Degradation Of Organic Pollutants Research Articles

Engineering a staggered type-II Bi2WO6/WO3 heterojunction with improved photocatalytic activity in wastewater treatment

In recent years, the removal organic pollutants from wastewater by advanced oxidation processes, especially photocatalysis, has become a meaningful approach due to its eco-friendliness and low cost. Herein, staggered type-II Bi2WO6/WO3 heterojunction photocatalysts were prepared by a facile hydrothermal route and investigated by modern physicochemical methods (X-ray diffraction, scanning electron microscopy, low-temperature nitrogen adsorption-desorption, and diffuse reflectance spectroscopy). The optimized BWOW-5 photocatalyst exhibited a H2O2-assisted photocatalytic methylene blue removal efficiency of 94.1% (k = 0.01414 min−1) within 180 min under optimal reaction conditions, which is much higher than that of unmodified Bi2WO6 and WO3 due to efficient separation of the photogenerated charge carriers. The trapping experiments demonstrated that photogenerated hydroxyl radicals and holes play a key role in the photodegradation reaction. Moreover, the optimized BWOW-5 heterojunction photocatalyst exhibited excellent activity in the H2O2-assisted degradation of other pollutants, namely phenol, isoniazid, levofloxacin, and dibenzothiophene with the removal rate of 63.1, 73.6, 95.0, and 72.4%, respectively. This investigation offers a design strategy for Bi2WO6-based multifunctional photocatalytic composites with improved activity for organic pollutant degradation.

Degradation of Methyl Red (MR) dye via fabricated Y2O3–MgO/g-C3N4 nanostructures: Modification of band gap and photocatalysis under visible light

In this study, graphitic carbon nitride (g-C3N4) composites with metal oxide nanoparticles (Y2O3, MgO) and their combination (CN, YCN, MCN and YMCN) were synthesized by an ultrasonic technique and were then characterized by different tools such as UV–Vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). From the XRD diffractograms of the YMCN ternary composite, the g-C3N4, cubic MgO and Y2O3 structural phases were identified. The morphology of the as prepared nanostructure from the SEM analysis revealed the dispersion of the metal oxides nanoparticles with the graphitic sheets and the presence of the corresponding elements were confirmed by the EDX and XPS data. The FT–IR bands confirmed the bonding of the metal oxides to the nitride host as indicated by the characteristic modes. A reduction of the band gap energies was confirmed by the UV–Vis to indicate its visible light possible photoactivity. Accordingly, its visible light driven photocatalytic performance was assessed for methyl red degradation. The degradation competence was highest for the ternary composite YMCN due to the coupling of the semiconductors which increases the absorption and the charge carriers’ separation as well. The kinetics of degradation was best described by pseudo-first-order, and the most active species were the holes and the hydroxyl radicals. Thus, the YMCN nanocomposite is a visible light-active photocatalyst which can be engaged in the degradation of organic pollutants.

Construction of TiO2@Cu2O-CuS heterostructures integrating RGO for enhanced full-spectrum photocatalytic degradation of organic pollutants

This study presents the development and optimization of TiO2@Cu2O-CuS heterostructures, enhanced with reduced graphene oxide (RGO), for efficient photocatalytic degradation of organic pollutants, focusing on imidacloprid. Two configurations, TiO2/RGO/Cu2O-CuS and Cu2O-CuS/RGO/TiO2, are explored to highlight the impact of material layering on photocatalytic efficiency. The strategic integration of RGO optimizes charge transfer, crucial for photocatalysis. Comprehensive characterization techniques, such as X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, and Nitrogen adsorption-desorption isotherms, provide insights into the crystalline structure, morphology, surface chemistry, and textural properties of the heterostructures. The TiO2/RGO/Cu2O-CuS configuration significantly outperforms its counterpart in photocatalytic activity under full-spectrum (UV–VIS–IR) illumination, due to improved charge carrier dynamics and synergistic interactions between the composite materials. Remarkably, the TiO2/RGO/Cu2O-CuS assembly achieved over 95 % degradation of imidacloprid under simulated solar irradiation, marking a breakthrough in solar spectrum utilization for photocatalysis and exhibits promising recyclability, maintaining its high photocatalytic efficiency even after multiple degradation cycles, highlighting its potential for sustainable pollutant removal applications. Additionally, this configuration demonstrates a twofold increase in degradation efficiency compared to separate UV and VIS irradiations, emphasizing its rapid pollutant removal capability. This research underscores the critical role of material layer sequencing in developing high-efficiency photocatalytic systems and marks a significant advancement in environmental remediation technologies that harness renewable energy sources.

