Mineralization Of Methylene Blue Research Articles

Visible light induced photocatalytic degradation of methylene blue using carbon fibre cloth - Bismuth oxybromide – Water hyacinth derived silver nanocomposite

Methylene Blue (MB), a frequently used cationic dye, is recognized for its persistence and probable toxicity, making its removal from wastewater an urgent environmental concern. This study reports the solar photocatalytic degradation efficiency of MB by bismuth oxybromide-green silver nanoparticles (AgNPs) as catalyst. AgNPs were produced by the green synthesis method from an invasive aquatic weed water hyacinth (Pontederia crassipes). The AgNPs were doped on Bismuth oxybromide (BiOBr) nanosheets formed on the surface of carbon fibre cloth (CFC) to form the catalyst CFC-BiOBr-Ag. Under optimum conditions of 5 mg/L of initial MB concentration and near-neutral pH, one piece of CFC-BiOBr-Ag photocatalyst (5.78 mg/L) exhibited 95.68% degradation efficiency of MB in 4 h. TOC removal studies showed a removal efficiency of 74.82% after 4 h, indicating the potential for mineralization of MB. Adsorption-photocatalysis-desorption study revealed complete degradation of adsorbed MB at the end of the photocatalytic degradation. Additionally, the catalyst exhibited good reusability, with more than 84.88% degradation efficiency even after five cycles of use. Under direct sunlight, the CFC-BiOBr-Ag catalyst demonstrated MB degradation efficiency of 97.52% after 3 h of treatment. MB breakdown was evidently done by the hole (h+) and the superoxide radical (O2•−). The mechanism of MB degradation was adsorption and subsequent degradation by the CFC-BiOBr-Ag photocatalyst. The prevalent degradation reactions such as demethylation, ring opening, hydroxylation, •OH radicle attack, desulfonication, hydrolysis etc. led to formation of various intermediates which further mineralized to CO2 and H2O.

Adsorptive removal of cationic dyes from wastewater using a novel sodium alginate-based iron oxide nanocomposite hydrogel: DFT and advanced statistical physics modelling

A novel Sodium alginate-based hydrogel reinforced with varying Fe2O3 nanoparticles loading (NCH) was synthesized to remove cationic dyes methylene blue (MB) and crystal violet (CV). The NCH, with 5 % Fe2O3 loading, demonstrated optimal removal efficiency for both dyes. Detailed spectroscopic, microscopic, and spectrometric characterization techniques verified the nanocomposite structure and dye adsorption. Batch experiments revealed that at pH: 9, with a 20 mg 100 mL−1 adsorbent dose and times of 60 min for MB and 40 min for CV, with an initial concentration of 500 mg L−1, maximum adsorption capacities were achieved. MB and CV adsorption onto NCH showed distinct mechanisms: MB via physical interaction, CV via both physical and chemical interactions, including electrostatic forces and hydrogen bonding. Despite differences, the Langmuir-Freundlich model best fit the equilibrium isotherms, suggesting monolayer adsorption dominated, even with heterogeneous surface sites on NCH. A dual-site M2 statistical physics model revealed that MB and CV adsorption occurred via a multi-molecular vertical configuration on the binding sites, with heterogeneous adsorption sites contributing to dye uptake. Density functional theory demonstrated higher adsorption affinity for MB over CV, primarily due to hydrogen bonding and electrostatic interactions. NCH exhibited 80 % dye removal efficiency after five cycles, highlighting its potential for industrial effluent treatment.

A ternary composite nanofibrous photocatalyst: FcLR-gC3N4/polyisothianaphthene/polyacrylonitrile for degradation of organic dyes

