Degradation Efficiency Of Methyl Orange Research Articles

CuCo and sulfur doped carbon nitride composite as an effective Fenton-like catalyst in a wide pH range.

The heterogeneous Fenton-like reaction, as an advanced oxidation process, is widely recognized attributed to its recyclability, wide pH response range, easy solid-liquid separation, and non-production of iron sludge. Recently, the bimetallic catalysts have attracted intense attention due to their high catalytic performance and excellent stability over a wide pH range. In this article, CuCo/SCN bimetallic catalyst was prepared by pyrolysis method with sulfur doped carbon nitride (SCN) as the carrier. Under the conditions of pH = 7, catalyst dosage of 0.8 g/L, and concentration of H2O2 of 15 mM, 20 mg/L of methyl orange (MO) can be completely removed within 1 h. With the synergistic action between bimetals and sulfur doped carbon nitride, the CuCO/SCN involved Fenton-like system exhibited excellent catalytic degradation efficiency and strong stability for MO in neutral and weak alkaline conditions. The EPR characterization proved that OH and O2 − were the main active components. Furthermore, CuCo/SCN involved Fenton-like system has good adaptability. Bimetallic CuCo/SCN catalyst has great application potential in the degradation of environmental pollutants.

Catalytic activity of magnetite fish-scales and tea-waste as heterogeneous photo-Fenton catalysts for removal of methyl orange through Cu(Ⅱ) adsorption

In this study, magnetite fish scales and tea waste (MFS and MTW) were first used to adsorb Cu(Ⅱ) cations (Cu-MFS and Cu-MTW) and were then applied as heterogeneous photo-Fenton catalysts to degrade methyl orange (MO) from an aqueous solution. The morphological and structural properties of the fabricated catalysts were characterized via SEM, XRD, EDX/MAP, VSM, BET and FTIR techniques. The effects of pH, catalyst dosage, initial concentration of MO, and the initial concentration of H2O2 on the degradation efficiency of MO were investigated. The degradation efficiency of MO through the use of MFS, Cu-MFS, MTW, and Cu-MTW in the photo-Fenton process was achieved 82.6%, 97.2%, 89.1%, and 96.9%, respectively, under optimum condition (pH of 3, 0.2 g/L of MFS and Cu-MFS and 0.4 g/L of MTW and Cu-MTW, an H2O2 concentration of 0.5 mM within 200 min). Additionally, the rate of degradation reactions followed the first-order kinetics. Catalytic action was assigned to the formation of hydroxyl radicals (OH•) via the reaction between H2O2 and Fe(II) and Cu(II) on the surface of Cu-MFS and Cu-MTW during the photo-Fenton process. Furthermore, not only did Cu-MFS and Cu-MTW exhibit negligible iron and copper leaching, but they also indicated long-term stability after three consecutive cycles.

Synergetic piezo-photocatalytic effect in SbSI for highly efficient degradation of methyl orange

SbSI nanowires (SbSI NWs) and SbSI microrods (SbSI MRs) were synthesized by simple sonochemical and hydrothermal methods, respectively. The SbSI NWs possess better catalytic performance due to the smaller size and larger specific surface area. Meanwhile, the piezoelectric effect and photocatalytic performance of SbSI were combined for the first time. The degradation rate of methyl orange (MO) solution (30 mg/L) by SbSI NWs reaches 97.1% within 2 min under the synergistic effect of visible light and ultrasonic vibration, which is 4.83 times of photocatalysis and 14.22 times of piezocatalysis. The reactive oxide species (ROS) such as hydroxyl radicals (•OH) and superoxide radicals (•O2−) were examined by radical trapping experiments to demonstrate their critical role in degrading MO molecule. Furthermore, a possible mechanism of the piezo-photocatalytic process was proposed and degradation pathway of MO dyes by SbSI NWs was suggested based on the HPLC-MS results. It shows that the degradation process of MO includes the breakage of azo double bond, the removal of sulfonic group, the breakage of carbon nitrogen bond, and finally the formation of NO3−, SO42−, CO2 and H2O. This work provides a promising case for the practical application in dye wastewater treatment of piezoelectric semiconductors.

