Photocatalytic degradation of commercial dye, CI Reactive Red 35 in aqueous suspension: Degradation pathway and identification of intermediates by LC/MS

Three-dimensional electro-Fenton system supplied with a nanocomposite of microbial cellulose/Fe3O4 for effective degradation of tetracycline

In this study, the catalytic activity of the modified microbial cellulose/Fe₃O₄ (MMC/ Fe₃O₄) composite was studied for tetracycline (TC) degradation and mineralization in a three-dimensional electro-Fenton system (3D-EF). The MC/Fe₃O₄ was modified at 400 °C for 60 min. The MMC/ Fe₃O₄ was fully analyzed (morphological, structural, chemical properties). Complete degradation and 65% mineralization of TC was achieved in the 3D-EF process (0.5 g L^-1 MMC/ Fe₃O₄, 10 mM NaCl electrolyte, and neutral pH) within 20 min and electrical energy consumption (EEC) 0.86 kwh g^-1 TC under the 6.66 mA cm^-2. High degradation efficiency TC, in 3D-EF system was attributed to significant single oxygen (¹O₂), superoxide(O₂^•-) participation and less to Hydroxyl radical (OH^•). Reusability of the MMC/ Fe₃O₄ was successfully carried out for five consecutive runs. Accordingly, greencompositeof MMC/ Fe₃O₄ can be considered as an efficient and durable particle electrode (PE) to degrade and mineralize emerging pollutants in an aquatic environment.

Enhanced photodegradation of reactive dyes in textile effluent with CoFe2O4/g-CN heterostructure-mediated peroxymonosulphate activation

Graphitic carbon nitride (g-C₃N₄) was employed as a sacrificial substructure and two-dimensional support to develop magnetic cobalt ferrite-carbon nitride (CoFe₂O₄/g-CN) composite via a one-step solid combustion method. The catalyst activated peroxymonosulphate (PMS), through the interconversion of Co^2 + /3+|_surf. and Fe^2 + /3+|_surf. on its surface for degradation of reactive dyes (RDs). Excellent ferromagnetic nature (44.15 emu g^-1) of the catalyst led to its efficient magnetic separation. With an optimum catalyst and PMS dose of 0.4 g L^-1 and 1.5 g L^-1, 99% RD removal was achieved for textile effluent (pH 9.5-10), under UV irradiation (48 W). In-depth radical scavenging experiments and EPR analysis confirmed the dominance of radical-based degradation process. Plausible degradation and mineralization pathways of RDs were proposed through identification of intermediates by LCMS/MS analysis. In brief, this study elucidates an exclusive strategy towards the use of g-C₃N₄ as fuel for facile synthesis of magnetic CoFe₂O₄/g-CN as a remarkable photocatalyst for activation of PMS towards mineralization of various industrially relevant RDs.

A comprehensive study on the heterogeneous electro-Fenton degradation of tartrazine in water using CoFe2O4/carbon felt cathode

In this study, cobalt ferrite coated carbon felt (CoFe₂O₄/CF) was synthesized by solvothermal method and applied as cathode for electro-Fenton (EF) treatment of tartrazine (TTZ) in water. The materials were characterized by SEM, XRD, FTIR, CV, and EIS to explore their physical, chemical, and electrical properties. The effects of solvothermal temperature and metal content on the TTZ removal were examined, showing that 220 °C with 2 mM of Co and 4 mM of Fe precursors were the best synthesis condition. Various influencing factors such as applied current density, pH, TTZ concentration, and electrolytes were investigated, and the optimal condition was found at 8.33 mA cm^-2, pH 3, 50 mgTTZ L^-1, and 50 mM of Na₂SO₄, respectively. By radical quenching test, , ¹O₂, and HO were recognized as the key reactive oxygen species and the reaction mechanism was proposed for the EF decolorization of TTZ using CoFe₂O₄/CF cathode. The reusability and stability test showed that the highly efficient CoFe₂O₄/CF cathode is very promising for practical application in wastewater treatment, especially for dyes and other recalcitrant organic compounds to improve its biodegradability.

Bimetallic Ag-Zn-BTC/GO composite as highly efficient photocatalyst in the photocatalytic degradation of reactive yellow 145 dye in water

