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The high internal resistance (Rint) that develops across the sediment microbial fuel cells (SMFC) limits their power production (~4/10 mW m−2) that can be recovered from an initial oil-contaminated sediment (OCS). In the anolyte, Rint is related to poor biodegradation activity, quality and quantity of contaminant content in the sediment and anode material. While on the catholyte, Rint depends on the properties of the catholyte, the oxygen reduction reaction (ORR), and the cathode material. In this work, the main factors limiting the power output of the SMFC have been minimized. The power output of the SMFC was increased (47 times from its initial value, ~4 mW m−2) minimizing the SMFC Rint (28 times from its initial value, 5000 ohms), following the main modifications. Anolyte: the initial OCS was amended with several amounts of gasoline and kerosene. The best anaerobic microbial activity of indigenous populations was better adapted (without more culture media) to 3 g of kerosene. Catholyte: ORR was catalyzed in birnessite/carbon fabric (CF)-cathode at pH 2, 0.8M Na2SO4. At the class level, the main microbial groups (Gammaproteobacteria, Coriobacteriia, Actinobacteria, Alphaproteobacteria) with electroactive members were found at C-anode and were associated with the high-power densities obtained. Gasoline is more difficult to biodegrade than kerosene. However, in both cases, SMFC biodegradation activity and power output are increased when ORR is performed on birnessite/CF in 0.8 M Na2SO4 at pH 2. The work discussed here can focus on bioremediation (in heavy OCS) or energy production in future work.

Divided electrochemical reactors allow the design of strategies to take advantage of the two reactions of the redox pair involved for wastewater treatment. Nafion membranes are the most used separators in these cells. These membranes have demonstrated high efficiency, but their high costs make the process more expensive. The present work focuses on the evaluation of the technical and economic feasibility of replacing the Nafion 117® membrane with a commercial polymeric membrane used in reverse osmosis (RO) treatments. In this study, a divided electrochemical cell was constructed with electrodes made of galvanized steel. The Fenton reaction was developed in the anode compartment using electrogenerated iron as a catalyst. An experimental design 23 was used to study the influence of three operating parameters (initial H2O2, membrane, voltage) on the H2O2 activation kinetics. The results demonstrated that the activation of H2O2 followed a pseudo-zero-order kinetic. The maximum rate constants obtained for Nafion 117® and RO membrane were 2.76 mM min−1 and 2.45 mM min−1, respectively. The optimization of H2O2 activation process was performed using a response surface methodology, where multiple regression models were used to figure out the best operation conditions when using both membranes. Finally, an extensive cost analysis of the process is included.

This study represents the first application of Fe–citrate-based photo-Fenton chemistry for the degradation of chlorpyrifos (CPF) spiked into agricultural runoff, and its phytotoxicity assessment. The effects of the initial CPF concentration, time and ratio of Fe–citrate/H2O2 on CPF removal during the photo-Fenton reaction were investigated and modeled with analysis of variance using R software by the response-surface methodology package. According to the stationary point in original units, the optimal condition for 70.00% CPF removal was as follows: CPF = 2.5 mg L−1 (0.0), time = 48.0 min (0.585) and Fe–citrate/H2O2 = 0.075 (0.539). Beside running the system at near-neutral pH, another strength of this study is related to the treatment of agricultural runoff contaminated with CPF with a raceway pond reactor, which has the advantages of simplicity of the facilities and procedures, as well as the possibility of using sunlight more efficiently in the field of applications. Finally, untreated and treated agriculture runoffs were used as irrigation to determine their phytotoxic effects on seed germination of cress (Lepidium sativum). Solar photo-Fenton treatment greatly reduced phytotoxicity of agriculture runoff and showed the highest germination percentage (70%) compared to both raw agricultural runoff (60%) and untreated CPF-spiked runoff (35%).

Hazardous organic compounds such as benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (known as BTEX) found at work and at home can cause adverse health effects of human beings throughout their lives. Biological monitoring, an exposure assessment method, considers all exposed organic and non-organic compounds. Our goal was to perform a systematic review and a statistical analysis (meta-analysis) of peer-reviewed publications to assess urinary concentrations of BTEX biomarkers in both occupationally-exposed population and the general population. Several major electronic databases, including Scopus, Embase, Medline, Web of Science, and Google scholar (grey literature), were searched for biomonitoring studies of BTEX. Overall, 33 studies met the eligible criteria for the systematic review and six met the full inclusion criteria for meta-analysis. For meta-analysis, we included studies in which unmetabolized BTEX compounds were measured in urine samples. Due to insufficient data, studies that measured BTEX metabolites in urine samples and unmetabolized BTEX compounds in blood samples were excluded from the meta-analysis but were analyzed in the qualitative synthesis. Most studies showed increased urinary concentrations of BTEX in exposed individuals (mainly workers) compared to unexposed individuals. The results showed that the highest total BTEX concentrations were recorded in painters and policemen. This study showed that the undoubted associations between lifestyle and environmental factors and urinary levels of BTEX or its metabolites have not yet been confirmed in current biomonitoring studies. This is attributed to the few studies reported in this research area, the lack of homogeneous information, and the disagreement in the published results of the studies.

