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This study presents a critical review on the application of magnetite-based catalysts to industrial wastewater decontamination by heterogeneous Fenton oxidation. The use of magnetic materials in this field started only around 2008 and continues growing increasingly year by year. The potential of these materials derives from their higher ability for degradation of recalcitrant pollutants compared to the conventional iron-supported catalysts due to the presence of both Fe(II) and Fe(III) species. In addition, their magnetic properties allow their easy, fast and inexpensive separation from the reaction medium. The magnetic materials applied up to now can be classified in three general groups: magnetic natural minerals, in-situ -produced magnetic materials and ferromagnetic nanoparticles. A survey of the catalysts investigated so far is presented paying attention to their nature and competitive features in terms of activity and durability. [ABSTRACT FROM AUTHOR]

The activity of monometallic (Pd or Rh) and bimetallic (iron-bearing) catalysts has been tested in the HDC of 4-chlorophenol (4-CP) in aqueous phase. The catalysts were prepared by a simple procedure consisting of incipient wetness impregnation followed by calcination and reduction at different temperatures. This allowed controlling the size, dispersion and oxidation state of the metallic nanoparticles. Increasing the temperature of calcination led to a higher dispersion of the active phase (from 21 to 46% by increasing the calcination temperature from 200 to 400 °C) and a higher ratio of zerovalent to electrodefficient palladium (M 0 /M n + values from 1.15 to 2.17) in the case of the Pd-catalysts. Those calcined in air at 400 °C and reduced with H 2 at 350 °C yielded the highest values of the pseudo-first-order rate constant of 4-CP dechlorination (16.2 L h −1 g cat −1 ). The introduction of iron reduced the metal dispersion of both Pd and Rh but the catalysts maintained their dechlorination activity and showed magnetic properties useful for further separation from the liquid phase. [ABSTRACT FROM AUTHOR]

Highlights: [•] The two-step reaction (HDC–CWPO) represents an efficient solution for chlorophenols breakdown. [•] A short-time HDC step before CWPO improves the rate of mineralization. [•] Complete dechlorination of chlorophenols and a high mineralization (80%) was reached. [•] The effluents obtained upon HDC–CWPO process presented negligible ecotoxicity values (<0.5TU). [•] Both HDC (Pd/γ-Al2O3) and CWPO (Fe/γ-Al2O3) catalysts showed a highly stable performance. [Copyright &y& Elsevier]

Highlights: [•] CWPO of chlorophenols with Fe x O y /γ-Al2O3 catalysts is more efficient than Fenton oxidation. [•] Increasing the temperature improves both the oxidation rate and mineralization degree. [•] The Fe x O y /γ-Al2O3 catalysts are highly active and stable upon CWPO of chlorophenols. [•] CWPO (Fe3O4/γ-Al2O3) at high temperature is the preferable strategy for chlorophenols oxidation. [•] Fe3O4/γ-Al2O3 catalyst can be easily recovered from the liquid phase by a magnet. [Copyright &y& Elsevier]

Abstract: A ferromagnetic γ-Al2O3-supported iron catalyst has been prepared and its activity and stability in catalytic wet peroxide oxidation (CWPO) have been compared with those of a previous iron-based conventional catalyst using the same support. Both catalysts were characterized by nitrogen adsorption–desorption isotherms, ICP, TXRF, XRD, XPS, elemental analysis and Mössbauer spectroscopy. The behavior of these catalysts in CWPO of chlorophenols has been related with the nature of the dominant iron species (magnetite or hematite). The results showed that the magnetic catalyst improved significantly the decomposition of H2O2 leading to an increased degradation and mineralization of chlorophenols. Complete conversion of those target pollutants and more than 75% TOC reduction were achieved after 4h under stoichiometric H2O2 dose, 100mgL−1 initial chlorophenol concentration, 1gL−1 catalyst, pH 3 and 50°C temperature. Moreover, complete dechlorination of all the chlorophenols tested was achieved, being the residual organic by-products short-chain acids without significance in terms of ecotoxicity. The catalyst showed a remarkable stability in long-term continuous experiments with limited Fe leaching, below 5% of the initial loading after 100h on stream. An additional clear advantage of the new catalyst is its easy separation and recovery from the reaction medium by applying an external magnetic field. [Copyright &y& Elsevier]

Abstract: Degradation of chlorophenols by a sequential combination of hydrodechlorination (HDC) and catalytic wet peroxide oxidation (CWPO) using a new magnetic Pd–Fe/γ-Al2O3 catalyst has been studied. This catalyst is active in both hydrodechlorination of chlorophenols and decomposition of H2O2 for the oxidation of organic compounds. The sequential combination of HDC and CWPO allows overcoming some of the drawbacks of both treatments applied independently. The HDC step achieves the complete dechlorination of chlorophenols, so that the subsequent CWPO does not lead to the formation of highly toxic chlorinated by-products and reduces significantly the organic load of the effluent. The results showed that the presence of iron in the Pd catalyst improved significantly its hydrodechlorination rate, achieving the complete dechlorination of chlorophenols in a short reaction time (≈15 min), giving rise to phenol and cyclohexanone. The CWPO of synthetic mixtures of phenol and cyclohexanone showed that a high phenol concentration promotes the oxidation of all the organic species, but the presence of cyclohexanone seems to hinder the formation of aromatic radicals limiting the effectiveness of the CWPO step. Therefore, the effective combination of HDC and CWPO requires that the HDC step achieves the complete dechlorination of chlorophenols but no further hydrogenation is needed. The Pd–Fe/γ-Al2O3 catalyst showed a high activity in both HDC and subsequent CWPO of chlorophenols being easily separated and recovered from the reaction medium due to its ferromagnetic properties. In spite of a moderate loss of activity, the complete dechlorination of chlorophenol and a negligible ecotoxicity of the final effluents were maintained upon successive applications of HDC + CWPO in a four-cycles test. [Copyright &y& Elsevier]

