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

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

In 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+

Influence of the supporting electrolyte on the removal of ionic liquids by electrolysis with diamond anodes

In this work, it is studied the electrolysis with diamond anodes of three different ionic liquids (ILs): 1-butyl-3-methylimidazolium chloride (BmimCl), 1-hexyl-3-methylimidazolium chloride (HmimCl) and 1-decyl-3-methylimidazolium chloride (DmimCl), which differ only in the length of the aliphatic carbon chain attached to the imidazolium group. In addition, the effect of the presence of sulfate in the electrolyte is also evaluated. Results confirmed that this type of ILs can be completely transformed into carbon dioxide, nitrates, ammonium (the imidazolium cation) and perchlorate and chloramines (the chloride anion) during the electrolysis of the synthetic waste containing sulfate. The electrolysis of wastes without sulfate anions leads to a much less efficient process, with the same final products in the case of the BminCl and HminCl ILs and with the formation of a polymer as the main final product in the case of the DmimCl. These results are of a paramount significance from a mechanistic point of view since, because of the high conductivity of the ILs, there is not a necessity of salt addition and they inform about the pure removal of these compounds by electrolysis with BDD, pointing out the important influence of peroxodisulfate on the electrolyses with diamond of organic wastes

Full-Scale Digesters: Model Predictive Control with Online Kinetic Parameter Identification Strategy

This work presents a nonlinear model predictive control scheme with a novel structure of observers aiming to create a methodology that allows feasible implementations in industrial anaerobic reactors. In this way, a new step-by-step procedure scheme has been proposed and tested by solving two specific drawbacks reported in the literature responsible for the inefficiencies of those systems in real environments. Firstly, the implementation of control structures based on modeling depends on microorganisms’ concentration measurements; the technology that achieves this is not cost-effective nor viable. Secondly, the reaction rates cannot be considered static because, in the extended anaerobic digestion model (EAM2), the large fluctuation of parameters is unavoidable. To face these two drawbacks, the concentration of acidogens and methanogens, and the values of the two reaction rates considered have been estimated by a structure of two observers using data collected by sensors. After 90 days of operation, the error in convergence was lower than 5% for both observers. Four model predictive controller (MPC) configurations are used to test all the previous information trying to maximize the volume of methane and demonstrate a satisfactory operation in a wide range of scenarios. The results demonstrate an increase in efficiency, ranging from 17.4% to 24.4%, using as a reference an open loop configuration. Finally, the operational robustness of the MPC is compared with simulations performed by traditional alternatives used in industry, the proportional-integral-derivative (PID) controllers, where some simple operational scenarios to manage for an MPC are longer sufficient to disrupt a normal operation in a PID controller. For this controller, the simulation shows an error close to the 100% of the reference valu

Full-scale digesters: an online model parameter identification strategy

This work presents a new standard in the model, identification, and control of monitoring purposes over anaerobic reactors. One requirement that guarantees a normal controller operation is for the faculty to measure the data needed periodically. Due to its inability to easily obtain the concentrations of acidogenic bacteria and methanogenic archaea periodically using reliable and commercial sensors, this paper presents an algorithm composed of an asymptotic observer (considering the reaction rates are unknown), aiming to estimate these concentrations. This method represents a significant advantage because it is possible to perform a resource-saving strategy using standard measurements, such as pH or alkalinity, to calculate them analytically in natural environments. Additionally, two yield parameters were included in the original anaerobic model two (AM2) to unlock implementations for a wide range of organic substrates. The static parameter identification was improved using a new method called step-ahead optimization. It demonstrates significant improvements fitting the mathematical model to data until a (Formula presented.) increase in efficiency (compared with the traditional optimization method genetic algorithm). After the period of convergence, the state observer evidences a small error with a maximum (Formula presented.) deviation. Finally, numerical simulations demonstrate the structure’s strengths, which constitutes a significant step in paving the way further to implement feasible, cost-effective controls and monitoring systems in the industr

Critical review of technologies for the on-site treatment of hospital wastewater: From conventional to combined advanced processes

