Removal Rate Of Methyl Orange Research Articles

Selective separation of methyl orange from water using magnetic ZIF-67 composites

Efficacious and convenient removal of organic dye contaminants from wastewater is a challenge for public health and ecosystem protection. Here we fabricate a novel type of Fe3O4@MOFs (Metal-organic frameworks) magnetic porous composite materials. ZIF-67 (Zeolitic imidazolate framework-67) nano-crystals as an attractive subfamily of MOF was selected to fabricate Fe3O4-PSS@ZIF-67 composites (defined as MZIF-67). MZIF-67 composites are core-shell structure, for which the aggregation core of Fe3O4 nanoparticles is coated with petal-like ZIF-67 crystals, in which Co2+ firstly combines with SO32− provided by PSS (poly (styrenesulfonate, sodium salt)) to form nucleation. MZIF-67 composites perform well on methyl orange (MO) adsorption, which could be attributed to the highly porosity and the nature of Lewis base of coordinated Co2+ centrals. The results show that the equilibrium adsorption capacity for MO is up to 738mg·g−1 (when pH=8.0, contact time is 7h, adsorbent dose is 5mg and initial MO concentration is 400mg·L−1). In addition, MZIF-67 composites could selectively separate MO from the mixture solution of MO and MB (methylene blue). The removal rate of MO is up to 92%. The concentration ratio of MO/MB is 0.04. And the separation efficiency is up to 96%. The results suggest MZIF-67 composites could be a good candidate for treatment of dye-bearing wastewater.

Controllable Synthesis of Mesoporous Sulfur-Doped Carbon Nitride Materials for Enhanced Visible Light Photocatalytic Degradation.

Mesoporous sulfur-doped graphitic carbon nitride (MCNS) materials were successfully synthesized using thiourea as a low-cost precursor and SiO2 gel solution as a template through a simple thermal condensation method. The effects of three synthesis key factors, namely, the reaction temperature, the reaction time, and the weight ratio of SiO2/thiourea, and also their interactions on the removal rate of methyl orange (MO) were investigated using response surface methodology, and the samples were subjected to several characterization techniques. Results showed that the optimized physicochemical properties could be achieved for the MCNS samples by controlling the synthesis key factors, and it was found that the reaction temperature and the reaction time had significant influences on the MO photocatalytic removal. Among bulk graphitic carbon nitride (g-C3N4), CN (undoped g-C3N4), CNS (sulfur-doped g-C3N4 without template), and TiO2 (Degussa P25) samples, the optimized MCNS-4 illustrated the highest photocatalytic activity toward the removal of MO under visible light irradiation. The enhanced performance originated from the synergistic effects of high surface area, mesoporous texture, sulfur doping, and high visible light absorption, which were helpful for the separation and transportation of the photogenerated electron-hole pairs. Furthermore, MCNS-4 revealed high reusability and stability without any significant decrease in its efficiency. Our findings not only confirm the importance of simultaneous sulfur doping and mesoporous structure to synthesize highly active photocatalysts but also might provide a new insight into textural engineering of carbon nitride materials only by the optimization of the synthesis key variables, considering their interactions without relying on extra metal oxides.

Enhancing Extracellular Electron Transfer of Shewanella oneidensis MR-1 through Coupling Improved Flavin Synthesis and Metal-Reducing Conduit for Pollutant Degradation.

Dissimilatory metal reducing bacteria (DMRB) are capable of extracellular electron transfer (EET) to insoluble metal oxides, which are used as external electron acceptors by DMRB for their anaerobic respiration. The EET process has important contribution to environmental remediation mineral cycling, and bioelectrochemical systems. However, the low EET efficiency remains to be one of the major bottlenecks for its practical applications for pollutant degradation. In this work, Shewanella oneidensis MR-1, a model DMRB, was used to examine the feasibility of enhancing the EET and its biodegradation capacity through genetic engineering. A flavin biosynthesis gene cluster ribD-ribC-ribBA-ribE and metal-reducing conduit biosynthesis gene cluster mtrC-mtrA-mtrB were coexpressed in S. oneidensis MR-1. Compared to the control strain, the engineered strain was found to exhibit an improved EET capacity in microbial fuel cells and potentiostat-controlled electrochemical cells, with an increase in maximum current density by approximate 110% and 87%, respectively. The electrochemical impedance spectroscopy (EIS) analysis showed that the current increase correlated with the lower interfacial charge-transfer resistance of the engineered strain. Meanwhile, a three times more rapid removal rate of methyl orange by the engineered strain confirmed the improvement of its EET and biodegradation ability. Our results demonstrate that coupling of improved synthesis of mediators and metal-reducing conduits could be an efficient strategy to enhance EET in S. oneidensis MR-1, which is essential to the applications of DMRB for environmental remediation, wastewater treatment, and bioenergy recovery from wastes.

