Sono- and photoelectrocatalytic processes for the removal of ionic liquids based on the 1-butyl-3-methylimidazolium cation

This Accepted Manuscript will be available for reuse under a CC BY-NC-ND license after 24 months of embargo periodIn this work, sono- and photoelectrolysis of synthetic wastewaters polluted with the ionic liquids 1-Butyl-3-methylimidazolium acetate (BmimAc)and chloride (BmimCl)were investigated with diamond anodes. The results were compared to those attained by enhancing bare electrolysis with irradiation by UV light or with the application of high-frequency ultrasound (US). Despite its complex heterocyclic structure, the Bmim+ cation was successfully depleted with the three technologies that were tested and was mainly transformed into four different organic intermediates, an inorganic nitrogen species and carbon dioxide. Regardless of the technology that was evaluated, removal of the heterocyclic ring is much less efficient (and much slower)than oxidation of the counter ion. In turn, the counter ion influences the rate of removal of the ionic liquid cation. Thus, the electrolysis and photoelectrolysis of BmimAc are much less efficient than sonoelectrolysis, but their differences become much less important in the case of BmimCl. In this later case, the most efficient technology is photoelectrolysis. This result is directly related to the generation of free radicals in the solution by irradiation of the electrochemical system with UV light, which contributes significantly to the removal of Bmim+The authors gratefully appreciate financial support from the Spanish MICINN (CTM2016-76197-R and CTM2016-76564-R, European Union (AEI/FEDER, UE) and Consejería de Educación of the CM (REMTAVARES S2013/MAE-2716). I. F. Mena wishes to thank the Spanish MINECO and the ESF for a research gran

Use of conductive diamond photo-electrochemical oxidation for the removal of pesticide glyphosate

In this work, the depletion of a commercial formulation of the pesticide glyphosate (RoundUp) using photolysis, electrolysis and photo-electrolysis with diamond anodes was studied. Results show that single photolysis is an inefficient technology for the removal of the pesticide; however, when coupled with electrolysis the removal yield significantly improves. The use of a combined process (photo-electrolysis) leads to the generation of higher concentrations of free radicals from the photo-activation of the oxidants electrogenerated. A major finding is that the supporting electrolyte plays a key role on the removal of glyphosate due to the generation of different oxidant species. Such species (peroxocarbonates, peroxosulfates and hypochlorite) also contribute to the depletion of the pesticide. Furthermore, the removal of glyphosate is clearly influenced by the current density because of the strong relationship between this parameter and the oxidants produced on the anode surface

Scaling up photoelectrocatalytic reactors: A TiO2 nanotube-coated disc compound reactor effectively degrades acetaminophen

Multiple discs coated with hierarchically-organized TiO2 anatase nanotubes served as photoelectrodes in a novel annular photoelectrocatalytic reactor. Electrochemical characterization showed light irradiation enhanced the current response due to photogeneration of charge carriers. The pharmaceutical acetaminophen was used as a representative water micropollutant. The photoelectrocatalysis pseudo-first-order rate constant for acetaminophen was seven orders of magnitude greater than electrocatalytic treatment. Compared against photocatalysis alone, our photoelectrocatalytic reactor at <8 V reduced by two fold, the electric energy per order (EEO; kWh m-3 order-1 for 90% pollutant degradation). Applying a cell potential higher than 8 V detrimentally increased EEO. Acetaminophen was degraded across a range of initial concentrations, but absorbance at higher concentration diminished photon transport, resulting in higher EEO. Extended photoelectrocatalytic reactor operation degraded acetaminophen, which was accompanied by 53% mineralization based upon total organic carbon measurements. This proof of concept for our photoelectrocatalytic reactor demonstrated a strategy to increase photo-active surface area in annular reactors