Abstract: Fenton-like oxidation has proved to be highly efficient for the removal of triclosan, a highly toxic emerging water pollutant. From 10mg/L starting aqueous solutions complete conversion of triclosan was achieved in less than 1h at 25°C and around 20min at 50°C with 1mg/L Fe3+ and H2O2 at the theoretical stoichiometric amount (25mg/L). From the evolution of byproducts a reaction pathway has been proposed according to which oxidation of triclosan gives rise to several aromatic intermediates (mainly, p-hydroquinone of triclosan and 2,4-dichlorophenol) which evolve to short-chain organic acids. These compounds are mineralized except oxalic acid. A dramatic decrease of ecotoxicity was achieved in a relatively short time (more than 95% in 15min at 35°C). The evolution of ecotoxicity is intimately related to the disappearance of triclosan, much more toxic than the aromatic oxidation intermediates. This disappearance was successfully described by a simple pseudo-first order rate equation with an apparent activation energy value close to 27kJ/mol. The apparent rate constant at 25°C was several orders of magnitude higher than the reported in the literature for other chlorophenolic compounds indicating a higher susceptibility of triclosan to OH radical attack. [Copyright &y& Elsevier]

Abstract: Homogeneous Fenton-like (H2O2/Fe3+) oxidation proved to be highly efficient in the degradation of monochlorophenols but some important issues need to be considered depending on the operating conditions. When using the stoichiometric amount of H2O2 and a dose of Fe3+ in the range of 10–20mg/L, complete breakdown of 4-CP up to CO2 and short-chain acids was achieved. Nevertheless, when substoichiometric amounts of H2O2 or lower concentrations of iron were used, significant differences between the TOC measured and the calculated from the identified species were found. These differences were attributed to condensation byproducts, including chlorinated species, formed by oxidative coupling reactions. PCBs, dioxins and dichlorodiphenyl ethers were identified. A solid residue was also formed consisting mainly in carbon, oxygen and chlorine including also Fe. The occurrence of these highly toxic species must be carefully considered in the application of Fenton oxidation to wastewaters containing chlorophenols. The possibility of reducing costs by lowering the H2O2 dose below the stoichiometric one needs to tke this into account. [Copyright &y& Elsevier]

Abstract: Hydrodechlorination of 4-chlorophenol using Pd/A2O3 as catalyst at mild conditions (30°C, 1atm) was carried out in plain water, buffered (CH3COOH/NaCH3COO, NaH2PO4/Na2HPO4 and NaHCO3/Na2CO3) and alkaline NaOH media at different pH. The highest reaction rate was achieved when the process was carried out at alkaline NaOH solution of pH=8.5. Continuous long term experiments (τ: 5.4kgcat h/mol) were performed in plain water and alkaline medium using Pd/Al2O3 and Pd/AC as catalysts. The former showed an appreciable loss of activity upon time on stream, which was associated with the formation of palladium chloride complexes. However, a residual activity remained practically stable, reaching very similar 4-chlorophenol conversion (36%) in both reaction media. The Pd/AC catalyst maintained a constant activity at a 70% 4-chlorophenol conversion once the steady state was reached. This suggests that the AC supported catalyst is less susceptible to the chloride poisoning produced during the reaction. [Copyright &y& Elsevier]

Abstract: The kinetics of gas-phase hydrodechlorination (HDC) of dichloromethane (DCM) with a Pd on activated carbon commercial catalyst has been studied in a fixed bed reactor within the 200–350°C temperature range. Different kinetic equations have been checked for describing the evolution of DCM. Statistical and physical reliable parameters were found for a Langmuir–Hinshelwood type expression with DCM adsorption as the controlling step. The reaction pathway and the kinetic model have been elucidated from the evolution of dichloromethane and the identified reaction products (methane, monochloromethane, ethane and ethylene). Adsorbed CH2Cl* radical, CH2 ** and C2H4 ** carbene species are proposed as the three intermediates evolving to the final reaction products. An apparent activation energy of 23.9±2.3kJmol−1 has been obtained for dichloromethane disappearance. [Copyright &y& Elsevier]

Abstract: We have examined the catalytic action of 1mol% Au/TiO2 and Ag/TiO2 in the continuous gas phase hydrogenation of a series of para-substituted (–H, –OH, –OCH3, –CH3, –Cl and –NO2) nitroarenes. Both catalysts promoted exclusive –NO2 group reduction, resulting in the sole formation of the corresponding amino-compound. The catalysts have been characterized in terms of temperature-programmed reduction (TPR), H2 chemisorption, BET area, diffuse reflectance UV–vis, X-ray diffraction and HRTEM measurements. The formation of zero valent Au and Ag is established post-TPR. Au/TiO2 showed a narrower metal particle size (1–10nm) distribution than Ag/TiO2 (1–15nm) but both catalysts exhibited a similar surface area weighted mean size (6–7nm). A time-invariant nitroarene conversion has been established where Au/TiO2 delivered higher specific hydrogenation rates. We associate this response to an enhanced reactant activation on Au/TiO2 to generate a negatively charged intermediate, consistent with a nucleophilic mechanism. The presence of electron-withdrawing substituents is shown to enhance –NO2 reduction rate. This effect is quantified in terms of the Hammett relationship where a linear correlation between the substituent constant (σ i ) and rate is established and a higher reaction constant (ρ) was recorded for Au/TiO2 (0.93) relative to Ag/TiO2 (0.22). The data generated provide the first direct comparison of the catalytic action of supported Au and Ag in the hydrogenation of substituted nitroarenes and establish the viability of both catalysts to promote selective –NO2 group reduction. [Copyright &y& Elsevier]