Synthesis of chitosan/polyvinyl alcohol/zeolite composite for removal of methyl orange, Congo red and chromium(VI) by flocculation/adsorption

A chitosan/polyvinyl alcohol (PVA)/zeolite composite was fabricated in this study. The composite was analyzed through field emission scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis, and weight loss test. FTIR and XRD results revealed a strong interaction among chitosan, PVA, and zeolite. Weight loss test results indicated that the composite was stable in acidic and basic media. Congo red was removed through flocculation, and the removal rate was 94% at an initial concentration of 100mg/L for a dose of 1g/L. The removal rate of methyl orange was controlled by adsorption at an initial concentration of less than 100mg/L. Flocculation occurred at high concentrations. The removal rate was also 94% at an initial concentration of 500mg/L for a dose of 5g/L. The adsorption behavior of the composite for the removal of methyl orange and Cr(VI) was described by using a pseudo-second-order kinetic model. The adsorption capacity of the composite for Cr(VI) was 450mg/g. Therefore, the synthesized composite exhibited versatility during the removal of dyes and heavy metals.

Preparation of CaF2/TiO2/Ln2Ti2O7 (Ln = Er, Tm, Yb) based magnetite near-infrared photocatalyst supported on waste ferrite

Fabrication of magnetite near-infrared (NIR) photocatalyst using the waste ferrite—mixed-ferrite (M-Fe3O4) derived from electroplating wastewater as the magnetic agent is a promising way to reduce environmental pressures. Here, the SiO2 coated M-Fe3O4 (M-Fe3O4@SiO2) is added to fabricate the magnetite NIR photocatalyst of Er3+/Tm3+/Yb3+-M-Fe3O4@SiO2/CaF2/TiO2/Ln2Ti2O7 (Ln=Er, Tm, or Yb) (ETY-FCTL). The spherical shaped ETY-FCTL contains the phases of anatase-TiO2, (Ca0.8Yb0.2)F2.2, Ln2Ti2O7, and the residual CaTiO3, and exhibits strong short-wavelength light absorption property. According to the broadband light absorption ability, most of the upconverted light (blue, green, UV light) can be used by ETY-FCTL for photocatalysis. Under the UV–vis-NIR irradiation, ETY-FCTL has higher removal rate of methyl orange (99.0%) compared to M-Fe3O4@SiO2/CaTiO3 (50.2%), Er3+/Tm3+/Yb3+-M-Fe3O4@SiO2/CaTiO3/TiO2 (68.0%), and Er3+/Tm3+/Yb3+-M-Fe3O4@SiO2/CaF2/Ln2Ti2O7 (20.8%). ETY-FCTL also possesses the highest removal efficiency of salicylic acid among the samples. The best photocatalytic activities of ETY-FCTL are resulted from its high light absorption property and efficient electron-hole pair separation.

