Acid Red G Research Articles

PANI grafted onto waste poros polyurethane for co-adsorption of multiple pollutants in industrial wastewater

Simultaneously up-taking multiple pollutants from industrial wastewater is an urgent challenge in the field of adsorption technology. In this study, a polyaniline (PANI)-based adsorbent supported by waste polyurethane (PU) was designed, and its capability for simultaneous adsorption of various pollutants was investigated. The results revealed that in a simulated multi-pollutant wastewater, the adsorbent demonstrated synchronous removal efficiencies of 88% for acid red G (ARG), 40% for methylene blue (MB), 90% for Cr(VI), 58% for phosphorus (TP), 42% for NH4+-N, 30% for NO3−-N, and 63% for chemical oxygen demand (COD). The corresponding adsorption capacities were 255.81, 22.57, 105.32, 10.04, 7.98, 23.03 and 236.31 mg/gP/T, respectively. The continuous flow column adsorption lasted for 1800 min (144 columns) before reaching saturation, and no significant decrease in adsorption efficiency was observed even after 5 cycles of regeneration. X-ray photoelectron spectroscopy (XPS) and excitation-emission matrix spectroscopy (EEM) analysis revealed that ARG, Cr(VI), NO3−-N, and TP competed for the same adsorption sites, with ARG exhibiting the highest affinity, followed by Cr(VI), TP, and NO3−-N. During the adsorption process, redox reactions occurred between Cr(VI) and =N- in the PANI chain, resulting in the formation of Cr(III) and -NH+- species, which further enhanced the adsorption of anionic pollutants such as H2PO4−. The interaction between pollutants before adsorption directly affected the subsequent adsorption process. Overall, these findings demonstrate the feasibility and effectiveness of the PU-P/T adsorbent as a potential engineering adsorbent for co-adsorption of a variety of pollutants.

Preparation and application of red mud-based heterogeneous Fenton catalyst

The zero-valent iron (ZVI) heterogeneous Fenton catalyst based on red mud (RM) was synthesized by direct reducing iron oxide in RM using H2 at 800 °C (RMH-800). X-ray diffraction analysis showed that Fe2O3 in RM was reduced to Fe0. Brunauer -Emmett-Teller, scanning electron microscopy and high-resolution transmission electron microscopy show that RMH-800 is a ZVI-loaded porous material. The catalysts were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Under the conditions of 2.86 mM H2O2, 100 mg/L Acid Red G (ARG) and 1 g/L RMH-800, 95 % of ARG was removed within 10 min. The RMH-800/H2O2 system also showed excellent degradability to antibiotics (Sulfamethoxazole, Ibuprofen and Primidone). •OH is the main species responsible for pollutants degradation. RMH-800 showed low iron leaching during the reaction process and excellent catalytic performance even after 6 repeats, indicating it a stable and low-cost material with great potential for wastewater treatment.

Activated Carbon Assisted Fenton-like Treatment of Wastewater Containing Acid Red G

The Fenton reaction as an effective advanced oxidation technology has been widely used in wastewater treatment for its stable effluent quality, simple operation, mild condition, and higher organic degradation with non-selectivity. However, the traditional Fenton reaction is limited by the sluggish regeneration of Fe2+, resulting in a slower reaction rate, and it is necessary to further increase the dosage of Fe2+, which will increase the production of iron sludge. Activated carbon (AC) has a strong adsorption property, and it cannot be ignored that it also can reduce Fe3+. In this study, the degradation of acid red G (ARG) by adding AC to the Fe3+/H2O2 system, the role of the reducing ability, and the reason why AC can reduce Fe3+ were studied. By adding three kinds of ACs, including coconut shell-activated carbon (CSPAC), wood-activated carbon (WPAC), and coal-activated carbon (CPAC), the ability of ACs to assist the Fe3+/H2O2 Fenton-like system to degrade ARG was clarified. Through the final treatment effect and the ability to reduce Fe3+, the type of AC with the best promotion effect was CSPAC. The different influence factors of particle size, the concentration of CSPAC, concentration of H2O2, concentration of Fe3+, and pH value were further observed. The best reaction conditions were determined as CSPAC powder with a particle size of 75 μm and dosage of 0.6 g/L, initial H2O2 concentration of 0.4 mmol/L, Fe3+ concentration of 0.1 mmol/L, and pH = 3. By reducing the adsorption effect of CSPAC, it was further observed that CSPAC could accelerate the early reaction rate of the degradation process of ARG by the Fe3+/H2O2 system. FT-IR and XPS confirmed that the C-O-H group on the surface of CSPAC could reduce Fe3+ to Fe2+. This study can improve the understanding and role of AC in the Fenton reaction, and further promote the application of the Fenton reaction in sewage treatment.