The advanced oxidation processes (AOPs), as an alternative technology to eliminate pesticides from aqueous environments, consist of several groups of technologies that have been used with high efficiency in the treatment of water and wastewater in recent decades. A systematic review of the scientific literature to evaluate the most common advanced oxidation processes (AOPs) for the removal of organophosphorus pesticides in aqueous matrices is addressed in this study. Meta-analysis is also performed to provide a precise and robust summary estimate after a systematic and rigorous integration of the available evidence. In the current study, 9 sub-groups of AOPs were reviewed, such as electrochemical, UV/H2O2 photolysis, photocatalysis, Fenton-type, plasma, gamma irradiation, sulfate-based catalyst, sonolysis and ozonation technology for organophosphorus pesticides degradation. The random effects model was used to estimate the pooled measurements and 95 % confidence intervals (95 % CI). In total, six studies were included in this review. All studies, except one, used the photocatalytic process as AOP. The average pooled percentage of AOP for pesticide degradation was 66.8 (95 % CI: 58.1–75.6). In addition, the most studied pesticides are chlorpyrifos and diazinon which, according to the results of the meta-analysis, the photocatalytic process has the highest efficiency of diazinon elimination with an average percentage of 79.2 (95 % CI: 76.8–81.5).

Anaerobic biodegradation of petroleum-contaminated sediments can be accomplished by a sediment microbial fuel cell (SMFC), but the recovered energy is very low (~4 mW m−2). This is due to a high internal resistance (Ri) that develops in the SMFC. The evaluation of the main experimental parameters that contribute to Ri is essential for developing a feasible SMFC design and this task is normally performed by electrochemical impedance spectroscopy (EIS). A faster and easier alternative procedure to EIS is to fit the SMFC polarization curve to an electrochemical model. From there, the main resistance contributions to Ri are partitioned. This enables the development of a useful procedure for attaining a low SMFC Ri while improving its power output. In this study, the carbon-anode surface was increased, the biodegradation activity of the indigenous populations was improved (by the biostimulation method, i.e., the addition of kerosene), the oxygen reduction reaction was catalyzed, and a 0.8 M Na2SO4 solution was used as a catholyte at pH 2. As a result, the initial SMFC Ri was minimized 20 times, and its power output was boosted 47 times. For a given microbial fuel cell (MFC), the main resistance contributions to Ri, evaluated by the electrochemical model, were compared with their corresponding experimental results obtained by the EIS technique. Such a validation is also discussed herein.

We report the fabrication of nitrogen-doped carbon dots-zinc oxide hybrid (NCDs-ZnO) nanostructures utilizing simple chemical procedures. The role of NCDs in ZnO nanostructured matrix has been analyzed through XRD, SEM, FTIR and PL characterization techniques. The introduction of NCDs was found to modify not only their aspect ratio, observed by a reduction in the preferredc-axis growth compared to thea- andb-axis, but also induced an additional emission around 441 nm, which is typical of NCDs. The hybrid nanostructures were utilized as catalyst for methylene blue dye degradation showing a 95% degradation after 2 h of UV irradiation in comparison to the ∼70% degradation obtained by utilizing pristine ZnO, while the dye half-life (t1/2) was reduced by ∼65% by utilizing NCDs-ZnO hybrid nanostructures when compared to the pristine ZnO. The reusability of the fabricated hybrid structures was tested up to eight times with no significant loss in their photocatalytic performance (>90%). The stability of the hybrid structures was verified through Z-potential measurements prior and after reutilization. Excellent reusability and simple processing presented by NCDs-ZnO hybrid nanostructures makes them promising for industrial level photocatalyst for the waste water treatment.

The photocatalytic activity of TiO

Milk-vetch (MV) and compact discs (CDs) wastes, as natural and synthetic carbonaceous precursors, were used to produce low-cost activated carbons. The efficiency of adsorption of these adsorbents was compared with commercial activated carbon (CAC) for the adsorption of bisphenol A (BPA) from aqueous solutions. The activated carbon prepared from MV (MVAC) had a higher adsorption capacity, 33.19 mg g(-1), than that of both CD wastes (CDAC), 12.15 mg g(-1), and CAC, 29.22 mg g(-1). These adsorbents were characterized using X-ray diffraction, scanning electron microscope, Brunauer-Emmett-Teller method, pH(zpc) and Fourier transform-infrared spectra techniques. The effect of operating parameters on the adsorption of BPA such as the pH, contact time, adsorbent dosages, initial BPA concentrations, temperature, and ionic strength were studied. The optimal removal of the BPA was achieved at neutral pH (pH 7) by three adsorbents. Equilibrium contact times of 90 min were achieved for all the investigated activated carbons. Based on the obtained results, the pseudo-second-order kinetic model and Langmuir isotherm fitted the experimental finding better than other isotherms and kinetics. Furthermore, thermodynamic parameters were calculated and Delta G, Delta H and Delta S indicate that the reaction is spontaneous and endothermic, and physisorption mechanism was the dominant mechanism in terms of adsorption of BPA onto the three adsorbents.

