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Acid mine drainage events have a negative influence on the water quality of fluvial systems affected by coal mining activities. This research focuses on the analysis of these events, revealing hidden correlations among potential factors that contribute to the occurrence of atypical measures and ultimately proposing the basis of an analytical tool capable of automatically capturing the overall behavior of the fluvial system. For this purpose, the hydrological and water quality data collected by an automated station located in a coal mining region in the NW of Spain (Fabero) were analyzed with advanced mathematical methods: statistical Bayesian machine learning (BML) and functional data analysis (FDA). The Bayesian analysis describes a structure fully dedicated to explaining the behavior of the fluvial system and the characterization of the pH, delving into its statistical association with the rest of the variables in the model. FDA allows the definition of several time-dependent correlations between the functional outliers of different variables, namely, the inverse relationship between pH, rainfall, and flow. The results demonstrate that an analytical tool structured around a Bayesian model and functional analysis automatically captures different patterns of the pH in the fluvial system and identifies the underlying anomalies. Ministerio de Ciencia e Innovación | Ref. PID2020-116013RB-I00

Reactive Black 5 (RB5) is an electroactive diazo dye compound derivate of H-acid (coupling reaction), which cannot be effectively degraded by conventional or biological processes. In this work, the feasibility of electro-Fenton (EF) process to treat a simulated effluent polluted by RB5 dye and the effectiveness of electroanalysis by Linear Sweep Voltammetry (LSV) to monitor RB5, intermediates and by-products during the EF treatment have been demonstrated. Several variables on the electrochemical behaviour of RB5 have been determined under EF experimental conditions. The key factors are scan rate and dye concentration (in the presence and the absence of iron) and their effect on shape, position and height of RB5 peaks have been determined to obtain the best sensitivity and selectivity in the voltammetric analysis. Moreover, the iron appears as a strong electrocatalyst that promotes the electron transfer for the oxidation reaction of RB5 on screen-printed carbon electrode, in part, due to a very stable coordinate complex formed with RB5. Besides that, the degradation profiles have revealed the main stages along the EF process and the voltammetric kinetic data has given selective information about the RB5 degradation and the evolution of the electroactive products generated. The formation of aromatic/cyclic organic intermediates, and evolution of carboxylic acids, as well as the inorganic ions released during the treatment were validated by other techniques and a plausible pathway is proposed based on the obtained results.

The presence of emerging contaminants like ionic liquids in the environment is prompting the search of new methods to remove them from environments. To our knowledge, there are only few studies reported in the literature regarding to the application of electro-Fenton to solve this problem. Nonetheless, during the last years it has demonstrated great effectiveness on the elimination of wide diversity of pollutants. For this reason, this study is focus on the degradation of a commonly used imidazolium ionic liquid 1-Butyl-3-methylimidazolium triflate ([C4mim][CF3SO3]) by electro-Fenton technology. Initial trials were performed using different supporting electrolytes, including NaNO3, Na2SO4 or NaCl. Voltammetric studies were carried out in order to elucidate the behavior of the studied pollutant at the anode surface in each tested electrolyte. Comparative experiments pointed out to NaNO3 (0.025 M) as the one yielding higher mineralization and degradation rates. Thus, [C4mim][CF3SO3], was completely degraded after 120 min with 87% of TOC reduction after 240 min. Moreover, these results can be improved by the increase of the NaNO3 concentration (0.075 M) and complete degradation and TOC reduction was attained at shorter treatment time. The ionic analysis ascertained these results, showing faster elimination under the use of NaNO3. Differential Pulse Voltammetry on this media revealed a strong interaction between the fluoride anion and the iron present in the medium and the formation of a complex between them. Finally, HPLC and GC/MS analysis permitted to follow the main intermediates formed along the treatment, thus proposing a plausible degradation pathway of [C4mim][CF3SO3].