A closed-loop electrokinetic system for recovery of PbO2@Fe composite derived from lead-containing sludge.

Lead-containing sludge produced from lead-acid battery factory will cause environmental hazards if they are not treated properly. A novel process was developed to recycle lead from sludge back into Fe-doped PbO2 electrodes and realize sludge reduction in this study. The effects of Fenton conditioning on Pb removal efficiency in electro-kinetic (EK) treatment process and its mechanism as well as electro-dewatering (ED) performance were investigated. It was found that the oxidation of Fenton can promote desorption and release of Pb from the organic binding state, and improve the removal efficiency of Pb during EK process, as well as enhance sludge ED performance. About 63.8wt% Pb can be removed from sludge during EK process, achieving sludge reduction of 63.5wt% by ED treatment. The composite PbO2@Fe electrode recovered from lead-containing sludge showed a high electrocatalytic activity for acid red G (ARG) degradation. The electrode obtained by electrodeposition at 20mAcm-2 had the largest exchange current density (3.26×10-5Acm-2). In the experiment of dye wastewater electrocatalytic degradation, over 99.5% organic matter was degraded within 80min.

Adsorption of anionic acid red G dye on polyaniline nanofibers synthesized by FeCl3 oxidant: Unravelling the role of synthetic conditions

Polyaniline (PANI) has been considered as a high-efficient adsorbent for the dye removal from wastewater. Different synthetic conditions could offer PANI with comparable adsorption performance and yield, which are crucial for its large-scale application. Herein, the adsorption performance of PANIs, which synthesized by one-step polymerization method under different temperature and amount of FeCl3, for the removal of a typical anionic dye, Acid Red G (ARG), were investigated. As-synthesized PANIs were characterized by scanning electron microscopy, FT-IR spectroscopy, nitrogen adsorption-desorption isotherms and X-ray diffraction. Adsorption isotherms study result showed that low temperature was beneficial for the formation of highly crystallized PANI nanofibers with high adsorption performance, and high amount of FeCl3 could increase the yield of PANI. An optimal synthetic condition, where temperature is 20 °C and molar of aniline to FeCl3 is 1:4, was determined for PANI when using FeCl3 oxidant (PANIopt). The adsorption including kinetics, isotherms, and regeneration of PANIopt on ARG was then systemically investigated. The maximum adsorption capacity of PANIopt for ARG was found to be 491.20 mg g−1 at 35 °C. Moreover, adsorption mechanism study suggested that the efficient adsorption performance was related with the highly crystalized polymer chain of PANI, which provides abundant active sites for the adsorption of ARG via electrostatic interaction.

Study on treatment of acid red G with bio-carbon compound immobilized white rot fungi.

