Solar Compound Parabolic Collector Research Articles

Study of the intensification of solar photo-Fenton degradation of carbamazepine with ferrioxalate complexes and ultrasound

The intensification of the solar photo-Fenton system with ferrioxalate photoactive complexes and ultrasound applied to the mineralization of 15mg/L carbamazepine aqueous solution (CBZ) was evaluated. The experiments were carried out in a solar compound parabolic collector (CPC) pilot plant reactor coupled to an ultrasonic processor. The dynamic behavior of hydroxyl radicals generated under the different studied reaction systems was discussed. The initial concentrations of hydrogen peroxide and ferrous/oxalic acid and pH were found to be the most significant variables (32.79%, 25.98% and 26.04%, respectively). Under the selected optimal conditions ([H2O2]0=150mg/L; [Fe2+]0=2.5mg/L/[(COOH)2]0=12.1mg/L; pH=5) CBZ was fully degraded after 5min and 80% of TOC was removed using a solar photo-Fenton system intensified with ferrioxalate (SPFF). However, no improvement in the mineralization using SPFF process combined with ultrasound was observed. More mild pH conditions could be used in the SPFF system if compared to the traditional photo-Fenton (pH 3) acidic systems. Finally, a possible reaction pathway for the mineralization of CBZ by the SPFF system was proposed and therein discussed.

Energy Utilization Efficiency and Entrepreneurial Potential of a Solarbiomass Integrated Drying System

In absence of grid power in most of the production catchments in the North Eastern states of India, coupled with disruptive power situation in areas where it is available, agricultural products are invariably dried under traditional sun drying. Ginger and turmeric with high intrinsic qualities are two major spices produced in a formidable quantity in the region. Truckloads of raw ginger are transported to Delhi and other places, causing huge transit losses. A solar-biomass integrated (IDS) batch drying system was thus designed and developed with a capacity of 100 kg/batch. A compound parabolic solar collector coupled with bio-waste fired combustion and heating assembly was designed and attached to a drying chamber consisting of six trays and a wind turbine on the top to create the necessary draft controlled by butterfly valves and sliding gates. Thin layer drying experiments were carried out for drying of sliced ginger and turmeric. Fluidized bed dryer (FBD), electrical oven (EO) and open sun drying (OSD) were used for comparison. Effective moisture diffusivity in case of turmeric drying was nearly 21% more in comparison to ginger drying. Minimum specific energy consumption (SEC) occurred in IDS, and was 14 and 30 times less compared to FBD and OSD, respectively. Considering total heat available in the plenum chamber and latent heat of vapourization, the IDS showed 36.33% of overall energy utilization efficiency. A run up of 10 years and a break-even of 17.70 % was estimated, reflecting high entrepreneurial possibility of the developed IDS.

Assessment of solar photocatalysis using Ag/BiVO4 at pilot solar Compound Parabolic Collector for inactivation of pathogens in well water and secondary effluents

Advanced oxidation processes (AOPs), such as photocatalysis driven by natural sunlight have been demonstrated to be a promising technology for degradation of hazardous chemical compounds and inactivation of microorganisms in water. Among already exiting photocatalysts, for solar water treatment, currently visible light-active photocatalysts such as bismuth vanadate (BiVO4), have received much attention from researchers. This work reports on the capacity of new synthetized Ag modified BiVO4 composite to inactivate E. coli, E. faecalis and spores of F. solani in different water matrices. Proof of principle experiments performed at laboratory scale (200mL of distilled water in stirred tank reactor) demonstrated the capability of this photocatalyst to inactivate those pathogens. A range of Ag loadings were investigated, demonstrating that 15% of Ag was the best option for water disinfection under natural sunlight. Although, TiO2-P25 is a better material for the solar photocatalytic disinfection of water under real sun. The cytotoxic effect of Ag/BiVO4 composites was investigated by testing its cytotoxicity in human dermal fibroblasts (HDF). This result was supported also by the lack of bactericidal effect of the composites as it was demonstrated to not compromise the viability of E. coli, E. faecalis and F. solani spores in dark (1gL−1 of Ag(15%)/BiVO4) for 3h in the case of E. coli and for 5h for the others. Up-scaling the treatment to CPC flow-reactor of 10L was successfully done in distilled water and well water; meanwhile inactivation of microorganism in secondary effluent (SE) from a Municipal Wastewater Treatment Plant was achieved only in the case of naturally occurring E. coli. Several concentrations of catalyst were investigated, and best inactivation efficiency was found to be 1gL−1 for all microorganisms, solar reactors and water matrices. The influence of chemical composition of the water matrix was also investigated. The presence of high concentrations of carbonates/bicarbonates (in well water) did not affect significantly the photocatalytic efficiency; while natural organic matter (in SE) strongly limited the process probably due to the competitiveness for the radicals generated.