In this work, a raw and low cost mineral, ilmenite (FeTiO3), has been tested for the first time as a photocatalyst paired with peroxymonosulfate (HSO5-; PMS) for the inactivation of Enterococcus faecalis as an alternative to conventional treatments to disinfect wastewater for reuse. The influence of some operational parameters such as reagent dosage, catalyst concentration, initial pH, or flow rate was also studied and optimized. After several tests, the scarce pure photoactivity under UV-A was remarked by ilmenite because of its high iron content, which favors photogenerated charge recombination. However, ilmenite activity was highly promoted when combined with low concentrations of PMS and UV-A light, reaching total inactivation of Enterococcus faecalis in 120 min. Quenching tests were performed using methanol, tert-butyl alcohol, furfuryl alcohol, and Cu(II) to assess the main reactive species involved in the disinfection process determining the critical role of both HO·and SO4·- radicals in the process. Finally, the influence of the water matrix was also evaluated by studying the effect of water hardness and the presence of nutrients on the system. Overall, the PMS/Ilmenite/UV-A system yielded promising results with a total removal of Enterococcus faecalis in 120 min. However, it also showed the need for further study and understanding of the disinfection mechanism to achieve the same level of performance in real wastewaterThe "Comunidad de Madrid" supported this research through REMTAVARES S2013/MAE-2716 and S2018/EMT-434

Evaluación de la planta Lemna Minor como biorremediadora de aguas contaminadas con mercurio

The catalytic hydrodechlorination of 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol in aqueous phase with a Pd/Al2O3 commercial catalyst (0.5 % w/w) under mild reaction conditions (30 ºC, 1 bar) was studied. The conversion of the reagents was completed in a short reaction time. From the analysis of the evolution of the concentration opposite to the time of each one of the reactants, intermediates and products of reaction, a parallel series scheme of reaction was established for each of the reactions of hydrodechlorination. A first order kinetic model was developed according to initial chlorophenol concentration that was validated by means of the suitable adjustment of the experimental results. The position of the atoms of chlorine in the organic molecule and the number of them influenced significantly not only in the reactivity of the chlorophenols tested but in the speed of dechlorination as well. So, the speed of dechlorination followed the next order: 4-chlorophenol > 2- chlorophenol > 2,4-dichlorophenol.En este trabajo se estudió la hidrodecloración catalítica de 2-clorofenol, 4-clorofenol y 2,4-diclorofenol en fase acuosa empleando un catalizador comercial de Pd/Al2O3 (0,5 % w/w), en condiciones suaves de operación (30ºC, 1 bar). La conversión de los reactivos resultó completa en tiempos cortos de reacción. Analizando la evolución de la concentración frente al tiempo de cada uno de los reactivos, intermedios y productos de reacción, se estableció un esquema de reacción serie-paralelo para cada una de las reacciones de hidrodecloración. Se desarrollo un modelo cinético de primer orden respecto al clorofenol de partida que se validó mediante el adecuado ajuste de los resultados experimentales. La posición de los átomos de cloro en la molécula orgánica y el número de los mismos influyeron significativamente tanto en la reactividad de los clorofenoles ensayados como en la velocidad de decloración. Así, la velocidad de decloración siguió el siguiente orden: 4-clorofenol > 2-clorofenol > 2,4-diclorofenol

Anaerobic Co-digestion of the Organic Fraction of Municipal Solid Waste and the Liquid Fraction From the Hydrothermal Carbonization of Industrial Sewage Sludge Under Thermophilic Conditions

7 Páginas.-- 3 Tablas.-- 2 FigurasThe anaerobic thermophilic co-digestion of mixtures of the organic fraction of municipal solid waste (OFMSW) and the liquid fraction from the hydrothermal carbonization (LFHTC) of dewatered secondary sludge was studied. Mixtures with a low OFMSW to LFHTC ratio (50, 75, and 100% LFHTC) exhibited accumulation of volatile fatty acids (VFA) as well as low degradation of organic matter and methane production. However, the mixture containing 25% LFHTC performed quite well in terms of methane production: (179 ± 3) mL CH STP g COD, which was only slightly lower than the value obtained with 100% OFMSW. The experimental results fitted the modified Gompertz model reasonably well and the maximum methane production rate for the mixture containing 25% LFHTC (11.96 mL CH g COD d) was 29.3% higher than that obtained with the substrate with 100% OFMSW. Therefore, centralized co-digestion of OFMSW in mixtures with 25% LFHTC seemingly provides an effective method for valorizing the latter substrate.The authors wish to express their gratitude to Spain's MINECO (CTM2016-76564-R) and UAM-Santander (Project CEAL-AL/2015-29) for funding this work. AR acknowledges additional funding from the Spanish Ministry of Economy and Competitiveness (RYC-2013-12549). The valuable contribution of A. Eguiluz is also acknowledged