Sn/Sb–assisted alum sludge electrodes for eliminating hydrophilic organic pollutants in self-produced H2O2 electro-Fenton system: Insights into the co-oxidation mediated by 1O2 and •OH(ads)

Few reports have focused on using particle electrodes with polar adsorbent properties in heterogeneous electro-Fenton (EF) system to improve the degradation of hydrophilic organic pollutants (HLOPs). In this study, a hydrophilic electrode Sn–Sb/AS was prepared by supporting metals Sn and Sb on alum sludge (AS), which can effectively degrade 91.68%, 92.54%, 89.62%, and 96.24% of the four types of HLOPs, chlorpyrifos (CPF), atrazine (ATZ), diuron (DIU), and glyphosate (PMG), respectively, within 40 min. The mineralization rates were 82.37%, 78.93%, 73.98%, and 85.65% for CPF, ATZ, DIU, and PMG, respectively. Based on the analysis of Electron Paramagnetic Resonance test, quenching test, and identified anthracene endoperoxide, the degradation at the cathode was attributed to non-radical oxidation via interaction with 1O2. In contrast, the anodic oxidation occurred via direct electron transfer at the anode and/or oxidation via interaction with adsorbed •OH (•OHads) around the particle electrodes. Furthermore, the reaction sites were calculated by Density functional theory (DFT) and Fukui function, corresponding to the electrophilic attack (fA-) of 1O2 and anodic direct oxidation, besides, the radical attack (fA0) of •OH(ads). Herein, this study proposes a targeted elimination strategy for HLOPs in wastewater treatment using particle electrodes with polar adsorbent properties in EF system.

Boosting tribo-catalytic degradation of organic pollutants by BaTiO3 nanoparticles through metallic coatings

Recently, tribo-catalysis has emerged as an appealing technology to harvest mechanical energy for environmental remediation. While most investigations have focused on catalyst optimization to enhance tribo-catalytic degradation, here we studied the effects of some metal disks placed on beaker bottoms (named coatings) on the tribo-catalytic degradation by BaTiO3 (BTO) nanoparticles under magnetic stirring. For 20 mg/L Rhodamine B (RhB) solution, Cr, Cu, and Ti coatings improved the kinetic constants of BTO nanoparticles by 3.1, 3.4, 5.2 folds, respectively. Ti coating was further found to result in 99 % degradation in just 3 h for 50 mg/L RhB solution, and elevate the kinetic constants by 19.1 and 16.6 folds for 20 mg/L methyl orange (MO) and 20 mg/L methylene blue (MB) solutions, respectively. EPR, FL and UV–vis spectroscopy verified that modifying vessel bottom with Ti coating enabled BTO nanoparticles to generate more active species. First-principles calculations of the work functions of Cr, Cu, and Ti surfaces, and the energy-band structure of BTO revealed a decreased electron-hole recombination rate due to the transfer of excited electrons to metallic coatings. These results suggest that modifying vessel bottoms with suitable metallic coatings is a simple, eco-friendly and efficient strategy to boost tribo-catalysis for environmental remediation.

Controlled preparation of bamboo charcoal/BiOCl with efficient visible-light-driven photocatalytic activity for organic pollutant degradation using the residues of bamboo processing