Solar Photoelectro-Fenton Degradation of Acid Orange 7 Azo Dye in a Solar Flow Plant: Optimization by Response Surface Methodology

The experimental variables to optimize the solar photoelectro-Fenton (SPEF) degradation of 10 L of Acid Orange 7 (AO7) azo dye in 0.05 M Na2SO4 of pH 3.0 have been determined from a central composite rotatable design and response surface methodology. Trials were performed with a solar flow plant with a Pt/air-diffusion reactor generating H2O2 and a solar compound parabolic collector photoreactor under an UV irradiation intensity of about 31 W m−2. Optimum variables of 4.0 A, 0.75 mM Fe2+, and 150 mg L−1 total organic carbon (TOC) of the azo dye were found for 90 % color and 70 % TOC removals. Under optimized conditions, total decolorization was achieved in 300 min, but AO7 decay obeyed a pseudo-first-order kinetics to disappear in 80 min, pointing to the generation of recalcitrant colored aromatic products. After 360 min of electrolysis, TOC was reduced by 96 %, with 64 % mineralization current efficiency and 133 kWh kg−1 TOC energy consumption. The final solution contained carboxylic acids like tartronic, oxalic, oxamic, and in larger proportion, formic. An almost total mineralization was achieved by SPEF due to the persistence of Fe(III)-formate complexes to be photolyzed by sunlight. The initial N of the azo dye was mainly released as NH4 +.

Solar photo-degradation of a pharmaceutical wastewater effluent in a semi-industrial autonomous plant

An industrial wastewater effluent coming from a pharmaceutical laboratory has been treated in a semi-industrial autonomous solar compound parabolic collector (CPC) plant. A photo-Fenton process assisted with ferrioxalate has been used. Up to 79% of TOC can be removed in 2 h depending on initial conditions when treating an aqueous effluent containing up to 400 ppm of initial organic carbon concentration (TOC). An initial ratio of Fe(II)/TOC higher than 0.5 guarantees a high removal.It can be seen that most of TOC removal occurs early in the first hour of reaction. After this time, mineralization was very slow, although H2O2 was still present in solution. Indeed it decomposed to form oxygen in inefficient reactions. It is clear that remaining TOC was mainly due to the presence of acetates which are difficult to degrade.

Optimal Positioning of Reflectors to Increase Heat Interception of a Compound Parabolic Solar Collector using Taguchi Method

This work represents the optimization of reflector positioning of compound parabolic collectors for enhanced heat interception. The heat intercepted by a compound parabolic collector can be improved either by increasing the quantity of incident solar radiation or by absorbing a greater percentage of the available radiation. In the redesigned system, the utilization of incident heat has been increased by increasing the utilization of incident heat, instead of increasing the quantity of incident heat. We have increased the overall efficiency of the compound parabolic collector by applying Taguchi’s method, increasing the maximum concentration ratio to a value almost equal to the geometric concentration ratio and therefore achieved maximum utilizations of the available solar radiation. We have increased the heat intercepted by 23% from 3.7 KW to 3.75 KW and by applying electronic and mechanical tracking, an increase in average solar flux concentration by 10 times is observed.