BackgroundWater pollution by organic dyes is one of the important environmental issues. When substances such as organic dyes are discharged into water, they can severely pollute the water and harm the life of living organisms. MethodsA new ternary composite nanofibrous photocatalyst, FcLR-gC3N4/PITN/PAN, was produced through 1) synthesis of a graphitic carbon nitride (g-C3N4)-based ferrocenyl dithiophosphonic acid, FcLR-gC3N4, by the attachment of Ferrocenyl Lawesson's Reagent (FcLR) to g-C3N4 nanosheets, 2) incorporation of the FcLR-gC3N4 into the polymeric matrix of as-prepared polyisothianaphthene (PITN) blending with polyacrylonitrile (PAN), and 3) fabrication of electrospun nanofibers (NFs) through electrospinning. Significant findingsThe degradation of methyl orange (MO) and methylene blue (MB) was more efficient on FcLR-gC3N4 compared to g-C3N4 alone, and on FcLR-gC3N4/PITN/PAN compared to FcLR-gC3N4, confirming the effective role of both FcLR and PITN/PAN matrix in the degradation of the dyes. The ternary composite nanofiber degraded 92% of MB and 29% of MO. The MB mineralization percentages of 65% (TOC), 60% (COD), and 55% (BOD) were achieved after 2 h and 30 min. Radical trapping experiments consistent with the Tauc plots and Mott-Schottky plots distinguished O2•- as the primary species in the degradation mechanism of MB. The MB degradation pathway was determined through LC-MS-MS. The electrochemical impedance spectrum (EIS) and photocurrent measurements confirmed the higher photocatalytic activity of FcLR-gC3N4 compared to g-C3N4 alone by studying the charge carrier's separation and recombination. A high recyclability was found for FcLR-gC3N4. The recycling stability of FcLR-gC3N4 increased after its embedding into the nanofibrous matrix of PITN/PAN.

Design and evaluation of a polyaniline-Azadirachta indica composite for efficient dye removal: Insights from experimental and theoretical simulations

In this study, a novel composite of polyaniline and Azadirachta indica sawdust (PAIS) was synthesized to explore its potential in the adsorptive removal of methylene blue (MB) and crystal violet (CV) dyes from aqueous solution. PAIS was characterized using various instrumental techniques, including FTIR, SEM/EDXS, XRD, TEM/SAED, BET, and TGA-DTG/DTA analyses. Batch adsorption tests revealed that pH, medium temperature, initial adsorbate concentration, adsorbent dose, and contact duration significantly influence adsorption efficiency. Adsorption equilibrium was reached at 30 min for MB and 90 min for CV in an acidic medium (up to pH 7), with minimal changes observed beyond these times. The Langmuir isotherm provided the best validation, with a maximum monolayer adsorption capacity of 454.54 mg/g for MB and 370.37 mg/g for CV, showcasing superior performance compared to most reported materials. The adsorption process adhered to a pseudo-second-order approach for both dyes, with a high coefficient of determination value. The adsorption of MB and CV by this innovative adsorbent was spontaneous, endothermic, and accompanied by entropy enhancement. The adsorbent loaded with dyes was subjected to different desorbing agents (HCl, NaOH, NaCl, CH3COOH, and H2O), and HCl was the most effective. Computational studies using Density Functional Theory supported the experimental results, confirming the higher efficiency of PAIS for MB removal over CV. It is submitted that PAIS uniquely exhibits highly adaptable, recyclable, and potent low-cost adsorbent properties for eliminating both dyes from aqueous systems, representing a significant advancement in the field of dye removal.

Synthesis Bi2O3/gC3N4 heterostructures: Investigation structural, morphological and photocatalytic activity towards methylene blue and rhodamine B

Waste from various dyes as a result of industrial development is an important source of pollutants for water resources; These wastes are frequently carcinogenic, mutagenic and toxic to aquatic life, so treating wastewater is vitally important. Photocatalytic purification is a popular method because it can break down dye molecules and change them into non-toxic, small and harmless species. Moreover, utilizing the power of sunlight, this technology holds significant promise for enabling environmentally friendly, sustainable, and economically viable technologies. The non-toxic polymeric photocatalyst graphitic carbon nitride (gC3N4) is an n-type semiconductor. Its facile and economical synthesis, effective band structure, and stability make it a popular option for photocatalytic investigations. It is crucial to develop nanocomposites to boost the capacity of materials for photocatalysis. The objective of this study is to fabricate nanocomposites of graphitic carbon nitride from thiourea, incorporating varying ratios of bismuth oxide through thermal condensation. The aim is to employ these composites for the catalytic degradation of Methylene Blue (MB) and Rhodamine B (Rh B) dyes. The synthesized samples' morphological and structural characteristics were studied. Their photocatalytic activity against methylene blue and rhodamine B dyes has also been reported. The Bi2O3/gC3N4 heterostructured samples were prepared considering bismuth nitrate and thiourea at weight ratios of 0.125:10, 0.25:10, and 0.5:10. In the study, the Bi2O3/gC3N4 heterostructured sample with the lowest bismuth doping rate was seen to have the highest photocatalytic degradation efficiency. A remarkable degradation rate, reaching 98.83 % within 70 min for MB and 98.59 % within 60 min for RhB dye was observed. The enhanced photocatalytic activities of the synthesized composite can be attributed to the synergistic effect of the heterostructure developed between graphitic carbon nitride and bismuth oxide. As a result, this study has shown promise that Bi2O3/gC3N4 composite photocatalysts can be an effective material for removing dyes.