Disinfection of urine by conductive-diamond 1 electrochemical oxidation

This work focuses on the application of electrolysis with diamond anodes for the disinfection of urine. To do this, a synthetic human urine was polluted with Escherichia coli and Pseudomonas aeruginosa and then, it was electrolyzed at current densities within the range 0–100 A m−2. Results show that it is possible to disinfect completely the effluent even at applied electric charges lower than 2 kAh m−3, regardless the current density applied. This good performance is related to the production of powerful oxidants from the oxidation of the ions present in synthetic urine. Likewise, these species also react with the organics contained in urine (urea, creatinine and uric acid), favoring their degradation. The process efficiency for both microorganisms and organics is higher when working at low current densities. The removal of organics leads to the release of significant amounts of nitrogen in the form of nitrate which are later electroreduced to ammonium, that, in turn, reacts with the electrogenerated hypochlorite, favoring the production of chloramines (which can also contribute to the disinfection process). Regarding the mineralization, TOC removal higher than 90% can be achieved but higher applied electric charges than those required for disinfection have to be applied (around 30 kAh m−3)

Enhancement of UV disinfection of urine matrixes by electrochemical oxidation

This work focuses on the removal of antibiotic-resistant bacteria (ARB) contained in hospital urines by UV disinfection enhanced by electrochemical oxidation to overcome the limitations of both single processes in the disinfection of this type of effluents. UV disinfection, electrolysis, and photoelectrolysis of synthetic hospital urine intensified with K. pneumoniae were studied. The influence of the current density and the anode material was assessed on the disinfection performance of combined processes and the resulting synergies and/or antagonisms of coupling both technologies were also evaluated. Results show that the population of bacteria contained in hospital urine is only reduced by 3 orders of magnitude during UV disinfection. Electrolysis leads to complete disinfection of hospital urine when working at 50 A m−2 using Boron Doped Diamond (BDD) and Mixed Metal Oxides (MMO) as anodes. The coupling of electrolysis to the UV disinfection process leads to the highest disinfection rates, attaining a complete removal of ARB for all the current densities and anode materials tested. The use of MMO anodes leads to higher synergies than BDD electrodes. Results confirm that UV disinfection can be enhanced by electrolysis for the removal of ARB in urine, considering both technical and economic aspects

Environmental applications of electrochemical technology. What is needed to enable full-scale applications?

In recent years, thousands of scientific articles have considered the application of electrochemical technologies to remediate environmental problems ranging from the treatment of polluted soils to the removal of hazardous species from industrial liquid wastes. New research topics continue to emerge. Despite such research efforts, the technology readiness level (TRL) for many of those technologies remains very low; although most are considered promising, many are far from being introduced as efficient processes into the market. Important barriers need to be overcome to reach high TRLs. Some of these are scientific or technological and generate the opportunity for critical, applied research. Others are related to the lack of components in the value chain of the technology and generate opportunities for entrepreneurs to benefit from an improvement in the TRL. In this short review, a brief description of the current state of the most relevant technologies which are still in low TRL is carried out, highlighting barriers that must be removed to achieve full-scale applications in industry

The Role of the Anode Material in Selective Penicillin G Oxidation in Urine

In this work, the removal of antibiotic penicillin G by electrolysis with boron doped diamond (BDD) and mixed metal oxide (MMO) anodes in urine media is evaluated. First, electrolysis in different water matrices (sulfate, chloride and urine) were carried out with diamond anodes to shed light on the contribution of mediated mechanisms. Results showed that penicillin G was completely removed by electrolysis for electric charges below 5 Ahdm 3 , regardless of the water matrix and the current density applied (10-100 mAcm 2 ). Then, the influence of the anode material was evaluated for the degradation of penicillin G in urine media. A complete removal of the antibiotic was attained, regardless of the tested anode material, although the BDD anode was found to be more efficient than MMO. Results also showed that, at the current charges in which the antibiotic is depleted, the removal of other organics was much lower and the formation of chlorates was negligible, especially operating at low current densities. Because of this selective oxidation of the pharmaceutical compound, electrolysis can be proposed to be used as a pretreatment technology for later and cheaper biological treatment

Electrochemical Technologies to Decrease the Chemical Risk of Hospital Wastewater and Urine