Electrocoagulation (EC) has long been considered a phase separation process, well suited for industrial wastewater treatment since it causes a quick, drastic decay of organic matter content. This research demonstrates that EC also behaves, at least for some molecules like the industrial preservative bronopol, as an effective transformation technology able to yield several breakdown products. This finding has relevant environmental implications, pointing to EC as a greener process than described in literature. A thorough optimization of EC was performed with solutions of bronopol in a simulated water matrix, yielding the complete disappearance of the parent molecule within 20 min at 200 mA (∼20 mA/cm(2)), using Fe as the anode and cathode. A 25% of total organic carbon (TOC) abatement was attained as maximum, with bronopol being converted into bromonitromethane, bromochloromethane, formaldehyde and formic acid. N atoms were accumulated as NO3(-), whereas Br(-) was stable once released. This suggests that mediated oxidation by active chlorine, as well as by hydroxyl radicals resulting from its reaction with iron ions, is the main transformation mechanism. Aiming to enhance the mineralization, a sequential combination of EC with electro-Fenton (EF) as post-treatment process was proposed. EF with boron-doped diamond (BDD) anode ensured the gradual TOC removal under the action of (•)OH and BDD((•)OH), also transforming Br(-) into BrO3(-).

Diatrizoic acid (DIA) is an iodinated X-ray contrast media commonly used in hospitals. It is persistent and recalcitrant in aquatic environments and difficult to biodegrade. Thus, we studied its removal from aquatic medium by two electrochemical advanced oxidation processes: anodic oxidation and electro-Fenton using BDD anode and carbon felt cathode. The effect of two of the most important variables on, i.e., applied current intensity (both processes) and catalyst concentration (electro-Fenton) was assessed to optimize oxidative degradation of DIA and mineralization rate of its aqueous solution. 1000 mA current intensity and 0.2 mM catalyst (Fe2 +) concentration (at pH 3) were determined as optimal operating values for its effective removal from water based on the following parameters: concentration decay of DIA, total organic carbon removal rate and mineralization current efficiency. The rate constant for oxidation of DIA by OH was determined using competition kinetics method and found be 3.96 × 108 L mol− 1 s− 1. Obtained results showed a quick and complete mineralization of DIA solution. In addition, the identification of aromatic intermediates, short-chain carboxylic acids and mineral ions released to the solution during electro-Fenton treatment allowed us proposing a plausible mineralization mechanism of DIA by OH generated in the process. Finally, the toxicity of treated solutions along time was assessed following the luminescence inhibition of the marine bacteria Vibrio fischeri, using Microtox® method.

The removal of radiocontrast agent diatrizoic acid (DIA) from water was performed using photo-Fenton (PF) process. First, the effect of H2O2 dosage on mineralization efficiency was determined using ultraviolet (UV) irradiation. The system reached a maximum mineralization degree of 60 % total organic carbon (TOC) removal at 4 h with 20 mM initial H2O2 concentration while further concentration values led to a decrease in TOC abatement efficiency. Then, the effect of different concentrations of Fenton's reagents was studied for homogeneous Fenton process. Obtained results revealed that 0.25 mM Fe(3+) and 20 mM H2O2 were the best conditions, achieving 80 % TOC removal efficiency at 4 h treatment. Furthermore, heterogeneous PF treatment was developed using iron-activated carbon as catalyst. It was demonstrated that this catalyst is a promising option, reaching 67 % of TOC removal within 4 h treatment without formation of iron leachate in the medium. In addition, two strategies of enhancement for process efficiency are proposed: coupling of PF with electro-Fenton (EF) process in two ways: photoelectro-Fenton (PEF) or PF followed by EF (PF-EF) treatments, achieving in both cases the complete mineralization of DIA solution within only 2 h. Finally, the Microtox tests revealed the formation of more toxic compounds than the initial DIA during PF process, while, it was possible to reach total mineralization by both proposed alternatives (PEF or PF-EF) and thus to remove the toxicity of DIA solution.

One of the bottlenecks often faced in environmental processes is focused on the design of efficient technologies. Thus, the hunt of suitable alternatives is a must to be tackled in order to improve the conventional methods. In this study the applicability of nickel foam as cathode in electro-Fenton's treatment of Poly R-478, a recalcitrant dye, was demonstrated. Linear sweep voltammetry and initial studies show the ability of nickel foam to increase the H2O2 generation during the electro-Fenton treatment, enhancing the removal yields achieved in comparison with other carbonaceous materials. Furthermore, complete mineralization of the pollutant was reached when using Boron Doped Diamond (BDD) as anode. A heterogeneous electro-Fenton process using iron loaded polyacrylamide hydrogels enhance the efficiency of the process with respect to homogeneous electro-Fenton and anodic oxidation technologies. Furthermore, the evaluation of the generated hydroxyl radicals confirms the obtained results. Finally, the reusability of the designed process was evaluated by decolorization of Poly R-478 in successive batches. SEM study of the nickel foam along the successive experiments confirms that no structure changes were detected. Summing up, nickel foam seems to be a suitable cathode material for the electro-Fenton treatment of recalcitrant compounds in continuous mode.