Wild reed waste as a biosorbent for toxicity lowering of selected pollutants: Isotherms, kinetic and thermodynamic studies

Wild reed (Raw-Mat) was used as an eco-friendly biosorbent to remove two basic dyes, Rhodamine B (Rh-B) and Methylene blue (MB), from their aqueous solutions. The prepared biosorbent was characterized by scanning electron microscopy (SEM), X-ray diffraction, thermogravimmetric analysis (TGA), FT-IR spectroscopy, pHzpc, Iodine number, and Methylene Blue index. Adsorption experiments were conducted by studying the effect of conventional parameters (biosorbent dose, contact time, pH, ionic strength and temperature). Adsorption equilibrium was reached at 60 min for MB and 120 min for Rh-B at biosorbent doses of 12 g/L and 8 g/L for MB Rh-B respectively corresponding to maximum adsorption capacities of 29 mg/L and 27.9 mg/L. Adsorption models of Langmuir, Freundlich and Temkin in their linear and nonlinear were fitted to the experimental data. Ionic strength effects indicated that hydrophobic-hydrophobic interactions could be the dominant attractive force for adsorption of both dyes. Dye uptakes increased with temperature for both dyes. Adsorption kinetics was found to comply with the pseudo second order with a good correlation factor (R2 > 0.99) with intra-particle diffusion as the rate determining steps. Both dyes adsorption processes were spontaneous (ΔGo <0) and endothermic (ΔHo >0). This study showed that wild reed as a waste could prove to be a very efficient adsorbent in removing toxic substances from wastewater.

Facile one-pot synthesis of ternary Fe doped Cu-ZnO nanocatalyst: An efficient and recyclable solar light driven photocatalyst

Currently, nanoparticles are regarded as excellent materials for degrading and removing dyes due to their beneficial surface features and chemical reactivity. Herein, Cu doped ZnO (CZ) was co-doped with Fe (FCZ) at different concentrations (2, 3, 4 and 8 wt% with respect to CZ) via simple one-step co-precipitation approach. The structural, surface morphology, surface properties, optical and photocatalytic performance of prepared samples were studied. Due to the doping of Fe, the band gap of CZ reduced from 2.7 eV to 2.29 eV, which is beneficial for absorbing visible light. Among doped CZs, 4 wt% Fe-doped CZ (4FCZ) exhibited 97.1% methylene blue (MB) degradation at neutral pH under 60 min of sunlight exposure. Furthermore, the effect of initial concentration of dye, catalyst load, and pH on the degradation process was investigated. The remarkable photocatalytic activity of 4FCZ nanoparticles can be attributed to their advantageous surface properties, such as their high specific surface area, heterostructure morphology, and mesoporous nature. Scavenger study identified •O2−, e−, and h+ as main reactive species. Pseudo-first order kinetics revealed degradation order: 4FCZ>8FCZ>3FCZ>2FCZ>CZ. 4FCZ showed recyclability with 90.9% MB degradation after three cycles. Mineralization of MB was analysed by COD and LC-MS studies. Fe-doped CZ emerges as a promising, cost-effective wastewater treatment under sunlight without special equipment. This study provides new insights on synthesis of ternary nanocatalyst for dye degradation.