Solar light (hv) and H2O2/hv photo-disinfection of natural alkaline water (pH 8.6) in a compound parabolic collector at different day periods in Sahelian region.

The photo-disinfection of natural alkaline surface water (pH 8.6 ± 0.3) for drinking purposes was carried out under solar radiation treatments. The enteric bacteria studied were the wild total coliforms/Escherichia coli (10(4) CFU/ml) and Salmonella spp. (10(4) CFU/ml) naturally present in the water. The photo-disinfection of a 25-l water sample was carried out in a solar compound parabolic collector (CPC) in the absence and in the presence of hydrogen peroxide (H2O2). The addition of H2O2 (10 mg/L) to the sample water was sufficient to enhance the photo-disinfection and ensure an irreversible lethal action on the wild enteric bacteria contents of the sample. The inactivation kinetic of the system was significantly enhanced compared to the one carried out without H2O2 addition. The effect of the solar radiation parameters on the efficiency of the photo-disinfection were assessed. The pH has increased during the treatment in all the photo-disinfection processes (hv and H2O2/hv). The Salmonella spp strain has shown the best effective inactivate time in alkaline water than the one recorded under acidic or near-neutral conditions. The evolution of some physico-chemical parameters of the water (turbidity, NO2(-), NO3(-), NH4(+), HPO4(2-), and bicarbonate (HCO3(-))) was monitored during the treatment. Finally, the possible mechanistic process involved during the enteric bacteria inactivation was suggested.

Degradation of four pharmaceuticals by solar photo-Fenton process: Kinetics and costs estimation

Solar photo-Fenton process for degradation of four types of pharmaceuticals namely amoxicillin, ampicillin, diclofenac, and paracetamol was studied. Experiments were carried out by solar compound parabolic collectors (CPCs) reactor with borosilicate tubes and capacity of 4.0L. Oxidation of each pharmaceutical was investigated individually using 100mg/L synthetic solution. The influence of irradiation time, initial pH value, and dosage of Fenton reagent were investigated. Paracetamol, and amoxicillin were completely removed after 60 and 90min of irradiation respectively. Complete degradation of ampicillin and diclofenac was occurred after 120min. The removal of pharmaceuticals was significantly affected by changing pH values from 3 to 10. Complete removal of all pharmaceuticals was achieved under acidic conditions (pH 3). The optimum H2O2 and FeSO4.7H2O dosage were 1.5 and 0.5g/L, respectively. The results of photo-Fenton experiments fitted the pseudo-first order kinetic equation with high correlation. Costs estimation of 30m3/d full scale solar photo-oxidation plant was assessed.

Solar photocatalytic degradation of phenol by TiO2/AC prepared by temperature impregnation method

Solar photocatalytic degradation of phenol by TiO2 (p25), which was immobilized on powdered activated carbon (TiO2/AC) by temperature impregnation method, was investigated. Solar compound parabolic collectors reactor with a capacity of 4.0 L was used. Characterization of TiO2/AC by Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, and scanning electron microscope revealed successful impregnation of TiO2 particles on activated carbon (AC). Fifty three percent degradation of phenol was recorded at irradiation time of 30 min and increased up to 80% after 150 min using TiO2. This was not the case for TiO2/AC, where the phenol was rapidly removed by a value of 40% within 15 min and complete degradation of phenol was attained at illumination time of 120 min. This indicates that immobilization of TiO2 on AC is very effective for phenol degradation. Moreover, in TiO2/AC photocatalysis, the presence of aromatic intermediates (catechol, hydroquinone, and p-benzoquinone) was relatively lower as compared to TiO2 photocatalysis. However, TiO2/AC photocatalysis of phenol degradation is strongly affected by pH values and dosage of the catalyst, i.e. complete degradation of phenol was occurred at pH value of 5.3 and dosage of 1.2 g/L. The photocatalytic degradation of phenol by TiO2/AC followed the pseudo-first-order kinetic according to Langmuir–Hinshelwood model. Costs estimation of full-scale solar oxidation plant with life time of 20 years was assessed. The results showed that complete removal of phenol using TiO2/AC costs 3.19 €/m3.