In this research, bamboo charcoal (BC)/BiOCl composites were successfully prepared by a simple hydrothermal method, where the BC was derived from the residues of bamboo processing. The BC/BiOCl composites displayed nanosheet structures with tight combination between bamboo charcoal and BiOCl. The oxygen vacancies (OVs) concentration and photoelectric properties of BC/BiOCl composites were boosted with the doped bamboo charcoal. The photocatalytic performance of the composites was evaluated by the degradation of RhB and TCH. Meanwhile, the possible intermediates, degradation pathways and toxicity of the pollutants in the photocatalytic process were elucidated. When the additive dosage of BC and hydrothermal temperature were 5% and 140°C, the 5BC-140 has highest photocatalytic efficiency under visible light irradiation, and the degradation rates of RhB and TCH over the 5BC-140 composite were 97.9% and 69% at 36 min and 120 min, with the kinetic constants of 6.2 times and 2.0 times as high as those of pure BiOCl, respectively. The establishment of Bi-O-C bonds in the BC/BiOCl played a pivotal role in constructing atomic-level interfacial channels to boost the charge carriers’ separation. The enhanced photocatalytic activity was originated from the robust interaction between bamboo charcoal and BiOCl, promoting the rapid transfer of electrons and suppressing the combination of photogenerated electron-hole pairs through the increased oxygen vacancies. In addition, incubation experiments on green beans demonstrated the nontoxicity of contaminant solution degraded by the BC/BiOCl composites.

Development of 2D/2D h-MoO3/Ag/g-C3N4 heterojunction photocatalyst with enhanced photocatalytic performance for the detoxification of methylene blue and tetracycline under solar light illumination

In this study, direct thermal polycondensation, hydrothermal, and ultrasonic techniques were used to fabricate photocatalysts consisting of bare g-C3N4 (GCN), h-MoO3 (MoO3), MoO3/g-C3N4 (MGCN), and MoO3/Ag/g-C3N4 (MAGCN) composites. These methods were used to improve the photocatalytic effect, especially for environmental applications. The surface and chemical properties of the fabricated samples were investigated by XRD, FT-IR, FE-SEM, HR-TEM, UV-DRS, XPS, and PL analysis. Bare and composite photocatalysts were tested for photodegradation of the methylene blue (MB) dye and tetracycline (TC) antibiotic under solar irradiation. The MAGCN composite material exhibits remarkable efficiency in degrading 99% of MB dye and 90% of TC antibiotic within a time frame of 60 min when exposed to sunlight irradiation. The degradation rate constants (k) of MB and TC in the most active MAGCN photocatalyst were 11.02 and 7.03 times higher than those of pristine GCN, respectively. The scavenger reaction shows that the most important reactive species in the photocatalytic process are superoxide and photogenerated holes. The outstanding photocatalytic efficiency of the MAGCN catalyst was demonstrated by the fact that Ag nanoparticles act as mediators of fast charge transfer, resulting in higher absorption of sunlight, enhanced charge separation/transfer, and regeneration by MoO3 and GCN. The MAGCN photocatalyst exhibits remarkable activity, maintains its performance over six consecutive reaction cycles, and exhibits excellent stability and reusability. Intermediates were analyzed by GC-MS, and suitable degradation pathways were proposed. These results enable the development of an effective Z-scheme heterojunction photocatalyst and facilitate its wide application in the degradation of organic pollutants in wastewater.

In-situ construction of AgI nanoparticle-decorated covalent triazine-based frameworks heterojunction with enhanced photocatalytic performance for the degradation of persistent organic pollutants

In this paper, a multitude of novel CTF-1/AgI (CTFA-x) type-Ⅱ heterojunction were fabricated by in-situ growth approach based on the stable covalent triazine-based framework CTFs. 2D CTF-1 with sufficient nitrogen sites anchored AgI to its matrix, supporting ample active sites for CTFA to degrade ciprofloxacin (CIP) in aqueous solution. The structural and physicochemical characteristic of the CTFA products were explored by TEM, XRD, XPS, FT-IR, BET and PL characterization. The respective roles and synergistic effects of AgI and CTF-1 are discussed. Benefiting from this unique structure, the CTF-1/AgI with the mass ratio of 1:1 (CTFA-50) demonstrated the highest photocatalytic capacity and showed a degradation efficiency of more than 90 % against CIP after 120 min under simulated sunshine irradiation. Compared to pure AgI and CTF-1, the apparent rate constant for the CIP photodegradation of CTFA-50 (0.0153 min−1) was found to be 6.7 and 8.5 times greater. The CTFA-50 catalyst possessed good structural stability and broad-spectrum applicability, and had the ability to efficiently degrade various stubborn organic matters including tetracycline (87.97 %), 2-sec-butyl-4,6-dinitrophenol (63.42 %), bisphenol A (68.22 %), rhodamine B (98.62 %), methyl orange (70.25 %), methylene blue (63.27 %). As demonstrated by the results of the radical trapping tests and EPR analysis, the photodegradation process of CIP was mostly mediated by •O2– and h+. In view of the LC/MS findings, all reaction intermediates could be determined and a reasonable photocatalytic mechanism was proposed.