The purpose of the present work was to prepare activated carbon (AC) from low-cost wastes, such as digital versatile discs (DVDs) and compact discs (CDs), coated with carbon nanotubes (CNTs) for adsorption of Acid Orange 7 (AO7) from dye-containing solutions. The surface morphology of the activated carbons from DVDs (DVDsAC), CDs (CDsAC), CNTs, CNTs/DVDsAC and CNTs/CDsAC was determined by XRD and SEM techniques. SEM micrographs of adsorbents clearly show a heterogeneous porous surface with irregular pores in the structure of the activated carbons. Results showed that CNTs/DVDsAC (30.3 mg/g) and CNTs/CDsAC (32.8 mg/g), in comparison with DVDsAC (15.1 mg/g) and CDsAC (9.9 mg/g), were more efficient adsorbents for the adsorption of AO7. The dye adsorption amount (qe) increases with a reduction in the solution pH, adsorbent dosage and an increase in the initial concentration of AO7 for these two more efficient adsorbents. Pseudo-second order model and Langmuir isotherm fitted with the experimental data. The spontaneous and endothermic processes were analyzed by the thermodynamic studies for the adsorption of AO7. The negative values of ΔG, and the positive values of ΔH and ΔS parameters indicate that the adsorption of AO7 onto CNTs/CDsAC and CNTs/DVDsAC was spontaneous and endothermic, respectively.

• Nonylphenol (NP) is a non-biodegradable compound with harmful effects on the endocrine system. The removal of NP in solution was investigated using visible light active carbon-doped TiO2 (CDT) with anatase/rutile (A/R) ratio and immobilized on the surface of granular activated carbon (GAC). The physicochemical characteristics of synthesized samples were determined in detail by means of XRD, SEM-EDX, TEM, BET, and UV–vis absorption spectra. The results showed the incorporation of C into TiO2 lattice and the identified A/R ratio of 53.06/46.94 can enhance the visible light utilization. It was observed that the band gap decreased from 3.17 eV to 2.72 eV after C doping, and to 2.66 eV by changing the calcination temperature from 475 °C to 600 °C. The maximum removal of NP was observed at pH of 9.5, initial NP concentration of 4 mg L−1, and optimal carrier dosage of 0.22 g in 0.1 L−1. The obtained findings showed that the scavenging agents compete with NP species for the OH, h+ and O 2− oxidizing species. The experimental data of photocatalytic degradation of NP using CDT (A/R)/GAC had highest correlation with Langmuir-Hinshelwood model and pseudo-first order kinetics and t1/2. Based on LC–MS analysis, the possible NP decomposition pathway was proposed.

This paper deals with the use of a raceway pond reactor (RPR) as an alternative photoreactor for solar photocatalytic applications. Raceway pond reactors are common low-cost reactors which can treat large volumes of water. The experiments were carried out with TiO2 in the agriculture effluent spiked with Chlorpyrifos (CPF) at circumneutral pH. The Response Surface Methodology (RSM) was used to find the optimum process parameters to maximize CPF oxidation from the mathematical model equations developed in this study using R software. By ANOVA, p-value of lack of fit > 0.05 indicated that, the equation was well-fitted. The theoretical efficiency of CPF removal, under the optimum oxidation conditions with UV solar energy of around 697 ± 5.33 lux, was 84.01%, which is in close agreement with the mean experimental value (80 ± 1.42%) confirming that the response model was suitable for the optimization. As far as the authors know, this is the first study of CPF removal using RPR in agriculture runoff at circumneutral pH.

The performance of UVA-LEDs assisted peroxymonosulfate (PMS)/Fe2+ system was evaluated on carmoisine (E122) decolorization. Complete color removal was obtained under the conditions of pH=3.0, PMS=1.5 mM, Fe2+=1 mM and 25 min reaction time. UVA-LEDs were preferable compared to conventional UVA lamp in terms of decolorization. The functions of Co2+, Cu2+, Mn2+ and Fe2+ were compared and their results showed that Co2+ and Fe2+ had the highest efficiencies. Moreover, the presence of chloride ion showed a double role in different concentrations in which promotional effect was observed in 100 mM Cl−

Central composite design with response surface methodology was applied to optimize the main experimental parameters such as current, time, As(III) concentration, and hardness for arsenic (III) removal in hard water by the electrocoagulation process. The main aim was to find the optimum process parameters to maximize arsenic removal from the mathematical model equations developed in this study using R software. By variance and regression analysis, the linear regression equation was established as a predicted model. The R2 of 0.93 indicated that the equation was well fitted. The optimum condition of 99% of As(III) removal for current (A), time (min), As(III) concentration (ppb), and hardness (mg/L as CaCO3) is 0.07, 37, 274, and 324, respectively. ANOVA analysis shows no significant difference between the observed and predicted values (p-value > 0.05) which shows good fit to the model.