Corn straw biochar was used as a carrier to immobilize white rot fungi and the removal performance of immobilized pellets for acid red G (ARG) dye was studied. The results showed that the removal rate of ARG could reach 96.17% under the best preparation conditions of immobilized pellets (3% sodium alginate concentration, 0.7% corn straw biochar, 5% white rot fungus mycelium suspension, 4% CaCl2, and 36 h immobilization time). The orthogonal test results showed that the best combination was the immobilized pellets dosage of 200/100 mL, pH of 4.5, rotation speed of 150 r/min, and initial concentration of 20 mg/L dye at 30 °C. The degradation pathway of ARG by immobilized microspheres was studied by ultraviolet-visible spectrometer, Fourier transform infrared spectroscopy, and liquid chromatography-mass spectrometry. The results showed that ARG was degraded into aniline and 5-(acetamino)-4-hydroxy-3-amino-2,7-naphthalene disulfonic acid. Aniline was further deaminated to form benzene, and benzene was ring opened to form other organic compounds; 5-(acetylamino)-4-hydroxy-3-amino-2,7-naphthalene disulfonic acid was dehydroxylated to form 5-(acetylamino)-3-amino-2,7-naphthalene disulfonic acid. This study shows that the prepared biochar immobilized pellets can be used as an efficient water treatment material to remove ARG dye from wastewater.

Facile fabrication of AgFe1−xCuxO2 composite with abundant oxygen vacancies for boosted photocatalytic Cr (VI) reduction and organic pollutants degradation under visible light

In order to enhance the utilization of visible light and improve photocatalytic performance of AgFeO2, in this work, a novel copper (Cu) doped AgFeO2 composite catalysts with abundant oxygen vacancies (OVs) were synthesized by the co-precipitation method. The results of X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) showed Cu was successfully doped in AgFeO2 to form lattice defects, resulting in a large number of oxygen vacancies, which is beneficial for oxygen molecules to be activated into superoxide radicals. Compared with pure AgFeO2, the Cu doped samples expand the absorption region of visible light, thereby enhancing photocatalytic activity in the oxidization of organic pollutants and the reduction of Cr (VI). In a mixed Cr (VI)/ Acid Red G (ARG) solution, the 20 mg/L of ARG could be almost completely degraded within 90 min by Cu doped AgFeO2 composite, while the reduction efficiency of Cr (VI) is up to 90.19%, which is 1.95 times higher than that of AgFeO2. After the fourth photocatalytic recycling experiment, the photocatalytic performance of Cu doped AgFeO2 composite is still superior. The results of scavenger experiments show that holes (h+) and superoxide anions (O2•-) were the main dominant reactive for promoting photocatalytic reduction of Cr (VI) and degradation of organic pollutants over the Cu doped AgFeO2 composites. Based on the results of photoluminescence spectra (PL) and electron spin resonance (ESR), the enhanced photocatalytic performance of the Cu doped AgFeO2 could be contributed to oxygen vacancy caused by doping defects and the enhancement of visible light absorption.

Efficient activation of peroxymonosulfate by porous Co-doped LaFeO3 for organic pollutants degradation in water

Sulfate radical-based advanced oxidation technology has been considered one of the most effective methods to remove organic pollutants from water. In this study, porous Co-doped LaFeO3 catalysts were synthesized by the sol-gel method and applied in peroxymonosulfate (PMS) activation for organic pollutants degradation. The effects of catalyst dosage, PMS concentration, initial pH of the solution and radical scavenger on the degradation of Acid Red G (ARG) were systematically studied. The porous LaFeO3 showed higher specific surface area (27.62 ​m2/g) and pore volume (0.15 ​cm3/g) than the traditional LaFeO3 (7.83 ​m2/g and 0.11 ​cm3/g), resulting in higher activity. After doping Co, more oxygen vacancies generated. The catalytic activity of LaFe1-xCoxO3 was remarkably enhanced. ARG could be completely degraded in LaFe0.90Co0.10O3/PMS system within 10 ​min. The degradation rate was 51 times higher than that in the porous LaFeO3/PMS system. The superior activity can be attributed to the oxygen vacancies and synergistic effect of Co and Fe, which facilitated the activation of PMS and generated SO4•- and HO•. It was SO4•- that mainly contributed to the degradation of ARG. The detailed degradation pathway was proposed, according to the intermediate products of ARG degradation. Besides, the degradation rate of ARG by the as-prepared catalyst exceeded 80% even after using for 5 times.