A novel iron metal organic framework-based nanocomposite for the synergistic degradation and adsorption of organic pollutants and Cr (Ⅵ) under visible light

In this work, a novel nitrogenous Fe-TPPE metal-organic-framework (MOF) with excellent visible light catalytic activity was successfully prepared, and a magnetic composite (Fe3O4@Fe-TPPE) with Z-type heterojunction structure was designed to synergistically treat organic pollutants and Cr(Ⅵ). The materials were carefully characterized by powder X-ray diffractometry, scanning electron microscope, Fourier transform infrared analysis, UV–visible diffuse reflectance spectra, X-ray photoelectron spectroscopy, thermogravimetric analysis, etc. The characterizations of photoelectric properties showed that the novel Fe-TPPE MOF exhibited strong response to visible light and Fe3O4@Fe-TPPE had even stronger response. Furthermore, the adsorption and photocatalytic degradation capabilities of Fe-TPPE and Fe3O4@Fe-TPPE, and the versatility as photocatalysts for aqueous pollutants were assessed through removal studies of the model pollutants tetracycline, rhodamine, methyl blue and Cr (VI). Additionally, the removal mechanism of the Fe3O4@Fe-TPPE for the above pollutants was explored. The high removal efficiency, fast magnetic separation, great recycling stability and minimal leak during application all demonstrate the good potential of Fe3O4@Fe-TPPE for practical and sustainable treatment of aqueous pollutants.

Organic pollutants degradation by a superb MXene-based Z-scheme heterojunction Photocatalyst: Synthesize, delamination process, mechanism and toxicity assessment

In this study, a new CeO2/MXene-TiO2 photocatalyst was created using a simple and economical approach and thoroughly characterized by different techniques, including TEM, XPS, BET, XRD, Raman, and SEM. The focus of this research was to improve the degradation of tetracycline (TC), a commonly used antibiotic with known environmental and health risks. To optimize the degradation process, RSM- CCD method was used to systematically vary key parameters including initial TC concentration, photocatalyst dosage, pH and irradiation time. The trapping experiments were revealed that the hydroxyl (•OH) and superoxide anion (•O2-) radicals played a crucial role in this process. An impressive degradation efficiency of 96.60 % was achieved under optimal conditions, attributed to the Z-scheme electron transfer heterojunction, which enhances the generation and separation of oxidant species. LC-MS analysis was employed to elucidate the photodegradation pathway of TC by identifying the reaction intermediates. This analysis facilitated the proposal of a plausible mechanism for TC degradation. The demonstrated efficacy of the CeO₂/MXene-TiO₂ photocatalyst suggests its potential application in wastewater treatment for the significant degradation of persistent organic contaminants.

MXene-based composite aerogels with bifunctional ferrous ions for the efficient degradation of phenol from wastewater

Herein, MXene-based composite aerogel (MXene-Fe2+ aerogel) are constructed by a one-step freeze-drying method, using Ti3C2Tx MXene layers as substrate material and ferrous ion (Fe2+) as crosslinking agent. With the aid of the Fe2+ induced Fenton reaction, the synthesized aerogels are used as the particle electrodes to remove phenol from wastewater with three-dimensional electrode technology. Combined with the dual roles of Fe2+ and the highly conductive MXene, the obtained particle electrode possesses extremely effective phenol degradation. The effects of experiment parameters such as Fe2+ to MXene ratio, particle electrode dosage, applied voltage, and initial pH of solution on the removal of phenol are discussed. At pH = 2.5, phenol with 50 mg/L of initial concentration can be completely removed within 50 min at 10 V with the particle electrode dosage of 0.56 g/L. Finally, the mechanism of degradation is explored. This work provides an effective way for phenol degradation by MXene-based aerogel, which has great potential for the degradation of other organic pollutants in wastewater.