Wool-ball-like BiOBr@ZnFe-MOF composites for degradation organic pollutant under visible-light: Synthesis, performance, characterization and mechanism

ZnFe-MOF was simply fabricated from iron chloride hexahydrate, zinc nitrate hexahydrate and terephthalic acid in a 1:1:1 M ratio by one-step solvothermal method. Wool-ball-like BiOBr@ZnFe-MOF composites were synthesized by addition of Bi3+, CTAB and ZnFe-MOF using a simple solvothermal process. The optimum BiOBr@ZnFe-MOF demonstrated excellent degradation performance for rhodamine B and tetracycline under visible light. The as-synthesized photocatalytic materials were characterized by XRD, SEM, EDS, XPS, FTIR, UV–vis, PL, EIS and BET analysis. It indicated that the doping of a certain amount of ZnFe-MOF on the BiOBr materials have improved the photocatalytic efficiency. The photocatalytic performances of BiOBr@ZnFe-MOF composites were studied by degradation of rhodamine B (RhB), methylene blue (MB), methyl orange (MO) and tetracycline (TC) under the visible-light irradiation, the degradation efficiency of RhB, MB, MO and TC were 99%, 84.1%, 10.9% and 79%, respectively. Moreover, BiOBr@ZnFe-MOF composite exhibited excellent reusability and stability during the process of cyclic experiments. The reaction mechanism and possible photocatalytic mechanism of RhB degradation were also discussed in detail by the free radical capture experiment.

Synthesis of rGO/g-C3N4 for methyl orange degradation in activating peroxydisulfate under simulated solar light irradiation

• Metal-free rGO/g-C 3 N 4 composite was synthesized successfully by a simple polymerization-hydrothermal method. • rGO/g-C 3 N 4 /PDS system exhibited superior degradation efficiency of MO under stimulated solar light irradiation. • SO 4 ¯ · , h + , O 2 ¯ · and non-radical reaction pathway were involved in the removal of MO. In this study, reduced graphene oxide-based graphitic carbon nitride (rGO/g-C 3 N 4 ) composite was fabricated via thermal polymerization-hydrothermal method and were utilized to activate peroxydisulfate (PDS) under simulated solar light irradiation. The as-synthesized rGO/g-C 3 N 4 was demonstrated to effectively remove methyl orange (MO) in wastewater. Notably, 92.3% of MO (15 mg/L) was removed within 120 min in the presence of 0.2 g/L rGO/g-C 3 N 4 and 0.225 g/L PDS. The influence of activator dosage, PDS concentration and co-existing solution matrix on the removal efficiency was investigated. Free radical capture experiments confirmed that SO 4 ¯ · , photogenerated holes (h + ), O 2 ¯ · and non-radical reaction initiated by rGO played a major role in MO removal. Furthermore, PDS and rGO acted as the electron acceptor and transfer carrier of the photogenerated charges, respectively, resulting in the efficient activation of PDS. The promoting visible light absorption might be ascribed to the defect sites on the surface of rGO/g-C 3 N 4 , which generated from the rGO loading. This study revealed that the as-synthesized rGO/g-C 3 N 4 composite exhibits wide promising application prospects as a photocatalytic activator of PDS for the degradation of azo dyes in textile wastewater.

Weak-visible-light-driven Fe doped TiO2 photocatalyst prepared by coprecipitation method and degradation of methyl orange

Fe doped TiO2 nanoparticles were synthesized by coprecipitation method under calcination temperatures between 200 °C and 400 °C with different Fe doping concentration from 0 to 1.8 at.%. The crystal structure, morphology, optical properties, energy band gap (Eg) and photocatalytic performance of synthesized nanoparticles were calculated and characterized by first-principles calculations, XRD, TG-DSC, FTIR, FESEM, EDS, TEM, SAED, XPS, UV–Vis and PL spectroscopy. Results showed that Fe doped TiO2 nanoparticles had pure anatase structure with spherical morphology of 4–12 nm in crystallite size which increased with calcination temperatures. The Eg of Fe doped TiO2 was decreased from 3.07 eV to 2.71 eV by the increase of Fe doping concentration. The maximum degradation efficiency of methyl orange (MO) was as high as 46.3% for Fe doped TiO2 nanoparticles calcined at 300 °C with Fe doping concentration of 0.3 at.% under 15 W visible light irradiation.

