Methyl Orange Removal Efficiency Research Articles

Calcined MgFe layered double hydroxides for magnetic separation and enhanced adsorption performance of methyl orange: Mechanism based on the memory effect

This study successfully synthesized magnetic MgFe-layered double oxides (MgFe-LDO-500 °C) by calcining MgFe-layered double hydroxides (MgFe-LDHs) at 500 °C. Calcination temperature was identified as a critical factor for optimizing adsorption capacity and activating a memory effect, with 500 °C being particularly effective. The adsorption performance of MgFe-LDO-500 °C towards methyl orange (MO) in aqueous solutions was evaluated across varying pH levels (2–12), initial MO concentrations (50–1800 mg/L), contact times (0–1440 min), and temperatures (25–45 °C). The results indicated that MgFe-LDO-500 °C adsorption conforms to the pseudo-second-order kinetic and Langmuir models, achieving a theoretical maximum adsorption capacity of 5087.76 mg/g. Characterization through scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Zeta potential analysis revealed that the outstanding adsorption performance of MgFe-LDO-500 °C towards MO involves a combination of electrostatic attraction, memory effect, and surface complexation. Moreover, after four regeneration cycles, the material maintained a 73 % MO removal efficiency and could be efficiently separated using magnetic separation technology. In conclusion, MgFe-LDO-500 °C represents a promising adsorbent for wastewater treatment.

Easily scale 3D conductive gradient fiber membrane for contaminants removal and fouling mitigation under electrochemical assistance

An electrochemical membrane filtration system provides an innovative approach to enhance contaminant removal and mitigate membrane fouling. There is an urgent need to develop portable, versatile, and efficient electrochemical membranes for affordable wastewater treatment. Here, a 3D conductive gradient fiber membrane (CC/PVDF) with a gradient porous structure was prepared using a two-step phase inversion method. Methyl orange (MO) was utilized as model organic substance to investigate the electrochemical performance of the CC/PVDF membrane. At applied potentials of +2 V, +3 V, −2 V and −3 V, the removal efficiency of MO was 5.1, 5.3, 4.8, and 5.1 times higher than at 0 V. A dramatic flux loss of 35.02% occurred on the membrane without electrochemistry, interestingly, whereas the flux losses were only 23.59%–10.24% in the applied potential after 30 min of filtration, which were approximately 1.18, 1.28, 1.29 and 1.38 times as high as that without electrochemistry, respectively. The enhanced removal and anti-fouling performances of the membranes were attributed to the functions of electrochemical degradation, electrostatic repulsion, and electrically enhanced wettability. Electrochemical generation of Hydrogen peroxide, along with HO• radicals, was detected and direct electron transfer and HO• were proved to be the dominant oxidants responsible for MO degradation. The intermediate oxidation products were identified by mass spectrometry, and an electrochemical degradation pathway of MO was proposed based on bond-breaking oxidation, ring-opening reactions, and complete oxidation. All the findings emphasize that the ECMF system possesses superior efficiency and creative potential for water purification applications.

Fenton-like degradation of methyl orange by alumina-supported Cu–Co catalysts at neutral pH: Optimization by the Taguchi method

Fenton oxidation is considered to be an effective method for removing non-biodegradable organic materials from industrial wastewater. However, several challenges need to be overcome for its utilization in industrial-scale applications. A series of alumina-supported Cu–Co samples were prepared via a simple sol–gel method, and their utility for Fenton-like degradation of methyl orange (MO) at neutral pH was assessed. In addition, various catalyst synthesis parameters, namely (Cu + Co)/Al molar ratio, Cu/Co molar ratio, water content, and treatment conditions, were optimized by the Taguchi method. The parameters were selected in three levels, and L9 from the orthogonal array design was used. The optimum synthesis parameters for the catalyst included a (Co + Cu)/Al molar ratio of 0.08, a Co/Cu molar ratio of 1/3, an H2O/Al molar ratio of 6, a calcination temperature of 400°C, and a calcination time of 8 h. Furthermore, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed reduction were employed to characterize the physical and chemical properties of the samples. The results revealed that the optimized catalyst achieved a 94% removal efficiency of MO and a 75% removal efficiency of total organic carbon. Compared to the data reported in similar previous studies, the catalyst prepared herein demonstrated promising development potential.