Abstract Aqueous-phase catalytic hydrodechlorination (HDC) has been scarcely explored in the literature for the removal of chlorinated micropollutants. The aim of this work is to prove the feasibility of this technology for the fast and environmentally-friendly degradation of such kind of compounds. Diclofenac (DCF), a highly consumed anti-inflammatory drug, has been selected as the target pollutant given its toxicity and low biodegradability. The commercial Pd/Al 2 O 3 (1% wt.) catalyst has been used due to its prominent role on this field. Complete degradation of DCF was achieved in a short reaction time (20 min) under ambient conditions (25 °C, 1 atm) at [DCF] 0 = 68 μM; [Pd/Al 2 O 3 ] 0 = 0.5 g L−1 and H 2 flow rate of 50 N mL min−1. Remarkably, the chlorinated intermediate (2-(2-chloroanilino)-phenylacetate (Cl-APA)) generated along reaction was completely removed at the same time, being the chlorine-free compound 2-anilinophenylacetate (APA) the only final product. A reaction scheme based on this consecutive pathway and a pseudo-first-order kinetic model have been proposed. An apparent activation energy of 43 kJ mol−1 was obtained, a comparable value to those previously reported for conventional organochlorinated pollutants. Remarkably, the catalyst exhibited a reasonable stability upon three successive uses, achieving the complete degradation of the drug and obtaining APA as the final product in 30 min. The evolution of ecotoxicity was intimately related to the disappearance of the chlorinated organic compounds and thus, the final HDC effluents were non-toxic. The versatility of the system was finally demonstrated in different environmentally-relevant matrices (wastewater treatment plant effluent and surface water). Graphical abstract Image 1 Highlights • HDC is a fast and environmentally-friendly technology for the removal of diclofenac. • The commercial Pd/Al 2 O 3 catalyst showed a high activity and a reasonable stability. • A kinetic model based on a consecutive reaction pathway fitted the experimental data. • Non-toxic effluents were achieved at the end of reaction. • The versatility of the system was proved in environmentally-relevant water matrices. [ABSTRACT FROM AUTHOR]

The removal of micropollutants in wastewater treatment plants (WTTPs) is a challenging issue which requires the development of effective but also green and low-cost strategies. In this work, we explore the capability of naturally-occurring magnetite combined with H 2 O 2 for the degradation of the highly persistent antibiotic sulfamethoxazole (SMX). A complete operating condition study has been performed to evaluate the effect of initial pH (3–7), temperature (15–50 °C), magnetite concentration (0.5–2 g L −1 ) and H 2 O 2 dose (12.5–100 mg L −1 ), using an initial SMX amount of 5 mg L −1 . Remarkably, complete removal of the target pollutant and the aromatic intermediates was achieved operating under ambient-like conditions (25 °C) and circumneutral pH (pH 0 = 5) using the stoichiometric dose of H 2 O 2 (25 mg L −1 ) and a catalyst load of 1 g L −1 . The mineralization yield was above 50%, being the final oxidation products short-chain organic acids. The oxidation pathway of SMX was accordingly proposed. The stability of magnetite was confirmed upon three sequential runs, where a similar catalytic activity and negligible iron leaching (<0.15% wt) were observed. As a proof of concept, the performance of the catalytic system was also evaluated in different real aqueous matrices, such as WWTP effluent, surface water and hospital wastewater. Although the catalyst did not show any sign of deactivation, partial inhibition of the oxidation reaction was observed due to scavenging effects. [ABSTRACT FROM AUTHOR]

CWPO has proved to be effective for the treatment of representative pharmaceuticals (sulfamethoxazole, atenolol, metronidazole, diltiazem, trimethoprim and ranitidine) in different water matrices (ultrapure water, surface water, WWTP effluent and hospital wastewater). Complete removal of the pollutants and the aromatic intermediates was achieved using the stoichiometric dose of H 2 O 2 , a catalyst (Fe 3 O 4 /γ-Al 2 O 3 ) load of 2 g L −1 , pH 3 and temperature of 50–75 °C. Accordingly, the ecotoxicity was reduced to negligible values. The degradation was faster when the pharmaceuticals were together, being the reaction time for the elimination of the most refractory species (metronidazole) shortened from 4 h to 1 h. The mineralization of the drugs was fairly different, being the most reactive species those containing several aromatic rings ( X TOC ∼ 80%) and the most refractory that bearing an imidazolium ring ( X TOC ∼ 35%). The water matrix affected the kinetics of the process but in all cases complete conversion of the drugs was reached within 1 h. The presence of dissolved organic matter (surface water) seemed to promote drugs degradation while the occurrence of inorganic ions (real WTTP and hospital effluents) partially inhibited it due to scavenging effects. Remarkably, the process was successfully operated at the typical concentrations of main micropollutant sources (μg L −1 ). [ABSTRACT FROM AUTHOR]

This work explores the potential application of naturally-occurring minerals as inexpensive catalysts in heterogeneous Fenton, namely catalytic wet peroxide oxidation (CWPO). The availability, low cost and environmentally friendly character of those materials make them interesting candidates for such application. The performance of magnetite, hematite and ilmenite as CWPO catalysts has been tested under different working conditions, which include temperature (25–90 °C), H 2 O 2 dose (250–1000 mg L −1 ) and catalyst concentration (1–4 g L −1 ). The operating temperature plays a key role on the rate of H 2 O 2 decomposition so that with magnetite H 2 O 2 conversion after 4 h increased from 8 to 99% by increasing the temperature from 25 to 90 °C. Based on the reaction mechanism proposed, a kinetic model was developed which successfully described the experimental results on H 2 O 2 decomposition. The catalytic performance of the minerals tested at temperatures above the ambient was demonstrated using phenol (100 mg L −1 ) as target pollutant. Unprecedented efficiencies of H 2 O 2 consumption, higher than 80% were achieved, allowing high oxidation and mineralization, i.e. complete phenol conversion and almost 80% TOC reduction at 75 °C with a catalyst loading of 2 g L −1 and the theoretical stoichiometric amount of H 2 O 2 for complete mineralization of phenol (500 mg L −1 ). Magnetite is particularly attractive, since it showed the highest activity and can be easily separated from the liquid phase given its magnetic properties. All the minerals tested suffered low iron leaching and magnetite and hematite showed a good reusability upon three consecutive runs. However, in this case long-term durability is not a crucial issue, given the availability and low cost of these minerals. [ABSTRACT FROM AUTHOR]