Engineering Shewanella carassii, a newly isolated exoelectrogen from activated sludge, to enhance methyl orange degradation and bioelectricity harvest

Electroactive microorganisms (EAMs) play important roles in biogeochemical redox processes and have been of great interest in the fields of energy recovery, waste treatment, and environmental remediation. However, the currently identified EAMs are difficult to be widely used in complex and diverse environments, due to the existence of poor electron transfer capability, weak environmental adaptability, and difficulty with engineering modifications, etc. Therefore, rapid and efficient screening of high performance EAMs from environments is an effective strategy to facilitate applications of microbial fuel cells (MFCs). In this study, to achieve efficient degradation of methyl orange (MO) by MFC and electricity harvest, a more efficient exoelectrogen Shewanella carassii-D5 that belongs to Shewanella spp. was first isolated from activated sludge by WO3 nanocluster probe technique. Physiological properties experiments confirmed that S. carassii-D5 is a Gram-negative strain with rounded colonies and smooth, slightly reddish surface, which could survive in media containing lactate at 30 °C. Moreover, we found that S. carassii-D5 exhibited remarkable MO degradation ability, which could degrade 66% of MO within 72 h, 1.7 times higher than that of Shewanella oneidensis MR-1. Electrochemical measurements showed that MFCs inoculated with S. carassii-D5 could generate a maximum power density of 704.6 mW/m2, which was 5.6 times higher than that of S. oneidensis MR-1. Further investigation of the extracellular electron transfer (EET) mechanism found that S. carassii-D5 strain had high level of c-type cytochromes and strong biofilm formation ability compared with S. oneidensis MR-1, thus facilitating direct EET. Therefore, to enhance indirect electron transfer and MO degradation capacity, a synthetic gene cluster ribADEHC encoding riboflavin synthesis pathway from Bacillus subtilis was heterologously expressed in S. carassii-D5, increasing riboflavin yield from 1.9 to 9.0 mg/g DCW with 1286.3 mW/m2 power density output in lactate fed-MFCs. Furthermore, results showed that the high EET rate endowed a faster degradation efficient of MO from 66% to 86% with a maximum power density of 192.3 mW/m2, which was 1.3 and 1.6 times higher than that of S. carassii-D5, respectively. Our research suggests that screening and engineering high-efficient EAMs from sludge is a feasible strategy in treating organic pollutants.

Ecofriendly synthesis of silver nanoparticles using Heterotheca subaxillaris flower and its catalytic performance on reduction of methyl orange

A green approach for the biosynthesis of silver nanoparticles (AgNPs) was developed using Heterotheca subaxillaris and their catalytic degradation efficiency of Methyl orange (MO) dye was explored. The formation of HS-AgNPs was monitored using UV–vis spectroscopy. The HR-TEM analysis confirmed quasi-spherical shape with the average particle size ranging from 20 to 30 nm and XRD patterns showed the face centered cubic structure. The survey scan XPS spectrum exhibited three major significant binding energy peaks at 285, 368 and 532 eV, which belong to C(1 s), Ag(3d) and O(1 s) levels of spin orbital splitting, respectively. The biosynthesized HS-AgNPs exhibited catalytic activity in the reduction of MO by NaBH4, which follows pseudo first order kinetics with the rate constant of 2.1 × 10−3 s−1. The results prove that HS-AgNPs have an extraordinary catalytic efficiency for the degradation of MO.

Self-Cleaning Coatings for the Protection of Cementitious Materials: The Effect of Carbon Dot Content on the Enhancement of Catalytic Activity of TiO2

The urgent demand for pollution protection of monuments and buildings forced the interest towards specific preservation methods, such as the application of photocatalytic coatings with self-cleaning and protective activity. TiO2 photocatalysts without and with a variety of carbon dots loading (TC0, TC25–75) were synthesized via a green, simple, low cost and large-scale hydrothermal method using citric acid, hydroxylamine and titanium isopropoxide (TTIP) and resulted in uniform anatase phase structures. In photocatalysis experiments, TC25 and TC50 composites with 1:3 and 1:1 mass ratio of C-dots solution to TTIP, respectively, showed the best degradation efficiency for methyl orange (MO) under UV-A light, simulated solar light and sunlight compared to TiO2, commercial Au/TiO2 (TAu) and catalysts with higher C-dot loading (TC62.5 and TC75). Treatment of cement mortars with a mixture of photocatalyst and a consolidant (FX-C) provided self-cleaning activity under UV-A and visible light. This study produced a variety of new, durable, heavy metal-free C-dots/TiO2 photocatalysts that operate well under outdoor weather conditions, evidencing the C-dot dosage-dependent performance. For the building protection against pollution, nanostructured photocatalytic films were proposed with consolidation and self-cleaning ability under solar irradiation, deriving from combined protective silica-based agents and TiO2 photocatalysts free or with low C-dot content.

