(2)O(2) + Fe(2+).

Photodegradation of Reactive Blue 4 solutions under ferrioxalate-assisted UV/solar photo-Fenton system with continuous addition of H 2O 2 and air injection

An experimental study based on the homogeneous ferrioxalate-assisted solar photo-Fenton process shows the effect of the continuous addition of hydrogen peroxide and air injection on the degradation of non-biodegradable dye Reactive Blue 4 (RB4) solutions. The reaction was carried out in a CPC (compound parabolic collector) solar pilot plant reactor. It was shown that the degree of dye solution mineralization was enhanced because the scavenger effect of H 2O 2 was minimized. Air bubbling had a negative effect because oxygen reacted with oxalyl radical anions, diminishing the amount of generated Fe(II), and consequently the concentration of hydroxyl radicals produced under irradiation of oxalate in the presence of peroxide was lower. In addition, this system permits the use of lower concentrations of ferrous ion, reducing the costs of the later iron removal process. Under the optimal conditions selected in this system, TOC removal was increased from 61% to 82% with a shorter reaction time as compared with a peroxide dose at the beginning of the reaction. The efficiency of the mineralization of RB4 solutions was enhanced when the solar CPC reactor worked together with an artificial UV-A/C pilot plant, increasing TOC removal up to 95%. Artificial UV lamps can be used either to improve the process or as an alternative to solar CPC on cloudy days.

Photo-Fenton degradation of the herbicide tebuthiuron under solar irradiation: Iron complexation and initial intermediates

The complexation of iron ions with the herbicide tebuthiuron (TBH), during a solar photo-Fenton process, was investigated using cyclic voltammetry with a glassy carbon electrode. An oxidation peak was observed at +0.64 V after addition of Fe(NO 3) 3 to TBH solution, indicating the formation of a Fe–TBH complex, which was not observed in the presence of ferrioxalate or citrate complexes. This complexation hinders photoreduction of Fe(III), and consequently TBH degradation. The main degradation route, in the presence or absence of citric acid (in the latter case with Fe(NO 3) 3 only), is initiated by the hydroxylation of a terminal methyl group of the urea, indicating an identical degradation mechanism. Hydroxylation of the central methyl of urea, and of the tert-butyl group, was also observed after extended irradiation periods in the presence of citric acid, but was not observed in the presence of Fe(NO 3) 3, due to a slower degradation rate in the absence of the citrate complex. No intermediate, generated from opening of the thiadiazole ring, was identified under the various different conditions.

Degradation of 4‐Chloroguaiacol by Dark Fenton and Solar Photo‐Fenton Advanced Oxidation Processes

This paper evaluates the dark Fenton and the solar photo-Fenton advanced oxidation processes for the treatment of solutions containing 4-chloroguaiacol (4-CG). The 4-CG was chosen as a model compound found in pulp and paper wastewater formed in the bleaching process in the pulp industry. The effects of operating parameters, including reaction time, hydrogen peroxide-to-ferrous iron molar ratio (H2O2/Fe2+), initial chemical oxygen demand (COD), pH value, and temperature, on 4-CG degradation efficiency using the solar photo-Fenton process were investigated. It was demonstrated that both processes could effectively degrade 4-CG in water and followed first-order kinetics. The degradation rate in solar photo-Fenton oxidation was much faster than that of the dark reaction. The 4-CG degradation depends on its concentration in the solution. The degradation efficiency decreases when the concentration of the 4-CG increases. Under the conditions of pH 3, H2O2/Fe2+ molar ratio 2, H2O2 16 mmol x L(-1), Fe2+ 8 mmol x L(-1), initial COD 640 mg x L(-1), reaction time approximately 24 minutes, and temperature 25 degrees C, the 4-CG and COD percent removal were greater than 80 and 89%, respectively.

Fenton degradation of 4-chlorophenol contaminated water promoted by solar irradiation

The degradation of 4-chlorophenol (4-CP) contaminated water by Fenton process with or without solar irradiation assistance were investigated. It was found that the COD degradation and mineralization efficiency of 4-CP were more than 90% when a 30 min treatment of solar photo-Fenton oxidation process was applied and under an optimum [H 2O 2] 0/[Fe 2+] 0 ratio of 40, the COD degradation and mineralization efficiency increased 65% as compared to Fenton oxidation. Meanwhile, the AOS values increased from −0.33 to 2.13 in solar photo-Fenton process while no significant improvement for AOS values was found in Fenton process, implying a higher degree of oxidation for 4-CP in solar photo-Fenton process. In addition, increasing the intensity of solar irradiation seemed to be beneficial for treatment of 4-CP contaminated water. Formation of chloride ion as a result of mineralization of organically bounded chlorine was identified during the treatment of 4-CP solution. Near-stoichiometric accumulation of chlorine was observed during the degradation of 4-CP in both Fenton and solar photo-Fenton processes. However, accumulation rate of chloride ions were much faster in solar photo-Fenton process. The degradation of 4-CP was found to obey a pseudo-first-order reaction kinetics. As compared to Fenton process, the presence of solar light in photo-Fenton process increases the reaction rate by a factor of 6.5 and 15.8 for COD and TOC degradation, respectively. In other words, during the treatment of 4-CP contaminated water, solar photo-Fenton process possesses notably higher mineralization efficiency in a relatively short radiation time as compared to Fenton process, and could enhance the degradation treatment of refractory organic wastewater such as 4-CP in a cost-effective approach.