可见光催化剂Fe<sub>3</sub>O<sub>4</sub>/BiOI的制备及其催化活性研究

采用水热法合成了磁性的、可见光响应的Fe3O4/BiOI复合光催化剂，运用X射线衍射(XRD)，扫描电子显微镜(SEM)，紫外–可见漫反射光谱(UV-vis DRS)对所制备的光催化剂进行了表征，结果显示所制备的复合光催化剂的粒径范围为0.5~2 μm且形貌呈球形结构。在可见光照射下，通过降解甲基橙测定不同比例复合光催化剂的活性大小，结果表明当Fe3O4的负载量为5%时，复合光催化剂具有最佳的光催化活性，甲基橙的降解率可达81%；而单纯的BiOI的降解率仅为40%。通过外部磁场的作用，Fe3O4/BiOI复合光催化剂能快速彻底地从体系中分离。复合光催化剂实现了外部磁场控制的循环回收利用，在实际应用中具有潜在的价值。 Magnetic Fe3O4/BiOI composite photocatalysts with visible light response were successfully fab-ricated through hydrothermal method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible diffuse reflection spectroscopy (UV-vis DRS) respectively. The characterization results show that the grain sizes of composite photocatalysts samples were varied from 0.5 μm to 2 μm and their morphologies were spheroid. The activities of composite photocatalysts with different proportions were evaluated by photodegradation of methyl orange under visible-light irradiation. Results show that the 5% Fe3O4/BiOI composite photocatalyst has the best photocatalytic activity. After 120 min of irradiation, removal rate of methyl orange reached to 81%, which was superior to the pure BiOI (40%). By the effect of the external magnetic field, the composite photocatalysts can be quickly and completely separated from the system, indicating a potential prospect in the practical application.

Energy-saving removal of methyl orange in high salinity wastewater by electrochemical oxidation via a novel Ti/SnO2-Sb anode—Air diffusion cathode system

Electrochemical oxidation is an effective method in removal of organic pollutant from high salinity wastewater (NaCl), by producing active chlorine at anode or hydrogen peroxide at cathode. To solve the existing problems including low efficiency, high cost and energy consumption, a Ti/SnO2-Sb anode (TSSA)-air diffusion cathode (TSSA-ADC) system was investigated for methyl orange (MO) removal from NaCl solution, using single TSSA system as control. The phase composition of TSSA was examined by X-ray diffraction. Accumulated concentrations of active chlorine, hydrogen peroxide, MO removal rate, TOC, pH value were recorded at different current densities. The results indicated that Sb-doped rutile SnO2 was formed on the TSSA. The TSSA and the ADC exhibited good catalysis to chlorine evolution and oxygen reduction, respectively. Although MO were almost completely removed in both systems, higher TOC removal, shorter running time and lower energy consumption were attained in the TSSA-ADC system. pH value was more stable (6.0–6.4) in the TSSA-ADC system than that in the TSSA system (6.0–9.4), predicting its stronger capacity in anti-scaling when treating high salinity wastewater with hard ions like Ca2+ and Mg2+.

Removal of Methyl Orange in Aquaculture Water by Spray-Coated Tio2 Photocatalysis

A major challenge for aquaculturists using recirculating aquaculture systems is the accumulation of off-flavor compounds, such as geosmin and 2-methylisoborneol (MIB), in the farmed fish. This work investigates the removal of off-flavor compounds in aquaculture systems using titanium dioxide (TiO2) photocatalysis. Due to concerns of TiO2 nanoparticles on fish, TiO2 was immobilized onto glass plates. A photodegradation reactor that incorporated the TiO2 coated plates was designed and operated as a recirculating system. Methyl orange was used as a surrogate compound for geosmin and MIB. In parameter optimization experiments, a flow rate of 2.5 mL/s, a water depth of 2 mm and a TiO2 dosage of 0.25 mg/cm3 were found to provide a high methyl orange removal rate constant of 0.77/h, when the compound was supplied in a solution made in deionized (DI) water. Due to the presence of natural organic matter (NOM) in the RAS water, the methyl orange removal rate constant decreased to 0.44/h. The results indicate that although NOM interferes with the photocatalysis process, if an extended reaction time is applied acceptable removal efficiencies can be achieved. This work is currently being applied in a photocatalysis study on removal of off-flavor compounds in RAS.