The production and application of ionic liquids (ILs) is often associated with the formation of aqueous effluents. Due to the well-known toxicity and poor biodegradability of those compounds, effective treatments for their removal from aqueous solutions are required. In this work, the Fenton oxidation methodology under optimum operating conditions (50 mg L −1 Fe 3+ , stoichiometric dose of H 2 O 2 , 70 °C and pH 0 = 3) was investigated in eleven different ILs, based in the imidazolium, phosphonium, quaternary ammonium, pyridinium and cholinium families, conjugated with various inorganic and organic anions such as chloride, cyanoborate, cyanamide, thiocyanate, dimethylphosphate and tosylate. The efficacy of the process was evaluated by the analysis of the chemical oxygen demand (COD), total organic carbon (TOC), the acids formed by ILs oxidation and the toxicity of the non-treated and treated aqueous effluents towards the Vibrio fischeri bacteria. It was possible to identify the main compounds produced upon Fenton oxidation in the final aqueous effluents (acetic, oxalic and formic acids) and the results seem to suggest that the Fenton oxidation is a good degradation methodology for most of the ILs tested, achieving TOC conversions in the range of 40–80% and 30–40% for aromatic and aliphatic ILs, respectively. Furthermore, non-toxic effluents were obtained at the end of the treatment for all the ILs investigated with the exception of the cyano-based ones due to the release of highly toxic cyanide species to the aqueous medium. [ABSTRACT FROM AUTHOR]

Fenton oxidation has proved to be an efficient treatment for the degradation of ionic liquids (ILs) of different families viz. imidazolium, pyridinium, ammonium and phosphonium, in water. The intensification of the process, defined as the improvement on the efficiency of H 2 O 2 consumption, by increasing the temperature is necessary to avoid high reaction times and the need of large excess of H 2 O 2 . In this work, temperatures within the range of 70–90 °C have been used, which allowed an effective breakdown of the ILs tested (1 g L −1 initial concentration) with the stoichiometric amount of H 2 O 2 and a relatively low Fe 3+ dose (50 mg L −1 ). Under these conditions conversion of the ILs was achieved in less than 10 min, with TOC reductions higher than 60% upon 4 h reaction time, except for the phosphonium IL. The remaining TOC corresponded mainly to short-chain organic acids. The treatment reduced substantially the ecotoxicity up to final values below 0.01 TU in most cases and a significant improvement of the biodegradability was achieved. Upon Fenton oxidation of the four ILs tested hydroxylated compounds of higher molecular weight than the starting ILs, fragments of ILs partially oxidized and short-chain organic acids were identified as reaction by-products. Reaction pathways are proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] The intensified Fenton process represents a cost-effective alternative for sawmill wastewater treatment. [•] Increasing temperature to 120°C and feeding H2O2 in 3 additions improved the H2O2 consumption efficiency. [•] High COD (≈80%) and TOC (≈70%) removal were achieved after 1h reaction time. [•] Fungicides were completely removed obtaining short-chain organic acids as main products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Advanced oxidation of NPs can be monitored by turbidity, TOC, COD, TEM and FTIR. • Turbidity and TEM analyses allow determining the conversion of the solids. • COD is an exceptional tool for evaluating the mineralization degree of NPs. • Morphology and particle size can be accurately determined by TEM and AFM. • Carbonyl index serves as a metric to monitor the oxidation progress on NPs surface. There is a growing interest in developing new targeted degradation technologies for the removal of micro- and nanoplastics (NPs) in water, corresponding to increased public concerns regarding their potential negative impacts on urban water systems, and consequently on human life quality. Recently, Advanced Oxidation Processes (AOPs) have been proposed as promising treatment alternatives for effective degradation of NPs in water. However, the selection of appropriate analytical methods for monitoring these oxidation tests remains a challenge. Herein, the feasibility of different characterization strategies for monitoring the evolution of NPs in water upon oxidation tests was systematically studied using polystyrene (PS) NPs of different particle sizes (D 0 = 140, 252, 460, and 909 nm) as model plastic pollutants. To quantify NPs in water, Total Organic Carbon (TOC), Chemical Oxygen Demand (COD) and turbidity measurements were assessed. Moreover, turbidity was correlated to the particle size and PS NPs concentration by developing a response surface. Among the analytical techniques employed to characterize the solid particles, transmission electronic microscopy (TEM) was used to evaluate morphology and particle size. Alternatively, the viability of Dynamic Light Scattering (DLS), Nanoparticle Tracking Analysis (NTA) and Atomic Force Microscopy (AFM) to determine particle size is discussed. Chemical surface modifications were explored by Fourier-Transform Infrared Spectroscopy (FTIR). As a proof of concept, the degradation of PS NPs in water upon photo-Fenton oxidation was investigated at ambient conditions and fully characterized using the mentioned techniques. [ABSTRACT FROM AUTHOR]

The increasing occurrence of cyanobacterial blooms worldwide represents an important threat for both the environment and public health. In this context, the development of risk analysis and management tools as well as sustainable and cost-effective treatment processes is essential. The research project TALGENTOX, funded by the Ibero-American Science and Technology Program for Development (CYTED-2019), aims to address this ambitious challenge in countries with different environmental and social conditions within the Ibero-American context. It is based on a multidisciplinary approach that combines ecology, water management and technology fields, and includes research groups from Chile, Colombia, Mexico, Peru and Spain. In this review, the occurrence of toxic cyanobacteria and cyanotoxins in freshwaters from these countries are summarized. The presence of cyanotoxins has been confirmed in all countries but the information is still scarce and further monitoring is required. In this regard, remote sensing or metagenomics are good alternatives at reasonable cost. The risk management of freshwaters from those countries considering the most frequent uses (consumption and recreation) has been also evaluated. Only Spain and Peru include cyanotoxins in its drinking water legislation (only MC-LR) and thus, there is a need for regulatory improvements. The development of preventive strategies like diminishing nutrient loads to aquatic systems is also required. In the same line, corrective measures are urgently needed especially in drinking waters. Advanced Oxidation Processes (AOPs) have the potential to play a major role in this scenario as they are effective for the elimination of most cyanotoxins classes. The research on the field of AOPs is herein summarized considering the cost-effectiveness, environmental character and technical applicability of such technologies. Fenton-based processes and photocatalysis using solar irradiation or LED light represent very promising alternatives given their high cost-efficiency. Further research should focus on developing stable long-term operation systems, addressing their scale-up. Unlabelled Image • Freshwater cyanobacteria and cyanotoxins occurrence in five Iberoamerican countries. • Risk assessment and decision-making systems in Ibero-America are reviewed. • AOPs offer a good removal efficiency for most classes of cyanotoxins. • Heterogeneous Fenton with magnetic iron minerals represents a promising low-cost alternative. • Photo-assisted processes using solar or LED light are also suitable cost-effective candidates. [ABSTRACT FROM AUTHOR]