Soil remediation using a coupled process: soil washing with surfactant followed by photo-Fenton oxidation

In the present work the use of a coupled process, soil washing and photo-Fenton oxidation, was investigated for remediation of a soil contaminated with p, p′-DDT (DDT) and p, p′-DDE (DDE), and a soil artificially contaminated with diesel. In the soil washing experiments, Triton X-100 (TX-100) aqueous solutions were used at different concentrations to obtain wastewaters with different compositions. Removal efficiencies of 66% (DDT), 80% (DDE) and 100% (diesel) were achieved for three sequential washings using a TX-100 solution strength equivalent to 12 times the effective critical micelle concentration of the surfactant (12 CMC eff). The wastewater obtained was then treated using a solar photo-Fenton process. After 6 h irradiation, 99, 95 and 100% degradation efficiencies were achieved for DDT, DDE and diesel, respectively. In all experiments, the concentration of dissolved organic carbon decreased by at least 95%, indicating that residual concentration of contaminants and/or TX-100 in the wastewater was very low. The co-extraction of metals was also evaluated. Among the metals analyzed (Pb, Cr, Ni, Cu, Cd, Mn and Co), only Cr and Mn were detected in the wastewater at concentrations above the maximum value permitted by current Brazilian legislation. The effective removal of contaminants from soil by the TX-100 washing process, together with the high degradation efficiency of the solar photo-Fenton process, suggests that this procedure could be a useful option for soil remediation.

Biodegradability of chlorophenol wastewater enhanced by solar photo-Fenton process

The combination of solar irradiation and Fenton reagent have been used to enhance the biodegradability (BOD(5)/COD) of chlorophenol wastewater, including 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), and 2,4-dichlorophenol (2,4-DCP). Results showed that the solar photo-Fenton process improved significantly the biodegradability of chlorophenol wastewater. Basically, increasing initial H(2)O(2) dosage was much more beneficial for increasing biodegradability of wastewater than increasing initial Fe(2 + ) dosage. Among the conditions studied, the optimum condition of increasing biodegradability of chlorophenol wastewater was found with a [H(2)O(2)](0)/[Fe(2 + )](0)/[chlorophenol](0) ratio of 10.0/0.2/1.0, 10.0/0.3/1.0, and 10.0/0.2/1.0 for 2-CP, 4-CP, and 2,4-DCP, respectively. As a result, the value of BOD(5)/COD was increased from 0 for untreated solution up to 0.231, 0.248, and 0.193 for 2-CP, 4-CP, and 2,4-DCP, respectively with a 15-min treatment. Under the operation of optimum conditions, the oxidative state of chlorophenol wastewater could be easily controlled into a higher biodegradability stage. The COD and TOC degradation efficiency could be in excess of 90% on the whole as the preoxidized chlorophenol solution was treated by a following batch-type biological unit. In the meanwhile, the microtoxicity of wastewater reduced more than 95%.

Effect of continuous addition of H2O2 and air injection on ferrioxalate-assisted solar photo-Fenton degradation of Orange II

An experimental study based on ferrioxalate-assisted solar photo-Fenton (SPFox) process shows how non-biodegradable azo dye Orange II (OII) solutions degradation can be enhanced or slowed down by continuous addition of hydrogen peroxide and air injection depending on operation conditions. The decoloration and mineralization of dye solution has been carried out in a solar Compound Parabolic Collector (CPC). An optimization study was done by using Multivariate Experimental Design including the following variables: flow rate of H2O2, air flow rate, pH and initial concentrations of Fe(II) and oxalic acid. The efficiency of photocatalytic degradation was determined from the analysis of color and Total Organic Carbon (TOC). Experimental data were fitted using neural networks (NNs) which allow the simulation of the process for any value of variables in the studied experimental range. The results reveal that the continuous addition of H2O2 improves the photocatalytic efficiency since the scavenger effect of peroxide is minimized. On the other hand, this system permits the use of a ferrous concentration below the discharge legal limit (2ppm) being bubbling of air not necessary in that conditions. In addition, oxalic acid can be used to pH adjustment, reducing the operation costs of Fe removal, chemicals and electric power. Under the optimal conditions, 100% decoloration of dye solution can be reached by using both processes (SPFox with H2O2 addition at the beginning or along the reaction) but with different reaction rates. However, the efficiency of TOC removal was higher in the SPFox process with continuous addition of H2O2 (95% TOC removal in SPFox system with continuous addition of peroxide versus 80% TOC removal in SPFox system when peroxide is added at the beginning of the reaction). Molecular and/or radical reaction pathway was studied by conducting the reaction in the presence and absence of tert-butylalcohol.