Process optimization and mechanism study of acid red G degradation by electro-Fenton-Feox process as an in situ generation of H2O2.

Dye-contaminated wastewaters are industrial wastewaters that are difficult to treat using traditional biochemical and physicochemical methods. In the present work, the acid red G was removed as a model pollutant by the electro-Fenton process for the first time. The anode and cathode used by the electro-Fenton process were iron plate and graphite felt, respectively. It was concluded that under the optimal conditions of current density = 20 mA cm-2, pH = 3 and initial Na2SO4 concentration = 0.2 M, the removal rate of acid red G (ARG) with an initial concentration of 300 mg L-1 could reach 94.05% after 80 min of electrolysis. This reveals that the electro-Fenton-Feox process used in this work has an excellent removal efficiency on acid red G. The required reagents (Fe2+ and H2O2) were generated by the electrode reaction, while the optimal generation conditions and mechanism of •OH, H2O2, and Fe2+ were investigated. By testing •OH, H2O2, and Fe2+ agents at different pH and current densities, it was revealed that the electro-Fenton reaction was most efficient when the current density was 20 mA cm-2, and the pH was 3. Moreover, the removal rate of ARG is consistent with first-order reaction kinetics.

Insight into the effect of surface carboxyl and amino groups on the adsorption of titanium dioxide for acid red G

In this study, TiO2 functionalized with organic groups were prepared to study the effect of carboxyl and amino groups on the adsorption behavior of TiO2 for the removal of acid red G (ARG) as an anionic dye from aqueous solution. TiO2 was successfully modified with carboxyl and amino groups by using the hydrolysis method with oxalic acid (OAD, with two carboxyl groups), ethylenediamine (EDA, with two amino groups) and DL-alanine (DLA, with one carboxyl group and one amino group) at low temperature (65 °C) and labeled as OAD-TiO2, EDA-TiO2 and DLA-TiO2, respectively. The ARG uptake by the functionalized TiO2 samples was largely dependent on the functional groups. The interaction between ARG and the functional organic groups on the TiO2 samples plays an important role in the adsorption process, which leads to the excellent adsorption performance (higher capacity and faster adsorption rate) of the functionalized TiO2 samples than that of P25 (commercial TiO2 without modification). Furthermore, there is no obvious loss of the adsorption capacity for the functionalized TiO2 even after 5 adsorption-desorption cycles, which indicated the good reusability of the modified TiO2 samples for anionic dye removal from aqueous solution.

Acid red G dye removal from aqueous solutions by porous ceramsite produced from solid wastes: Batch and fixed-bed studies

AbstractA novel porous ceramsite was made of municipal sludge, coal fly ash, and river sediment by sintering process, and the performance of batch and fixed-bed column systems containing this material in the removal of acid red G (ARG) dye from aqueous solutions was assessed in this study. The results of orthogonal test showed that sintering temperature was the most important determinant in the preparation of porous ceramsite, and it possesses developed pore structure and high specific surface area. Batch experiment results indicated that the adsorption process of ARG dye toward porous ceramsite was a spontaneous exothermic reaction, which could be better described with Freundlich–Langmuir isotherm model (R2 > 0.992) and basically followed the pseudo-first-order kinetic equation (R2 > 0.993). Column experiment results showed that when the porous ceramsite was used as packing material, its adsorption capacity was roughly improved by 3.5 times compared with that in batch system, and the breakthrough behavior was simulated well with Yoon–Nelson model, with R2 > 0.954. This study suggested that the novelty man-made porous ceramsite obtained from solid wastes might be processed as a certain cost-effective treatment material fit for the dye removal in aqueous solutions.

