Removal Rate Of Methyl Orange Research Articles

Preparation and characterization of cellulose-chitosan/β-FeOOH composite hydrogels for adsorption and photocatalytic degradation of methyl orange

Biopolymer-based hydrogels have received great attention in wastewater treatment due to their excellent properties, e.g., high adsorption capacity, fast kinetics, reusability and ease of operation. In the present work, cellulose-chitosan/β-FeOOH composite hydrogels were prepared via co-dissolution and regeneration process as well as hydrothermal in situ synthesis of β-FeOOH. Effect of β-FeOOH loading on the properties of the composite hydrogels and the removal efficiency of methyl orange (MO) was investigated. Results showed that β-FeOOH was uniformly loaded onto the hydrogel framework, and the nanoporous structure of composite hydrogels could increase not only the effective contact area between β-FeOOH and the pollutants but also the active sites. Moreover, the increased β-FeOOH loading led to the enhanced MO removal rate under light conditions. When the loading time was extended from 6 h to 9 h, the MO removal rate increased by 21%, which can be mainly due to the photocatalytic degradation. In addition, MO removal rate reached 97.75% within 40 min under optimal conditions and attained 80.81% after five repetitions. The trapping experiment and EPR results indicated that the main active species were hydrogel radicals and holes. Consequently, this work provides an effective preparation approach for cellulose-chitosan/β-FeOOH composite hydrogel with high adsorption and photocatalytic degradation, which would hold great promise for wastewater treatment applications.

Bioaugmented biological contact oxidation reactor for treating simulated textile dyeing wastewater

In this study, modified polyamide fibers were used as biocarriers to enrich dense biofilms in a multi-stage biological contact oxidation reactor (MBCOR) in which partitioned wastewater treatment zone (WTZ) and bioaugmentation zone (BAZ) were established to enhance the removal of methyl orange (MO) and its metabolites while minimizing sludge yields. WTZ exhibited high biomass loading capacity (5.75 ± 0.31 g/g filler), achieving MO removal rate ranging from 68 % to 86 % under different aeration condition within 8 h in which the most dominant genus Chlorobium played an important role. In the BAZ, Pseudoxanthomonas was the dominant genus while carbon starvation stimulated the enrichment of chemoheterotrophy and aerobic_chemoheterotrophy genes thereby enhanced the microbial utilization of cell-released substrates, MO as well as its metabolic intermediates. These results revealed the mechanism bioaugmentation on MBCOR in effectively eliminating both MO and its metabolites.

Synthesis, magnetic properties, biotoxicity and potential mechanism of modified nano zero-valent iron for decolorization of dye wastewater

ABSTRACT SiO2-coated nano zero-valent iron (nZVI) has emerged as a fine material for the treatment of dye wastewater due to its large specific surface area, high surface activity, and strong reducibility. However, the magnetic properties based on which SiO2-coated nZVI (SiO2-nZVI) could effectively separate and recover from treated wastewater, and the biotoxicity analysis of degradation products of the dye wastewater treated by SiO2-nZVI remain unclear. In this study, SiO2-nZVI was synthesized using a modified one-step synthesis method. The SiO2-nZVI nanoparticles were characterized using Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Fully automatic specific surface and porosity analyzer, Vibrating sample magnetometer, and Zeta potential analyzer. The removal rate of methyl orange (MO) by SiO2-nZVI composite reached 98.35% when the degradation performance of SiO2-nZVI treating MO was optimized. Since SiO2-nZVI analysed by magnetic hysteresis loops had large saturation magnetization and strong magnetic properties, SiO2-nZVI exhibited excellent ferromagnetic behaviour. The analysis of the degradation products showed that the MO treated by SiO2-nZVI was converted into a series of intermediates, resulting in reducing the toxicity of MO. The potential mechanism of MO degradated by SiO2-nZVI was speculated through degradation process and degradation kinetics analysis. Overall, the SiO2-nZVI composite may be regarded as a promising catalyst for decolorization of dye wastewater.