Ti3C2 MXene co-catalyst assembled with mesoporous TiO2 for boosting photocatalytic activity of methyl orange degradation and hydrogen production

Photocatalytic degradation and hydrogen production using solar energy through semiconductor photocatalysts are deemed to be a powerful approach for solving environmental and energy crisis. However, the biggest challenge in photocatalysis is the efficient separation of photo-induced carriers. To this end, we report that the mesoporous TiO2 nanoparticles are anchored on highly conductive Ti3C2 MXene co-catalyst by electrostatic self-assembly strategy. The constructed mesoporous TiO2/Ti3C2 composites display that the mesoporous TiO2 nanoparticles are uniformly distributed on the surface of layer structured Ti3C2 nanosheets. More importantly, the as-obtained mesoporous TiO2/Ti3C2 composites reveal the significantly enhanced light absorption performance, photo-induced carriers separation and transfer ability, thus boosting the photocatalytic activity. The photocatalytic methyl orange degradation efficiency of mesoporous TiO2/Ti3C2 composite with an optimized Ti3C2 content (3 wt%) can reach 99.6% within 40 min. The capture experiments of active species confirm that the •O2− and •OH play major role in photocatalytic degradation process. Furthermore, the optimized mesoporous TiO2/Ti3C2 composite also shows an excellent photocatalytic H2 production rate of 218.85 μmol g–1 h–1, resulting in a 5.6 times activity as compared with the pristine mesoporous TiO2 nanoparticles. This study demonstrates that the MXene family materials can be applied as highly efficient noble-metal-free co-catalysts in the field of photocatalysis.

Efficient degradation of methyl orange and methylene blue in aqueous solution using a novel Fenton-like catalyst of CuCo-ZIFs

Abstract In this study, the synthesized CuCo-zeolitic imidazolate framework (ZIF) catalyst was used to degrade methyl orange (MO) and methylene blue (MB) in water via a novel Fenton-like catalytic reaction. Effects of catalyst dosage, H2O2 concentration, initial concentration of the contaminants, and reaction time were evaluated. The results showed that MO and MB decomposition efficiencies were highly influenced by CuCo-ZIF concentration. The presence of H2O2 accelerated the degradation reaction of both MO and MB. Although it took 100 min to complete the removal of MB, it was 60 min for MO. At concentrations of MO and MB lower than 40 mg·L−1, the catalyst showed an almost complete degradation. The CuCo-ZIF catalyst presented a good recyclability with more than 90% removal of MO and MB after four times and five times reuse, respectively. These results demonstrated that MO and MB were efficiently degraded by a Fenton-like catalyst of CuCo-ZIFs and its potential in industrial wastewater treatment.

Preparation, structural and photocatalytic activity of Sn/Fe co-doped TiO2 nanoparticles by sol-gel method

Pure and Sn/Fe co-doped (0.2 at.% Sn and 0.6 at.% Fe, 0.6 at.% Sn and 0.2 at.% Fe, 1.0 at.% Sn and 1.0 at.% Fe) TiO2 nanoparticles were synthesized via a sol-gel method and subsequently calcined at different temperatures. Furthermore, the particles were analyzed by TG-DSC, XRD, TEM, HRTEM, EDS, SAED and UV–Vis for investigating the influences of dopant and calcination temperature on the thermal effect, composition, morphology, energy band gap (Eg) and the degradation efficiency of methyl orange (MO) under various light irradiations respectively. Results indicated that Sn/Fe co-doping inhibited the crystallization transformation from anatase to rutile phase of TiO2 and decreased the Eg. The increased calcination temperature and Sn/Fe co-doped effect brought about the abnormal grain growth of TiO2 nanoparticles. 0.6 at.% Sn/0.2 at.% Fe and 1.0 at.% Sn/1.0 at.% Fe co-doped TiO2 nanoparticles presented better photocatalytic performance than pure and 0.2 at.% Sn/0.6 at.% Fe co-doped TiO2 nanoparticles under visible light irradiation mainly due to the decreased Eg. On the contrary, 0.2 at.% Sn and 0.6 at.% Fe co-doped TiO2 nanoparticles calcined at 650 °C showed the most excellent photocatalytic performance under UV light irradiation, which was about twice as large as that of pure TiO2 possibly due to the formed hybrid structure of anatase and rutile phase as well as the h+-mediated decomposition pathway.