This study is focused on the selection of the best piping arrangement for a pilot scale annular channel reactor intended for the remediation of waters and wastewaters. Two annular channel reactors composed of a single UV lamp and distinct piping arrangements were considered: (i) a novel reactor with tangential inlet/outlet pipes – the FluHelik reactor, and (ii) a conventional Jets reactor. These two reactors were manufactured at lab scale and characterized in terms of residence time distribution (RTD), radiant power and ability to degrade aqueous solutions spiked with a model compound – 3-amino-5-methylisoxazole (AMI) – by H 2 O 2 /UVC and UVC processes. Computational fluid dynamics (CFD) simulations were used to assess the hydrodynamics, RTD and UV radiation intensity distribution of both reactors at pilot scale. In general, experimental results at lab scale revealed quite similar RTDs, radiant powers and AMI degradation rates for both reactors. On the other hand, CFD simulations at pilot scale revealed the generation of a helical motion of fluid around the UVC lamp in the FluHelik reactor, inducing: (i) a longer contact time between fluid particles and UV light, (ii) more intense dynamics of macromixing as a result of larger velocity gradients, turbulent intensities and dispersion of RTD values around the peak, and (iii) a more homogeneous UV radiation distribution. In addition, the design of the FluHelik reactor can favor the implementation of various reactors in series, promoting its application at industrial scale. The FluHelik reactor was chosen for scaling-up. A pre-pilot scale treatment unit containing this reactor was constructed and its feasibility was proven.

In this study, the removal of five imidazolium-based ionic liquids (ILs) from water was accomplished by a heterogeneous electro-Fenton treatment. Different ILs were selected in order to study the effect of the alkyl chain length and the nature of the anion. Initially, the effect of the catalyst (iron alginate beads) dosage and current were evaluated. The results showed that the optimum conditions were attained when operating with 4.27 g of catalyst and 0.3 A, achieving degradation yields and TOC reductions higher than 95% after 90 min and 80% after 480 min, respectively. Regarding the ILs with common cations, lower degradation rates were obtained for those with longer alkyl chains, thus 1-ethyl-3-methylimidazolium dicyanamide, exhibits faster degradation than 1-hexyl-3-methylimidazolium dicyanamide and 1-butyl-3-methylimidazolium dicyanamide. In addition, the influence of the counter anions on the oxidation rate of different ILs under an electro-Fenton treatment was demonstrated, following the order: methylsulfate > dicyanamide > acetate. The Microtox ecotoxicity tests of the initial and treated samples revealed that none of the three studied ILs with shorter alkyl chain lengths showed toxicity and only 1-hexyl-3-methylimidazolium dicyanamide and 1-butyl-3-methylimidazolium dicyanamide presented toxic levels, with EC50 values of 269.85 and 47.55 mg L−1, respectively. Nonetheless, after 480 min of heterogeneous electro-Fenton treatment at 0.3 A, the toxicity of both was completely reduced. Finally, to confirm the mineralization of these compounds, the identification of several reaction intermediates in the heterogeneous electro-Fenton treatment of three ILs was assayed and a plausible degradation pathway was proposed.

Society technological advances and environmental requirements claim for the development of highly effective, low cost and environmental friendly technologies able to degrade emerging organic pollutants widely used such as pharmaceuticals. The development of electrochemical advanced oxidation processes may increase the efficiency of the traditional treatments used on the remediation of polluted water. Therefore, this work has been devoted to the design of a cathode that permits to enhance the generation of hydroxyl radicals on the system. The best results were obtained when a cathode made with granular activated carbon and carbon fiber (SGAFC) was used. After determining the efficiency of this cathode on the decoloration of two model dyes, its application to the chloramphenicol antibiotic reduction was evaluated, obtaining near complete removal after 120 min. In addition, the treatment on successive batches and different continuous electrochemical cell configurations has emphasized the ability of this new cathode to be used on different water treatment facilities.