Photo-decolorization and ecotoxicological effects of solar compound parabolic collector pilot plant and artificial light photocatalysis of indigo carmine dye

The aim of this study was to analyze the photocatalytic degradation of C.I. Food Blue 1 under artificial and solar irradiation using titanium dioxide and to evaluate the ecotoxicity of the photodegradation products in organisms of two different food chain levels. Three different artificial-light and geometric photoreactors were evaluated for the ideal amount of catalyst and UV-light time irradiation. The optimized experiments were performed in a solar compound parabolic collector pilot plant with different water matrices (distilled water, freshwater, synthetic and real MWWTP) at Plataforma Solar de Almería. Photodegradation of the indigo dye was followed by UV–Vis spectroscopy, high performance liquid chromatography, total organic carbon and ion chromatography. Solar pilot plant photocatalysis was efficient for different water matrices but the photodegradation was found to be somewhat slower for the more complex matrixes. Ecotoxicological evaluation with Daphnia similis and Pseudokirchneriella subcapitata showed that photodegradation products were more toxic than untreated indigo carmine and that titanium residues affected the two tested species.

Potential application of solar powered adsorption cooling systems in the Middle East

This paper presents a theoretical investigation on the performance of solar powered silica gel/water based adsorption cooling system working under climate conditions of the Middle East region. Actual solar data of Cairo and Aswan located, respectively, in the north and south of Egypt and the coastal city Jeddah on the Red Sea in Saudi Arabia are used in this study. Dynamic behavior of adsorption chillers driven by compound parabolic solar collector is presented. Two system configurations have been considered herein; (i) adsorption chiller is directly connected to the solar collectors, (ii) hot water buffer storage is installed between adsorption chiller and solar collectors. Temporal history of solar collector, sorption reactors, evaporator and condenser has been predicted. System performance in terms of cooling capacity, daily average cooling capacity, cycle COP and solar COP has been estimated. Results show that the maximum cyclic cooling capacity of the system working under Cairo and Jeddah climate conditions reaches about 14.8kW and about 15.8kW for Aswan climate conditions.

Advances in solar photoelectro-Fenton: Decolorization and mineralization of the Direct Yellow 4 diazo dye using an autonomous solar pre-pilot plant

Here, an overview on the advances in solar photoelectro-Fenton (SPEF) is initially presented to show that it is the more potent electrochemical advanced oxidation process based on Fenton's reaction chemistry to remove organic pollutants from waters, due to the synergistic action of generated hydroxyl radicals and solar irradiation. As a novel advance for SPEF, an autonomous solar pre-pilot plant is proposed to make an energetically inexpensive process that can be viable at industrial level. The plant of 10dm3 capacity contained a Pt/air-diffusion cell with 90.2cm2 electrode area, coupled to a solar compound parabolic collectors (CPCs) photoreactor of 1.57dm3 irradiation volume and to a solar photovoltaic panel that provides a maximum average current of 5.0 A. The oxidation ability of this plant was assessed by studying the degradation of Direct Yellow 4 (DY4) diazo dye, which involved the predominant destruction of organics by OH formed from Fenton's reaction between H2O2 generated at the cathode and added Fe2+, along with the photolysis of Fe(III)-carboxylate complexes with sunlight in the CPCs photoreactor. The effect of Fe2+ and dye contents as well as current on decolorization rate, substrate decay and mineralization rate was examined. About 96-97% mineralization was rapidly attained using 0.50mmoldm−3 Fe2+ and up to 0.32mmoldm−3 DY4 at 5.0 A. The DY4 decay always obeyed a pseudo-first-order kinetics. Eleven aromatic products, twenty two hydroxylated derivatives and nine short-linear carboxylic acids were identified as intermediates. The Fe(III) complexes of most acids were rapidly removed, pre-eminently photolyzed by sunlight, except those of acetic and oxamic acids that were slowly destroyed. The initial N of the dye was mainly released as NH4+ ion and its initial S was lost as SO42− ion. A plausible reaction sequence for DY4 mineralization involving all the detected products was finally proposed.