Enhancing solar photocatalytic activity of Bi5O7I photocatalyst with activated carbon heterojunction

Passive solar photocatalysis is one of the most efficient ways for the treatment of dye industry wastewater. Some dyes such as methyl orange are recalcitrant to photolysis; therefore, photocatalysts are used to expedite their degradation. Photocatalysts are semiconductors, and their activity can be improved by creating heterojunctions. In the current work, an active photocatalyst, Bi5O7I, was modified with activated carbon (AC), obtained by controlled carbonization of pistachio shells, to give xAC-Bi5O7I photocatalysts. AC loading improved the surface area of the catalyst and decreased its bandgap to 1.8 eV, making it suitable for use as a visible light photocatalyst. Activated carbon enhances adsorption, while Bi5O7I scavenges adsorbed molecules increasing the efficiency. 5AC-Bi5O7I catalyst containing 5% activated carbon displayed the optimum photocatalytic activity, which was 3.4-fold higher than that of pristine Bi5O7I. 5AC-Bi5O7I achieved 99.9 % reduction in the concentration of methyl orange in 80 min under sunlight irradiation. 5% AC-Bi5O7I is more efficient than commercial Degussa P25 photocatalyst as well. The methyl orange degradation efficiency of the catalysts studied was: 5AC-Bi5O7I > Bi5O7I > Degussa P25.

Preparation and characterization of rutile TiO2 nanoparticles by HCl-water volatilization-assisted precipitation method

TiO2 nanoparticles were prepared by HCl-water volatilization-assisted precipitation method. Results indicated that the single anatase and mixed phase TiO2 containing rutile and anatase can be fabricated at the short HCl-water volatilization time of one and eight days calcined between 150 °C and 250 °C possessing spherical morphology. The elongated HCl-water volatilization time significantly influenced the phase transformation and morphology of TiO2 nanoparticles. The single rutile TiO2 was obtained at the calcination temperature of 200 °C when the HCl-water volatilization time was 5 months (150 days, atmospheric environment), possessing bamboo leaf-like morphology rather than spherical morphology. The degradation efficiency of methyl orange (MO) using rutile TiO2 calcined at 200 °C reached 87 % and 49.1 % after 2 h of ultraviolet and visible light irradiation respectively, being better than that of the low temperature-synthesized anatase TiO2, high temperature-synthesized rutile TiO2 and commercial Degussa P25.

Experimental and Density Functional Theory Studies on a Zinc(II) Coordination Polymer Constructed with 1,3,5-Benzenetricarboxylic Acid and the Derived Nanocomposites from Activated Carbon.

A coordination polymer with the composition C12H20O16Zn2 (ZnBTC) (BTC = benzene-1,3,5-tricarboxylate) was synthesized under hydrothermal conditions at 120 °C, and its crystal structure was determined using single-crystal X-ray crystallography. First-principles electronic structure investigation of the compound was carried out using the density functional theory computational approach. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, the energy gap, and the global reactivity descriptors of ZnBTC were investigated in both the gas phase and the solvent phase using the implicit solvation model, while the donor–acceptor interactions were studied using natural bond orbital analyses. The results revealed that ZnBTC is more stable but less reactive in solvent medium. The larger stabilization energy E(2) indicates a greater interaction of ZnBTC in the solvent than in the gas phase. Orange peel activated carbon and banana peel activated carbon chemically treated with ZnCl2 and/or KOH were used to modify the synthesis of ZnBTC to obtain nanocomposites. ZnBTC and the nanocomposites were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis, and Fourier transform infrared. The specific surface area (SBET) and the average pore diameter of the materials were determined by nitrogen sorption measurements using the Brunauer–Emmett–Teller (BET) method, while scanning electron microscopy and transmission electron microscopy were used to observe their morphology and particle size, respectively. The PXRD of all the activated carbon materials exhibited peaks at 2θ values of 12.7 and 13.9° corresponding to a d-spacing of 6.94 and 6.32 Å, respectively. The N2 adsorption–desorption isotherm of the materials are of type II with nanocomposites showing enhanced SBET compared to the pristine ZnBTC. The results also revealed that activated carbons from the banana peel and the derived nanocomposites exhibited better porous structure parameters than those obtained from orange peel. The degradation efficiency of methyl orange in aqueous solutions using ZnBTC as a photocatalyst was found to be 52 %, while that of the nanocomposites were enhanced up to 79 %.