Design of magnetically assembled electrode (MAE) with Ti/PbO2 and heterogeneous auxiliary electrodes (AEs): The functionality of AEs for efficient electrochemical oxidation

Heterogeneous auxiliary electrodes (AEs, Fe3O4/Sb-SnO2 or Fe3O4/Pb3O4 granules) with different amount were loaded on foil Ti/PbO2 (main electrode, ME) and thereby formed series of so-called magnetically assembled electrode (MAE) for more efficient, flexible and versatile electrochemical oxidation (EO) treatment of organic wastewater. Diverse material characterizations and electrochemical characterizations were performed to investigate the nature of the AEs and the effects of AEs type and assembling amount on the electrochemical behaviors of the MAE, respectively. Azo dye Acid red G (ARG) and lignosulphonate (lignin) were selected as the target pollutants to examine the effects of AEs type and assembling amount on the EO performance of MAE. Results show that both two types of AEs could increase the electrochemical roughness and the active sites, but with different optimum amount. Compared with 2D Ti/PbO2, a series of MAEs exhibited about 18%-30% higher efficiency in ARG degradation, among which the MAE with higher Fe3O4/Pb3O4 AEs amount had better performance. However, in breaking lignin macromolecule structure into smaller molecules, the MAE with higher Fe3O4/Sb-SnO2 AEs amount was better. The different synergisms between the two heterogeneous AEs and the ME in EO were proposed, and the relationship of the chemical composition, structure and electrocatalytic activity of the MAEs were further revealed. Finally, stability experiment results showed that the MAEs were safe and reliable.

Promotion effect of PANI on Fe-PANI/Zeolite as an active and recyclable Fenton-like catalyst under near-neutral condition

A Fenton-like catalyst, Fe doped PANI loaded on zeolite (Fe-PANI/Zeolite) was synthesized by polymerizing aniline (PANI) and loading iron via a one-pot in-situ hydrothermal process. The XPS and UV–Vis spectra indicated that the Fe2+ and Fe3+ were doped into PANI and formed a complex via Fe-N interaction, and the TEM image showed that no Fe oxides particles were formed. The Fe-PANI/Zeolite showed significant Fenton-like catalytic activity in a wide pH range (3.0–8.0), and its catalytic activity was studied in detail at pH 6. With the optimized FeCl3-to-aniline molar ratio of 3:1, the Fe-PANI/Zeolite synthesized at 130 °C for 12 h showed the highest efficiency for Fenton-like catalytic degradation of Acid Red G (ARG). The active species of the Fe-PANI/Zeolite were Fe and PANI, and especially under near-neutral condition the PANI played the key role by promoting the reduction of Fe3+ to Fe2+, resulting in enhancing the Fenton-like reaction activity. Fe-PANI/Zeolite catalyst shows high potential in organic pollutants removal in wastewater treatment without any additional assistant measure to enhance its activity.

A 2.5D Electrode System Constructed of Magnetic Sb–SnO2 Particles and a PbO2 Electrode and Its Electrocatalysis Application on Acid Red G Degradation

A novel electrode consisting of a Ti/PbO2 shell and Fe3O4/Sb–SnO2 particles was developed for electrochemical oxidation treatment of wastewater. Scanning electron microscope (SEM), X-ray diffraction (XRD), the current limiting method, toxicity experiments, and high-performance liquid chromatography were adopted to characterize its morphology, crystal structure, electrochemical properties, the toxicity of the wastewater, and hydroxyl radicals. Acid Red G (ARG), a typical azo dye, was additionally used to test the oxidation ability of the electrode. Results indicated that the 2.5D electrode could significantly improve the mass transfer coefficient and •OH content of the 2D electrode, thereby enhancing the decolorization, degradation, and mineralization effect of ARG, and reducing the toxicity of the wastewater. The experiments revealed that, at higher current density, lower dye concentration and higher temperature, the electrochemical oxidation of ARG favored. Under the condition of 50 mA/cm2, 25 °C, and 100 ppm, the ARG, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal efficiency reached 100%, 65.89%, and 52.52%, respectively, and the energy consumption and the current efficiency were 1.06 kWh/g COD, 8.29%, and energy consumption for TOC and mineralization current efficiency were 3.81 kWh/g COD, 9.01%. Besides, the Fe3O4/Sb–SnO2 particles after electrolysis for 50 h still had remarkable stability. These results indicated that the ARG solution could be adequately removed on the 2.5D electrode, providing an effective method for wastewater treatment.