• HDC is an effective technology for the removal of chlorpromazine. • The Pd/Al 2 O 3 catalyst suffered a dramatic loss of activity due to promazine-Pd interaction. • Several thermal and chemical treatments were investigated for catalyst regeneration. • Complete catalyst regeneration was achieved after its treatment with NaOCl solution. The abatement of dissolved organochlorinated pharmaceuticals from water by catalytic hydrodechlorination has been scarcely studied so far, but it represents a promising process for such goal. This work aims to evaluate the feasibility of this system for the removal of chlorpromazine, one of the most used pharmaceuticals for mental disorders treatment, paying special attention to the deactivation and regeneration of the catalyst (commercial Pd/Al 2 O 3 , 1% wt.). Complete conversion of chlorpromazine (3 mg L−1) was achieved in 90 min reaction time at 25 °C and 1 atm, using a catalyst load of 0.25 g L−1 and 50 N mL min−1 H 2 flow rate. Remarkably, the chlorine-free compound promazine was the single reaction product, which allowed to reduce significantly the ecotoxicity of the starting effluent (0.9 TUs) to negligible values. The experimental data were properly described by a pseudo-first order kinetic equation, obtaining a rate constant value of 5.9·10−2 min−1 at 25 °C, and 30 kJ mol−1 as activation energy. Despite the high activity of the catalytic system, it suffered a significant deactivation upon consecutive uses, which was associated to the selective interaction between promazine and Pd active sites. A number of regeneration methods including both thermal (calcination, calcination-reduction) and chemical (NaClO, H 2 O 2 , KMnO 4) treatments were investigated. Remarkably, aqueous-phase NaClO (750 mg L−1) regeneration allowed to recover completely the activity of the initial fresh catalyst. Its suitability was further demonstrated in consecutive HDC-regeneration runs where the catalyst showed a constant activity. This regeneration procedure is particularly promising given its fast mode of action, simplicity and low-cost. [ABSTRACT FROM AUTHOR]

• CWPO of the neonicotinoid pesticides listed in the EU Watch List was investigated. • Fast elimination (20 min) of all pesticides and aromatic by-products was achieved. • Mineralization yields above 50% were reached, being the final products short-chain acids. • The application of CWPO warranted the complete removal of ecotoxicity. • The versatility of the process was demonstrated in different water matrices. Neonicotinoid pesticides family is nowadays identified as the most important type of insecticides in the world. Their consequent widespread occurrence in the environment represents not only a well-known risk for bees but also a significant negative impact in aquatic ecosystems. In this work, the capability of catalytic wet peroxide oxidation (CWPO) (Fe 3 O 4 -R400/H 2 O 2) as a low-cost and environmentally-friendly system for the treatment of the neonicotinoid pesticides listed in the EU Watch List (Decision 2018/840) (acetamiprid (ACT), clothianidin (CLT), imidacloprid (IMD), thiacloprid (THC) and thiamethoxam (THM)) has been investigated. Remarkably, complete elimination of the pollutants (1000 μg L−1) and the aromatic by-products was reached in 20 min reaction time operating at 25 °C, 1 atm, and pH 0 = 5, with the stoichiometric H 2 O 2 amount (~4–5 mg L−1) and 1 g L−1 catalyst load. The reactivity order of the insecticides decreased as follows: THC > IMD > THM > CLT > ACT, being the pseudo-first order rate constant values within the range of 0.26–0.61 min−1. Notably, high mineralization yields were obtained (>50%), being the final effluents non-toxic. As example, the oxidation pathway of ACT was proposed. Finally, the catalytic system was tested in real surface water. [ABSTRACT FROM AUTHOR]

• The removal of all the pharmaceuticals included in the EU Watch List was investigated. • The inexpensive magnetite catalyst showed a high activity and a reasonable stability in CWPO. • Total conversion of all drugs was reached under ambient temperature and circumneutral pH. • The pollutants were highly mineralized (>50%), being the final products short-chain acids. • The process was successfully tested in three real WWTP effluents. The European Union (EU) approved in 2015 a Watch List of pollutants of emerging concern especially harmful for the aquatic environment (Decision 2015/495/EU). In this work, we explore the application of an inexpensive and environmentally-friendly catalytic system based on modified natural magnetite (Fe 3 O 4 -R400) and H 2 O 2 for the removal of all the pharmaceuticals included in the EU Watch List (hormones: estrone, 17-beta-estradiol and 17-alpha-ethinylestradiol; macrolide antibiotics: azithromycin, clarithromycin and erythromycin; and the non-steroid anti-inflammatory diclofenac). The experiments were carried out with a representative initial concentration of the drugs (1000 μg L−1) at a circumneutral pH value (pH 0 = 5) within the temperature range of 17–50 °C. A low catalyst concentration (0.2 g L−1) was used while the applied amount of H 2 O 2 corresponded to the stoichiometric one for the complete mineralization of the drugs (4–6 mg L−1). Operating under ambient-like conditions, total conversion of the target pollutants as well as the aromatic intermediates was achieved. Notably, total organic carbon was strongly reduced (>50%), being the residual carbonaceous products short-chain organic acids. The applicability of the catalytic system was demonstrated using different real wastewater treatment plant (WWTP) effluents spiked with the mixture of pharmaceuticals. Apart from the complete removal of pharmaceuticals in relatively short reaction times (60–90 min), the disappearance of total coliforms was warranted. Remarkably, the catalyst showed a reasonable stability, with low iron leaching (<0.7 mg L−1) and maintaining its magnetic properties almost unchanged. [ABSTRACT FROM AUTHOR]