Prediction of pollutant removal from aqueous solutions using magnetic photocatalysts

In this research, magnetic nanocomposite (MGO@TiO2) consisting of Fe3O4, TiO2 and graphene oxide is synthesized for the photocatalytic removal of methyl orange, and its photocatalytic activity is compared with the nanohybrid (Fe3O4@TiO2) without graphene oxide. The crystalline phases of both photocatalysts are determined using X-ray diffraction patterns. The results show that the removal efficiency of methyl orange using the synthesized nanohybrid and nanocomposite is affected by the irradiation time and the pH of the suspension. Comparing the removal efficiency of methyl orange using synthesized photocatalysts shows that the photocatalytic activity of nanocomposite is much higher than that of nanohybrid. The statistical analysis of the experimental data using the response surface method led to the selection of the quadratic model as the best statistical model to estimate the removal efficiency of methyl orange. Also, the numerical and graphical methods confirmed the adequacy of the quadratic statistical model.

Enhanced photocatalytic activity of CeO2 and magnetic biochar-CeO2 nanocomposite prepared from Murraya koenigii stem for degradation of methyl orange under UV light

This paper discusses the synthesis and characterization of CeO2 nanoparticles (NPs), magnetic biochar-CeO2 (MBC-CeO2) nanocomposites (NCs), and their photocatalytic analysis in methyl orange (MO) degradation. MBC-CeO2 material is synthesized on the basis of carbonization of iron oxide precursor treated with Murraya koenigii (curry leaf) stem powder. CeO2 with crystallite size 7.78 nm and MBC-CeO2 with crystallite size 14 nm are identified from XRD, with band gap energies 3.16 and 2.84 eV respectively. XPS, SEM, TEM, BET, UV–visible, FTIR, and PL characterizations are conducted to study the morphology, oxygen vacancy concentration in the samples. The removal efficiency of Methyl Orange (MO) is studied by changing both pH and concentration of MO solution. The decolorization of MO is observed at an optimum level of pH 4, with a catalyst dosage of 50 mg, which obeys pseudo-first-order kinetic theory. Under 16 min UV irradiation treatment, the decolorization efficiency of the as-prepared MBC-CeO2 is 96.7 % and total organic carbon (TOC) is ∼94 %, and for the as-prepared CeO2 it is 87.5 % and ∼ 81 % respectively. The plausible degradation pathway of MO is analyzed through LC-MS method. Regression studies are conducted to assess the suitability of all models towards photocatalytic degradation. The recycling experiment showed that both MBC-CeO2 and CeO2 are excellent stable catalysts for the activation of MO.

Activation of peroxymonosulfate by a novel stratiform Co-MOF as catalyst for degradation of dyes in water

Cobalt-based metal-organic frameworks (MOFs) have been used as catalysts to remove macromolecular organic pollutants from wastewater. In this work, a novel type of cobalt-based MOF, CUST-593, was synthesized from cobalt nitrate hexahydrate (Co(NO3)2·6H2O), 2,2-bipyridine (BIPY), and 4,4ˊ,4ˊˊ-nitrilotrisbenzoic acid (NTB) using solvothermal method. The catalytic properties of CUST-593 for degrading dyes in water were then investigated. CUST-593, with the chemical formula {Co(NTB)(BIPY)(H2O)·0.5H2O·0.1DMA}, exhibited excellent catalytic activity in degrading dyes such as methyl orange (MO) and rhodamine B (RhB) in aqueous solutions. CUST-593 has a multi-layered structure, connected by carboxylate hydrogen bonds, which is beneficial to improving its water stability. Synthetic test results showed that CUST-593 effectively attacked dyes by primarily generating sulfate radicals (SO4•−) and a portion of hydroxyl radicals (•OH). Under the testing conditions, MO removal efficiency reached approximately 95 %. Moreover, CUST-593 exhibited remarkable cycling catalytic properties, broad pH range applicability, and long-term effectiveness. A mechanism for the degradation of dyes by CUST-593 was proposed. The experimental findings in this study collectively support the conclusion that CUST-593 serves as a green and environmentally friendly catalyst for the degradation of dyes in polluted water.