Ag_x-Zn_100-x-BTC/GO composites (BTC: benzene-1,3,5-tricarboxylic, GO: graphene oxide) with different Ag/Zn molar ratios were synthesized using microwave-assisted hydrothermal treatment. The Ag_x-Zn_100-x-BTC/GO exhibited excellent photocatalytic performance in the reactive yellow 145 dye (RY-145) degradation under irradiation of visible light with nearly 100% of RY-145 removal after 35 min, as compared to Zn-BTC/GO and Ag-BTC/GO. Reactive oxygen species scavenging assays have shown that the holes (h⁺) and superoxide radical anion (O₂^-•) play a primary role in RY-145 degradation. Based on the band structure of materials, the Z-scheme photocatalytic mechanism was suggested. The effect of catalyst dosage, pH and dye concentration on the efficiency of photocatalytic activity of bimetallic Ag₅₀-Zn₅₀-BTC/GO was also investigated. The improvement in photocatalytic activity of bimetallic Ag₅₀-Zn₅₀-BTC/GO could be given by the synergism of (i) absorption of visible light confirmed by UV-Vis diffuse reflectance spectra; (ii) the increased lifetime as evidenced by photoluminescence spectra and transient photocurrent response; (iii) the increased oxygen vacancy defects as confirmed by X-ray photoelectron spectroscopy results. The degradation pathway of RY-145 dye was also predicted based on liquid chromatography-mass spectrometer analysis. The removed chemical oxygen demand, biological oxygen demand, total organic carbon outcomes indicated the high mineralization ability for RY-145 degradation over Ag₅₀-Zn₅₀-BTC/GO.

High efficiency photocatalytic degradation of Ambroxol over Mn doped TiO2: Experimental designs, identification of transformation products, mineralization and mechanism

Ambroxol (AMB) is a drug commonly used for chronic bronchitis prevention. Once released in surface water, this recalcitrant chemical becomes a hazardous pollutant. Here, we investigated the ability of 1% Mn-doped TiO₂ (Mn-TiO₂) to mineralize AMB by photocatalysis. We studied the morphology, and the physical and electrochemical properties of Mn-TiO₂ using X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, X-ray fluorescence, BET method, UV-visible, and electrochemical study and optimized the AMB degrading experimental conditions through response surface methodology (RSM). Mn-TiO₂ at the dose of 0.625 g·L^-1 allowed the complete photodegradation of AMB (30 ppm) at pH 7 under UVA light irradiation for 30 min while total mineralization in CO₂ (>96%) was achieved after 24 h of irradiation. Mn-TiO₂ was 1.6-time more efficient than TiO₂ Degussa P25. Product studies were also carried out by liquid chromatography coupled to electrospray high resolution mass spectrometry. Twenty-one photodegradation products were detected and identified. In addition, ionic chromatography analyses revealed the release of Br^-, NH₄⁺, and NO₃^- at respectively 97, 63 and 35% of the total Br, and N initially present in AMB. Finally, the reusability of the photocatalyst was also tested. After four cycles, the almost complete photodegradation of AMB was achieved showing that Mn-TiO₂ was highly stable. This work brings new physical characteristics on Mn-TiO₂ photocatalyst. Moreover, it is the first study investigating the photocatalytic degradation of recalcitrant AMB drug.

Characterization of synthetic dyes for environmental and forensic assessments: A chromatography and mass spectrometry approach

Dyes have become common substances since they are employed in mostly all objects surrounding our daily activities such as clothing and upholstery. Based on the usage and disposal of these objects, the transfer of the dyes to other media such as soil and water increases their prevalence in our environment. However, this prevalence could help to solve crimes and pollution problems if detection techniques are proper. For that reason, the detection and characterization of dyes in complex matrices is important to determine the possible events leading to their deposition (natural degradation, attempts of removal, possible match with evidence, among others). Currently, there are several chromatographic and mass spectrometric approaches used for the identification of these organic molecules and their derivatives with high specificity and accuracy. This review presents current chromatographic and mass spectrometric methods that are used for the detection and characterization of disperse, acid, basic, and reactive dyes, and their derivatives.

Experimental design based response surface methodology optimization of ultrasonic assisted adsorption of safaranin O by tin sulfide nanoparticle loaded on activated carbon

In this research, the adsorption rate of safranine O (SO) onto tin sulfide nanoparticle loaded on activated carbon (SnS-NPAC) was accelerated by the ultrasound. SnS-NP-AC was characterized by different techniques such as SEM, XRD and UV-Vis measurements. The present results confirm that the ultrasound assisted adsorption method has remarkable ability to improve the adsorption efficiency. The influence of parameters such as the sonication time, adsorbent dosage, pH and initial SO concentration was examined and evaluated by central composite design (CCD) combined with response surface methodology (RSM) and desirability function (DF). Conducting adsorption experiments at optimal conditions set as 4 min of sonication time, 0.024 g of adsorbent, pH 7 and 18 mg L(-1) SO make admit to achieve high removal percentage (98%) and high adsorption capacity (50.25 mg g(-)(1)). A good agreement between experimental and predicted data in this study was observed. The experimental equilibrium data fitting to Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show that the Langmuir model is a good and suitable model for evaluation and the actual behavior of adsorption. Kinetic evaluation of experimental data showed that the adsorption processes followed well pseudo-second-order and intraparticle diffusion models.