Preparation of BiOBrxCl1‐x solid solution photocatalyst with oxygen vacancies for degradation of methyl orange under simulated sunlight

AbstractBiOBrxCl1‐x solid solution with oxygen vacancies was synthesized using a simple one‐step hydrothermal method. The sample was characterized using comprehensive characterization techniques, and the results showed that the solid solution material was successfully prepared. Adjusting the relative proportion of halogens in BiOBrxCl1‐x solid solution has a significant impact on the morphology, optical properties, and photocatalytic activity of the sample, and oxygen vacancies are introduced into the material. The presence of oxygen vacancies improves the separation efficiency of charge carriers and facilitates the activation of oxygen molecules into superoxide radicals. Among them, BiOBr0.2Cl0.8 showed flower‐like microspheres morphology and exhibited the best photocatalytic activity. After 30 min of dark adsorption and 1 h of simulated sunlight exposure, the removal rate of methyl orange (MO) was 92.5%, which was 2.38 times higher than that of pure BiOBr (38.9%) and 2.09 times higher than that of pure BiOCl (44.3%), respectively.

A water stable Cu-MOF/GO composite as a persulfate activator for efficient degradation of dye wastewater

Water pollution caused by textile dyes is considered a major and growing issue. To address this challenge, in this research, water-stable Cu-MOFs/GO composite catalysts were produced using the hydrothermal synthesis method as an efficient persulfate (PDS) activator for methyl orange (MO) degradation. We also explored the changes in surface morphology, crystal structure, surface functional groups, and valence states of the materials before and after the introduction of GO by Cu-MOFs. It was shown that Cu-MOFs/GO demonstrates a more stable surface structure, and the unique folded structure of GO provides a better hydrophobic environment for Cu metal cluster hence making MOF easier to grow. The Cu-MOFs/GO-PDS system showed a high activation performance on persulfate in a wide pH range (3–11), meanwhile, was less affected by the presence of natural anions in the environment and more inhibited by natural organic matter citric acid. Furthermore, the Cu-MOFs/GO had excellent stability, reusability and structural integrity, and the removal rate of MO was maintained after five cycles. In terms of oxidation mechanism, in addition to the generation of ·SO4− and OH· radicals, there were also singlet oxygen 1O2 and active Cu(III) in the system, and all of these active substances contributed to the removal of pollutant MO.

Smart pillar[5]arene-based PDMAEMA/PES beads for selective dye pollutants removal: design, synthesis, chemical-physical characterization, and adsorption kinetic studies.

This article reports on the synthesis of an innovative smart polymer, P5-QPDMAEMA, opportunely developed with the aim of combining the responsiveness of PDMAEMA polymer and the host-guest properties of covalently linked pillar[5]arenes. Thanks to a traditional Non-Induced Phase Separation (NIPS) process performed at various coagulation pH, the blending of P5-QPDMAEMA with polyethersulfone gave rise to the formation of functional beads for the removal of organic dyes in water. Adsorption tests are carried out on all the produced blend-based beads by employing two representative dyes, the cationic methylene blue (MB), and the anionic methyl orange (MO). In particular, the P5-QPDMAEMA based beads, prepared at acidic pH, featured the best MO removal rate (i. e., 91.3 % after 150 minutes starting from a 20 mg ⋅ L-1 solution) and a high selectivity towards the removal of the selected anionic dye. Based on the adsorption kinetics and isotherm calculations, the pseudo-first order and Freundlich models were shown to be the most suitable to describe the MO adsorption behavior, achieving a maximum adsorption capacity of 21.54 mg ⋅ g-1. Furthermore, zwitterionic beads are obtained by a post-functionalization of the PDMAEMA and the P5-QPDMAEMA based beads, to test their removal capability towards both anionic and cationic dyes, as shown.