The inefficiency of conventional biological processes to remove pharmaceutical compounds (PhCs) in wastewater is leading to their accumulation in aquatic environments. These compounds are characterized by high toxicity, high antibiotic activity and low biodegradability, and their presence is causing serious environmental risks. Because much of the PhCs consumed by humans are excreted in the urine, hospital effluents have been considered one of the main routes of entry of PhCs into the environment. In this work, a critical review of the technologies employed for the removal of PhCs in hospital wastewater was carried out. This review provides an overview of the current state of the developed technologies for decreasing the chemical risks associated with the presence of PhCs in hospital wastewater or urine in the last years, including conventional treatments (filtration, adsorption, or biological processes), advanced oxidation processes (AOPs) and electrochemical advanced oxidation processes (EAOPs).La ineficiencia de los procesos biológicos convencionales para eliminar los compuestos farmacéuticos (PhC) de las aguas residuales está provocando su acumulación en los medios acuáticos. Estos compuestos se caracterizan por una alta toxicidad, alta actividad antibiótica y baja biodegradabilidad, y su presencia está provocando graves riesgos ambientales. Debido a que gran parte de los PhC consumidos por los seres humanos se excretan en la orina, los efluentes hospitalarios se han considerado una de las principales vías de entrada de PhC al medio ambiente. En este trabajo se realizó una revisión crítica de las tecnologías empleadas para la remoción de PhCs en aguas residuales hospitalarias. Esta revisión proporciona una visión general del estado actual de las tecnologías desarrolladas para disminuir los riesgos químicos asociados con la presencia de PhC en las aguas residuales hospitalarias o en la orina en los últimos años

Removal of antibiotic resistant bacteria by electrolysis with diamond anodes: A pretreatment or a tertiary treatment?

In the present work, the influence of the water matrix on the removal of antibiotic resistant bacteria during the electro-disinfection with diamond anodes was studied, paying special attention to the disinfection efficiency and the prevention of the formation of hazardous disinfection by-products. This will allow to evaluate if electrolysis is more suitable as pretreatment of the main pollution source or as tertiary treatment of urban wastewater. To do this, electrolysis of synthetic wastewater rich in ammonium (simulating the effluent of an oxidation pond) and hospital urine intensified with three different bacteria (E. faecalis, K. pneumoniae, and E. coli) were carried out. Results show that the disinfection efficiency is higher in the synthetic wastewater for all the bacteria tested, but chlorate is formed as disinfection by-product. Electrogenerated hypochlorite and chloramines are the main responsible species for bacteria depletion. Presence of organics (urea, creatinine and uric acid) as additional ammonia precursors in hospital urine leads to the well-known breakpoint reaction with electrogenerated active chlorine, yielding an increasing concentration of chloramines. This helps to prevent the formation of chlorate in hospital urine because hypochlorite is mainly wasted in the oxidation of organics and the formation of chloramines. These results are of a great significance because they indicate that antibiotic resistant bacteria can be efficiently removed in complex matrixes without the formation of hazardous chlorine by-products if it is carried out as a pretreatment before discharge to WWTP

Depletion of ARGs in antibiotic-resistance Klebsiella, Pseudomonas and Staphylococcus in hospital urines by electro and photo-electro disinfection

The depletion of blaKPC (K. pneumoniae), blaOXA-50 (P. aeruginosa) and mecA (S. aureus) genes from hospital urines is evaluated to contribute to solve the silent pandemic of antibiotic-resistance bacteria. A microfluidic flowthrough reactor with MMO anode and CB/PTFE cathode working at 50 A m− 2 is employed during electrodisinfection and photo-electrodisinfection processes. The electrodisinfection process only achieves an almost negligible removal of DNA and slightly log ARG increments of 0.18, 0.19 and 0.71 for blaOXA-50, mecA and blaKPC genes, respectively. Conversely, the photo-electrodisinfection process attains the complete disinfection for all ARB tested and logarithmic removals of 3.70, 2.25 and 0.82 for blaOXA-50, mecA and blaKPC genes, respectively. These outcomes emphasize the potential of the UV light coupled to the electrodisinfection process to promote the formation of not only hypochlorite but also chlorine and even nitrogen radicals, which contribute to enhance the disinfection efficiency of the target ARB and their ARGs