Enhanced catalytic degradation performance of azo dyes based on Janus emulsification

Amphiphilic Janus nanosheets with an asymmetric structure of non-polar phenyl side and polar ionic liquid side (1-Butyl-3-methylimidazolium chloride, [BMIM]Cl), denoted as Janus-[BMIM]Cl, were prepared and used as a carrier to achieve the integration of catalyst and emulsifier. Catalytic heteropolyanions (e.g., [PW12O40]3-, [PMo12O40]3- or [SiW12O40]4-) were selectively decorated on the polar side induced by anion-exchange of [BMIM]Cl moieties, Janus catalysts (Janus-[BMIM][heteropolyanions]) were assembled and utilized as an open degradation platform for azo dyes such as methyl orange (MO). Morphology, structure, and properties were characterized by SEM, FT-IR, XPS, UV–Vis, Zeta potential, etc. The inbuilt amphipathy of Janus nanosheets endowed the decolorization process of dyes to perform in the emulsified system. The extremely increased interface coupled with the effective dispersion of catalysts at the interface synergistically improved the catalytic degradation performance. Compared with the decolorization catalyzed in a conventional immiscible system, the removal efficiency of MO achieved in the Janus emulsion greatly improved from 78.6 to 98.2% within 3 h. Besides, the Janus emulsion could be demulsified easily by centrifugation, and the degradation efficiency was still maintained at 93.7% after five cycles. These results provide valuable information for exploring and enriching the applications of Janus functional materials.

In Situ Synthesis of 3D BiOCl-Graphene Aerogel and Synergistic Effect by Photo-Assisted Activation of Persulfate for Methyl Orange Degradation.

BiOCl/graphene aerogel graphene (BGA) was successfully obtained by in situ hydrothermal synthesis, and the chemical, structural, morphological, and photocatalytic properties were systematically characterized. BGA with the doping amount of BiOCl at 20% (BGA-4) exhibited the optimal activation efficiency for persulfate (PDS) on the degradation of methyl orange (MO) under simulated sunlight (SSL) illumination as compared to the pure graphene (GA) and aerogel composites with different BiOCl content. The influence of various reaction parameters on the MO removal efficiency, such as the reaction system, catalyst activator dose, PDS concentration, BiOCl doping amount, and the initial pH of the solution, was investigated. Under optimum conditions, the catalytic efficiency of BiOCl-doped GA with the mass ratio of 20% (BGA-4) was 5.61 times that of GA. The strengthening effect of BGA-4 benefited from the synergistic effect of 1O2, O2·- and the generation and rapid electron transfer of photo-induced electron (e-) in the BGA-4/SSL/PDS system. Considering the superior stability and recyclability of BGA-4, the BGA-4/SSL/PDS system exhibits great potential in actual wastewater treatment.

Magnetic photocatalysts based on graphene oxide: synthesis, characterization, application in advanced oxidation processes and response surface analysis

The decomposition rate of methyl orange (MO) is studied in aqueous solution of magnetic photocatalysts based on graphene oxide (GO). ZnO photocatalytic nanoparticles are synthesized with controlled amounts on magnetized graphene oxide and two photocatalytic samples including GFZ1 and GFZ2 are prepared for use in advanced oxidation process. The characterization of the synthesized photocatalysts is done by XRD, FTIR and VSM. The crystal structure of magnetic Fe3O4 nanoparticles as well as photocatalytic ZnO nanoparticles on the graphene oxide network has been confirmed by XRD analysis in both synthesized samples. FTIR analysis of both GFZ1 and GFZ2 also shows the stretching vibration of Fe–O and Zn–O bonds in Fe3O4 and ZnO, respectively. The superparamagnetic properties of both samples can be confirmed using VSM analysis. It is also observed that with the increase of ZnO nanoparticles in GFZ2, the magnetic properties decrease compared to GFZ1. The effect of irradiation time time (between 5 and 40 min), weight fraction of the synthesized photocatalysts (0.1%wt, 0.2%wt, and 0.3%wt) and pH of the suspension (3, 7, and 11) on the changes in MO decomposition rate was investigated and the response surface method (RSM) was used to study the effect of the simultaneous change of two parameters of the mentioned factors on the MO removal efficiency. The results show that with the increase of irradiation time and also the weight fraction of both photocatalysts, the decomposition rate of MO also increases significantly. So that in all time intervals and weight fractions, the photocatalytic activity of GFZ2 is much higher than that of GFZ1. The effect of pH also shows that the maximum and minimum decomposition rates occur in acidic and neutral conditions, respectively.