Disinfection of urban effluents using solar TiO2 photocatalysis: A study of significance of dissolved oxygen, temperature, type of microorganism and water matrix

The enhancement of current technologies used to treat polluted water is one of the most important challenges in water research. The application of physico-chemical treatments could reduce the load of chemical and biological pollutants present in WW reducing the pressure over water requirements, allowing the reclaim of the treated water. Advanced Oxidation Processes (AOPs) and, in particular, photocatalysis using titanium dioxide (TiO2) have shown a great potential for chemicals removal as well as for pathogens reduction in water. Moreover, the use of solar Compound Parabolic Collectors (CPC) reactors has been also shown to be very effective for water treatment purpose by solar photocatalysis. Nevertheless, the effects of some key parameters in photocatalytic disinfection have not been already investigated at pilot scale in solar reactors; like dissolved oxygen concentration, water temperature, water matrix composition and the type of microorganism. The roles of these parameters in photocatalytic processes are individually known for chemicals degradation, but their relative significance in water photocatalytic disinfection has been never studied at pilot scale. The aim of this work was to investigate the influence of these parameters on the disinfection efficiency using a solar 60L-CPC reactor with suspended TiO2 (100mg/L). The following variables were experimentally evaluated: injection of air in the reactor (160L/h); different controlled temperatures (15, 25, 35 and 45°C); two very different models of water pathogen, Escherichia coli (model of fecal water contamination) and Fusarium solani spores (a highly phytopathogenic fungus); and the chemical composition of the water comparing urban WW effluents (UWWE) and simulated urban WW effluent (SUWWE). The increase of water temperature (from 15 to 45°C) had a benefit on the disinfection rate for both pathogens in all the experimental conditions evaluated. The air injection led to an important enhancement on the inactivation efficiency, which was stronger for F. solani spores, the most resistant microorganisms to TiO2 photocatalysis. The composition of the water matrix significantly affected the efficiency of the photocatalytic treatment, showing a better inactivation rate in SUWWE than for UWWE.

Solar CPC pilot plant photocatalytic degradation of bisphenol A in waters and wastewaters using suspended and supported-TiO2. Influence of photogenerated species

Photocatalytic degradation of bisphenol A (BPA) in waters and wastewaters in the presence of titanium dioxide (TiO2) was performed under different conditions. Suspensions of the TiO2 were used to compare the degradation efficiency of BPA (20 mg L(-1)) in batch and compound parabolic collector (CPC) reactors. A TiO2 catalyst supported on glass spheres was prepared (sol-gel method) and used in a CPC solar pilot plant for the photodegradation of BPA (100 μg L(-1)). The influence of OH·, O2 (·-), and h (+) on the BPA degradation were evaluated. The radicals OH· and O2 (·-) were proved to be the main species involved on BPA photodegradation. Total organic carbon (TOC) and carboxylic acids were determined to evaluate the BPA mineralization during the photodegradation process. Some toxicological effects of BPA and its photoproducts on Eisenia andrei earthworms were evaluated. The results show that the optimal concentration of suspended TiO2 to degrade BPA in batch or CPC reactors was 0.1 g L(-1). According to biological tests, the BPA LC50 in 24 h for E. andrei was of 1.7 × 10(-2) mg cm(-2). The photocatalytic degradation of BPA mediated by TiO2 supported on glass spheres suffered strong influence of the water matrix. On real municipal wastewater treatment plant (MWWTP) secondary effluent, 30 % of BPA remains in solution; nevertheless, the method has the enormous advantage since it eliminates the need of catalyst removal step, reducing the cost of treatment.

