A novel Fe-PTFE magnetic composite prepared by ball milling for the efficient degradation of imidacloprid: Insights into interaction mechanisms based on ultrasonic piezoelectric catalysis

In this study, a novel magnetic poly (tetrafluoroethylene, PTFE) (Fe@PTFE) piezoelectric catalytic material was successfully prepared by a simple ball milling treatment. The prepared piezoelectric catalytic material Fe@PTFE exhibited excellent catalytic performance under the activation of ultrasonic (US) and realized the efficient degradation of imidacloprid (IMI) at low concentrations in an aqueous environment. It was demonstrated by various characterization methods that Fe⁰ was successfully loaded onto PTFE particles (1-15 μm) by ball milling. The US/Fe@PTFE system exhibited superior IMI degradation efficiency (99 %) and degradation rate (7.81× 10^-2 min^-1) under ultrasonic polarization with high efficiences of IMI degradation after five cycles. In addition, the system maintained excellent removal efficiencies in the real water matrixes. The mechanism study demonstrated that Fe@PTFE generated a variety of reactive oxygen species (^•OH, ¹O₂ and O₂^•-) and H₂O₂ under the irradiation of US, and the production of H₂O₂ provided the conditions for the continuation of the Fenton-like reaction. Furthermore, the presence of O₂^•- in the system enhanced the recycling efficiency of Fe(III) and Fe(II), which further enhanced the degradation efficiency of the Fenton-like process. This study provides a novel perspective on a PTFE-based ultrasonic piezoelectric catalytic system for the efficient removal of organic pollutants in the environmental field.

Fabrication of Fe-BTC on aramid fabrics for repeated degradation of isoproturon

Catalytic degradation is a promising and ideal technology in environmental remediation. Among them, catalytic oxidation and photocatalysis respectively based on catalysts and photocatalysts both trigger broad interests because of their high removal activity. However, the reusability of the powder catalysts still faces substantial challenges. Here, a simple strategy is proposed to load Fe-BTC catalyst on aramid fabrics (AF) to construct Fe-BTC MOF @ aramid fabric (Fe-BTC@AF) composite materials with layer-by-layer in situ self-assembly methods. The experimental results illustrated that 98% isoproturon could be removed by Fe-BTC@AF₂₀ with oxidant H₂O₂, while the single Fe-BTC@AF₂₀ could photo-degrade 99% isoproturon within 7 h. Meanwhile, it could sustain a high degradation rate of more than 80%, even if it had gone through 5 degradation cycles. Thus, the Fe-BTC@AF composite has a significant advantage in the recycling ability for degradation of isoproturon, which will have potential applications in the efficient removal of organic contaminants in water.

Structure and QSAR analysis of photoinduced transformation products of neonicotinoids from EU watchlist for ecotoxicological assessment

Current research is increasingly focusing on the ecotoxicity of anthropogenic micro-pollutants and their degradation and transformation products resulting from biological and chemical treatment processes. These products enter the aquatic environment through various routes and may endanger aquatic organisms and plants. In this study, five neonicotinoids from the EU watchlist and their degradation products induced by UVC irradiation were examined. All identified photoinduced degradation or transformation products were subsequently submitted to Quantitative Structure Activity (QSAR) analysis. Among the investigated structures, 15 substances already identified in previous studies and eleven new transformation products were analyzed. By using QSAR analysis, it became possible to predict ecotoxicity of individual substances with mere computational effort. Starting from the chemical structure, lower toxicity against green algae and invertebrates was predicted for the transformation products in general. For other aquatic target organisms, such as branchiopoda, actinopterygii and fathead minnow, the residual hazardous effect as compared to the initial compound depends on the presence of specific structural elements. For the neonicotinoids investigated, the cleavage or elimination of the nitrile or nitro group through the degradation process, was predicted to increase toxicity.

CeO2 for Water Remediation: Comparison of Various Advanced Oxidation Processes

Three different Advanced Oxidation Processes (AOPs) have been investigated for the degradation of the imidacloprid pesticide in water: photocatalysis, Fenton and photo-Fenton reactions. For these tests, we have compared the performance of two types of CeO2, employed as a non-conventional photocatalyst/Fenton-like material. The first one has been prepared by chemical precipitation with KOH, while the second one has been obtained by exposing the as-synthetized CeO2 to solar irradiation in H2 stream. This latter treatment led to obtain a more defective CeO2 (coded as “grey CeO2”) with the formation of Ce3+ sites on the surface of CeO2, as determined by Raman and X-ray Photoelectron Spectroscopy (XPS) characterizations. This peculiar feature has been demonstrated as beneficial for the solar photo–Fenton reaction, with the best performance exhibited by the grey CeO2. On the contrary, the bare CeO2 showed a photocatalytic activity higher with respect to the grey CeO2, due to the higher exposed surface area and the lower band-gap. The easy synthetic procedures of CeO2 reported here, allows to tune and modify the physico-chemical properties of CeO2, allowing a choice of different CeO2 samples on the basis of the specific AOPs for water remediation. Furthermore, neither of the samples have shown any critical toxicity.