Assembling flower-like MgAl-LDH nanospheres and g-C3N4 nanosheets for high efficiency removal of methyl orange

Flower-like Mg–Al–CO3 layered double hydroxide (MgAl-LDH) nanospheres with specific surface area of 221.95 m2/g were synthesized by modified aqueous miscible organic solvent treatment method. Via the electrostatic self-assembly method, MgAl-LDH and g-C3N4 nanosheets (CNNS), with the mass ratio of 1:10, 3:10, 5:10, 7:10, and 10:10, respectively, were assembled to prepare MgAl-LDH/g-C3N4 composites (MCN-X, X = 1, 3, 5, 7, and 10). The mass ratio of MgAl-LDH to g-C3N4 nanosheets affected the microstructure, optical and photo-electrochemical properties, and the removal efficiency toward methyl orange (MO), of MCN-X composites. The adsorption and photocatalytic degradation performance for MO by all MCN-X composites were better than those by pure g-C3N4 nanosheets. With the increasing of MgAl-LDH content, the adsorption rate and removal rate of MO by MCN-X composites increased firstly and then decreased gradually. The optimum performance was achieved by MCN-5, which removed 93.58 % of MO molecules after 30 min of dark adsorption and 120 min of photocatalytic degradation, and its pseudo-first-order reaction rate constants (k) value (0.0177 min−1) was 3.4 times that of CNNS. Reasons for these results were the enhanced specific surface area, the narrowed band gap, the inhibited recombination and the improved separation and migration of photo-generated carriers, as well as the excellent adsorption ability of MCN-5. This work provides a feasible strategy for synthesizing high performance MgAl-LDH/g-C3N4 composite photocatalyst.

Application of 3D printing technology for green synthesis of Fe2O3 using ABS/TPU/chlorella skeletons for methyl orange removal.

Photocatalysis is widely acknowledged as an efficient and environmentally friendly method for treating dye-contaminated wastewater. However, the utilization of powdered photocatalysts presents significant challenges, including issues related to recyclability and the potential for secondary pollution. Herein, a novel technique based on 3D printing for the synthesizing of iron oxide (Fe2O3) involving chlorella was presented. Initially, chlorella powders were immobilized within acrylonitrile butadiene styrene (ABS) and thermoplastic polyurethane (TPU) substrate plastics using melt extrusion technology. Subsequently, these composite materials were transformed into ABS/TPU/chlorella skeletons (ATCh40), through fused deposition molding (FDM) technology. The integration of Fe2O3 onto the ATCh40 (ATCh40-Fe2O3) skeletons was accomplished by subjecting them to controlled heating in an oil bath. A comprehensive characterization of the synthesized materials confirms the successful growth of Fe2O3 on the surface of 3D skeletons. This strategy effectively addresses the immobilization challenges associated with powdered photocatalysts. In photocatalytic degradation experiments targeting methyl orange (MO), the ATCh40-Fe2O3 skeletons exhibited a remarkable MO removal rate of 91% within 240 min. Under conditions where the pH of MO solution was maintained at 3, and the ATCh40-Fe2O3 skeletons were subjected to a heat treatment in a 150 °C blast drying oven for 2 hours, the degradation rate of MO remained substantial, achieving 90% removal after 6 cycles. In contrast, when the same synthetic procedure was applied to ABS/TPU (AT) skeletons, the resulting product was identified as α-FeOOH. The MO removal rate by the AT-α-FeOOH skeletons was considerably lower, reaching only 49% after 240 min. This research provided a practical approach for the construction of photocatalytic devices through the use of 3D printing technology.

Acetylene black doped zinc oxide (AB-ZnO) nanorods activated peroxydisulfate for degradation of dyeing wastewater