Analysis of a Low Concentration Solar Plant with Compound Parabolic Collectors and a Rotary Expander for Electricity Generation

In the last decade many studies have been carried out on low temperature solar compound parabolic collectors (CPC) that are able to collect solar direct and diffuse radiation without the need of a tracking system, especially if coupled with small scale Organic Rankine Cycles for electricity and heat combined production.This paper presents a study on a thermal power plant that uses an expansion device driven with pressurized vapor generated with the heat collected by a CPC solar field. The numerical model of the expansion device was developed with the simulation tool AMESim v.12 and allowed the simulation of the indicated cycle of this machine for the evaluation of delivered power, isentropic efficiency and specific working fluid consumption.At the same time in this paper an analytical model of the evacuated solar CPC is presented for the evaluation of the collected heat as a function of sun incidence angle, external temperature, inlet carrier fluid temperature and mass flow rate.These two models were used in conjunction for the analysis of the electricity that may be generated as a function of the ambient and working conditions. This study was performed in steady state conditions and with several working fluids to evaluate the power that would be delivered by a given displacement expander rotating at a fixed speed.The results are given in terms of delivered power, thermal efficiency and amount of collecting surface needed for a given displacement expansion machine, calculated for several working fluids and different operating conditions.

Relevant impact of irradiance (vs. dose) and evolution of pH and mineral nitrogen compounds during natural water disinfection by photo-Fenton in a solar CPC reactor

The inactivation of total coliforms/E. coli (104CFU/mL) and Salmonella spp. (105CFU/mL) in well water naturally containing dissolved (Fe2+/3+) and solid iron forms (e.g. iron oxides) was carried out by photo Fenton treatment (Fe2+,3+/H2O2/hv). In a preliminary run under simulated solar radiation, beyond 4mg/L of added H2O2, the enteric bacteria were totally inactivated after 90min. Thereafter, 25L of well water were treated in the compound parabolic collector (CPC) under direct solar radiation. Three irradiation periods (i) 8 am to 2 pm (8–14h), (ii) 10 am to 4 pm (10–16h) and (iii) 12 pm to 6 pm (12–18h) were evaluated for assessing the impact of different solar irradiances (Wm−2) on the enteric bacterial inactivation rates. Both studied strains were totally inactivated under sole exposure to solar radiation in the CPC when the experiments were conducted from 8 to 14h or 10 to 16h. However, Salmonella spp. strains regrowth was noticed after the 24h dark storage in all the samples previously treated with bare solar radiation. As the treated water contained Fe, the photo-Fenton disinfection at field scale in the CPC was carried out with the addition of H2O2 (10mg/L). Significant enhancement of the enteric bacteria inactivation rate was therefore recorded comparatively to the one obtained under bare solar treatment. No regrowth was observed in water treated by photo-Fenton disinfection one week after the treatment. The comparative evaluation of photo-Fenton disinfection rate as a function of different irradiation periods was based on the monitoring of the effective disinfection time (EDT), or required time to acquire the total inactivation of targeted bacteria in defined conditions. Therefore, significant impact of the irradiance on the process was noticed. High average irradiance (AI) of 35Wm−2 led to the total inactivation of Salmonella spp. in an EDT of 45min and a dose of 26Whm−2; while low irradiance of 20Wm−2 required an EDT of 180min for a dose 60Whm−2. Thus, the experiments revealed that lower irradiance level leads to higher doses to achieve the bacterial disinfection. pH, as well as nitrite and nitrate concentration, increased during the photo-disinfection processes, while depletion was recorded for aqueous ammonia concentration.