Polyarylimide-Based COF/MOF Nanoparticle Hybrids for CO2 Conversion, Hydrogen Generation, and Organic Pollutant Degradation

Polyarylimide-Based COF/MOF Nanoparticle Hybrids for CO₂ Conversion, Hydrogen Generation, and Organic Pollutant Degradation

Reinforcing 2D Single-Crystal Bi2O2CO3 with Additional Interlayer Carbonates by CO2-Assisted Solid-to-Solid Phase Transition.

A facile gaseous CO2 mediated solid-to-solid transformation principle is adopted to insert additional CO3 2- anions into the thin single-crystal nanosheets of Bi2O2CO3, which is built of periodic arrays of intrinsic CO3 2- anions and (Bi2O2)2+ layers. The additional CO3 2- anions create abundant defects. The Bi2O2CO3 nanosheets with rich interlayer CO3 2- exhibit superior electronic properties and charge transfer kinetics than the pristine single-crystal 2D Bi2O2CO3 and display enhanced catalytic activity in photocatalytic CO2 reduction reaction and the photocatalytic oxidative degradation of organic pollutants. This work thus illustrates interlayer engineering as a flexible means to build layered 2D materials with excellent properties.

Enhanced photocatalytic degradation of organic pollutants by green-synthesized gold nanoparticles using polysaccharide for environmental remediation

The recent rise in textile dye wastewater discharge into the environment has detrimental effects on living organisms and human health. The present study reports a facile approach to green-synthesized AuNPs employing sesbania gum for catalytic and photocatalytic degradation of organic pollutants. The obtained AuNPs were characterized by various techniques such as UV–vis, FT-IR, SEM, TEM, AFM, zeta potential, LC-MS, and XPS. The XRD patterns revealed a highly crystalline and face-centered cubic structure. XPS and EDX analysis defined the chemical composition and product purity of SBG-AuNPs. Photocatalytic degradation of hazardous dyes congo red and safranin-O using SBG-AuNPs showed a rapid decomposition rate with 94.69 % under visible light irradiation. The effect of pH, dye concentration, and catalyst dose on photodegradation and recyclability was also studied. The kinetic plots were used to calculate the rate constant, showing a pseudo-first-order reaction. Scavenger trap experiments confirmed the role of h+ and superoxide(.O2−) as active species, and LCMS analysis was used to identify the degradation intermediates. The catalytic reduction of SBG–AuNPs was studied for brilliant green (BG) and methylene blue (MB) in the presence of NaBH4, resulting the degradation efficiency of 90.37 % and 84.52 %, respectively. This study presents an innovative approach for designing highly efficient photocatalysts for environmental remediation and wastewater treatment from textile dyes.

Ultrathin Sulfur‐Doped g‐C3N4 Nanosheets Controlled by Steam Activation for Enhanced Visible‐Light Photocatalytic Performance

AbstractGraphite carbon nitride (g‐C3N4) has garnered considerable attention due to its excellent photocatalytic properties for the degradation of organic matter in wastewater treatment. Herein, sulfur‐doped g‐C3N4 nanosheets (CN−S‐X) were successfully synthesized via physical steam activation using thiourea and urea as precursors. Comprehensive characterizations demonstrate that the enhanced photocatalysis is attributed to the ultrathin structure, highly active site, vacancy defects, and high specific surface area due to the synergy of S doping and steam activation. The as‐prepared CN−S‐25 photocatalyst exhibits a desirable degradation efficiency of 95.4 % for methylene blue dye with a high degradation rate of 2.65×10−2 min−1 under visible‐light irradiation, which are 2.1 and 5.52 times those for bulk g‐C3N4, respectively as well as good reusability and stability. This study provides a simple and promising strategy to regulate the nanostructure of g‐C3N4 for highly efficient photocatalytic degradation of organic pollutants.

Rational design of CdS-enwrapped polypyrrole nanoparticles for wastewater treatment: removal of hazardous pollutants in aqueous solutions.