Synthesis of alumina-carbon framework for efficient sorption of methyl orange from wastewater with factorial design and mechanisms

A series of different activated carbon (AC) based composites were synthesized from municipal agricultural wastes and applied as a support for gamma alumina loading. The adsorptive removal activities on Al2O3 doped ASAC (almond shell activated carbon), PSAC (pea shell AC), and PNSAC (peanut shell AC) adsorbents were evaluated for methyl orange removal from water. The higher breakthrough adsorbent efficacy of the AC-Al2O3 adsorbents is influenced by the H+ ions released from AC and undergoes a chemical ion exchange reaction with the terminal dimethyl nitrogen and produces a positive charge on methylene orange. These materials were characterized using several techniques. Adsorptive activities show that ASAC-Al2O3 achieved an excellent methyl orange removal efficiency of up to 86% responsible for 56.5 mg/g adsorption capacity. In comparison with ASAC-Al2O3, PSAC-Al2O3 and PNSAC-Al2O3 achieved compromising the adsorptive capacity of 77.6% and 60% accountable for the 52 and 45 mg/g adsorption efficiency, respectively. According to the findings, a mechanism for dye adsorption over AC-Al2O3 material was presented. Hence, it can be concluded that the prepared material showed enhanced adsorption efficiency and hence enhance the water quality. Thus, it is recommended to be tested on a larger scale.

S-doped biomass catalyst triggered peroxydisulfate activation for methyl orange degradation

Utilizing biomass as carbon precursor for peroxydisulfate (PDS) catalyst preparation could solve the problem of solid waste and water pollution treatment synergistically. However, the poor activity of pure biomass catalyst (BC) still needs further improvement. In this study, novel S-doped BC (S-BC) was prepared from chitosan (waste from agriculture and food industry) for PDS activation. With S doping, superior conductivity and defect (active sites) degree were achieved in S-BC. About 99.73% removal efficiency of methyl orange (MO) could also be achieved under the conditions of 3 mM PDS, 1.0 g L−1 S-BC, 10 mg L−1 MO, and initial pH of 3. This removal efficiency is higher than that of BC at 58.46%. Density functional theory calculation showed that the S2O82− ions were favorably adsorbed on the S-BC surface due to the negative adsorption energy of −3.048 eV. The O atoms in S–O bond (in S2O82−) could capture electrons from S atoms (in S-BC), leading the favorable breaking of this bond. Thus, resulting in the formation of surface attached radicals, O2·− and 1O2 for MO degradation, rather than SO4−· radicals in solution.

Methyl orange adsorption by modified montmorillonite nanomaterials: Characterization, kinetic, isotherms and thermodynamic studies

Clays intercalated with cetyltrimethylammonium bromide (CTAB-Mt) and hydroxyl aluminium polycation have been prepared and analysed by X-ray fluorescence spectrometry, X-ray diffraction, fourier transform infrared spectroscopy, nitrogen adsorption-desorption at 77 K and thermal gravimetric analysis. The adsorption capacities of modified montmorillonite nanomaterials to remove methyl orange (MO) from aqueous solutions have been studied as a function of contact time, solution pH, adsorbent dosage and initial MO concentration at room temperature. The maximum removal efficiency of MO has been found in acidic medium, with 60 min equilibrium time and 1 g/L adsorbent dosage. The adsorption kinetics and isotherms have been well fitted by pseudo-second order and Langmuir models. The montmorillonites intercalated with both cetyltrimethylammonium bromide and hydroxyl aluminium polycation (CTAB-Al-Mt) have shown a high affinity for MO molecules. Thermodynamic results have indicated an exothermic, spontaneous and physical adsorption process. The characterization and adsorption performance of CTAB-Mt and CTAB-Al-Mt toward MO has also been compared with that of the hydroxyl-aluminium pillared montmorillonite (OH-Al-Mt) and purified montmorillonite (Na-Mt).