• HDC is an effective technology for the removal of chlorinated micropollutants. • HDC effluents are non-toxic, with only chlorine-free compounds as reaction products. • The Pd/Al 2 O 3 catalyst shows a relatively high stability upon consecutive applications. • The process versatility is proved in relevant aqueous matrices (mineral, surface and tap water). • HDC shows a high potential as polishing step in DWTPs as it also removes THMs. The presence of micropollutants in fresh waters represents an important challenge for drinking water treatment plants (DWTPs). In particular, the chlorinated ones are especially harmful given their high toxicity and strong bioaccumulation potential. The aim of this work is to evaluate the feasibility of catalytic hydrodechlorination (HDC) for the removal of a representative group of chlorinated micropollutants commonly found in the source waters of DWTPs: the antibiotic chloramphenicol (CAP), the anti-inflammatory diclofenac (DCF), the antibacterial agent triclosan (TCL) and the antidepressant sertraline (SRT). The complete degradation of the isolated micropollutants (3 mg L−1) was achieved in 1 h reaction time using a Pd/Al 2 O 3 catalyst load of 0.25 g L−1 and a H 2 flow rate of 50 N mL min−1. The experimental data were properly described by a pseudo-first order kinetic equation, obtaining degradation rate constants in the range of 0.32–1.56 L g cat −1 min−1 and activation energy values within 42–52 kJ mol−1. In all cases, the final reaction products were chlorine-free compounds and thus, HDC effluents were non-toxic (<0.1 TU). Remarkably, the catalyst showed a suitable stability upon five consecutive applications. The versatility of the process was demonstrated in the treatment of the micropollutants mixture in different aqueous matrices (mineral, surface and tap waters). Strikingly, the removal rate was not affected by the presence of co-existing substances, being the micropollutants completely removed in 15 min with 1 g L−1 catalyst concentration. Finally, the potential of HDC for the removal of trihalomethanes, by-products formed along the oxidation step by chlorination in DWTPs, was also demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • HDC is an effective technology for the removal of chlorinated azole pesticides. • HDC effluents are non-toxic, with only chlorine-free compounds as reaction products. • Intermediates were identified and the reaction mechanism was proposed. • The Pd/Al 2 O 3 catalyst shows a relatively high stability upon consecutive applications. • The process versatility was proved in relevant aqueous matrices (DWTP and tap water). Catalytic hydrodechlorination (HDC) is regarded as a promising purifying technology for drinking water treatment. So far, it has proved to be highly effective for the removal of different groups of chlorinated micropollutants including pharmaceuticals, neonicotinoid pesticides, personal care products or chloroacetic acids. The azole pesticides, recently included in the EU Watch Lists (Decisions 2020/1161 and 2022/1307), are a group of micropollutants of particular concern for drinking water given their high toxicity, persistence, and bioaccumulation potential. In this work, the feasibility of HDC for the removal of a representative group of chlorinated azole pesticides tebuconazole (TEB), tetraconazole (TET), prochloraz (PCZ), penconazole (PEN), metconazole (MET) and imazalil (IMZ)) is demonstrated, and their reactivity is compared with that observed for other halogenated micropollutant groups. Notably, all the pesticides investigated in this work (100 μg L−1) were completely dechlorinated within 30 min under ambient conditions using a 1 wt% Pd/Al 2 O 3 catalyst concentration of 0.25 g L−1 and a H 2 feeding of 50 mL N min−1. The experimental data were accurately described by a pseudo-first order kinetic equation and rate constant values in the range from 1.08 to 2.60 L g cat −1 min−1 were obtained. These values are quite close to those achieved for the most reactive neonicotinoid pesticides and significantly higher than the obtained for chloroacetic acids and most pharmaceuticals (e.g. diclofenac, sertraline or chlorpromazine). From the identification of the generated reaction intermediates and the final non-chlorinated products, sequential reaction pathways were proposed for each pollutant. Remarkably, despite the high toxicity exhibited by the azole pesticides tested, with LC 50 values within the 0.4–7.0 mg L−1 range using A. salina , HDC effluents were non-toxic in all cases. Furthermore, the catalyst showed a remarkable stability upon three consecutive runs. Finally, the versatility of the process was demonstrated in the treatment of real aqueous matrices such as DWTP and tap water, where no significant differences were found either in terms of activity or stability. [ABSTRACT FROM AUTHOR]

In this work, we evaluate the feasibility of carbide-derived carbons (CDCs) as reliable and highly efficient adsorbents for the removal of pharmaceuticals from water. CDCs were produced from titanium carbide at temperatures within the range of 800–1400 °C employing chlorine as extraction agent. The materials were physicochemically characterized and tested in the adsorption of two relevant pharmaceuticals (diclofenac (DCF) and metronidazole (MNZ)) in aqueous solutions. We found that the specific surface area in combination with a low functionalized surface plays a key role on the adsorption capacity of the material while the average pore size determines the kinetics of the process. Notably, the CDCs showed an outstanding adsorptive behaviour compared to different conventional carbon materials under the same operating conditions, which was attributed not only to their high surface areas but mainly to their strong hydrophobic properties. The optimum material (specific surface area of 1676 m 2  g −1 ) showed extremely high adsorption capacity values (551 and 410 mg g −1 for DCF and MNZ, respectively). Remarkably, the process was very fast (10 min of equilibrium time) even using low doses of adsorbent (0.3 mg mL −1 ). The performance of the optimum CDC was also demonstrated in bi-component systems while its versatility was demonstrated in a real wastewater treatment plant (WWTP) effluent, obtaining a good performance in terms of adsorption capacity (up to ∼400 mg DCF  g −1 ) and kinetics (equilibrium time of 10 min). These results demonstrate the promise of CDCs for reliable, effective and fast flow-through tertiary water treatment. [ABSTRACT FROM AUTHOR]

In this work, polymer-based spherical activated carbon (PBSAC) (dp = 500 μm) has been used as support to synthesize several Pd/PBSAC (1% wt.) catalysts. These catalysts have been tested in the hydrodechlorination (HDC) of 4‐chlorophenol (4-CP) in aqueous phase under ambient-like conditions (30 °C, 1 atm) at [4-CP] 0 = 3.9 mmol L −1 ; [catalyst] 0 = 1 g L −1 and 50 N mL H 2 min −1 . A sequential calcination (200 °C, air atmosphere) − reduction (80 °C, H 2 atmosphere) treatment was required to obtain active HDC catalysts with a convenient proportion of zero-valent and electrodefficient Pd species. This catalyst allowed to achieve complete conversion of 4-CP in 90 min reaction time, giving rise to phenol as main reaction product. An expanded kinetic model accounting for both consecutive reaction and sorption processes was used to successfully fit the experimental data. The values obtained for the effective rate constant of 4-CP disappearance (3.26–10.88 × 10 −4 s −1 ) and apparent activation energy (31.6 kJ mol −1 ) were close to the previously reported for powdered supported Pd catalysts. Remarkably, the catalyst showed a high stability in long-term continuous application (100 h on stream). [ABSTRACT FROM AUTHOR]