Zinc oxide (ZnO) nanorods and acetylene black (AB) doped ZnO (AB-ZnO) nanorods were fabricated by the hydrothermal method, and characterized by various methods (XRD, EDS, SEM, BET, FT-IR, Zeta potential). The photo-catalytic degradation ability of AB-ZnO/PDS/vis system on simulated dyeing wastewater was studied with methyl orange (MO) as the target pollutant. The effects of AB doping ratio, AB-ZnO dosage, PDS concentration, initial pH, and temperature on MO degradation were comprehensively investigated. The AB-ZnO/PDS/vis system has a wide range of pH applications from 3 to 11. The prepared material of AB-ZnO had excellent stability that the degradation efficiency on MO remained above 90 % after 4 cycles. The theoretical optimal removal rate of MO was 98.59 % when AB-ZnO dosage was 1.0 g/L, PDS concentration was 2.0 mmol/L, initial pH was 5, and temperature was 50 °C. Furthermore, degradation kinetic model, the orthogonal experiment and the degradation mechanisms were elaborated. By using methanol and tert-butanol as free radical inhibitors, it was confirmed that SO4·- and ·OH were the main active free radicals in AB-ZnO/PDS/vis system.

Adsorption of cationic/anionic dyes and endocrine disruptors by yeast/cyclodextrin polymer composites.

Factory and natural wastewaters contain a wide range of organic pollutants. Therefore, multifunctional adsorbents must be developed that can purify wastewater. Phytic acid-cross-linked Baker's yeast cyclodextrin polymer composites (IBY-PA-CDP) were prepared using a one-pot method. IBY-PA-CDP was used to adsorb methylene blue (MB), bisphenol A (BPA), and methyl orange (MO). Studies on the ionic strength and strongly acidic ion salts confirmed that IBY-PA-CDP adsorbs MO through hydrophobic interactions. This also shows that Na+ was the direct cause of the increased MO removal. Adsorption studies on binary systems showed that MB/MO inhibited the adsorption of BPA by IBY-PA-CDP. The presence of MB increased the removal rate of MO by IBY-PA-CDP due to the bridging effect. The Langmuir isotherm model calculated the maximum adsorption capacities for MB and BPA to be 630.96 and 83.31 mg g-1, respectively. However, the Freundlich model is more suitable for fitting the experimental data for MO adsorption. To understand the rate-limiting stage of adsorption, a mass-transfer mechanism model was employed. The fitting results show that adsorption onto the active sites is the rate-determining step. After five regeneration cycles, IBY-PA-CDP could be reused with good stability and recyclability.

A Novel Recyclable Magnetic Nano-Catalyst for Fenton-Photodegradation of Methyl Orange and Imidazole Derivatives Catalytic Synthesis.

A magnetite chlorodeoxycellulose/ferroferric oxide (CDC@Fe3O4) heterogeneous photocatalyst was synthesised via treated and modified cotton in two steps. The designed nanocomposites were characterised by FTIR, TGA, XRD, SEM, and VSM analyses. The Fenton-photocatalytic decomposition efficiency of the synthesised magnetic catalyst was evaluated under visible sunlight using Methyl Orange (MO) as a model organic pollutant. The impacts of several degradation parameters, including the light source, catalyst load, irradiation temperature, oxidant dose, and pH of the dye aqueous solution and its corresponding concentration on the Fenton photodegradation performance, were methodically investigated. The (CDC@Fe3O4) heterogeneous catalyst showed a remarkable MO removal rate of 97.9% at 10 min under visible-light irradiation. (CDC@Fe3O4) nanomaterials were also used in a heterogeneous catalytic optimised protocol for a multicomponent reaction procedure to obtain nine tetra-substituted imidazole derivatives. The green protocol afforded imidazole derivatives in 30 min with good yields (91-97%) at room temperature and under ultrasound irradiation. Generally, a synthesised recyclable heterogeneous nano-catalyst is a good example and is suitable for wastewater treatment and organic synthesis.