A comparative study in single- and binary-contaminant systems: the photodegradation of tetracycline and imidacloprid on flower-shaped Ag/AgBr/BiOBr under visible-light irradiation

A synergistic effect demonstrated in binary-contaminant systems is shown to be caused by the mutually complementary utilization of active species during photodegradation.

Potential use of waste foundry sand in dual process (photocatalysis and photo-Fenton) for the effective removal of phenazone from water: Slurry and fixed-bed approach

In this study, degradation of a pharmaceutical drug, Phenazone (PNZ) has been carried out via heterogeneous photocatalysis, photo-Fenton and in-situ dual process (photocatalysis + photo-Fenton) in suspension and fixed-mode under artificial UV-A as well as under natural solar radiations. Waste material such as foundry sand (FS) was exploited as a supplement for iron in case of photo-Fenton reaction. The distinct processes including photocatalysis and photo-Fenton were found to be competent for the degradation of PNZ as both processes revealed an almost 90-95% removal of PNZ after 180 min of UV irradiations. The degradation was improved to a great extent with remarkable reduction in treatment time of PNZ to almost 105 min when these two individual processes were combined together within the same unit. An almost 14% synergy of dual process over distinct processes was obtained. For fixed-bed studies, TiO₂ immobilized hollow circular composite disc already containing FS was utilized which yielded an almost 96% reduction in the concentration of PNZ after 4 h of solar irradiations. The disc was recycled 10 times and its stability and activity was confirmed through XRD, SEM/EDS, and DRS. The mineralization of PNZ was confirmed through significant reduction in COD and generation of anions during the treatment process. The transformation products were examined through GC-MS analysis. The novel technique of in-situ dual process especially in fixed-mode visualized in this study by employing renewable energy and durable catalyst can represent a viable solution to various industries for the treatment of wastewater comprising of bio-recalcitrant pollutants.

Analysis of a Hybrid Suspended-Supported Photocatalytic Reactor for the Treatment of Wastewater Containing Benzothiazole and Aniline

In this work, a study of the main operating variables affecting TiO2/UV photocatalysis was carried out. The treatment of an industrial effluent containing aniline and benzothiazole from the manufacture of accelerants for vulcanization was performed in a TiO2-supported commercial photoreactor. The degradation of both contaminants was monitored by GC-MS analysis. The proposed experiments were able to properly identify the phenomenon of adsorption, as well as to improve the performance of the commercial photoreactor by adding small amounts of TiO2 in suspension. The removal performance, durability of the photocatalytic material, and energy costs were analysed. The results showed that the use of suspensions intensifies the degradation obtaining an improvement of 23.15% with respect to the use of the supported catalyst. For an aniline and benzothiazole solution, the best operating conditions were found at pH = 12.0, introducing 60.0 mg L−1 of suspended TiO2 together with the existing supported catalyst.

N, Ag co-doped TiO2 mediated modified in-situ dual process (modified photocatalysis and photo-Fenton) in fixed-mode for the degradation of Cephalexin under solar irradiations

Novel FeNAgTiO₂ composite beads possessing unusual characteristics of modified in-situ dual process (modified photocatalysis and photo-Fenton) resulted in reduction in treatment time of Cephalexin (CEX). These composite beads were prepared using NAgTiO₂ and waste foundry sand (FS) and fly-ash (FA) as alternative source of iron. The modified TiO₂ was characterized through SEM/EDS, DRS, XRD, TGA, FTIR, XPS and Raman spectroscopy to affirm the distribution of Ag and N on TiO₂ surface. The modified in-situ dual process using FeNAgTiO₂ composite beads yielded 77% degradation of CEX after 60 min of solar irradiations with overall synergy of 24% over individual processes. FeNAgTiO₂ composite beads were characterized through SEM/EDS, XRD and DRS to confirm the presence of Fe along with Ag, N and TiO₂ on the surface of beads. These composite beads were stable and active even after 15 recycles. The mineralization of CEX was validated through reduction in COD and TOC along with generation of anions while intermediates were identified through GC-MS analysis.