This work aims at evaluating the fate of microplastics (MPs) along Fenton oxidation. For such goal, realistic MPs (150–250 μm) of five representative polymer types (PET, PE, PVC, PP and EPS) were obtained from commercial plastic products by cryogenic milling. Experiments (7.5 h) were performed under relatively severe operating conditions: T = 80 °C; pH 0 = 3; [H 2 O 2 ] 0 = 1000 mgL−1 (15 doses, 1 every 0.5 h); [Fe3+] 0 = 10 mgL−1 (5 doses, 1 every 1.5 h). Slight MPs weight losses (∼10%) were achieved after Fenton oxidation regardless the MP nature. Nevertheless, oxidation yield clearly increased with decreasing the particle size given their higher exposed surface area (up to 20% weight loss with 20–50 μm EPS MPs). Clearly, MPs suffered important changes in their surface due to the introduction of oxygenated groups, which made them more acidic and hydrophilic. Furthermore, MPs progressively reduced their size. In fact, they can be completely oxidized to CO 2 , as demonstrated in the oxidation of PS nanoplastics (140 nm), where 70% mineralization was achieved. The nature of the plastic particles had a relevant impact on its overall oxidation, being more prone to be oxidized those polymers which contain aromatic rings in their structures (EPS and PET) compared to those formed by alkane chains (PE, PP and PVC). In the latter, the presence of substituents also reduced their oxidation potential. Remarkably, possible leachates released along reaction were more quickly oxidized than the MPs/NPs, so it can be assumed that these dissolved compounds would be completely removed once the solid particles are eliminated. Notably, the leachates obtained upon MPs oxidation were more biodegradable than the released from the fresh solids. All this knowledge is crucial for the understanding of MPs oxidation by the Fenton process and opens the door for the design and optimization of this technology either for water treatment or for analytical purposes (MPs isolation). [Display omitted] • Oxidation reaction proceeds from the surface to the core of plastic particles. • MPs suffered physical alterations and chemical changes along Fenton oxidation. • MPs decreased their size upon oxidation, eventually leading to their mineralization. • MPs bearing aromatic rings showed higher oxidation yields than the alkane-based MPs. • Dissolved leachates generated along the treatment did not inhibit bacterial growth. [ABSTRACT FROM AUTHOR]

This work aims at evaluating the role of nature, size, age, and natural organic matter (NOM) fouling of realistic microplastics (MPs) on the adsorption of two persistent micropollutants (diclofenac (DCF) and metronidazole (MNZ)). For such goal, four representative polymer types (polystyrene (PS), polyethylene terephthalate (PET), polypropylene (PP) and high-density polyethylene (HDPE)) were tested. MPs were obtained by cryogenic milling of different commercial materials (disposable bottles, containers, and trays), and fully characterized (optical microscopic and SEM images, FTIR, elemental analysis, water contact angle and pH slurry). The micropollutants hydrophobicity determined to a high extent their removal yield from water. Regardless of the MP's nature, the adsorption capacity for DCF was considerably higher than the achieved for MNZ, which can be related to its stronger hydrophobic properties and aromatic character. In fact, aromatic MPs (PS and PET) showed the highest adsorption capacity values with DCF (~100 μg g−1). The MP size also played a key role on its adsorption capacity, which was found to increase with decreasing the particle size (20–1000 μm). MPs aging (simulated by Fenton oxidation) led also to substantial changes on their sorption behavior. Oxidized MPs exhibited acidic surface properties which led to a strong decrease on the adsorption of the hydrophobic micropollutant (DCF) but to an increase with the hydrophilic one (MNZ). NOM fouling (WWTP effluent, river water, humic acid solution) led to a dramatic decrease on the MPs sorption capacity due to sorption sites blocking. Finally, the increase of pH or salinity of the aqueous medium increased the micropollutants desorption. [Display omitted] • The capacity of PS, PET, PP and HDPE realistic microplastics for DCF and MNZ uptake was evaluated. • Hydrophobic interactions governed the adsorption, being DCF adsorbed to a higher extent. • MPs oxidation led to their surface acidification, modifying their adsorption performance. • NOM fouling led to a decrease on MPs adsorption capacity due to sorption sites blocking. • The increase of pH or salinity increased the desorption of micropollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Pd-based catalytic membrane reactor with controlled feeding of H 2 was developed. • The Pd/CMR was tested in continuous flow HDC under ambient conditions. • The Pd/CMR showed an outstanding activity and stability for up to 200 h. • The activity of the catalytic system was not affected by the initial DCF concentration. • The versatility of the system was successfully demonstrated in a tap water matrix. This work is focused on the development of a Pd-based catalytic membrane reactor (Pd/CMR) for its application in continuous flow hydrodechlorination (HDC) of chlorinated micropollutants. A cylindrical inert porous alumina membrane was decorated on the outer with well-dispersed Pd nanoparticles (0.2 % wt.). The Pd/CMR was fully characterized by different techniques. The catalytic system was applied for the degradation of the persistent anti-inflammatory drug diclofenac (DCF) under ambient conditions. A remarkable stability was observed upon long-term HDC reaction, with a reasonable DCF conversion (60 %). Notably, as the process could be described by pseudo-first order kinetic, the initial concentration did not affect the final conversion achieved. Finally, the versatility of the system was successfully demonstrated using a real aqueous matrix (tap water). All in all, Pd/CMR exhibited a remarkable feasibility for the implementation of the HDC technology on a larger scale, showing an extraordinary catalytic performance for up to 200 h. [ABSTRACT FROM AUTHOR]

