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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]

• 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]

[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]