Enhanced adsorption performance of PPy/TiO2 prepared on surface of TiO2 without calcination

The PPy/TiO2 composites were synthesized by polymerizing pyrrole monomer on the surface of TiO2 calcined at different temperatures. The results of Fourier Transform Infrared spectroscopy, X-ray diffraction, Temperature programmed desorption, X-ray photoelectron spectroscopy and Zeta potential showed that the type and amount of the active groups on TiO2 surface decreased with the increase of calcination temperature, leading to a significant decline in its adsorption capacity for Acid Red G (ARG) and Methylene Blue (MB). This also had a significant influence on the physicochemical property and adsorption performance of PPy/TiO2. The prepared PPy/TiO2 composite exhibited an enhanced adsorption capacity for ARG and MB. The adsorption ability of PPy/TiO2 was the strongest when TiO2 was not calcined and gradually decreased with the increase of the calcination temperature of TiO2. The PPy/TiO2 composite without calcination was chosen to investigate its adsorption performance. The results showed that the adsorption behaviors of ARG and MB on PPy/TiO2 were described by the pseudo-second-order and Langmuir isotherm models with the maximum adsorption amount of 424.75 and 439.61 mg/g for ARG and MB, respectively. Finally, the surface chemical properties of TiO2 seriously affected the adsorption performance of PPy/TiO2. The PPy/TiO2 composite could possess excellent adsorption performance when the selected TiO2 contained more hydroxyl and carboxyl groups.

Facile synthesis of coral-like hierarchical polyaniline micro/nanostructures with enhanced supercapacitance and adsorption performance

We presented a newly facile approach to scalable synthesize three-dimensional (3D) coral-like polyaniline (CL-PANI) hierarchical micro/nanostructures. The CL-PANI composed of well-defined nanowires with ca.20 nm was self-assembled by in situ conventional chemical polymerization with a different charging sequence. Electron microscopy, UV-Vis spectroscopy, X-ray diffraction, and nitrogen adsorption-desorption studies showed that CL-PANI possessed unique mesoporous structure and highly crystallinity which could promote rapid ion diffusion and charge transfer. Electrochemical experimental results showed that the as-prepared CL-PANI electrode had a superior electrochemical capacitance performance with a relatively high specific capacitance of 817 F g−1 at a current density of 0.5 A g−1 and a great rate capability of 67% specific capacitance retaining from 0.5 to 20 A g−1. Meanwhile, CL-PANI exhibited an enhanced adsorption performance of azo dye Acid Red G (ARG) from aqueous solution with a Langmuir maximum adsorption of 310.2 mg g−1 at pH 2.0, 298 K. This study offers a simple and cost effective path for scalable synthesis of PANI materials for supercapacitor and adsorption application.

Highly crystalline polyaniline nanofibers coating with low-cost biomass for easy separation and high efficient removal of anionic dye ARG from aqueous solution

The separation of nanostructured absorbents from the aqueous solution has been the challenge for their practical application due to their small colloidal size. Here, highly polyaniline nanofibers, prepared via a simple polymerization method at room temperature using ferric chloride (FeCl3) as an oxidant, were coated on the alkali-pretreated cost-efficient and reusable biomass, i.e, sawdust (PANI-NFs/SD). The obatined PANI-NFs/SD was demonstrated to exhibit easy separation characteristic from SD and highly effective adsorption performance from PANI-NFs. It was characterized via FT-IR spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction and Zeta potential measurements. The adsorption of anionic azo dye Acid Red G (ARG) onto PANI-NFs/SD from aqueous solution was carried out at different solution pH, initial dye concentration, adsorbent dosage and temperature. The calculated thermodynamic parameters suggested the feasible, spontaneous and endothermic nature of ARG adsorption onto PANI-NFs/SD. The fitted data showed that the adsorption process followed pseudo-second-order kinetics model and Freundlich isotherm model. The maximum experimental adsorption capacity for ARG at pH 2.0 was found to be 212.97 mg g−1 at 308 K. Moreover, the regeneration experiment revealed that PANI-NFs/SD was an effective reusable adsorbent without obvious loss of its original capacity after 29 sequential adsorption-desorption cycles. Mechanism studies indicated that the excellent effective adsorption performance of PANI-NFs/SD was associated with highly doping chemistry of PANI-NFs with high crystallinity.