A new approach on heterogeneous electro-Fenton of winery wastewater was investigated. The high organic load and the dependence on the wine industry period makes necessary to find an appropriate treatment able to efficiently reduce the environmental risk of this waste. For this purpose, the electro-Fenton process was improved by searching different catalyst supports (manganese alginate gel beads (Mn-AB); iron alginate gel beads (Fe-AB) and iron loaded activated carbon (Fe-AC)) and evaluating the applied potential difference effect. Fe-AC attained a fast decolorization and high degradation results at 15 V. To further understand the main degradation mechanisms on this new catalyst, the contribution of the HO generated in solution and on the anode surface was analyzed. In addition, the positive effect of nickel foam on an extra input of H 2 O 2 production through the generation of O 2 − and its effect on the treatment were proved.

In this study, electrokinetic-Fenton treatment was used to remediate a soil polluted with PAHs and the pesticide pyrimethanil. Recently, this treatment has emerged as an interesting alternative to conventional soil treatments due to its peculiar advantages, namely the capability of treating fine and low-permeability materials, as well as that of achieving a high yield in the removals of salt content and inorganic and organic pollutants. In a standard electrokinetic-Fenton treatment, the maximum degradation of the pollutant load achieved was 67%, due to the precipitation of the metals near the cathode chamber that reduces the electro-osmotic flow of the system and thus the efficiency of the treatment. To overcome this problem, different complexing agents and pH control in the cathode chamber were evaluated to increase the electro-osmotic flux as well as to render easier the solubilization of the metal species present in the soil. Four complexing agents (ascorbic acid, citric acid, oxalic acid and ethylenediaminetetraacetic acid) in the Fenton-like treatment were evaluated. Results revealed the citric acid as the most suitable complexing agent. Thereby its efficiency was tested as pH controller by flushing it in the cathode chamber (pH 2 and 5). For the latter treatments, near total degradation was achieved after 27 d. Finally, phytotoxicity tests for polluted and treated samples were carried out. The high germination levels of the soil treated under enhanced conditions concluded that nearly complete restoration was achieved.

BACKGROUND Electro-Fenton technology has already demonstrated its ability to degrade organic pollutants. In this treatment hydroxyl radicals are formed due to the reaction of the iron catalyst along with in situ electrogenerated H2O2. However, one of the main limitations of this system is the iron released in the treated effluent. Therefore, retention of iron is required, and in this study, the use of a new cathode in which the iron is fixed on nickel foam is proposed as a solution to the electro-Fenton treatment in continuous processes. RESULTS The retention of iron was ensured by its fixation on nickel foam using chitosan, an eco-friendly polymer, as coating agent. Different chitosan coatings were tested to optimize the manufacturing process of the new cathode. It was concluded that the best electrode for the electro-Fenton treatment of different dyes (Poly R-478 and Lissamine Green B) was obtained using a half-coating electrode cover with iron–chitosan of medium molecular weight. Furthermore, its reusability was positively evaluated in successive cycles. Finally, a continuous treatment using a fluidized bed reactor was successfully performed for the treatment of dye Lissamine Green B. CONCLUSION Summarizing, this new cathode is a suitable alternative for the treatment of coloured wastewater by continuous electro-Fenton treatment. © 2014 Society of Chemical Industry

The design of microbial fuel cells (MFCs) should account for realistic conditions to have an MFC considered to be a reliable energy source. For this reason, this study focused on the design of a simple and economical cell, such as a benthonic microbial fuel cell (BMFC). Moreover, it was demonstrated that the stable energy generated in the best configuration of MFCs drives external advanced oxidation processes (electrochemical and electro-Fenton). Finally, a new hybrid cell (BMFC anode and electro-Fenton cathode) was designed to obtain a dual benefit: dye decolourisation and an increase in the produced energy.