2,4-Dichlorophenol degradation by means of heterogeneous photocatalysis. Comparison between laboratory and pilot plant performance

In order to compare their performance, a 2,4-dichlorophenol (DCP) solution was treated by heterogeneous photocatalysis in a small laboratory set-up irradiated with artificial light and in a solar Compound Parabolic Collectors pilot plant. DCP and TiO2 concentration were varied to check possible different behaviors. DCP removal and TOC mineralization were monitored and fitted to a semiempiric model. DCP degradation rates show similar values in both installations, if comparison is based on entering UV photon flux. However, lab installation mineralizes lower amounts of TOC for the same accumulated UV photons, probably due to the different radiation intensity supplied in each set-up. Finally, some actinometric experiments to characterize the solar pilot plant are also presented, analyzing the collector and clouds effect.

Study of the performances of different configurations of seawater desalination with a solar membrane distillation

The object of this study is the comparison between two configurations of hollow fiber module for seawater vacuum membrane distillation. The first one is a module membrane in series with a solar compound parabolic collector (CPC). The second configuration is a hollow fiber module integrated in a cylindrical absorber of CPC. A model describing the operation of a hollow fiber module, with and without recycling, will be developed. This model determines the instantaneous variation of the temperature of each element of the installation with the distillate flow variation. A comparison of each module production is carried out. A mathematical model describing the performances of different configurations for membrane hollow fibers shows that: (1) The permeate flow for the integrated configuration is always higher than that of not integrated. It can be multiplied by two and even more. (2) The recycling of concentrate makes it possible to improve the production. This is due to the high level temperature at the exit of the module. (3) The energy recovery from the distillate will make it possible to increase the production and to reduce the plant size.

Solar photocatalytic treatment of landfill leachate using a solid mineral by-product as a catalyst

The treatment of municipal solid waste landfill leachate in a pilot plant made up of solar compound parabolic collectors, using a solid industrial titanium by-product (WTiO2) containing TiO2 and Fe(III) as a photocatalyst, was investigated. In the study evidence was found showing that the degradation performed with WTiO2 was mainly due to the Fe provided by this by-product, instead of TiO2. However, although TiO2 had very little effect by itself, a synergistic effect was observed between Fe and TiO2. The application of WTiO2, which produced coupled photo-Fenton and heterogeneous catalysis reactions, achieved a surprisingly high depuration level (86% of COD removal), higher than that reached by photo-Fenton using commercial FeSO4 (43%) in the same conditions. After the oxidation process the biodegradability and toxicity of the landfill leachate were studied. The results showed that the leachate biodegradability was substantially increased, at least in the first stages of the process, and again that WTiO2 was more efficient than FeSO4 in terms of increasing biodegradability.

Solar photoelectro-Fenton degradation of the herbicide 4-chloro-2-methylphenoxyacetic acid optimized by response surface methodology

A central composite rotatable design and response surface methodology (RSM) were used to optimize the experimental variables of the solar photoelectro-Fenton (SPEF) treatment of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA). The experiments were made with a flow plant containing a Pt/air-diffusion reactor coupled to a solar compound parabolic collector (CPC) under recirculation of 10 L of 186 mg L −1 MCPA solutions in 0.05 M Na 2SO 4 at a liquid flow rate of 180 L h −1 with an average UV irradiation intensity of about 32 W m −2. The optimum variables found for the SPEF process were 5.0 A, 1.0 mM Fe 2+ and pH 3.0 after 120 min of electrolysis. Under these conditions, 75% of mineralization with 71% of current efficiency and 87.7 kWh kg −1 TOC of energy consumption were obtained. MCPA decayed under the attack of generated hydroxyl radicals following a pseudo-first-order kinetics. Hydroxyl radicals also destroyed 4-chloro-2-methylphenol, methylhydroquinone and methyl- p-benzoquinone detected as aromatic by-products. Glycolic, maleic, fumaric, malic, succinic, tartronic, oxalic and formic acids were identified as generated carboxylic acids, which form Fe(III) complexes that are quickly photodecarboxylated by the UV irradiation of sunlight at the CPC photoreactor. A reaction sequence for the SPEF degradation of MCPA was proposed.