At the end of December 2019, the rapid spread of the COVID-19 (SARS-CoV-2) disease and, subsequently, deaths around the world, lead to the declaration of the pandemic situation in the world. At the beginning of the epidemic, much attention is paid to person-to-person transmission, disinfection of virus-contaminated surfaces, and social distancing. However, there is much debate about the routes of disease transmission, including airborne transmission, so it is important to elucidate the exact route of transmission of the COVID-19 disease. To this end, the first systematic review study was conducted to comprehensively search all databases to collect studies on airborne transmission of SARS-CoV-2 in indoor air environments. In total, 14 relevant and eligible studies were included. Based on the findings, there is a great possibility of airborne transmission of SARS-CoV-2 in indoor air environments. Therefore, some procedures are presented such as improving ventilation, especially in hospitals and crowded places, and observing the interpersonal distance of more than 2 m so that experts in indoor air quality consider them to improve the indoor air environments. Finally, in addition to the recommendations of the centers and official authorities such as hand washing and observing social distancing, the route of air transmission should also be considered to further protect health personnel, patients in hospitals, and the public in other Public Buildings., Graphical abstract Image 1, Highlights • The SR was conducted to compile studies on airborne transmission of virus in indoor air. • In total, 14 relevant and eligible studies were included. • There is a great possibility of airborne transmission of SARS-CoV-2 in indoor air. • Improving ventilation is essential, especially in hospitals and crowded places.

Environmental exposure to nonylphenol (NP) can adversely affect human and wildlife health. A systematic review was conducted to evaluate the relationship between environmental NP exposure and cancer progression risk. Literature surveys were conducted within several international databases using appropriate keywords. A comprehensive search yielded 58 eligible studies involving a wide range of adverse effects, exposure assessment methods, study designs, and experimental models. Most studies reported that NP strongly induced breast cancer progression in intended experiments. Positive associations between NP exposure and ovarian, uterine, pituitary, and testicular cancers were also reported. Although some studies reported no relation between environmental NP exposure and tumour and/or cancer progression, NP (a known endocrine disrupting chemical) induced action mechanisms in multiple experimental models and may interfere with/hyper-activate oestrogen signalling. Secretion of oestrogen and development of reproductive tissues like breasts, uteruses, and ovaries showed strong associations with possible neoplasia (i.e., uncontrolled development of tumours and/or malignant cancers). Findings of this study are important for informing policymakers to pass legislation limiting the use of environmental contaminants such as NP before all adverse effects of exposure have been determined.

Chitosan (CS), synthesized from chitin chemically extracted from shrimp shells, was used for the synthesis of magnetic chitosan nanoparticles (Fe3O4-CSN), which makes the adsorbent easier to separate. Fe3O4-CSN was used for the removal of toxic metals such as vanadium (V(V)) and palladium (Pd(II)) ions from aqueous solutions. Influencing factors on the adsorption process such as pH, contact time, adsorbent dosage, and agitation speed were investigated. A competitive adsorption of V(V) and Pd(II) ions for the active sites was also studied. The monolayer maximum adsorption capacities (Qm) of 186.6 and 192.3 mg/g were obtained for V(V) and Pd(II) ions, respectively. The pseudo-second-order equation gave the best fit for the kinetic data, implying that chemisorption was the determining step. Freundlich model yielded a much better fit than the other adsorption models assessed (Langmuir, Temkin and Dubinin-Radushkevich). Thus, the adsorption of V(V) and Pd(II) ions onto Fe3O4-CSN is a combination of physical and chemical adsorption, as based on the kinetics and equilibrium study. Generally, physical adsorption is the mechanism that governs the system, while chemical adsorption is the slowest adsorption step that takes place. Thermodynamic studies displayed that the adsorption process was exothermic and spontaneous. Removal efficiencies of 99.9% for V(V) and 92.3% for Pd(II) ions were achieved, implying that Fe3O4-CSN adsorbent had an excellent ability for the removal of the metal ions from real industrial wastewaters without remarkable matrix effect.

TiO 2 electrode was used as photo-driven anode for oxygen reduction at carbon-felt cathode to produce H 2 O 2 used in the Fenton reaction to decompose an acid green 50 textile dye (AG50). The H 2 O 2 generated was catalyzed with ferrous ions in the photoelectroFenton process to decompose AG50 in cathode compartment. TiO 2 nanocomposite electrode was prepared by electrochemical anodization of pure Ti substrates. The results showed that TiO 2 anode exhibited a porous surface and organized nanotubes annealed at 450 °C and 600 °C with anatase phase, while a surface with less porous density with compact bars was obtained at 700 °C with anatase/rutile phase. The influence of applied bias potential, concentration of methanol in the anolyte, annealing temperature of TiO 2 nanocomposite and pH of the anolyte were studied on the photoelectrocatalytic degradation of methanol, whereas the catholyte composition remained unchanged for H 2 O 2 electrogeneration. Higher mineralization of both organic compounds was obtained by increasing the annealing temperature under acidic conditions using a bias potential of 1.02 V.