Doping TiO2 with sludge-derived activated carbon by UV light irradiation method: Molecular dynamic simulation and experimental study

Sludge-derived activated carbon (SDAC) is prepared from sewage sludge and can be used to treat pollutants. SDAC can also be used to dope catalytic materials to improve their pollutant degradation ability. However, there needs to be more research on doping TiO2 with SDAC. In this study, TiO2 was doped with SDAC by Ultraviolet light irradiation method under room temperature. The doping process saved a large amount of energy. The TiO2 doped with SDAC had the ability to degrade dyes under visible light. The results showed that the removal rates of SDAC-doped TiO2 for methyl orange (MO) and methylene blue (MB) were over 90% and 94% under visible light conditions. After five cycles, the removal rate of MO was 75%, while the removal rate of MB decreased to 45%. Molecular dynamics simulation results showed that the valence band and conduction band of SDAC-doped TiO2 shifted downward, and three apparent impurity levels appeared near the Fermi level after SDAC doping.

Composites of W18O49 Nanowires with g-C3N4/RGO Nanosheets for Broadband Light-Driven Photocatalytic Wastewater Purification.

Developing a photocatalyst that can effectively utilize the full solar spectrum remains a high-priority objective in the ongoing pursuit of efficient light-to-chemical energy conversion. Herein, the ternary nanocomposite g-C3N4/RGO/W18O49 (CN/RGO/WO) was constructed and characterized by a variety of techniques. Remarkably, under the excitation of photon energies ranging from the ultraviolet (UV) to the near-infrared (NIR) region, the photocatalytic performance of the CN/RGO/WO nanocomposite exhibited a significant enhancement compared with single component g-C3N4 or W18O49 nanosheets for the degradation of methyl orange (MO). The MO photodegradation rate of the optimal CN/1.0 wt% RGO/45.0 wt% WO catalyst reached 0.816 and 0.027 min-1 under UV and visible light excitation, respectively. Even under low-energy NIR light, which is not sufficient to excite g-C3N4, the MO degradation rate can still reach 0.0367 h-1, exhibiting a significant enhancement than pure W18O49. The outstanding MO removal rate and stability were demonstrated by CN/RGO/WO nanocomposites, which arise from the synergistic effect of localized surface plasmon resonance effect induced by W18O49 under vis-NIR excitation and the Z-scheme nanoheterojunction of W18O49 and g-C3N4. In this work, we have exploited the great potential of integrating nonmetallic plasmonic nanomaterials and good conductor RGO to construct high-performance g-C3N4-based full-solar spectral broadband photocatalysts.

Construction of R-TiO2/n-TiO2 heterophase photocatalysts for efficient degradation of organic pollutants

In this study, a commercial rutile titanium dioxide (R-TiO2) with a particle size of 200–300 nm was used as a carrier to prepare R-TiO2/n-TiO2 photocatalysts through wet co-grinding in a stirred grinder, along with commercial TiO2 (n-TiO2). The structure of R-TiO2/n-TiO2, its photocatalytic degradation performance towards methyl orange, and the enhancement mechanism were investigated. The results demonstrated that under the optimized conditions of grinding time and n-TiO2 loading ratio, the prepared R-TiO2/n-TiO2 composite (with a n-TiO2 ratio of 30%) exhibited excellent photocatalytic degradation and recyclability. After 30 min of UV irradiation, the removal rate of methyl orange was 99%, which was comparable to that of pure n-TiO2 (degradation rate of 99.5%). The degradation rate of methyl orange using R-TiO2/n-TiO2 was 4.5 times higher than that of an equivalent proportion of n-TiO2, and the degradation performance remained nearly unchanged after five cycles of recycling. R-TiO2/n-TiO2 exhibits features such as effective dispersal and even distribution of n-TiO2 onto the surface of R-TiO2, coupled with the establishment of chemical bonding at the interface between the two constituents. The existence of R-TiO2 improved the dispersion of n-TiO2 and promoted the formation of an interfacial anatase/rutile heterophase junction, which are intrinsic mechanisms for enhancing the efficiency of TiO2 photocatalysis and achieving a reduction in the application process.