Comparative study of visible-light active BiOI and N,Pd-TiO2 photocatalysts: Catalytic ozonation for dye degradation

The increasing demand for clean water requires the development of simple, cheap, and efficient catalysts systems for water pollution remediation. To develop cheap yet efficient hybrid advanced oxidation processes for degradation of organic pollutants in water requires their systematic comparison under similar conditions to make informed decisions of economically feasible and sustainable systems. Visible light active single BiOI and N, Pd co-doped TiO2 were investigated for photocatalytic ozonation (PCO) for methylene blue (MB) degradation. Metal and non-metal co-doping improved morphology, band structure and active sites on the surface of TiO2 to shift its light absorption into the visible region. The degradation of MB with BiOI PCO and N,Pd-TiO2 PCO was practically similar but showed improvement of the ozonation mineralization efficiency. However, mineralization of MB on BiOI PCO surpassed that of N,Pd-TiO2 PCO due to band structure that influenced generated free radicals during the PCO processes. BiOI PCO system progressed through the existence and involvement of strongly oxidizing and non-selective hydroxyl radicals towards enhanced mineralization of dye and intermediates while N,Pd-TiO2 PCO was steered by the superoxide radical that is selective and had lower mineralization efficiency of formed intermediates despite its high initial degradation efficacy. The work demonstrated cheap and efficient visible light active semiconductors like BiOI as potential candidates for application in photocatalytic ozonation for real applications with matching activities to that of co-doped UV active semiconductors like TiO2. This work advances the use of visible light active semiconductors towards PCO based processes for environmental pollution remediation.

Development and characterization of solar active Ag-ZnO/g-C3N4 as a highly efficient photocatalyst for the detoxification of organic pollutant

In today's biosphere, a major problem is water pollution caused by the discharge of effluents from dying industries, such as the printing and textile industries. In our current work, we have successfully fabricated photocatalytic bare and composite material 1%Ag-ZnO/6% g-C3N4 (Ag-ZnO/gCN), along with pristine ZnO and g-C3N4 (gCN), for the efficient degradation of dye wastewater. Structural investigations performed using FT–IR, XRD, FE–SEM/EDS, XPS, PL, EIS, and HR-TEM/EDS confirmed the structures of the pristine and composite photocatalysts. According to XPS studies, Ag exists in the metallic form. The photocatalytic performance of all the catalysts was evaluated by degrading methylene blue (MB) dye in an aqueous solution under direct sunlight illumination, and the most active composite catalyst was utilized for conducting dye degradation under visible light in the optimized experimental conditions. The effects of operating parameters, such as catalyst amount and initial pH, on MB degradation have been evaluated. Under solar irradiation, the photodegradation of MB dye over the Ag-ZnO/gCN composite catalyst was measured to be ≈ 100% in 50 min, and its degradation rate constant Kapp (0.1266 min–1) was higher than that of other pristine and composite catalysts. A Total Organic Carbon (TOC) study validated MB mineralization. Further experimental results corroborate the conclusion that superoxide radical anions (O2•–) play a pivotal role in this degradation process, with hydroxyl radicals (•OH) and photogenerated holes (h+) following suit insignificant. Moreover, after undergoing 5 consecutive cycles, the catalysts exhibited a remarkable photostability of 88%. A possible photocatalytic mechanism was proposed for the improved photocatalytic activity.

Multifunctional Ni(OH)2/Ag composites for ultrasensitive SERS detection and efficient photocatalytic degradation of ciprofloxacin and methylene blue

To enable the widespread application of surface-enhanced Raman scattering (SERS) technique in practical sensing of organic pollutants, it is essential to develop a reliable SERS substrate that offers both high sensitivity and reusability. In this study, we employed a simple and rapid in-situ deposition method to coat Ag nanoparticles onto flower-like Ni(OH)2 spheres, resulting in the formation of Ni(OH)2/Ag composites with excellent photocatalytic performance and SERS activity. These composites were used as a promising SERS analysis tool for effective detection of organic pollutants, including ciprofloxacin hydrochloride (CIP) and methylene blue (MB). Notably, the composites exhibited outstanding detection limits of 10−8 M for MB and 10−7 M for CIP, respectively, and showed a strong linear relationship between SERS intensities and the logarithmic concentration (R2 ≥ 0.97). Moreover, under simulated sunlight irradiation, the Ni(OH)2/Ag composites efficiently degraded MB and CIP molecules within a short period of 120 min for MB and 130 min for CIP. This demonstrated their practical reusability, as evidenced by their consistent performance over five cycles of SERS sensing. These findings underscore the significant potential of these composites for SERS-based detection of trace pollutants and ecological restoration through photocatalytic reactions in the future.