Magnetic Nanoscaled Fe<sub>3</sub>O<sub>4</sub> as an Efficient and Reusable Heterogeneous Catalyst for Degradation of Methyl Orange in Microwave-Enhanced Fenton-Like System

In this study, the Fe3O4magnetic nanoparticles (MNPs) were synthesized as heterogeneous catalysts to effectively degrade methyl orange. The coulping method of microwave irradiation and Fenton-like reaction was used for degradation of methyl orange waste water. The effects of Fe3O4dosage, initial H2O2concentration, catalyst cycles, reaction temperature and so on were assessed systematically. The experimental results showed that the microwave-assisted Fenton-like process using H2O2/Fe3O4was the most effective treatment process compared with other traditional methods. According to degradation of methyl orange, it has been found that the oxidation by Fenton-likes reagent is dependent on Fe3O4dosage, H2O2dosage, reaction temperature. The results indicate that under the optimal conditions, the removal rate of methyl orange could reach nearly 100%. Moreover, six cyclic tests for methyl orange degradation showed that the magnetic catalyst was very stable, recoverable, highly active, and easy to separate using an external magnet. Hence, the coulping method of microwave irradiation and Fenton-like reaction with magnetic nanomaterials of Fe3O4as the catalyst has potential use in organic pollutant removal.

Preparation of TiO2/mesoporous carbon composites and their photocatalytic performance for methyl orange degradation

Mesoporous carbon (MC) prepared using colloidal silica templates was used as a support to synthesize TiO 2 /MC composites using a sol–gel method. The TiO 2 content and the crystalline structure of TiO 2 /MC photocatalysts can be tuned by the precursor composition and calcination temperature, respectively. MC and TiO 2 /MC composites were characterized by nitrogen adsorption, XRD, TG, SEM, TEM and electron energy dispersive spectroscopy. Results showed that the anatase TiO 2 nanoparticles were highly dispersed on the surface of the carbon framework. As-prepared composites exhibited high photocatalytic activities for methyl orange (MO) degradation under UV irradiation, and a synergistic effect of adsorption and photocatalytic degradation was observed. The MO removal rate reached 89% after UV irradiation for 75 min. The kinetics of MO degradation can be well fitted with a first-order reaction model and the largest rate constant observed was 0.015 min −1 . [New Carbon Materials 2013, 28(1): 47–54]

Preparation of TiO2/mesoporous carbon composites and their photocatalytic performance for methyl orange degradation

Mesoporous carbon (MC) prepared using colloidal silica templates was used as a support to synthesize TiO2/MC composites using a sol-gel method. The TiO2 content and the crystalline structure of TiO2/MC photocatalysts can be tuned by the precursor composition and calcination temperature, respectively. MC and TiO2/MC composites were characterized by nitrogen adsorption, XRD, TG, SEM, TEM and electron energy dispersive spectroscopy. Results showed that the anatase TiO2 nanoparticles were highly dispersed on the surface of the carbon framework. As-prepared composites exhibited high photocatalytic activities for methyl orange (MO) degradation under UV irradiation, and a synergistic effect of adsorption and photocatalytic degradation was observed. The MO removal rate reached 89% after UV irradiation for 75 min. The kinetics of MO degradation can be well fitted with a first-order reaction model and the largest rate constant observed was 0.015 min−1.

Nano-Iron Hydroxides/Oxides Modified Slag on the Treatment of Simulated Methyl Orange Wastewater

Degradation of simulated methyl orange (MO) was studied by combined adsorption treatment and advanced oxidation processes with nano-iron hydroxides/oxides modified slag. The adsorption treatment of nano-iron hydroxides/oxides/slag shows that with the increased of adsorbent from 0.1% to 0.5%, the removal of MO can change from 23.2% to 92.8%. While combination of the adsorption treatment and the advanced oxidation processes exhibits the enhanced disposal ability, in which the removal rate of MO changed from 23.2% to 99.9%.