Graphene hydrogel improves S. putrefaciens' biological treatment of dye wastewater: Impacts of extracellular electron transfer and function of c-type cytochromes

Biocompatible materials and biocarriers have attracted great attention in biological wastewater treatment owing to their excellent performance in improving pollutant removal. Graphene-based material, a biocarrier candidate, with excellent adsorbability and conductivity was increasingly applied in anaerobic digestion due to its exceptional potential in the adsorption and electron transfer process. Nevertheless, the green approach for the formation of bio-graphene complexes and their mechanism in dye removal is limited. The aim of this study is to investigate and assess the performance of biological graphene hydrogel (BGH) formed by Shewanella putrefaciens CN32 on the removal of methyl orange (MO) and methylene blue (MB). The results showed that the formation of BGH is determined by the physicochemical characteristics of graphene oxide, including sheet size, oxidation degree, and interlayer distance. BGHs significantly increased the removal efficiency of dyes in comparison to non-graphene samples, with a 24-h removal rate of MO and MB reaching 92.9% and 91%, respectively. The synergetic mechanism of BGH on the enhanced removal rate of organic dye can be ascribed to GO's ability in accelerating extracellular electron transfer and stimulating biodegradation pathways relating to c-type cytochromes, including MtrA and MtrC. These findings provided an understanding of the relationship between graphene-based nanomaterials and Shewanella, which facilitated their future application in environmental biotechnology.

Synthesis of a novel magnetic CuFe2O4/zeolite composite catalyst and its catalytic oxidation performance

A new magnetic CuFe2O4/zeolite (CFZ) catalyst was synthesized via a simple hydrothermal method. Characterization results suggest that CuFe2O4 and the zeolite are compounded together. CFZ has a specific surface area of 149.2 m2/g, indicating that CFZ has a porous structure. The removal rate of methyl orange in the CFZ/PMS system could reach 97.3%, showing the excellent catalytic oxidation performance of CFZ. After 5 cycles, the degradation efficiency declined by only 1.6%. In the catalytic degradation process, O2•− and 1O2 are the main reactive oxygen species.

Study on Adsorption and Photocatalytic Properties of Zinc Ferrite

In this study, methyl orange, methylene blue, and amido black 10B were removed as target dyes using purified, synthetic, and purchased zinc ferrite as adsorbents and photocatalysts. The highest removal rates of amido black 10B by these adsorbents ranged from 81.62% to 88.33%. The removal rate of methyl orange was approximately 1%, and the removal rate of methylene blue was approximately 2%. Hence, an investigation was conducted to elucidate the factors that influence the removal efficacy of purified zinc ferrite on amido black 10B. Titanium dioxide prepared at different calcination temperatures was unsuccessful in removing amido black 10B, but the physical mixing of titanium dioxide prepared at suitable calcination temperatures with purified zinc ferrite had a positive effect on amido black 10B removal. Since zinc ferrite could not be used as an adsorbent to remove methyl orange and methylene blue, the photocatalytic degradation properties of zinc ferrite and its influencing factors were studied. The optimal conditions for the photocatalytic degradation of methylene blue and methyl orange by zinc ferrite are as follows: a zinc ferrite catalyst dosage of 0.15 g, an initial solution concentration of 20 mg/L, and a pH of 6.0. The dosage of the zinc ferrite/titanium dioxide composite catalyst is 0.15 g, the initial solution concentration is 20 mg/L, and the pH is 6.5.

Optimized Removal of Azo Dyes from Simulated Wastewater through Advanced Plasma Technique with Novel Reactor