Zn-based MOF-chitosan-Fe3O4 nanocomposite as an effective nano-catalyst for azo dye degradation

Metal-organic frameworks (MOFs) have been fascinating catalysts for decolorization of azo pigments. A novel and easy approach to the preparation of a magnetic Zn2(BDC)2(DABCO) MOF has been reported as Fenton-like heterogeneous nano-catalyst for the degradation of azo dyes from aqueous samples. The samples were characterized by Fourier transform infrared spectroscopy (FTIR) for the evaluation of functional groups, X-ray diffraction (XRD) analysis for the investigation of crystal structure, nitrogen adsorption-desorption for the measurement of surface area, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) for the determination of size and morphology, energy-dispersive X-ray spectroscopy (EDX) to evaluate the chemical composition, and zeta potential for the investigation of surface charge. In this work, the MOF-chitosan-Fe3O4 nanocomposite (NC) was reported for azo dye degradation. To obtain high degradation efficiency, the effects of different parameters including nano-catalyst dose, temperature, contact time and oxidant volume on the decolorization efficiency were measured using experimental design approaches. Under optimized conditions, the degradation efficiency of methyl orange (MO) using MOF-chitosan-Fe3O4 nano-catalyst was obtained to be >99%. The results showed that the magnetic MOF could be used as a promising recyclable magnetic nano-catalyst for colored wastewater treatment.

Heterogeneous photo-fenton oxidation degradation of methyl orange using Alg-m, Alg-HAp, and Alg-mHAp catalysts

ABSTRACT Removal of methyl orange (MO) anionic dye was investigated by composite beads of sodium alginate-magnetic hydroxyapatite (Alg-mHAp), sodium alginate-magnetite (Alg-m), and sodium alginate-hydroxyapatite (Alg-HAp) as catalysts of heterogeneous photo-Fenton process. Evaluation of XRD and FT-IR analysis proved the presence of magnetite and hydroxyapatite nanoparticles in the structure of synthesised catalysts. SEM analyses showed that the surface of the Alg-mHAp catalyst is rougher than the other two catalysts. The results demonstrated the effluent discoloration of 79.41%, 71.42, and 84.28% for Alg-m, Alg-Hap, and Alg-mHAp, respectively, at an optimum pH = 3. By increasing the pH to more than 3, the removal rate decreased. In addition, it was found that by increasing the hydrogen peroxide concentration from 0.5 to 3 , photo-Fenton activity can be further enhanced to effectively degrade MO. However, with increasing the concentration of H2O2 from 3 to 20 , the removal percentage of Alg-m, Alg-HAp, and Alg-mHAp catalysts decreased to 92.70%, 86.20%, and 95.62, respectively. The results revealed with increasing initial dye concentration, the removal percentage decreased for all three catalysts. Also, by increasing the catalyst dosage from 0.5 to 2 , the removal percentage for Alg-m, Alg-HAp, and Alg-mHAp catalysts increased 16, 21, and 12%, respectively. Furthermore, it was determined that as the UV intensity increased, the removal percentage increased by an average of 26%. The first-order kinetic equation was most consistent with the experimental results of MO degradation in all three catalysts. This study confirmed the feasibility of a heterogeneous photo-Fenton system of Alg-mHAp for the highly efficient degradation of MO in wastewater.