−Shewanella putrefaciens Bioelectrochemical systems Metal-deposition a b s t r a c t The microbiological influence of gram negative dissimilative bacteria on the electrodeposition of gold [AuCl4] − ion is analysed. Previous investigations have shown positive shifts in revisable potentials of gold in the presence of initially live gram negative bacterial cells, Shewanella putrefaciens in the electrolyte bath. This manuscript gives further analysis of the experimental data, with hypothetical influences of bacterial cells on gold nucleation and electrodeposition reaction mechanisms, kinetics and mass transfer as a basis for further investigation and strategies for the engineering of robust bioelectrochemical systems (BES), for novel metal ions recovery from aqueous process streams.

Atrazine is a highly persistent and carcinogenic compound used as herbicide around the world. This compound has been banned in USA and some European countries but in Mexico it is still widely used in the agriculture. In order to achieve a high mineralization of atrazine, present as active compound in the Gesaprim commercial herbicide, detoxification studies in two-compound parabolic solar reactors by means of photo-Fenton process followed by TiO 2 photocatalysis was carried out. The atrazine contents in the Gesaprim solutions tested were 35 mg L −1 (19.0 mg L −1 of TOC) and 20 mg L −1 (9.5 mg L −1 of TOC). [H 2 O 2 ] 0 /COD 0 ratios of 1, 3 and 5 (1.5 × 10 −3 , 4.5 × 10 −3 and 7.5 × 10 −3 mol L −1 H 2 O 2 , respectively) were evaluated in combination with 5 mg L −1 and 10 mg L −1 Fe 2+ at pH 2.8 in the photo-Fenton oxidation; whereas, in the photocatalytic process, the influence of the pH (4.8, 7.0 and 11.0) and type of TiO 2 (Degussa P25 and HB) were studied with TiO 2 content of 200 mg L −1 . The study showed that photo-Fenton process followed by TiO 2 photocatalysis produce a 72% of mineralization (for an initial TOC of 19 mg L −1 ) and decrease above 90% of toxicity in compliance with NMX-AA-110-1995-SCFI1 Mexican Norm. In order to established a minimum amount of chemical reagents these photodegradation processes were carried out with special emphasis on the optimization of experimental parameters such as concentrations of photocatalyst and oxidant. Atrazine mineralization was influenced by the pH of the solution, the initial concentration of hydrogen peroxide and iron ions.

The oxidation of Acid Green 50 (AG50) textile dye using Fe2O3–Al2O3, prepared from the calcination of FeIII–Al(OH)4-gel, as a highly active catalyst in the heterogeneous Fenton oxidation process was studied. It was found that the ferric ions loaded on the surface of neutral Al(OH)4− gel and then calcined at different temperatures is an efficient catalyst in the heterogeneous Fenton reaction for the mineralization of aqueous AG50. According to the X-ray analysis, the iron catalyst is a mix of Fe2O3 and Al2O3. The thermal treatment gives long-term stability to the catalyst because it minimizes iron leaching from the catalyst. The catalyst was used in four successive recycling heterogeneous Fenton oxidations generating a colorless solution with the removal of over 95% of total organic carbon (TOC) in 90 min. This shows that the Fe2O3–Al2O3 catalyst is highly efficient for the degradation of AG50 after being used in several cycles during the dye treatment. It was also found that the degradation of AG5...

TiO 2 and silver doped TiO 2 films (photoanodes) were prepared by the sol–gel method using silver contents of 1%, 3% and 5% (w/w). Photoelectrocatalytic activity of these photoanodes was evaluated by monitoring the photocatalytic decomposition of methanol and basic orange II (BOII) in aqueous solution under visible light illumination at pH 3 adjusted with HClO 4 by the application of potential bias. Enhanced photoelectrocatalytic activity was found by the application of 0.4 V ( vs . SCE) bias potential under visible light illumination. A detrimental effect was observed on the photoelectrocatalytic activity of the TiO 2 photoanodes in the presence of BOII, and is evident from the low photocurrents; however, the presence of silver in the TiO 2 films increased the photoelectrocatalytic activity. Also the photoelectrolysis of methanol removed over 80% of total organic carbon in 5 h of reaction under visible light and 0.4 V ( vs . SCE) bias potential. Nevertheless, negligible TOC removal was observed for the BOII photoelectrolysis with or without bias potential and under visible light illumination or in dark. Less than 9% of discoloration was achieved at the 3% Ag–TiO 2 photoanode under visible light illumination and bias potential.

We report influences of the gamma proteobacteria Shewanella putrefaciens CN32 on electronation and electrodeposition phenomena of gold, cobalt and iron ionic species dissolved in aqueous effluents of low pH as novel strategies for the recovery and remediation of these metals. Linear sweep and cyclic voltammetry was used and analysed for the evaluation of changes of respective electron transfer reactions occurring at the electrified interface of graphite electrode for electrolytes of pH 2 and low metal ion concentrations of 200 ppm. This study focuses on changes in electronation thermodynamics, preliminary results show shifts in the reverse potentials of gold electrodeposition and ferric iron electronation with implications for energy savings.

