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This work aims to develop highly stable iron oxide foams for the continuous Catalytic Wet Peroxide Oxidation (CWPO) of micropollutants in a structured fixed-bed reactor. Homogeneity and adhesion of the active phase were achieved by adjusting the preparation methodology. Three structured catalysts based on Al 2 O 3 , SiC and ZrO 2 foams were obtained with Fe content of 2.5%, 2.1% and 0.90% wt., respectively. The catalytic foams were tested in the CWPO of a mixture of three pharmaceuticals (metronidazole (MNZ), sulfamethoxazole (SMX) and carbamazepine (CBZ)), with a concentration of 100 µg L−1 each. The catalysts resulted active and stable up to 200 h of CWPO carried out at ambient conditions, with the exception of Fe/ZrO 2 , which showed a progressive deactivation due to the iron leaching from the solid. An increase in space time led to an enhanced performance achieving remarkable conversion levels of 73%, 83% and 90% for MNZ, SMX and CBZ, respectively. The effect of H 2 O 2 dose was also evaluated revealing the development of competing side reactions for supra - stoichiometric dosages. Moreover, the scavenging effect of the water matrix was assessed operating in presence of humic acid as representative natural organic matter (NOM). In this case, the conversion levels for SMX and CBZ resulted alike to the ones obtained for ultrapure water and only a slight decrease in MNZ removal rate was detected. After 400 h of usage at different steady-state conditions, the outstanding catalytic performance of Fe/Al 2 O 3 and Fe/SiC was sustained in the long-term operation. [Display omitted] • Innovative iron oxide foams based on Al 2 O 3 , SiC and ZrO 2 were developed. • The structured catalysts were tested in the continuous flow CWPO of persistent micropollutants. • Fe/Al 2 O 3 and Fe/SiC catalytic foams showed an outstanding activity and stability for 400 h. • The H 2 O 2 dose revealed competing reactions for supra-stoichiometric doses. • The versatility of the system was demonstrated in the presence of NOM. [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 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]

• Intensification of CWPO by electro-magnetic induction heating (MIH) was investigated. • MIH application led to a remarkable increase of CWPO kinetics but also to a temperature rise. • At the same bulk solution temperature, MIH-CWPO showed faster oxidation rates than CWPO. • The localized heating of the catalyst particles is the reason behind kinetics enhancement. • The actual temperature of the catalyst particles in MIH-CWPO was estimated. This work aims to evaluate the intensification of CWPO by the application of electro-magnetic induction heating (MIH) using an inexpensive magnetite mineral as catalyst. Experiments were carried out at pH 0 = 5 using the persistent antibiotic sulfamethoxazole (SMX) as target pollutant (5 mgL−1) and the stoichiometric H 2 O 2 dose (25 mgL−1). The effect of electro-magnetic field intensity (200–350 A, at a frequency of 223 kHz) and catalyst concentration (0.25–1.5 gL−1) on the kinetics as well as on the bulk solution temperature, were systematically evaluated. A clear increase on the oxidation rate of SMX was observed with increasing the electro-magnetic field intensity (2.1 × 10−2–6.9 × 10−2 min−1 by increasing the electro-magnetic field from 0 to 350 A), which was accompanied by a significant temperature rise (from 26 to 48 °C). Remarkably, even operating under the same bulk solution temperature, the MIH-CWPO process led to oxidation rates significantly faster than the achieved with the non-MIH assisted CWPO system (e.g. up to three times higher at 350 A, being both operated at 56 °C). The effect of temperature on the process kinetics was finally evaluated, obtaining an activation energy value of 41 kJmol−1. On the basis of these results, the actual temperature of the solid particles in the MIH-CWPO system was accordingly estimated. The localized heating of these particles led to temperatures much higher than those of the surrounding liquid phase (e.g. 79 vs. 56 °C at 350 A), which was the reason behind the process kinetics enhancement. [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]