Synergetic adsorption and Fenton-like degradation of tetracycline hydrochloride by magnetic spent bleaching earth carbon: Insights into performance and reaction mechanism

Facile Fabrication of Zeolitic Imidazolate Framework-8@Regenerated Cellulose Nanofibrous Membranes for Effective Adsorption of Tetracycline Hydrochloride

The excessive utilization of antimicrobials in humans and animals has resulted in considerable environmental contamination, necessitating the development of high-performance antibiotic adsorption media. A significant challenge is the development of composite nanofibrous materials that are both beneficial and easy to fabricate, with the aim of improving adsorption capacity. Herein, a new kind of zeolitic imidazolate framework-8 (ZIF-8)-modified regenerated cellulose nanofibrous membrane (ZIF-8@RC NFM) was designed and fabricated by combining electrospinning and in situ surface modification technologies. Benefiting from its favorable surface wettability, enhanced tensile strength, interconnected porous structure, and relatively large specific surface area, the resulting ZIF-8@RC NFMs exhibit a relatively high adsorption capacity for tetracycline hydrochloride (TCH) of 105 mg g-1 within 3 h. Moreover, a Langmuir isotherm model and a pseudo-second-order model have been demonstrated to be more appropriate for the description of the TCH adsorption process of ZIF-8@RC-3 NFMs. Additionally, this composite fibrous material could keep a relatively stable adsorption capability under various ionic strengths. The successful fabrication of the novel ZIF-8@RC NFMs may shed light on the further development of wastewater adsorption treatment materials.

Photocatalytic oxidation of Reactive Red 195 by bimetallic Fe-Co catalyst: Statistical modeling and optimization via Box-Behnken design

Response surface methodology (RSM) is an effective tool for process optimization with multi-complex operational factors. The present work aims to model and optimize the photocatalytic oxidation (PCO) parameters of Reactive Red 195 (RR195) dye decoloration with the SiO2-supported Fe-Co catalyst (FCS) derived from a novel catalyst synthesis method, fluidized-bed crystallization (FBC) process, using Box-Behnken design (BBD) as the RSM statistical model. The Fe-Co@SiO2 catalyst was successfully fabricated using the FBC process, and it showed good catalytic activity and performance toward the degradation of RR195. The extent of the effects of pH, H2O2 dosage (HD), catalyst loading (CL), and operating time (t) on the decoloration of RR195 was studied. Hence, the order of variable significance follows the sequence: pH > t > CL > HD. pH has the most significant effect among the variables for RR195 decoloration. The decoloration efficiency predicted by the BBD model was 88.3% under the optimized operation conditions of initial pH of 3.15, 0.76 mM H2O2, 1.18 g L-1 FCS and 59.4 min of operating time. The actual decoloration efficiency was very close to the predicted value indicating that BBD can efficiently be utilized to optimize RR195 degradation with FCS under the PCO system.

Enhanced Heterogeneous Fenton-like Process for Sulfamethazine Removal via Dual-Reaction-Center Fe-Mo/rGO Catalyst

A heterogeneous Fenton-like catalyst with single redox site has a rate-limiting step in oxidant activation, which limited its application in wastewater purification. To overcome this, a bimetallic doping strategy was designed to prepare a heterogeneous Fenton-like catalyst (Fe-Mo/rGO) with a double-reaction center. Combined with electrochemical impedance spectroscopy and density functional theory calculation, it was confirmed that the formation of an electron-rich Mo center and an electron-deficient Fe center through the constructed Fe-O-Mo and Mo-S-C bonding bridges induced a higher electron transfer capability in the Fe-Mo/rGO catalyst. The designed Fe-Mo/rGO catalyst exhibited excellent sulfamethazine (SMT) degradation efficiency in a broad pH range (4.8-8.4). The catalytic performance was hardly affected by inorganic anions (Cl^-, SO₄^2- and HCO₃^-) in the complicated and variable water environment. Compared to Fe/rGO and Mo/rGO catalysts, the SMT degradation efficiency increased by about 14.6 and 1.6 times in heterogeneous Fenton-like reaction over Fe-Mo/rGO catalyst. The electron spin resonance and radical scavenger experiments proved that ·O₂^-/HO₂· and ¹O₂ dominate the SMT removal in the Fe-Mo/rGO/H₂O₂ system. Fe and Mo, as active centers co-supported on rGO, significantly enhanced the electron transfer between catalyst, oxidant, and pollutants, which accelerated the reactive oxygen species generation and effectively improved the SMT degradation. Our findings offer a novel perspective to enhance the performance of heterogeneous Fenton-like catalysts by accelerating the electron transfer rate in the degradation of organic pollutants.