Superior degradation of organic pollutants and H2O2 generation ability on environmentally-sound constructed Fe3O4-Cu nanocomposite

The present work aimed to account for the first time green, and eco-friendly synthesis of Fe3O4/Cu nanocomposite as magneto-recyclable photocatalyst using Rosmarinus officinalis leaves aqueous extract. R. officinalis leaves extract played three significant roles in improving physicochemical properties of Fe3O4 nanoparticles as reducing, stabilizing and capping agents and can convert Cu2+ ions into Cu0. Several characterization techniques were employed to investigate the crystal structure, surface chemistry, morphology, and optical properties of the produced nanomaterials. The UV–Vis DRS spectra exhibited a low band-gap (1.7 eV), appropriate for an effective visible-light degradation. Effectiveness of Fe3O4 nanoparticles and Fe3O4/Cu nanocomposite as photocatalysts were examined under visible light illumination on an aqueous contaminant solution. Degradation efficiencies of methyl orange, imipenem, and imatinib mesylate, three types of organic contaminations were about 50–96% after 5400 s irradiation over Fe3O4 nanoparticles and Fe3O4/Cu nanocomposite. Total organic carbon analysis results confirmed degradation efficiencies of all samples. Trapping experiments results verified that O2− was the main oxidative species in the degradation of organic contaminations. The as-prepared photocatalysts could be reused after five successive cycles with no significant reduction in degradation efficiency. Besides, biogenic nanoparticles and nanocomposite were promoted H2O2 production. The photochemical production of H2O2 was achieved under visible light irradiation toward the two-electron oxygen reduction reaction. The plausible mechanisms for photocatalytic and degradations were proposed, which suggested the prepared photocatalysts' remarkable potential for removing contaminants with complex structures.

Sustainable chemical processing of flowing wastewater through microwave energy

Iron oxide nanostructured catalysts have emerged as potential candidates for efficient energy conversion and electrochemical energy storage devices. However, synthesis and design of nanomaterial plays a key role in its performance and efficiency. Herein, we describe a one-pot solution combustion synthesis (SCS) of α-Fe2O3 with glycine as a fuel, and a subsequent reduction step to produce iron-containing catalysts (i.e., Fe3O4, Fe–Fe3O4, and Fe0). The synthesized iron-based nanoparticles were investigated for methyl orange (MO) degradation through Microwave (MW) energy under continuous flow conditions. Fe–Fe3O4 showed higher MO degradation efficiency than α-Fe2O3, Fe3O4 and Fe0 at low absorbed MW power (i.e. 5–80 W). The enhanced degradation efficiency is associated to the combination of higher availability of electron density and higher heating effect under MW energy. Investigation of dielectric properties showed relative dielectric loss of Fe3O4, Fe–Fe3O4, and Fe0 as 3847, 2010, and 1952, respectively. The calculated average local temperature by the comparative analysis of MW treatment with conventional thermal (CT) treatment showed a marked thermal effect of MW-initiated MO degradation. This work highlights the potential of microwave-driven water depollution under continuous-flow processing conditions and demonstrates the positive impact that earth-abundant Fe catalyst synthesized by green SCS method can have over the treatment of wastewater.

Investigation onto the performance and mechanism of visible light photodegradation of methyl orange catalyzed by M/CeO2 (M=Pt, Ag, Au)

In this paper, M/CeO2 (M=Pt, Ag, Au) photocatalysts were prepared and used for visible light degradation of methyl orange (MO) with H2O2 as a sacrificial reagent. Utilizing X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), N2 physical adsorption (BET), X-ray photoelectron spectroscopy (XPS), photocurrent characterization and electrochemical impedance spectroscopy, etc., the structure, morphology, chemical state, and optical properties of the catalyst were investigated. The effects of the amount of catalyst, the initial concentration of methyl orange, the pH value of the solution and the number of reuses on the photocatalytic degradation efficiency of MO were studied. The results showed that under optimized reaction condition of 15 mg 2Pt/CeO2 catalyst, the initial concentration of MO was 20 mg/L, pH=5, the reaction time was 195 min and the amount of H2O2 was 0.2 mL, the degradation percentage of MO reached 75.8%. The main active species of photodegradation are hydroxyl radicals and superoxide radicals, which was determined by free radical capture experiments and combined electron spin resonance (ESR). The photocatalytic mechanism based on work function difference and electron transfer was also discussed in detail.