BACKGROUND Electro-Fenton technology has demonstrated great potential for the degradation of recalcitrant organic contaminants in polluted wastewaters. In this technology, the decomposition of hydrogen peroxide is catalysed by the presence of iron, and powerful oxidants, hydroxyl radicals, are generated. However, there is concern over the reduction of iron released in the treated effluent. Therefore, retention of catalyst is required, and advances in electro-Fenton heterogeneous catalysis are necessary. In this study, the use of polyacrylamide hydrogel was evaluated as a support for the iron, and the performance of the catalyst (Fe-PH) developed was assayed in the electro-Fenton degradation of two dyes, Reactive Black 5 and Blue Sella Solid. RESULTS First, the synthesis of Fe-PH catalyst was studied. The results showed that the loaded hydrogel with a mixture of Fe(II) and Fe(III) in 1:2 molar ratio reached the highest decolourization efficiency. The performance of the optimized Fe-PH catalyst was evaluated in the decolourization of the selected dyes. These studies demonstrated the satisfactory performance of electro-Fenton using Fe-PH catalyst as well as its reusability. CONCLUSION In summary, the Fe-PH catalyst developed gives the promise of wastewater treatment by means of an electro-Fenton process. © 2014 Society of Chemical Industry

This article analyses three of the Sustainable Development Goals (SDGs) gathered by the 2030 Agenda and adopted by the United Nations, and how online educational models may help to reach these goals. Specifically, the three goals discussed through this article are: (i) Ensure inclusive and equitable quality education and promote lifelong learning opportunities for all (Goal 4), (ii) reduce inequality within and among countries (Goal 10), and (iii) take urgent action to combat climate change and its impacts (Goal 13). This work delves fundamentally into aspects related to online engineering education, such as the impact of the carbon footprint in online education, the reduction of geographical barriers and the social gap, and the complete online accessibility to the educational environment. Finally, this article presents the case of the International University of La Rioja with its 100% online methodology, and approximately 42,000 students distributed throughout the world. This institution is supported by tools that facilitate engineering training for people with reduced mobility and who are geographically dispersed, reducing the carbon footprint through remote training.

This article provides a deep analysis of the water quality at the upper basin of the Bogota River (Colombia) between 2008 and 2017. The Water Quality Index has been the indicator employed to determine the ecological status of the river. This index was chosen in order to normalize the analysis, given that it is commonly used by the Institute of Hydrology, Meteorology and Environmental Studies, a government agency of the Ministry of Environment and Sustainable Development of Colombia, to determine the state of surface effluents. The results obtained were organized in a double-entry matrix in order to relate the variables of the sample period and the sampling station. The research revealed an insufficient quality of water, demonstrating that the high stretch of the Bogota River basin has, in general, regular or acceptable water quality, while only five stations showed an acceptable status. Surprisingly, the stations located close to the wastewater treatment plants of the municipalities of Choconta, Suesca, Gachancipa, and Tocancipa, as well as Rio Negro, have a poor water quality, discharging a high load of contaminants into the river. Although great efforts have been made by Colombian authorities to restore the critical state of the majority of their aquatic ecosystems, recent implementation of policies and instruments have not shown significant achievements yet. For this reason, this study aims to present a powerful decision-tool for the monitoring and evaluation of correction measures implemented on this river basin. The data used in this research were provided by the Regional Autonomous Corporation of Cundinamarca.

The feasibility of the electrokinetic-Fenton technology coupled with surfactants in the treatment of real historically hydrocarbons polluted soils has been studied. The characterisation of these soils from Spain and Romania was performed and identified as diesel and diesel-motor oil spillages, respectively. Moreover, the ageing of the spillages produced by the soil contamination was estimated showing the historical pollution of the sites (around 11 and 20 years for Romanian and Spanish soils, respectively). An ex-situ electrochemical treatment was performed to evaluate the adequacy of surfactants for the degradation of the hydrocarbons present in the soils. It was found an enhancement in the solubilisation and removal of TPHs with percentages increasing from 25.7 to 81.8% by the presence of Tween 80 for Spanish soil and from 15.1% to 71.6% for Triton X100 in Romanian soil. Therefore, the viability of coupling enhanced electrokinetic and Fenton remediation was evaluated through a simulated in-situ treatment at laboratory scale. The results demonstrated that the addition of the selected surfactants improved the solubilisation of the hydrocarbons and influenced the electroosmotic flow with a slight decrease. The efficiency of the treatment increased for both considered soil samples and a significant degradation level of the hydrocarbons compounds was observed. Buffering of pH coupled with the addition of a complexing agent showed to be important in the treatment process, facilitating the conditions for the degradation reactions that take place into the soil matrix. The results demonstrated the effectiveness of the selected techniques for remediation of the investigated soils.