An efficient ultrasonic-assisted bleaching strategy customized for yak hair triggered by melanin-targeted Fenton reaction

Promoting processing efficiency and taking advantage of agricultural by-products are two promising ways to achieve sustainable textile industry. This study presents a customized efficient ultrasonic-assisted bleaching strategy for yak hair - a widely existing but underexploited secondary dark shade fibre from yak. A melanin-targeted Fenton oxidation process is established which involves three phases, i.e., (I) incorporation of Fe²⁺ ions with melanin, (II) catalytic oxidative bleaching using hydrogen peroxide (H₂O₂), and (III) reductive cleansing. The bleaching efficacy, dyeing performance and tensile property of yak hair treated with and without ultrasound were explored and compared. Further, the ultrasonic bleaching mechanism in terms of the catalytic effect of Fe²⁺ ions, the promotion of H₂O₂ decomposition, removal of melanin granule from yak hair, were demonstrated. Finally, the main effects and interactions of parameters in phase II, and optimal condition were obtained through mathematical modelling based on a central composite design (CCD). Results reveal that ultrasonic bleaching dramatically enhances the whiteness index (WI) of yak hair from 11 to 45 which is 44.6% higher than those bleached without ultrasound, and also promotes the uptake of acid dyes. There is only 15% tensile strength loss and 14% elongation increment of yak hair after ultrasonic bleaching, rising from a slight damage of cuticle layer and cleavage of disulfide bonds, respectively. In the study of bleaching mechanism, Fe²⁺ ion is confirmed to improve the H₂O₂ decomposition rate by 20.9% which further runs up to 35.9% after introducing ultrasound. Ultrasound increases the concentration of hydroxyl radicals (HO) by 94% which are the main oxidative species participating in bleaching confirmed by HO scavenging experiment. The porous structure was observed on the cross section of yak hair stemming from the removal of melanin granules contributed by the cleaning action of ultrasound. A theoretical highest WI of 52.4 can be achieved under an optimal condition based on the CCD study. In general, the proposed melanin-targeted bleaching strategy for yak hair that integrates ultrasonic technology and Fenton reaction, is beneficial to the development of sustainable textile industry from material and processing perspectives.

Oxidative Degradation of Tetracycline by Magnetite and Persulfate: Performance, Water Matrix Effect, and Reaction Mechanism

This study presents a strategy to remove tetracycline by using magnetite-activated persulfate. Magnetite (Fe3O4) was synthesized at high purity levels-as established via X-ray diffractometry, transmission electron microscopy, and N2 sorption analyses-and tetracycline was degraded within 60 min in the presence of both magnetite and persulfate (K2S2O8), while the use of either substance yielded limited degradation efficiency. The effects of magnetite and persulfate dosage, the initial concentration of tetracycline, and the initial pH on the oxidative degradation of tetracycline were interrogated. The results demonstrate that the efficiency of tetracycline removal increased in line with magnetite and persulfate dosage. However, the reaction rate increased only when increasing the magnetite dosage, not the persulfate dosage. This finding indicates that magnetite serves as a catalyst in converting persulfate species into sulfate radicals. Acidic conditions were favorable for tetracycline degradation. Moreover, the effects of using a water matrix were investigated by using wastewater treatment plant effluent. Comparably lower removal efficiencies were obtained in the effluent than in ultrapure water, most likely due to competitive reactions among the organic and inorganic species in the effluent. Increased concentrations of persulfate also enhanced removal efficiency in the effluent. The tetracycline degradation pathway through the magnetite/persulfate system was identified by using a liquid chromatograph-tandem mass spectrometer. Overall, this study demonstrates that heterogeneous Fenton reactions when using a mixture of magnetite and persulfate have a high potential to control micropollutants in wastewater.