Transformation of Mytella falcata residual shell into CaAl/LDH adsorbent: Removal of methyl orange and methylene blue dyes

AbstractThis study analyzed the viability of using malacoculture residue (Mytella falcata) to produce layered double hydroxides (LDHs) and for its subsequent use as an adsorbent. The CaAl/LDH‐RE material was produced with calcium oxide from the residue and the CaAl/LDH‐AP was produced with a commercial reagent. Both were used to remove methyl orange (MO) and methylene blue (MB) dyes. The CaAl/LDH‐RE presented a surface area of 28.54 m2 g−1, being 65.62% larger than the CaAl/LDH‐AP material (17.23 m2 g−1). The adsorbents showed mesopores distributed on a surface formed by plates in the form of hexagonal sheets arranged in an overlapping manner. The dosage of 0.05 g L−1 obtained the removal of 95% and 97% for MO, while for MB it was 94% and 93% using the adsorbents LDH/CaAl‐AP and LDH/CaAl‐RE, respectively. The system reached equilibrium at 90 min for MO and 120 min for MB. The pseudo‐second order model well represented the kinetic data reaching 11.36 mg g−1 (CaAl/LDH‐RE) and 8.42 mg g−1 (CaAl/LDH‐AP) for MO, and 4.47 mg g−1 (CaAl/LDH‐RE) and 4.14 mg g−1 (CaAl/LDH‐AP) for MB. The Freundlich model better represented the isothermal data, where the temperature exerted little influence. Adsorbents showed similar removal percentages in real and synthetic matrices. The LDH/CaAl‐RE can be applied in up to 3 cycles, maintaining its adsorption capacity. These results corroborate the use of MFW to produce CaAl/LDH‐RE, which can be used for the efficient removal of organic pollutants in an aqueous solution.

Photoinduced Absorption Spectroscopy of Photoelectrocatalytic Methylene Blue Oxidation on Titania and Hematite: The Thermodynamic and Kinetic Impacts on Reaction Pathways.

Photoelectrochemical oxidation of methylene blue is investigated, with particular focus on the difference in kinetics and thermodynamics of decoloration and mineralization employing photoinduced absorption spectroscopy. Hematite and titania photoanodes are used for the comparison of both reactions, which is determined to be associated with the depth of the valence band (3.2 vs 2.5 Vfor titania and hematite, respectively). Methylene blue is mineralized by the titania photoanode, however it is only oxidized to small fragments by hematite. Such difference is related to the valence band potential that provides the thermodynamic driving force for photogenerated holes in both materials. In addition, the kinetic competition of water oxidation is found to occur on titania by controlling the pH of the electrolyte. In the pH 14 electrolyte, mineralization of methylene blue is suppressed due to the faster and dominant kinetics of water oxidation, in contrast to the complete mineralization in the near neutral electrolyte where water oxidation kinetics are modest. These results clearly address the importance considering both thermodynamic and kinetic challenges of methylene blue oxidation, which has been thought to be an easy molecule to oxidize, as the model reaction in the application of photo(electro)catalysis using metal oxides.

Coupling ZnO with CuO for efficient organic pollutant removal.