Ba5Ta4O15 Nanosheet/AgVO3 Nanoribbon Heterojunctions with Enhanced Photocatalytic Oxidation Performance: Hole Dominated Charge Transfer Path and Plasmonic Effect Insight

Heterojunction photocatalysts for environmental pollutant removal have attracted great attention because of their excellent photocatalytic efficiency. In this study, we report a novel Ba5Ta4O15/AgVO3 heterojunction photocatalyst with excellent photocatalytic activity, which was synthesized by a facile, two-step, self-assembly strategy. Transmission electron microscopy (TEM) reveals that Ba5Ta4O15 nanosheets adhered to the surface of AgVO3 nanoribbons to form Ba5Ta4O15/AgVO3 heterojunctions. The as-obtained photocatalysts exhibited enhanced photocatalytic activities for Acid Red G (ARG) degradation, which are almost 2.7 times higher than that of AgVO3. The trapping experiments, electrochemical and electron paramagnetic resonance analyses altogether indicate that the enhanced photocatalytic performance could be attributed to the synergy effect of the hole dominated charge transform path and localized surface plasmon resonance (LSPR). Finally, a possible photocatalytic mechanism of the photocatalytic progres...

Removal of Acid Red G dye from aqueous solutions by adsorption to MCM-41-layered double hydroxides composite

MCM-41 supported layered double hydroxides (LDH) composite materials (ML) were synthesized and studied for removal of Acid Red G (ARG), an anionic dye, with the adsorption method. ML was prepared using in situ synthesis procedure for the low supersaturation coprecipitation method, and ML10 and ML20 presented promising application towards ARG dye adsorption capacity in industrial wastewater. Powder samples were characterized by Xray diffraction, FTIR spectroscopy, scanning electron microscopy and energy dispersive spectrometry. The effects of different reaction time, initial solution pH and temperature on the dye adsorption capacity were investigated. Adsorption process was well described by pseudo-second-order kinetic model and Langmuir isotherm model. The fitting curves showed that ML10 and ML20 had higher adsorption rates and maintained a certain theoretical saturated adsorption capacity (92.19807mg/g and 96.41947mg/g, respectively) compared with LDH.

Synthesis of stable burger-like α-Fe2O3 catalysts: Formation mechanism and excellent photo-Fenton catalytic performance

Abstract The application of iron-based photocatalysts has attracted wide attention. Herein, we reported a novel burger-like α-Fe2O3 catalyst, which was synthesized via facile hydrothermal method and used as a heterogeneous catalyst for photo-Fenton degradation of aquatic organic pollutants. More interesting, the α-Fe2O3 samples with spherical, elliptic, olive-like and burger-like morphologies could be obtained by adjusting the hydrothermal reaction time, respectively. Field emission scanning electron microscopy (FESEM) analysis showed that the burger-like α-Fe2O3 particles have convex waists and hemispherical ends, and are composed of many irregular nanoparticles. Furthermore, we proposed the probable growth mechanism involving oriented aggregation and Ostwald ripening of the burger-like structures. Under the optimum operating conditions, the burger-like α-Fe2O3 catalyst exhibited 98% degradation efficiency and 62% removal rate of COD for acid red G (ARG) in aqueous solution. In addition, the spheroidal structure showed the excellent stability, the burger-like α-Fe2O3 catalyst still remained high catalytic activity after six cycling experiments, and the leached iron value accounted for only 0.32 wt‰ of the iron content in the catalyst. This work might offer a new viewpoint for the development of sufficiently stable and highly efficient iron-based heterogeneous catalyst.