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• 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]

[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]

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]

[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]

• 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]

• 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]

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]

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]

The development of cost-efficient and environmentally friendly technologies for the removal of cyanotoxins from water is crucial, given the increasingly frequent appearance of toxic cyanobacterial blooms. In this work, the application of catalytic wet peroxide oxidation (CWPO) promoted by natural magnetite for the removal of the highly toxic cyanotoxin cylindrospermopsin (CYN) has been investigated. A fixed-bed reactor packed with magnetite powder and granules was used to treat a continuous flow of CYN-bearing water. Experiments were carried out under ambient conditions and circumneutral pH (pH0 = 5). The effect of the main variables of the process, viz. magnetite load (8–14 g), feed flow rate (0.1–0.25 mL min−1), H2O2 dose (0.5–8 mg L−1) and initial CYN concentration (25–100 μg L−1), were systematically analyzed. CYN conversion values and kinetic constants were calculated to evaluate the feasibility of the catalytic system. The process was highly effective in the removal of the cyanotoxin, achieving up to 80% CYN conversion under optimized conditions (flow rate = 0.2 mL min−1, [H2O2]0 = 5 mg L−1, WFe3O4 = 14 g, pH0 = 5, T = 25 °C). It also showed reasonable activity (~55% CYN conversion) in two real samples (pond and river water). The decay on CYN conversion in these cases was mainly due to the scavenging of hydroxyl radicals by the co-existing species present in the matrices. Remarkably, the catalytic system showed high stability with limited iron leaching (the iron leached at the end of the experiments represented less than 0.2 wt.% of the catalyst's initial iron content) in all cases. Its stability was further confirmed in a long-term continuous experiment (60 h time on stream). Furthermore, the magnetite granules at the top layer of the packed bed avoided the loss of magnetite powder from the reactor, confirming the suitability of the system for continuous long-term application. [ABSTRACT FROM AUTHOR]