A novel tubular up-flow magnetic film photocatalytic system optimized by main factors control for efficient removal of chlorophenols wastewater

Bimetallic FeO x -MO x Loaded TiO2 (M = Cu, Co) Nanocomposite Photocatalysts for Complete Mineralization of Herbicides

A series of monometallic and bimetallic cocatalyst(s), comprising FeO _x , CuO _x , CoO _x , FeO _x -CuO _x , and FeO _x -CoO _x loaded TiO₂ catalysts prepared by the surface impregnation method, were investigated for the photocatalytic mineralization of the widely used four herbicides: 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). It was found that FeO _x -CoO _x /TiO₂ showed the highest photocatalytic efficiency toward mineralization of selected herbicides. FeO _x -CoO _x /TiO₂ achieves 92% TOC removal in 180 min, representing nearly three time activity of the benchmark PC50 TiO₂. From XPS analysis, FeOOH, CuO, and CoO were determined to be loaded onto the TiO₂ surface. The outstanding photocatalytic performance of the optimized FeO _x -CoO _x /TiO₂ sample for herbicides mineralization is due to an increased charge separation and enhanced hydroxyl radicals production monitored by diverse spectroscopies. Based on the proposed charge transfer mechanism, FeO _x -CoO _x cocatalyst species accelerate the transfer of photogenerated holes on TiO₂, thus facilitating hydroxyl radicals production.

Degradation of Dye Wastewater by a Novel mBT-MPR Visible Light Photocatalytic System

The high efficiency and low consumption green wastewater treatment technology has important practical significance for the recycling of printing and dyeing wastewater. The efficiency of visible light catalytic degradation of organics is greatly affected by the performance of the catalyst and the photo reactor. Therefore, Bi₂WO₆/TiO₂/Fe₃O₄ (mBT) visible light photocatalyst was accurately prepared by the ammonia iron double drop method. In order to improve the photodegradation efficiency, a tubular magnetic field-controlled photocatalytic reactor (MPR) was developed. The novel mBT-MPR visible light photocatalytic system was proposed to treat RhB simulated wastewater. The experimental results showed that when the dosage of mBT catalyst was 1 g/L and visible light was irradiated for 60 min, the average removal rate of rhodamine B (RhB) with initial an concentration of 10 mg/L in the simulated wastewater for four times was 91.7%. The mBT-MPR visible light photocatalysis system is a green and efficient treatment technology for organic pollutants in water with simple operation, low energy consumption, and no need for catalyst separation.

Simultaneous Phenol Removal and Resource Recovery from Phenolic Wastewater by Electrocatalytic Hydrogenation

Efficient pollutants removal and simultaneous resource recovery from wastewater are of great significance for sustainable development. In this study, an electrocatalytic hydrogenation (ECH) approach was developed to selectively and rapidly transform phenol to cyclohexanol, which possesses high economic value and low toxicity and can be easily recovered from the aqueous solution. A three-dimensional Ru/TiO₂ electrode with abundant active sites and massive microflow channels was prepared for efficient phenol transformation. A pseudo-first-order rate constant of 0.135 min^-1 was observed for ECH of phenol (1 mM), which was 34-fold higher than that of traditional electrochemical oxidation (EO). Both direct electron transfer and indirect reduction by atomic hydrogen (H*) played pivotal roles in the hydrogenation of phenol ring. The ECH technique also showed excellent performance in a wide pH range of 3-11 and with a high concentration of phenol (10 mM). Moreover, the functional groups (e.g., chloro- and methyl-) on phenol showed little influence on the superiority of the ECH system. This work provides a novel and practical solution for remediation of phenolic wastewater as well as recovery of valuable organic compounds.

Green synthesis of MIL-100(Fe) derivatives and revealing their structure-activity relationship for 2,4-dichlorophenol photodegradation

MIL-100(Fe), a kind of iron-based metal-organic framework materials (MOFs), can be synthesized at room temperature or hydrothermal conditions, which are promising precursor materials for preparing photocatalysts to degrade some recalcitrant chlorophenols in industrial wastewater. However, the relationship between the structural characterization of MIL-100(Fe) derivatives and their photodegradation behavior of chlorophenol pollutants is still unclear. Thus, in this work, a porous Z-scheme α-Fe₂O₃/MIL-100(Fe) composite was successfully fabricated via partial-pyrolysis of MIL-100(Fe) precursor synthesized through green synthesis route, which was further used for degrading high-concentration of 2,4-dichlorophenol under visible-light illumination (λ > 420 nm). The effects of synthesis route and pyrolysis temperature of MIL-100(Fe) on the degradation efficiencies of as-derived materials for 2,4-dichlorophenol were investigated. The structure-activity relationship was illuminated in detail. Otherwise, the influence of several process factors, i.e., initial concentration and pH of the 2,4-dichlorophenol solution, catalyst dosage on the degradation efficiency of 2,4-dichlorophenol has also been performed. The removal efficiency of 2,4-dichlorophenol with the initial concentration of 100 mg L^-1 reached up to 87.65% under optimized conditions. Lastly, the possible mechanism was explored based on trapping experiments and some other characterization results. The study in this paper not only exhibited new insight into the modified α-Fe₂O₃ material with high photocatalytic activity but also provided a promising method for treating wastewater containing 2,4-dichlorophenol or other similar organic pollutants.