Photocatalysis has shown the ability to inactivate a wide range of harmful microorganisms with traditional use of chlorination. Photocatalysis combined with applied bias potential (photoelectrocatalysis) increases the efficiency of photocatalysis and decreases the charge recombination. This work examines the inactivation of fecal coliform bacteria present in real urban wastewater by photoelectrocatalysis using nanoparticulated films of TiO

Arsenic pollution is a worldwide problem that severely affects the human health, since the ingestion of arsenic is through contaminated drinking water and food harvested and prepared with arsenical water. Anthropogenic activities contribute to increase the levels of the natural occurrence of inorganic and organic arsenic in the environment. Inorganic arsenic in groundwater is mainly present as nonionic As (III) and ionic As (V) forms, and its speciation depends on the redox conditions, pH, biological activity, and adsorption reactions in the aquatic environment. In this study a direct artificial neural network (ANNs) approach was developed to predict the removal of As (III) and As (V) from aqueous solution under various experimental conditions. The arsenic removal was carried out using a natural sorbent prepared by the modification of solid waste vegetable oil industry with Fenton reagent (FMSWVOI). The maximum arsenic removal by the FMSWVOI was achieved at Fe 2+ /H 2 O 2 = 1:17 and 30 min of contact time, with 81% As (III) removal at pH 2 and 75% As (V) removal at pH 5. The artificial neural network (ANNs) was found to interpolate the data with good accuracy. The simulations of the trained network were in close agreement with the actual values. It was also observed that the Fenton process is an effective method for the modification of the solid waste vegetable oil industry to remove arsenic (III) and (V) from aqueous solution.

The removal of total organic carbon (TOC) from wastewater generated from phenolformaldehyde resin manufacturing industry using the electrocoagulation process was studied in this paper. Experiments were carried out at current densities of 5.0, 7.5 and 10.0 mA/cm2 using iron electrodes connected in parallel arrangement in an undivided electrochemical reactor. TOC content was determined during the different stages of electrolysis in order to know the feasibility of the electrocoagulation treatment for highly concentrated bio-refractory organic pollutants present in the industrial wastewater. Different operational conditions such as pH, time, and electrical conductivity were studied for TOC removal. Experimental values indicated that the electrocoagulation process showed high TOC removal efficiencies, 78.7% within 60 min of electrolysis, with an initial concentration of 23.8 × 103 mg/l TOC. Thus, these results showed that the electrocoagulation process is effective for the removal of initially high T...

Fe III supported on ceria as an effective catalyst for oxidation was prepared and used for the degradation of basic orange 2 azo textile dye (BO2). BO2 was chosen as a model pollutant and the catalytic oxidation was carried out in a batch reactor using hydrogen peroxide as the oxidant at pH 3. The influent factors on BO2 oxidation, such as catalyst dosage, H 2 O 2 concentration, and BO2 concentration were studied by considering the BO2 conversion and chemical oxygen demand (COD) removal. The Fe III –ceria catalyst showed a high catalytic activity for the oxidation of BO2 in aqueous solution. It was observed that the solution became colorless after 5 h of oxidation and over 90% COD removal was achieved with all the Fe III –ceria catalysts used under dark conditions in the catalytic oxidation system. The catalytic removal of BO2 during BO2 oxidation was improved under solar radiation, which notably increased the BO2 degradation rate. Consecutive BO2 oxidation cycles carried out with the same Fe III –ceria catalyst and untreated fresh dyestuff solution showed that the catalyst had good stability and good degradation performance, thus evidencing the possibility of being used in continuous processes. This study showed that the Fe III –ceria catalytic oxidation process is an efficient method for the treatment of BO2 aqueous solutions.

This paper describes modification of LECA (light expanded clay aggregate) with Fenton reagent and determines removal of arsenite and arsenate ions from an aqueous solution. The influence of pH, contact time and Fe 2+ /H 2 O 2 on modification were investigated and adsorption characteristics were examined before and after modification. Isotherm studies were carried out by studying the effects of various parameters such as pH, contact time, adsorbent concentration and initial concentration of arsenite and arsenate. The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models, and the model parameters were evaluated. One gram of LECA is found enough to remove 96% and 99% of the As (III) and As (V) from an aqueous solution of 150 μg L −1 at pH 2 and 4 respectively with a shaking time of 60 min. Column adsorption results indicated that no arsenic was found in the effluent solution up to about 10 and 18 bed volumes of As (III) and As (V), respectively.

Fe-doped TiO2 was prepared by the sol gel method and characterized by X-ray diffraction. All the Fe-doped TiO2 were composed of an anatase crystal form. The activity of the Fe-doped TiO2 for the degradation of the gesaprim commercial herbicide (which contains atrazine as active compound and formulating agents) was studied by varying the iron content during UV (15 W), visible light and solar irradiations. The visible light came from commercial saving energy lamps (13, 15 and 20 Watts). The gesaprim degradation rate depended on the iron content in the photo catalyst. The Fe-doped TiO2 (0.5% by weight of TiO2) showed higher TOC removal under visible light and was more active than the undoped TiO2 photo catalyst under the light irradiation sources tested. Over 90% of chemical oxygen demand abatement was achieved with both UV and visible light but less time was required to decrease the chemical oxygen demand content by using the catalyst doped with iron at 0.5% under visible light. It was observed that the degradation of gesaprim increased by increasing the iron content in the catalyst under visible light.