Sequential degradation of organochlorinated herbicides by catalytic hydrodechlorination and photocatalysis

Trabajo presentado en el 3rd Latin-American Congress of Photocatalysis, Photochemistry and Photobiology, celebrado en San Luis Potosí (México) del 14 al 17 de octubre de 2014.In the last decade, there has been growing interest in development strategies more efficient to treat wastewater with organochlorinated compounds. The use of sequential or simultaneous hybrid configurations can improve both their detoxification and their final mineralization. One promising strategy is to couple an advanced catalytic process, as hydrodechlorination (HDC), with an advanced oxidation process, as heterogeneous photocatalysis. HDC undertakes an essential detoxification by means of transformation of organochlorinated compounds into their dechlorinated species, while photocatalysis can lead to complete mineralization to CO2 and H2O [2]. In this work, the combination of HDC and photocatalysis as an attractive sequential process to the degradation of chlorinated herbicides widely used in agriculture (MCPA, 2,4-D), has been evaluated. Both reactions were carried out in ambient conditions, using Pd/Al2O3 and P25 as catalysts, respectively. Ecotoxicity of the starting compounds and the reaction samples was determined by the Microtox Toxicity Test. Upon HDC, both chlorinated herbicides were completely degraded at 45 min reaction time, achieving an important decrease of the effluent ecotoxicity. However, upon photocatalysis, the original herbicides reached higher photodegradation rates, with more than 80 % of TOC removal, than the corresponding HDC effluent. Taking into account that the photo-efficiency of titania based-catalysts are usually related to a complex balance between their surface, textural, structural, morphological and electronic properties, the obtained results seem to indicate that the charge and the acidic/basic character of TiO2 surface is playing an important role on the final photodegradation of chlorinated herbicides at the acid pH values studied here.Wish to thank the Spanish MICINN and Comunidad de Madrid for their financial support for the projects CTQ 2010-14807, CTM 2010-14883 and S-2009/AMB-1588, respectively.Peer Reviewe

Mesophilic anaerobic co-digestion of the organic fraction of municipal solid waste with the liquid fraction from hydrothermal carbonization of sewage sludge

32 Páginas.-- 3 Tablas.-- 3 FigurasIn the present study, the influence of substrate pre-treatment (grinding and sieving) on batch anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) was first assessed, then followed by co-digestion experiments with the liquid fraction from hydrothermal carbonization (LFHTC) of dewatered sewage sludge (DSS). The methane yield of batch anaerobic digestion after grinding and sieving (20 mm diameter) the OFMSW was considerably higher (453 mL CH4 STP g−1 VSadded) than that of untreated OFMSW (285 mL CH4 STP g−1 VSadded). The modified Gompertz model adequately predicted process performance. The maximum methane production rate, Rm, for ground and sieved OFMSW was 2.4 times higher than that of untreated OFMSW. The anaerobic co-digestion of different mixtures of OFMSW and LFHTC of DSS did not increase the methane yield above that of the anaerobic digestion of OFMSW alone, and no synergistic effects were observed. However, the co-digestion of both wastes at a ratio of 75% OFMSW-25% LFHTC provides a practical waste management option. The experimental results were adequately fitted to a first-order kinetic model showing a kinetic constant virtually independent of the percentage of LFHTC (0.52–0.56 d−1) and decreasing slightly for 100% LFHTC (0.44 d−1).The authors wish to express their gratitude to the Spanish MINECO (CTM2016-76564-R) for providing financial support. M.A. de la Rubia received financial support from the Spanish Ministry of Economy and Competitiveness (RYC-2013-12549). The authors are grateful to A.G. Jouve for her involvement in this research.Peer reviewe