Fabrication of heterojunction semiconductors for the photodegradation of toxic organic dyes under sunlight exposure has earned significant recognition from researchers nowadays. On that account, we have synthesized and explored a comparative photodegradation study of ZnO/CuO nanocomposite with ZnO and CuO nanoparticles. ZnO and CuO nanoparticles have been synthesized by biosynthesis methods usingFicus benghalensisleaf extract. As-synthesized ZnO and CuO nanoparticles have been further utilized for the synthesis of ZnO/CuO nanocomposite by the mortar pestle crushing/milling method. Both biosynthesis methods and mortar pestle crushing/milling methods are simple, low-cost, and environmentally friendly. Structural, optical, and morphological analysis of all the synthesized nanomaterials havebeen doneby powder X-ray diffraction (PXRD), scanning electron microscopy (SEM),transmission electron microscopy (TEM),Brunauer-Emmett-Teller (BET),field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), fourier transform infrared spectroscopy (FTIR), and UV-visible spectroscopy.PXRD data reveal that synthesized ZnO nanoparticles are in the hexagonal wurtzite phase, CuO nanoparticles in the monoclinic phase, and ZnO/CuO nanocomposite in the hexagonal wurtzite as well as in monoclinic phase. FE-SEM and TEM images of ZnO/CuO nanocomposite reveal the nanorod-shaped morphology along with micro-sized and nano-sized flakes. The BET analysis shows the surface areas 18.128 m2/g for ZnO nanoparticles, 16.653 m2/g for CuO nanoparticles, and 19.580 m2/g for ZnO/CuO nanocomposite, respectively. Theenergyband gap values of ZnO/CuO nanocomposite are obtained 3.13eV for ZnO and 2.76eV for CuO, respectively. The photocatalytic behaviors of all the synthesized nanomaterialsareexamined against aqueous dye solutions of methylene blue (MB), rhodamine B (RhB), and methyl orange (MO) under sunlight irradiation. The results reveal that the photocatalytic degradation efficiency of ZnO/CuO nanocompositehasbeen found higher than with ZnO and CuO nanoparticles for all the dyes. Also, all the synthesized nanomaterialsindicatehigher photocatalytic degradation efficiency for methylene blue dye among allthreedyes. The kinetics of photodegradation of all the dye solutions has also been investigated in the presence of ZnO, CuO, and ZnO/CuO photocatalysts separately. The results exhibit that rate constant values for all the dyes are higher with ZnO/CuOnanocompositethan with ZnO and CuOnanoparticles.ZnO/CuO nanocomposite demonstrates degradation efficiency for MB dye99.13%, for RhB80.21%, and for MO67.22%after 180min of sunlight exposure.ZnO/CuO nanocomposite and ZnO and CuO nanoparticles also show thebestreusability and stability up to three cycles for photocatalytic degradation of MB dyes amongall the dyes.Therefore, green synthesized ZnO/CuO nanocomposite could be used asan efficientphotocatalyst for the degradation of various toxic dyes.The mineralization of different dyes using ZnO/CuO nanocomposite has been examined by FTIR analysis. Furthermore, the mineralizationof MB dye has been done by total organic carbon (TOC)measurements.

Photocatalytic activation of Ag-doped SrSnO3 nanorods under visible light for reduction of p-nitrophenol and methylene blue mineralization

The utilization of solar energy for the treatment of wastewater pollutants by photocatalysts has been considered a promising solution to address environmental problems. Herein, we have synthesized silver nanoparticle-doped strontium stannate (Ag-doped SrSnO3) nanorods by hydrothermal method followed by ultrasonic treatment. The developed nanocomposites were applied for photocatalytic reduction of p-nitrophenol (4-NP) and methylene blue (MB) mineralization under visible light illumination. The effect of hydrothermal duration time (16–25) h, Cetyltrimethylammonium bromide (CTAB) and silver nanoparticles (Ag NPs) concentration (0.5–2.5) wt% on the crystal, surface, optical, photoluminescence as well as photocatalytic activity were studied. A well-defined crystalline cubic phase of SrSnO3 was obtained. CTAB inhibits the crystal growth of SrSnO3. Reduction of 4-NP and MB mineralization were used as two-model reactions for testing the effect of Ag doping concentration on the photocatalytic activities of Ag/SrSnO3 under visible light illumination. The obtained results show that 2.0 wt% of Ag-doped SrSnO3 exhibits efficient photocatalytic reduction of 4-NP with 98.2% conversion within 5 min of reaction time. Also, 87% of the MB sample was mineralized after 1 h of visible illumination using 2.0% Ag/SrSnO3 in the presence of H2O2. Besides, we have discussed the possible photocatalytic mechanism for reduction of 4-NP and mineralization of MB using 2.0 wt% of Ag doped SrSnO3 under visible light illumination.

Green Synthesis of Iron Oxide Nanoparticles Using Psidium guajava L. Leaves Extract for Degradation of Organic Dyes and Anti-microbial Applications

Among various metal and metal oxide nanoparticles, iron-oxide nanoparticles (IONPs) have been more widely used for the degradation of harmful organic dyes and the inhibition of microbial growth; on the other hand, it positively affects mammalian cells. Green synthesis of IONPs has piqued the interest of researchers because it improves stability and is an environmentally friendly method of avoiding the use of harmful chemicals as a reducing agent. In this study, IONPs were synthesized using Psidium guajava leaf extract, which was further applied for its industrial dye degradation and anti-microbial activities. UV–visible spectroscopy, FTIR, XRD, XPS, EDX, FE-SEM, HR-TEM, and Zeta potential analysis were used to characterize the synthesized nanoparticles. The synthesized IONPs managed to degrade methylene blue (MB) and methyl orange (MO) in the presence of H2O2. The degradation efficiency was 82.1% in 95 min and 53.9% in 205 min for MB and MO, respectively. Likewise, the synthesized IONPs showed good anti-bacterial activity with a ZOI of 13 mm for both Shigella sonnei and Staphylococcus aureus gram-positive bacteria. Similarly, they demonstrated good anti-fungal activity with ZOI of 15 mm and 13 mm for Candida tropicalis and Candidaalbicans, respectively. Thus, the IONPs can combat harmful organic dyes, and they can terminate the pathogenicity of several human pathogens.