The Ca₃Zr₂S₇ films were deposited by electrodeposition by means of linear voltammetry with a potential applied in the range of -0.1 to -3.0 V vs. SCE. The precursors used for Ca, Zr and S were calcium acetate, zirconium acetate and sodium sulfite, respectively. The films were characterized optically, morphologically and structurally. The presence of Ca, Zr and S elements was verified by energy dispersion spectroscopy analysis. The results of the X-ray diffraction showed the presence of peaks related to a structure belonging to the perovskite family, and the chemical bonds were confirmed by photoelectron spectroscopy emitted by X-rays. The electrical resistivity in the dark and light was also measured. The surface roughness of the Ca₃Zr₂S₇ film was estimated at 3.05 nm with a thickness of 600 nm. It was found that the material absorbs in the visible region of the electromagnetic spectrum with a wavelength of less than 500 nm. The Ca₃Zr₂S₇ film also exhibits ferroelectric properties at room temperature.

Results of voltammetry and spectrophotometry analyses revealed that upon sunlight exposure, the conversion of ferricyanide to ferrocyanide, and the reverse reaction, in the absence and in the presence of TiO2 catalyst depends strongly on pH. Thus, the pH of the solution dictates whether the redox reactions will proceed under illumination. In addition, the extent of the heterogeneous photocatalytic degradation of ferricyanide was influenced by pH. The initial concentration of ferricyanide did not affect its degradation.

The sonophotocatalytic degradation of basic blue 9 industrial textile dye has been studied in the presence of ultrasound (20 kHz) over a TiO(2) slurry employing an UV lamp (15 W, 352 nm). It was observed that the color removal efficiency was influenced by the pH of the solution, initial dye concentration and TiO(2) amount. It was found that the dye degradation followed apparent first order kinetics. The rate constant increased by decreasing dye concentration and was affected by the pH of the solution with the highest degradation obtained at pH 7. The first order rate constants obtained with sonophotocatalysis were twofold and tenfold than those obtained under photocatalysis and sonolysis, respectively. The chemical oxygen demand was abated over 80%.

The degradation of water soluble corn oil wastes was carried out by Fenton reaction and also under mildly basic media in the presence of oxidants, such as hydrogen peroxide and persulfate, assisted with solar light. The degradation efficiency was obtained by analysis of chemical oxygen demand, carbon dioxide and gas chromatography. Over 90% of both chemical oxygen demand abatement and carbon dioxide recovery was accomplished by Fenton reaction. The presence of oxidants during the photodegradation resulted in high chemical oxygen demand abatement of the oil waste with the disappearance of the majority of the initial fatty acids present in the oil waste before treatment.

The photocatalytic degradation of alazine and gesaprim commercial herbicides was carried out in aqueous TiO 2 suspensions under UV light (15 W, 352 nm). Degradation of these herbicides was also observed by the combined effects of photocatalysis with sonolysis (sonophotocatalysis) using an ultrasound source of 20 kHz. Degradation profiles were recorded by measuring the concentration of the active compounds present in the alazine (alachlor and atrazine) and gesaprim (atrazine) by HPLC as a function of irradiation time (sound and/or light). Over 90% of the active component in the gesaprim was abated and those in alazine were completely degraded. The content of total organic carbon and chemical oxygen demand was also monitored. Mineralization of the commercial herbicides was achieved. Over 80% of chemical oxygen demand abatement was attained for both herbicides with sonophotocatalysis at 150 min of irradiation time. The photocatalytic degradation of the herbicides followed a pseudo-first order kinetics and their rate constant was increased by the combined effects of sonolysis.

High purity hydrogen was generated from the chemical reaction of aluminum and sodium hydroxide. The aluminum used in this study was obtained from empty soft drink cans and treated with concentrated sulfuric acid to remove the paint and plastic film. One gram of aluminum was reacted with a solution of 2 mol dm - 3 of sodium hydroxide to produce hydrogen. The hydrogen produced from aluminum cans and oxygen obtained from a proton exchange membrane electrolyzer or air, was fed to a proton exchange membrane (PEM) fuel cell to produce electricity. Yields of 44 mmol of hydrogen contained in a volume of 1.760 dm 3 were produced from one gram of aluminum in a time period of 20 min.

Photocatalytic degradation of acid orange 7 (AO7) in aqueous systems was successfully achieved by the combination of TiO 2 with potassium persulphate under solar light using a photochemical reactor with recirculation. Degradation of AO7 involves color removal and mineralization. The employment of TiO 2 removed ∼85% of color from the 0.2 mM AO7 aqueous solution under solar light; while, ∼66% of color was abated using the persulphate ion as oxidant in the absence of TiO 2 under similar conditions in 2 h. However, over 90% of color removal was achieved by combining TiO 2 and the persulphate ion for the same solution under similar conditions. Color removal was faster at pH 3. Mineralization of AO7 was followed by measuring chemical oxygen demand (COD). Negligible COD abatement of the textile dye was observed in the absence of persulphate ions (S 2 O 8 2− ) while over 70% of COD abatement was observed for the initial dye concentrations of 0.2–0.7 mM employing a mix of TiO 2 –S 2 O 8 2− under solar light.