Enhanced Adsorption of Methyl Orange by Vermiculite Modified by Cetyltrimethylammonium Bromide (CTMAB)

CTMAB-vermiculite, which can improve the vermiculite interlayer space and adsorption capacity of organic matter, has been obtained by using cetyltrimethylammonium bromide. The effects of the dosage of material, shaking time, the concentration of methyl orange, and the pH on the absorbent characteristics of methyl orange are studied by spectrophotoscopy. The structural characteristics of vermiculite and CTMAB-vermiculite have been studied through SEM. The results show that CTMAB-vermiculite changes dramatically -- its interlayer space becomes larger. The methyl orange removal rate of CTMAB-vermiculite is better than that of vermiculite. In about 30 minutes. CTMAB-vermiculite can reach absorption equilibrium. Low pH conditions are conducive to CTMAB-vermiculite adsorption of methyl orange. The activated temperature should be controlled under the initial decomposition temperature of CTMAB, which can improve the reusability of recycled vermiculite.

Removal of methyl orange from aqueous solution using bentonite-supported nanoscale zero-valent iron

Zero-valent iron (ZVI) nanoparticles tend to agglomerate, resulting in a significant loss in reactivity. To address this issue, synthesized bentonite-supported nanoscale zero-valent iron (B-nZVI) was used to remove azo dye methyl orange (MO) in aqueous solution. Batch experiments show that various parameters, such as pH, initial concentration of MO, dosage, and temperature, were affected by the removal of MO. Scanning electron microscopy (SEM) confirmed that B-nZVI increased their reactivity and a decrease occurred in the aggregation of iron nanoparticles for the presence of bentonite (B). Using B-nZVI, 79.46% of MO was removed, whereas only 40.03% when using nZVI after reacting for 10min with an initial MO concentration of 100mg/L (pH=6.5). Furthermore, after B-nZVI reacted to MO, XRD indicated that iron oxides were formed. FTIR showed that no new bands appeared, and UV–vis demonstrated that the absorption peak of MO was degraded. Kinetics studies showed that the degradation of MO fitted well to the pseudo first-order model. A degradation mechanism is proposed, including the following: oxidation of iron, adsorption of MO to B-nZVI, formation of Fe(II)–dye complex, and cleavage of azo bond. Finally, the removal rate of MO from actual wastewater was 99.75% when utilizing B-nZVI.

Electrolytic treatment of methyl orange in aqueous solution using three‐dimensional electrode reactor coupling ultrasonics

The treatment of wastewater containing methyl orange was investigated experimentally using a three‐dimensional electrode reactor coupling ultrasonics and the effect of ultrasonics on the degradation was studied. The effects of cell voltage, original concentration of methyl orange, pH value and the concentration of electrolyte on the removal efficiency were considered. The experimental results indicated that the removal rate of methyl orange exceeded 99% and the removal of chemical oxygen demand (CODCr) approached 84% under the optimum conditions. Using ultraviolet‐visible spectrum analysis, a general degradation pathway for methyl orange was proposed based on the analysis of intermediate compounds. According to the ultraviolet‐visible spectral changes during degradation of methyl orange, it can be presumed that the removal of CODCr lags behind the removal of methyl orange because the structure of the benzene ring was more difficult to destroy compared with the azo double bonds.

Modeling and experimentation of a novel labyrinth bubble photoreactor for degradation of organic pollutant

A novel labyrinth flow bubble photoreactor (LBPR) was designed and the model of multiple mixed flow reactors (MMFRs) in series was established to describe the behavior of the LBPR during batch recirculation system of low concentration organic pollutant degradation by photocatalysis. This model was developed by the mass balance combining the rate equation of the photocatalytic reaction. The influence of the structural parameters, such as the number of baffle plates, the space between the baffle plates and the height of liquid exit in the reactor, on the photocatalytic degradation of organic pollutant was mainly investigated. The relationships between the final conversion rate and the liquid rate, liquid volumes, light intensity and catalyst amounts were also predicted by this model. TiO 2 was immobilized on quartz glass particles by sol–gel method and used as the photocatalysts; the degradation experiment of methyl orange (MO) was performed in a 2 l LBPR reactor to validate the above model. The experimental results showed that the removal rate of MO could reach 100% with 12 baffle plates and 4 cm height of liquid exit after 1.5 h treatment when the flow rate was 0.0111 m 3 h −1 and the particle catalysts was 4.8 g l −1. The prediction of the model is consistent with the experimental results. This research provides exploratory work for the design of a novel commercial scale photocatalytic reactor.