Development of an effective asphaltene-derived adsorbent for wastewater treatment: Characterization and methyl orange removal study

Conversion of asphaltene, an undesirable and abundant waste from the petroleum industry, to value-added products can offer sustainability and economic benefit. In this study, asphaltene was acid-treated to become a low-cost and effective adsorbent for removing dye from wastewater. It was hypothesized that asphaltene functionalization with acids will change the surface properties of asphaltene, leading to improved adsorption capabilities. Through acid treatment, the surface area of asphaltenes was increased and oxygen or nitrogen functionalities were incorporated into their structure confirmed by Fourier-transform infrared spectroscopy (FTIR), elemental analysis, Scanning Electron Microscopy (SEM) images, and nitrogen adsorption-desorption isotherm. Batch adsorption experiments were conducted to evaluate the capacity of modified asphaltenes to remove methyl orange (MO) from aqueous solutions. The effect of asphaltene modification techniques, MO solution pH (3−11), asphaltene dosage (0.5–10.0 g/L), contact time, and experimental temperature (25–45 °C) were evaluated. The adsorption removal percentage of MO by modified asphaltene was about three times higher than that of non-modified asphaltene. Modified asphaltene had a maximum adsorption capacity of 7.9 mg/g at 25 °C and a solution pH of 3. Moreover, it is shown that Freundlich isotherm, pseudo-second-order, and intra-particle diffusion kinetic models describe the adsorption process very well. Finally, the regeneration of the asphaltene was achieved using ethanol, and the MO removal efficiency can still be as high as 64 % after 5 cycles (initial removal efficiency is 96 %). This study indicates that the modified asphaltene can be used as a low-cost adsorbent for treating wastewater containing dyes and other organic contaminants.

Development of high reusability trifunctional polyethersulfones microspheres for the removal of methyl orange

This study focused on the synthesis of trifunctional microspheres with adsorption, degradation, and magnetic responsive properties. Firstly, polyethersulfones (PES) encapsulated poly(diallyldimethyl ammonia) chloride (PDDA) functionalized iron oxide (Fe3O4) microspheres were produced via phase inversion method. The PDDA/Fe3O4-PES microspheres were further coated with Fe3O4 nanoparticles (NPs) on the surface to provide the degradation ability to the formed c-PDDA/Fe3O4-PES microspheres. Characterization results such as FTIR analysis confirmed the coating of PDDA on Fe3O4 NPs, while the TGA analysis proved the excellent thermal stability of microspheres after the incorporation of PDDA/Fe3O4 NPs. BET specific surface area of microspheres was measured at 13.90 m2/g. Besides, the pH drift method confirmed the presence of positive charge on microspheres surface, which is important for the removal of anionic pollutants. Moreover, porous structure of microspheres was also observed under SEM. Formulation study was also carried out to investigate the suitable concentration for the synthesis of microspheres, including the concentration of PES polymer (1–20 wt%), the loading of PDDA/Fe3O4 NPs (1–5 wt%), and the concentration of polyethylene glycol (PEG) (1–20 wt%). The microspheres synthesized from different formulations were subjected to the batch removal of methyl orange (MO). Results showed that a 72.53 % removal of MO can be obtained under the following microspheres synthesis formulations: 10wt% of PES polymer, 2 wt% of PDDA/Fe3O4 NPs, and 5 wt% of PEG polymer. Lastly, the c-PDDA/Fe3O4-PES microspheres also demonstrated an excellent reusability as compared to pure PES microspheres. The c-PDDA/Fe3O4-PES microspheres could be reused up to 5 cycles without the need of regeneration while still maintaining high MO removal efficiency.

Synthesis of novel graphene aerogel encapsulated bismuth oxyiodide composite towards effective removal of methyl orange azo-dye under visible light.

Development of novel and eco-friendly composite photocatalysts for the efficient removal of contaminants from wastewater is the need of the hour. In this study, visible light responsive novel graphene aerogel/bismuth oxyiodide (GA/BiOI) composite was synthesized via low-temperature solvothermal method. The synthesized GA/BiOI composite was tested for methyl orange (MO) azo-dye degradation under visible light. The graphene aerogel nanosheets were wrapped onto the surface of the each individual BiOI microsphere, which encourages the interconnection charge transfer process. The light absorption properties of GA/BiOI composite were increased with the addition of graphene aerogel. The optimal 5%-GA/BiOI composite displayed higher MO removal efficiency, which is ∼2 fold more than the bare BiOI photocatalyst. This enhanced photocatalytic activity was on account of lower recombination rate of charge carriers, improved light absorption, and the high surface area. In addition, the 5%-GA/BiOI composite showed good stability until 3 cycles without deactivation. The plausible MO degradation mechanism was also proposed over GA/BiOI under visible light. This work provides a new perspective on the design and synthesis of graphene aerogel-based composite for environmental applications.