High-purity hydrogen gas was generated from the chemical reaction of aluminum with sodium hydroxide. Several molar relations of sodium hydroxide/aluminum were investigated in this study. The experimental results showed that hydrogen yields are acceptable and its purity was good enough to be used in a proton exchange membrane (PEM) fuel cell to produce electricity. An estimation of the amount of energy produced from the reaction of 100 aluminum cans with caustic soda showed that the hydrogen production is feasible to be scaled up to reach up to 5 kWh in a few hours. This study is environmentally friendly and also shows that green energy can be produced from aluminum waste at a low cost.

The effect of electrolytically generated silver and copper ions on the abatement of iron-related bacteria, sulfate-reducing bacteria, slime-forming and coliform bacteria in the cooling systems was investigated in this work. These bacteria, commonly found in cooling tower systems, are usually controlled with chlorine. The effect of chlorine and its combination with these ions was also studied on the microbiology of the water. Silver/copper/chlorine concentration relationships ( 1.2 mg l −1 silver /0.6 mg l −1 copper /0.0 mg l −1 chlorine and 0.2 mg l −1 silver /1.2 mg l −1 copper /0.3 mg l −1 chlorine) proved to be good alternatives to replace or decrease appreciably the chlorine consumption in the cooling systems using relatively low concentrations of silver and copper with a minimum environmental impact. These relationships established a very effective treatment with 99% of control for the iron-related bacteria, sulfate-reducing bacteria and slime-forming bacteria abating more than 99% of such bacteria. Chlorine concentrations of 1.0 and 3.0 mg l −1 decreased more than 90% of some of the iron-related bacteria population. These systems have shown to decrease the aggressiveness of bacteria population that promote microbiologically influenced corrosion and biofilm formation to levels that compete with the traditional water treatment of cooling water. Coliform bacteria were also reduced below the levels accepted by the Mexican Official Norm.

Passivated electrode surfaces of aluminium and lead have been employed to investigate individual erosion corrosion events produced by ultrasound. Individual events are recorded with a resolution within the sub-millisecond time scale. The probability of the recorded events was found to fit with the expected physical model of the system. Distance dependence of the erosion corrosion currents recorded are reported showing that the active transient cavitation zone of the sound field employed is within the first ca. 5 mm of the sound emitting surface. The electrode material is also shown to have a marked effect on the distance dependence of surface erosion. The extent of surface damage, as the result of individual cavitation events, are calculated from the current time transients recorded on passivated lead electrodes.

The degradation of azure B dye (C15H16ClN3S; AB) has been studied by Fenton, sonolysis and sono-electroFenton processes employing ultrasound at 23 kHz and the electrogeneration of H2O2 at the reticulated vitreous carbon electrode. It was found that the dye degradation followed apparent first-order kinetics in all the degradation processes tested. The rate constant was affected by both the pH of the solution and initial concentration of Fe2+, with the highest degradation obtained at pH between 2.6 and 3. The first-order rate constant decreased in the following order: sono-electroFenton > Fenton > sonolysis. The rate constant for AB degradation by sono-electroFenton is ∼10-fold that of sonolysis and ∼2-fold the one obtained by Fenton under silent conditions. The chemical oxygen demand was abated ∼68% and ∼85% by Fenton and sono-electroFenton respectively, achieving AB concentration removal over 90% with both processes.

The removal of low concentration of chlorbromuron herbicide in aqueous systems was carried out by electro-Fenton process comprised of three-electrode divided and undivided cell with a reticulated vitreous carbon cathode and platinum anode. The electro-Fenton was also carried out in a two-electrode undivided cell in which ferrous ion forms from a sacrificial iron anode. It was observed that the total organic carbon (TOC) removal efficiency was influenced by the cell voltage, the pH of the solution and initial herbicide concentration during the electro-Fenton treatment with a stainless steel anode. The Fe(2+)/Fe(3+) activity in the Fenton chemistry (regardless if it is hydroxyl radical or ferryl ion) was improved by the electrochemical catalysis leading to a TOC analysis below the detection limit (0.2 mg l(-1)) corresponding to a TOC removal over 98%. It was found that TOC removal during chlorbromuron degradation followed apparent first order kinetics. The rate constant was increased by decreasing the initial concentration of chlorbromuron.

Homogeneous and heterogeneous aqueous systems of the herbicides of chlorbromuron, atrazine, and alachlor were irradiated with a nonexpensive solar irradiation using a photoreactor with recirculation. Photodegradation of these herbicides occurred in both aqueous systems; however the presence of TiO2clearly accelerated the degradation of the three herbicides in comparison with direct photolysis. Degradation was followed by measuring the chemical oxygen demand (COD) as a function of reaction time for each aqueous system. Over 90% of COD abatement in the heterogeneous aqueous system was obtained in a short time period showing that mineralization of chlorbromuron, atrazine, and alachlor was achieved.