A robust biocatalyst based on laccase immobilized superparamagnetic Fe3O4@SiO2-NH2 nanoparticles and its application for degradation of chlorophenols

The presence of chlorophenols in water and wastewater is considered a serious environmental issue. To eliminate these micropollutants, biodegradation of chlorophenols using enzyme-nanoparticle conjugated biocatalyst, is proposed as an economical and eco-friendly method. Herein, amino-functionalized superparamagnetic Fe₃O₄@SiO₂-NH₂ nanoparticles with core-shell structure were constructed as a promising carrier for immobilization of laccase from Trametes versicolor. Compared with free laccase, Fe₃O₄@SiO₂-NH₂-Laccase displayed remarkable outcomes in all major areas such as temperature and storage stabilities, and tolerance to organic solvents and metal ions. The biocatalytic performance and reusability of Fe₃O₄@SiO₂-NH₂-Laccase were evaluated for the degradation of 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) in repeated cycles. Even after 10 successive reuses, the degradation rate of 2,4-DCP and 2,4,6-TCP were found to be 54.9% and 68.7%, respectively. The influences of solution pH, initial chlorophenol concentration, and temperature on the degradation rate of these two chlorophenols were evaluated. The degradation intermediate products including dimers, trimers, and tetramers of 2,4-DCP and 2,4,6-TCP were identified. Release of chloride ions was observed during the enzymatic degradation of these two chlorophenols. Based on the determination of intermediate products and released chloride ions, the degradation pathway that was involved in dehydrogenation, reactive radical intermediates formation, dechlorination, self-coupling and oligomers/polymers formation was proposed. The toxicity of these two chlorophenols and their intermediates was substantially reduced during the enzymatic degradation. The results of this study might present an alternative clean biotechnology for the remediation of 2,4-DCP and 2,4,6-TCP contaminated water matrices.

Facile synthesis of novel NH2-MIL-53(Fe)/AgSCN heterojunction composites as a highly efficient photocatalyst for ciprofloxacin degradation and H2 production under visible-light irradiation

A novel NH2-MIL-53(Fe)/AgSCN composite photocatalyst was successfully prepared by a one-step chemical precipitation method, the composite show high photocatalytic activity for antibiotics degradation and H2 evolution under visible light irradiation.

Life time enhanced Fenton-like catalyst by dispersing iron oxides in activated carbon: Preparation and reactivation through carbothermal reaction

Heterogeneous Fenton-like catalyst prepared by dispersing iron oxides in activated carbon (FeOx@AC) has frequently been assembled for advanced oxidation processes (AOPs). An intriguing but barely emphasized property of FeOx@AC is that it can be easily reactivated through a simple carbothermal reaction. Importantly, by this manner the life time of FeOx@AC could be effectively enhanced. We herein reported the synthesis of FeOx@ACs hydrothermally with assistance of several commercially available surfactants and their performance in degrading real dye wastewater were evaluated. In general, as-synthesized FeOx@ACs were noted to equip high Fe content. Deposited FeOx reduced the fraction of micropores but simultaneously introduced additional mesopores and macropores. Elevated magnetite content was observed in FeOx@AC equipped with high fraction of micropore and mesopore and macropore but fast dye degradation occurred at FeOx@AC possessing low fraction of micropore along with low mesopores and macropores. Reactivation via carbothermal reaction redistributed the deposited FeOx by increasing micropores while decreasing mesopores and macropores. Importantly, well dispersed FeOx synthesized with the assistance of surfactants exhibited high resistance to the corrosion in the degradation process. For the perspective of circular economy, deep understanding the material chemistry of FeOx@AC would be of particularly interest for further enhancing its life time.

Examination of Photocatalyzed Chlorophenols for Sequential Photocatalytic-Biological Treatment Optimization

Given the known adverse effect of chlorophenols for the aquatic environments which they can reach, the development of efficient methods both technically and economically to remove them has gained increasing attention over time. The combination of photocatalytic oxidation with biological treatment can lead to high removal efficiencies of chlorophenols, while reducing the costs associated with the need to treat large volumes of aqueous solutions. Therefore, the present paper had as its main objective the identification of the minimum photocatalytic oxidation period during which the aqueous solutions of 4-chlorophenol and 2,4-dichlorophenol can be considered as readily biodegradable. Thus, the results of photocatalytic oxidation and biodegradability tests showed that, regardless of the concentration of chlorophenol and its type, the working solutions become readily biodegradable after up to 120 min of irradiation in ultraviolet light. At this irradiation time, the maximum organic content of the aqueous solution is less than 40%, and the biochemical oxygen demand and chemical oxygen demand (BOD/COD) ratio is much higher than 0.4. The maximum specific heterotrophic growth rate of activated sludge has an average value of 4.221 d−1 for 4-chlorophenol, and 3.126 d−1 for 2,4-dichlorophenol. This irradiation period represents at most half of the total irradiation period necessary for the complete mineralization of the working solutions. The results obtained were correlated with the intermediates identified during the photocatalytic oxidation. It seems that, working solutions initially containing 4-chlorophenol can more easily form readily biodegradable intermediates.