Increasing attention has been paid to removal of aqueous contaminations resulting from azo dyes in water by plasma technology. However, the influence factors and removal mechanism of plasma technology were still obscure, moreover, energy consumption and oxidized degradation efficiency of plasma reactor were also inferior. In the present study, a comparative analysis was performed using 100 mg/L of Methyl Orange (MO) in the simulated wastewater with a novel plasma reactor to achieve the ideal parameters involving voltage, discharge gap, and discharge needle numbers. Therefore, the optimal removal rate for MO could be up to 95.1% and the energy consumption was only 0.26 kWh/g after the plasma treatment for 60 min, when the voltage was set as 15 kV, the discharge gap was 20 mm, and the discharge needle numbers was 5. Based upon the response surface methodology (RSM), the removal rate of MO was predicted as 99.3% by massive optimization values in software, and the optimum conditions were confirmed with the plasma treatment period of 60 min, the voltage of 14.8 kV, the discharge gap of 20 mm, and the discharge needles of 5. Plasma associated with catalysts systems including plasma, plasma/Fe2+, plasma/PS, and plasma/PS/Fe2+ were further investigated, and the best removal rate for MO reached 99.2% at 60 min under the plasma/PS/Fe2+ system due to simultaneously synergistic reactions of HO• and SO4•−. Moreover, it was also revealed that –N=N– bond was attacked and broken by active species like HO•, and the oxidized by-products of benzenesulfonic acid and phenolsulfonic acid might be generated, via the analysis of the variation in the absorbances through UV-Vis spectrophotometry during the plasma treatment. As a result, the advanced plasma technique in this study presented excellent efficacy for MO removal from simulated wastewater with low energy consumption.

Novel adsorption-photocatalysis integrated bismuth tungstate modified layered mesoporous titanium dioxide (Bi2WO6/LM-TiO2) composites

Using cetyltrimethylammonium bromide (CTAB) as the soft template and titanium sulfate as the titanium source, the layered mesoporous TiO2 (LM-TiO2) was prepared by the novel precipitation-peptization method, then bismuth tungstate was synthesized and coupled with layered mesoporous titanium dioxide by the hydrothermal process to obtain adsorption-photocatalysis integrated Bi2WO6/LM-TiO2 composites. The surface morphology, transmission morphology and elemental mapping, particle size, crystal phase composition, ultraviolet absorption band, fluorescence intensity, functional group structure, element composition and valence state of the samples were characterized using scanning electron microscopy (SEM), transmission electron microscope (TEM), laser particle size analyzer, X-ray diffraction (XRD), ultraviolet visible absorption spectrum (UV–Vis-Abs), Molecular fluorescence spectrophotometer (PL) and X-Ray photoelectron spectroscopy (XPS), respectively. Taking methyl orange as the target substance, the adsorption and photocatalytic performances of the samples were studied. The results indicate that Bi2WO6/LM-TiO2 composites have excellent adsorption and photocatalytic degradation performances. When irradiated with a 500 W metal halide lamp for 20 min, the removal rate of methyl orange by 8% Bi2WO6/LM-TiO2 reaches 93.60% which is greatly improved compared with simple LM-TiO2, and is twice as that of P25. By coupling LM-TiO2 with Bi2WO6, the composites show a spherical structure, and the crystallinity does not change significantly. Moreover, the light absorption band edge has a certain red shift and the photogenerated electron-hole recombination is restrained, thereby improving the photocatalytic performance.

Degradation of methyl orange by pyrite activated persulfate oxidation: mechanism, pathway and influences of water substrates.

Degradation mechanism of methyl orange (MO), a typical azo dye, with pyrite (FeS2) activated persulfate (PS) was explored. The results showed that when the initial concentration of MO was 0.1 mM, FeS2 was 1.6 g/L and PS was 1.0 mM, the removal rate of MO could reach 92.9% in 150 min, and the removal rate of total organic carbon could reach 14.1%. In addition, both pH ≤ 2 and pH ≥ 10 could have an inhibitory effect in the FeS2/PS system. Furthermore, Cl- and low concentrations of HCO-3 had little effect on the degradation of MO with FeS2/PS. However, H2PO-4 and high concentrations of HCO-3 could inhibit the degradation of MO in the system. Besides, MO in river water and tap water were not degraded in FeS2/PS system, but acidification (pH = 4) would greatly promote the degradation. In addition, the removal rate of MO with FeS2/PS could still reach about 90% after five cycles of FeS2. Furthermore, the intermediates and possible degradation pathways were speculated by LC-MS, and the degradation mechanism of MO by FeS2/PS was that the cycle of Fe(III)/Fe(II) could continuously activate persulfate to produce SO4•-. The results could provide technical support for azo dye degradation in the FeS2/PS system.