Molten salt synthesis of Z-scheme CeO2/C3N4 photocatalysts with excellent properties for removal of organic pollutants: Characterization, kinetics and mechanisms

In this work, we firstly synthesized a CeO2/C3N4 photocatalyst with Z-scheme heterojunction by a facile LiCl–KCl molten salt method. The synthesized catalyst has an excellent quality for removing organic pollution of dyes and antibiotics in wastewater. As an example, the CeCN–1:5 prepared with a mass ratio of Ce2(CO3)3·xH2O:C3H3N6 = 1:5 exhibits a methylene blue (MB) removal capacity of 100% within 90 min and tetracycline (TC) removal capacity of 94.6%. After 4 cycles, the CeCN–1:5 keeps a removal efficiency of nearly 100% in 150 min for MB and 85.7% for TC. The kinetics study reveals that the MB removal process with the CeCN–1:5 fits the modified Elovich model with strong adsorption while TC removal fits the first-order model. The large surface area (238 m2/g) and negative zeta potential (−39.3 mV) of CeCN–1:5 contribute to superior adsorption capacity to MB. However, the adsorption of TC is restricted due to the positive surface/pore potential in acidic solution. CeCN–1:5 has combined Z-scheme heterojunction and exhibits a low recombination rate of electrons (e–)/holes (h+) and the photo-generated active radicals of ·OH/·O2– that promotes the photocatalytic performance. This novel CeO2/C3N4 photocatalyst with an excellent photocatalysis removal activity has an enormous potential for photocatalytic applications.

Determination of antioxidant and catalytic activity of bio-synthesized Ag-MgO nanocomposite from peels extract of Citrus aurantium in the rapid treatment of wastewater management

Fig.2. Schematic illustration for the synthesis of Ag-MgO nanocomposite. • Nanocomposite, reduction catalyst, antioxidant, Citrus aurantium. In this research article, the bio-synthesis of Ag-MgO NCs were synthesized by employing peels extract as a renewable, mild reducing, and stabilizing agent. Bio-synthesized Ag-MgO NCs was characterized by different spectroscopic methods like UV–visible spectroscopy, XRD, SEM, EDX, and TEM. In UV spectra of the nanocomposite, two peaks were obtained at 342 nm and 290 nm for Ag and MgO respectively, during the synthesis of Ag-MgO nanocomposite. The characteristic peak for Ag shows a hypsochromic (blue) shift from 465 nm to 342 nm. XRD results show that the synthesized NCs are cubic in nature considering both Ag-NPs and MgO-NPs and the average crystal size was found to be 16.40 nm. SEM images confirm that the synthesized Ag-MgO NCs are poly dispersive and crystalline in nature. The catalytic activity of Ag-MgO NCs was examined by reduction of toxic dyes such as methylene blue (MB), Rose Bengal (RB), and acridine orange (AO) by using NaBH 4 as a reducing agent and NCs as a catalyst. The synthesized Ag-MgO NCs exhibits enhanced catalytic reduction of dyes up to 89.77%, 83.38%, and 87.34% in 7 min, 4 min, and 5 min for MB, RB, and AO respectively. Antioxidant activity of synthesized Ag-MgO nanocomposite was determined by H 2 O 2 free radical scavenging activity, and DPPH free radical scavenging activity. On the premises of our findings the synthesized NCs can be considered as excellent catalyst for degradation of mentioned toxic dyes, Further, these Ag-MgO can act as an efficient antioxidant based on their activity comparable to butylated hydroxy toluene (BHT).