The modern world requires a chemical industry that can run at low production costs while producing high-quality products with minimal environmental impact. The development of environmentally friendly, cost-effective, and efficient wastewater treatment materials remains a majorproblem for the sustainable approach. We prepared nanoscale cadmium sulfide (CdS)-enwrapped polypyrrole (PPy) polymer composites for degradation of organic pollutants. The prepared CdS@PPy nanocomposites were characterized by powder X-ray diffraction, scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible(UV) absorption spectroscopy, indicating proper intercalation between CdS and PPy. Consequently, the catalytic efficiency of the synthesized hybrid nanocomposites was analyzed through the degradation of methylene blue (MB) and rhodamine B (Rh B) under visible light irradiation. The measured degradation efficiency of the dye solutions under the photolysis process is about 18% and 23% for MB and Rh B dye, respectively. Furthermore, the recycle test result concludes that the CdS@PPy composite exhibits 91% and 89% of MB and Rh B dye degradation efficiency even at the 4th cycle, respectively. The positive synergistic impact of CdS and PPymay be the result of effective photocatalytic degradation of MB and RhB.

Investigation of singlet oxygen and superoxide radical produced from vortex-based hydrodynamic cavitation: Mechanism and its relation to cavitation intensity

Presently, the hydroxyl radical oxidation mechanism is widely acknowledged for the degradation of organic pollutants based on hydrodynamic cavitation technology. The presence and production mechanism of other potential reactive oxygen species (ROS) in the cavitation systems are still unclear. In this paper, singlet oxygen (1O2) and superoxide radical (·O2−) were selected as the target ROS, and their generation rules and mechanism in vortex-based hydrodynamic cavitation (VBHC) were analyzed. Computational fluid dynamics (CFD) were used to simulate and analyze the intensity characteristics of VBHC, and the relationship between the generation of ROS and cavitation intensity was thoroughly revealed. The results show that the operating conditions of the device have a significant and complicated influence on the generation of 1O2 and ·O2−. When the inlet pressure reaches to 4.5 bar, it is more favorable for the generation of 1O2 and ·O2− comparing with those lower pressure. However, higher temperature (45 °C) and aeration rate (15 (L/min)/L) do not always have positive effect on the 1O2 and ·O2− productions, and their optimal parameters need to be analyzed in combination with the inlet pressure. Through quenching experiments, it is found that 1O2 is completely transformed from ·O2−, and ·O2− comes from the transformation of hydroxyl radicals and dissolved oxygen. Higher cavitation intensity is captured and shown more disperse in the vortex cavitation region, which is consistent with the larger production and stronger diffusion of 1O2 and ·O2−. This paper shed light to the generation mechanism of 1O2 and ·O2− in VBHC reactors and the relationship with cavitation intensity. The conclusion provides new ideas for the research of effective ROS in hydrodynamic cavitation process.

MoSe2 with Ultra-Fine Pt Decoration for Efficient Photodegradation

Transition metal dichalcogenides are widely studied for their photocatalytic ability due to the adjustable bandgap, high carrier mobility and possibility of foreign-element doping. In this work, multilayer molybdenum diselenide (MoSe2) was decorated with ultra-fine Pt nanoparticles through the mild hydrothermal method. MoSe2-Pt nanocomposites were synthesized and showed good structural and chemical stabilities. The incorporation of Pt nanoparticles provides plenty of active sites for MoSe2. The dominant Pt particle sizes are 1.8 nm, 1.8 nm, and 1.9 nm for the three synthesized samples, respectively. The mean crystal sizes of Pt (111) were calculated from X-ray diffraction patterns and we found that they were in accordance with the particle sizes. Both the particle sizes and mean crystal sizes are related to the synthesis conditions. X-ray photoelectron spectroscopy (XPS) characterizations revealed the formation of Se–Pt bonding. The relative contents of Pt–Se bonding were also calculated from XPS results, and they show the same trends as the optical absorption properties. Combining the XPS and optical absorption results, the effects of Se–Pt bonding during the photo-related process could be further confirmed. By degrading methylene blue (MB) under visible light, the synthesized nanocomposites proved promising for application in real-case degradation of organic pollutants. The sample synthesized with a moderate content of MoSe2 exhibited the best photodegradation efficiency, which could be explained by the maximum Pt-Se contents. Based on the experimental findings, we proposed a possible photodegradation mechanism.