The feasibility of catalytic wet air oxidation, intensified homogeneous Fenton and heterogeneous Photo-Fenton systems for the treatment of real hospital wastewater has been investigated. Wastewater samples were collected from a hospital sewer, during a weekly monitoring program, and fully characterized. Up to seventy-nine pharmaceuticals, including mostly parent compounds and some of their transformation products, were analyzed. Catalytic wet air oxidation allowed the complete removal of several pharmaceutical groups, but it did not allow to eliminate analgesics/anti-inflammatories and antibiotics, whose average removal was around 85%. Intensified Fenton oxidation was the most efficient process for all the drugs removal with an almost complete reduction of the initial pharmaceutical load (99.8%). The heterogeneous Photo-Fenton system reached a 94.5% reduction of the initial pharmaceutical load. The environmental risk of the treated samples by the hazard quotient (HQ) method was also evaluated. Fenton oxidation was the most effective system with a final ∑HQ of 5.4. Catalytic wet air oxidation and Photo-Fenton systems achieved total ∑HQ values of 895 and 88, respectively. This fact was related to the presence of refractory antibiotics in the treated catalytic wet air oxidation samples. On the opposite, the Photo-Fenton system provided the elimination of most pharmaceutical pollutants that pose a high environmental risk such as antibiotics. Simplified cost estimation was finally performed as a preliminary approach of the economy of the three oxidation processes for the hospital wastewater treatment. [Display omitted] • Seventy-nine pharmaceuticals were identified in real hospital wastewater. • CWAO, Intensified Fenton and heterogeneous Photo-Fenton technologies were tested for the treatment of hospital wastewater. • Intensified Fenton oxidation achieved the best performance for the reduction of pharmaceutical compounds. • Remaining antibiotics in the treated effluents revealed a significant impact on the environmental risk assessment. • The operating costs are significantly increased for the heterogeneous catalytic systems. [ABSTRACT FROM AUTHOR]

• Carbon-encapsulated iron nanoparticles (CE-nFe) prepared by hydrothermal carbonization. • CE-nFe showed a core-shell structure composed by zero-valent iron and graphitized carbon. • The adsorbent led to a fast removal of DCF, MNZ and SMX (less than 30 min). • The saturated adsorbents were effectively regenerated by heterogeneous Fenton oxidation. • The micropollutant's nature affected the regeneration yield in the order: SMX > DCF > MNZ. Adsorption represents the most plausible technology for micropollutants removal from water nowadays. Nevertheless, the regeneration of the saturated carbon materials is still an important challenge, being these solids in practice commonly disposed. This work aims at overcoming this issue by using innovative carbon-encapsulated iron nanoparticles (CE-nFe). This material was synthesized by a low-cost and green method viz. hydrothermal carbonization (HTC), using olive mill wastewater as carbonaceous source. The solid was fully characterized by different techniques (magnetic properties, elemental analyses, N 2 -sorption isotherms, pH PZC , ICP, XRD and TEM). It showed a clear core-shell structure of around 40 nm in diameter. The core was mainly formed by zero-valent iron and the shell by graphitized carbon. Accordingly, it showed an essentially mesoporous structure, with a specific surface area of 169 m2 g−1, and a clear hydrophobic character (pH PZC = 10). Its adsorption performance was investigated using three relevant micropollutants (diclofenac (DCF), sulfamethoxazole (SMX) and metronidazole (MNZ)). A very fast removal of the micropollutants was achieved (30 min at the most, with rate constants in the range of 0.11–0.41 g mg−1 min−1). The adsorption isotherms revealed the vertical packing of the adsorbate molecules onto the adsorbent active centers, being the data successfully described by the GAB model. The saturated adsorbents were effectively regenerated by heterogeneous Fenton oxidation, taking advantage of the iron core of CE-nFe and the opened mesoporous carbon shell. The regeneration efficiency increased with increasing the operating temperature (25–75 °C) and contact time (1–4 h), as well as the H 2 O 2 dose up to 6 g L-1. The micropollutant nature affected the adsorbent regeneration yield in the order: SMX > DCF > MNZ, consistent with their reactivity towards Fenton oxidation. [ABSTRACT FROM AUTHOR]

The occurrence of harmful cyanobacterial blooms has unabated increased over the last few decades, posing a significant risk for public health. In this work, we investigate the feasibility of catalytic wet peroxide oxidation (CWPO) promoted by modified natural magnetite (Fe 3 O 4 -R400/H 2 O 2), as an inexpensive, simple-operation and environmentally-friendly process for the removal of the cyanotoxins that show the major impact on drinking water: microcystins (MC-LR and MC-RR), cylindrospermopsin (CYN), anatoxin- a (ATX) and saxitoxin (STX). The performance of the system was evaluated under ambient conditions and circumneutral pH (pH 0 = 5) using relevant cyanotoxin concentrations (100–500 μg L−1). The nature of the cyanotoxins determined their reactivity towards CWPO, which decreased in the following order: MC-RR > CYN > MC-LR ≫ ATX > STX. In this sense, microcystins and CYN were completely removed in short reaction times (1–1.5 h) with a low catalyst concentration (0.2 g L−1) and the stoichiometric amount of H 2 O 2 (2–2.6 mg L−1), while only 60–80% conversion was achieved with ATX and STX in 5 h. In these cases, an intensification of the operating conditions (1 g L−1 catalyst and up to 30 mg H 2 O 2 L−1) was required to remove both toxins in 1 h. The impact of the main components of freshwaters i.e. natural organic matter (NOM) and several inorganic ions (HCO 3 −, HPO 4 2-, SO 4 2-) on the performance of the process was also investigated. Although the former led to a partial inhibition of the reaction due to HO· scavenging and catalyst coating, the latter did not show any remarkably effect, and the versatility of the process was finally confirmed in a real surface water. To further demonstrate the effectiveness of the catalytic system, the toxicity of both the initial cyanotoxins and the resulting CWPO effluents was measured with the brine shrimp Artemia salina. Remarkably, all CWPO effluents were non-toxic at the end of the treatment. Image 1 • The catalytic system Fe 3 O 4 -R400/H 2 O 2 is effective for the removal of cyanotoxins. • The reactivity of cyanotoxins decreased in the order: MC-RR > CYN > MC-LR ≫ ATX > STX. • The versatility of the process was demonstrated in different water matrices. • Oxidation effluents were non-toxic to the brine shrimp Artemia salina. [ABSTRACT FROM AUTHOR]