More effective organics removal by amorphous MnOx assisted by micro-current than peroxymonosulfate addition: Performance and mechanism

Peroxymonosulfate (PMS) addition into a MnOx system is generally believed to be an effective way for expediting organics removal. Whereas in this work, we found single MnOx with a micro-current got an even better oxidation performance comparing that with PMS addition. The carbon paper electrodeposited by amorphous MnOx (AMO) was used as cathode, and the micro-current (55 µA/cm2) increased the methylene blue (MB) degradation rate by 6.1 times through enhancing the AMO oxidative ability in acidic media. At the same pH, the MB degradation rate in AMO (AMO-MC) system was close to that in AMO system with PMS addition (AMO-MC-PMS). More importantly, the MB mineralization in AMO-MC was about 1.6 times higher than that in AMO-MC-PMS. Similar phenomena were also investigated when using tetracycline (TC) as organic pollutant. The mechanisms of AMO-MC and AMO-MC-PMS for MB removal were comprehensively studied and compared. It was found that the micro-current prompted the Mn valence converting from high to low. Conversely, the PMS addition hindered this converting and impeded the direct oxidation of AMO. The GC-MS analysis indicated that the presence of PMS induced the formation of sulfoxide-containing intermediates (SCIs) which were difficult to be further degraded and resulted in the suppression of MB mineralization. Density functional theory (DFT) calculation indicated that the intermediates from AMO-MC were more facile to be attacked in an electrophilic way and adsorbed on the cathode than the SCIs. It proposed that the AMO with micro-current had the potential to remove organics efficiently, and blind PMS addition should be avoided.

Study on negative pressure assisted hydrodynamic cavitation (NPA-HC) degradation of methylene blue in dye wastewater

Hydrodynamic cavitation (HC), as a new AOP, has been tried to treat some organic dye wastewater. In traditional HC equipment only positive pressure from water pump was used, which results in a low degradation extent. In this paper, the negative pressure from water pump is used to intensify the whole HC effect for enhancing the decolorization and mineralization of methylene blue (MB) in wastewater. Some influence factors (orifice plate hole number, inlet pressure, initial concentration and solution temperature) on MB degradation efficiency are studied. The determined results of Total Organic Carbon (TOC) and Liquid Chromatograph-Mass Spectrometer (LC-MS) were used to identify MB mineralization extent and confirm the intermediate products during MB degradation, respectively. The results showed that, under the conditions of low temperature, high inlet pressure and moderate dye concentration, the negative pressure assisting hydrodynamic cavitation (NPA-HC) system displayed a significantly enhanced MB degradation effect. The most efficient combination of 25 hole negative pressure assisted 3 hole positive pressure is obtained. At 30 °C in 10 mg/L MB solution, the degradation ratios are 27.43% (in NPA-HC) and 97.48% (in NPA-HC+H2O2 (MB/H2O2 = 1.0:7.5 in molar ratio)), respectively. And that, in single positive pressure HC system the MB degradation ratio is only 16.23%. This study provides a feasible method for intensifying organic dye HC degradation and enlarging wastewater treatment scale.

Highly effective and stable MWCNT/WO3 nanocatalyst for ammonia gas sensing, photodegradation of ciprofloxacin and peroxidase mimic activity

The present study discusses the ammonia (NH3) sensing characteristics, photocatalytic degradation of emerging pollutants, and peroxidase mimic activity of multifunctional multi-walled carbon nanotube-tungsten oxide nanocomposite (MWCNT/WO3) prepared by conventional solvothermal method. The prepared MWCNT/WO3 nanocomposites were characterized by various analytical techniques like XRD, Raman, XPS, N2 adsorption, FESEM with elemental analysis and diffuse reflection spectroscopy. The prepared 1% MWCNT/WO3 nanocomposite showed better gas sensing performance for the NH3 vapors at 10–100 ppm than the pristine WO3 and the response and recover time of about 13 and 15s towards 20 ppm of ammonia (NH3) was achieved. The photocatalytic activity of MWCNT/WO3 towards organic dyes such as Rhodamine-B (Rh.B) methylene blue (MB) and pharmaceutical compound ciprofloxacin (CIP) were studied and achieved above 90% degradation at 160 min for CIP and 60 min for MB and Rho-B respectively. The radicle scavenging activity for MWCNT/WO3 nanocomposite showed the predominant formation of hydroxyl (OH•) and superoxide radicle (•O2−). Further, the MWCNT/WO3 nanocomposite showed peroxidase mimic activity and exhibit the limit of detection (LOD) of about 321 nM. From the overall analysis, MWCNT/WO3 hybrid seems to have potential characteristics that can be explored for multiple functional applications.