Sn-based precursors dependence for electrocatalytic degradation of organic pollutants on Ti/SnO2-Sb electrode

The utilization of SnO2-based coated electrodes prepared through thermal decomposition process for degrading organic pollutants is a prominent topic in the field of wastewater treatment. However, the impact of precursor salts on the structure and catalytic degradation activity of Sn oxide coatings still lacks research. This study examined the procedures for synthesizing SnO2 coatings by high-temperature oxidation of two common Sn chlorides with different valences. Through systematic characterization, it was revealed that the high boiling point of SnCl2 makes it less volatile during the high-temperature oxidation stage, allowing for maximum retention of Sn source on the substrate, thereby forming a dense and stable oxide coating structure (Ti/SnO2-Sb(II)). On the other hand, the low boiling point of SnCl4 makes it easily volatile during heating, resulting in a thin and loose structure coating (Ti/SnO2-Sb(IV)). Due to these factors that the electrical conductivity of Ti/SnO2-Sb(II) is significantly superior to Ti/SnO2-Sb(IV). Moreover, at 20 mA·cm−2, Ti/SnO2-Sb(II) can achieve almost complete decolorization of methylene Blue (MB) in just 40 minutes, while achieving the same decolorization rate with Ti/SnO2-Sb(IV) requires over 90 minutes. Furthermore, stability tests demonstrated that after 5 cycles of reaction, Ti/SnO2-Sb(II) showed no significant decrease in decolorization rate of MB, whereas Ti/SnO2-Sb(IV) exhibited a decline in decolorization performance towards MB starting from the 2nd cycle. This study revealed the crucial role of precursor salt boiling points in the formation of stable SnO2-based coated electrodes, providing a theoretical basis for the development of structurally stable and highly catalytic oxidation active coating electrodes.

Efficient removal of environmental pollutants by green synthesized metal nanoparticles of Clitoria ternatea

Prevention and management of water pollution are becoming a great challenge in the present scenario. Different conventional methods like carbon adsorption, ion exchange, chemical precipitation, evaporation, and biological treatments remove water pollutants. Nowadays, the requirement for effective, non-toxic and safe waste management strategies is very high. Nanomaterials have been explored in various fields due to their unique characteristics. Green synthesis of nanomaterial is becoming more popular due to their safety, non-toxicity, and ease of scale-up technology. Metal nanoparticles can be synthesized using a green synthesis method using biological sources provided by eco-friendly, non-hazardous nanomaterials with superior properties to bulk metals. Hence, this study has designed a green synthesis of magnetic (cobalt oxide) and noble (gold) nanoparticles from the fresh flowers of Clitoria ternatea. The flavonoids and polyphenols in the extract decreased the energy band gap of cobalt oxide and gold nanoparticles; hence, the capping of the natural constituents in Clitoria ternatea helped form stable metal nanoparticles. The cobalt oxide and gold nanoparticles are evaluated for their potential for eliminating organic pollutants from industrial effluent. The novelty of this present work represents the application of cobalt oxide nanoparticles in the removal of organic pollutants and a comparative study of the catalytic behaviour of both metal nanoparticles. The degradation of bromophenol blue, bromocresol green, and 4–nitrophenol in the presence of gold nanoparticles was completed in 120, 45, and 20 min with rate constants of 3.7 × 10−3/min, 6.9 × 10−3/min, and 16.5 × 10−3/min, respectively. Similarly, the photocatalysis of bromophenol blue, bromocresol green, and 4–nitrophenol in the presence of cobalt oxide nanoparticles was achieved in 60, 90, and 40 min with rate constants of 2.3 × 10−3/min, 1.8 × 10−3/min, and 1.7 × 10−3/min, respectively. The coefficient of correlation (R2) values justify that the degradation of organic pollutants follows first-order kinetics. The significance of the study is to develop green nanomaterials that can be used efficiently to remove organic pollutants in wastewater using a cost-effective method with minimal toxicity to aquatic animals. It has proved to be useful in environmental pollution management.