Enhanced visible-light activation of persulfate by g-C3N4 decorated graphene aerogel for methyl orange degradation

In the present work, the degradation of methyl orange (MO) by visible-light-driven photocatalytic activation of persulfate (PDS) was studied. Macro-aerogel g-C3N4-doped graphene aerogel (GA) composite with stratified structure was fabricated by a simple hydrothermal method and applied as a recoverable heterogeneous catalyst along with visible light (VL) irradiation for activation of PDS. The microstructure, physical-chemical and photoelectrochemical properties of composite catalysts were characterized and various reaction parameters including the reaction systems, catalyst activator dose, PDS concentration, g-C3N4 doping amount and the initial pH of the solution were evaluated on the MO removal efficiency. Photocatalytic activation of GA for MO degradation was enhanced significantly after modified by g-C3N4. Under optimum conditions (15 mg/L MO, 75 mg/L PDS and 0.012 g/L GCN-3), the catalytic efficiency of g-C3N4 doped GA with the mass ratio of 3:7 (GCN-3) was 2.96 times than that of GA. The strengthening effect of GCN-3 benefited from the synergistic effect of the photogenerated hole (h+), the CO functional groups and rapid electron transfer in GCN-3/VL/PDS system. Given the flexibility and recyclability of GCN-3, the GCN-3/VL/PDS system is a promising technique for practical wastewater purification.

Electrocatalytic degradation of methyl orange and 4-nitrophenol on a Ti/TiO2-NTA/La-PbO2 electrode: electrode characterization and operating parameters.

The anode material plays a crucial role in the process of electrochemical oxidation. Herein, a TiO2 nanotube arrays (TiO2-NTA) intermediate layer and La-PbO2 catalytic layer were synthesized on a Ti surface by the electrochemical anodic oxidation and electrochemical deposition technology, respectively. The prepared Ti/TiO2-NTA/La-PbO2 electrode was used as an electrocatalytic oxidation anode for pollutant degradation. Scanning electron microscopy (SEM) analysis showed that the TiO2-NTA layer possessed a highly ordered and well-aligned nanotube array morphology, and the La-PbO2 layer with angular cone cluster was uniform and tightly bonded. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis indicated that the intermediate layer primarily consisted of the anatase crystal structure of TiO2 and the catalyst layer was made of La-PbO2. Electrochemical analysis revealed that Ti/TiO2-NTA/La-PbO2 electrode exhibited higher oxidation peak current, electrochemical active surface area, and oxygen evolution potential (OEP, 1.64V). Using methyl orange and 4-nitrophenol as model pollutants, electrocatalytic properties of the prepared Ti/TiO2-NTA/La-PbO2 electrode were systematically investigated under different conditions, and the electrochemical degradation fitted well with the pseudo-first-order kinetics model. Efficient anodic oxidation of model pollutants was mainly attributed to the indirect oxidation mediated by hydroxyl radicals (•OH). The total organic carbon (TOC) removal efficiency of methyl orange and 4-nitrophenol was 70.2 and 72.8%, and low energy consumption (2.50 and 1.89 kWh g-1) was achieved after 240min of electrolysis under the conditions of initial concentration of model pollutant, electrode spacing, and electrolyte concentration were 50mg L-1, 2cm, and 0.1mol L-1, respectively. This work provided a new strategy to develop the high-efficiency electrode for refractory pollutants degradation.

A porous Fe‐based porphyrinic metal–organic framework for highly effective removal of organic azo‐dye

With the rapid development of the global dye industry, a series of environmental problems affecting the ecosystem and human health has been perceived. In this work, a porous porphyrin catecholate iron‐based metal–organic framework (MOF) (PorphCat‐Fe) has been prepared and evaluated for the first time for adsorptive removal of azo‐dye methyl orange (MO) pollutant from aqueous media. Consequently, various MO adsorption factors using PorphCat‐Fe MOF were studied and optimized. PorphCat‐Fe was able to remove about 98% of the pollutant from the water within 20 min in the batch experiments with maximum adsorption capacity of 232.5 mg g−1. Under optimum conditions, the limit of detection (LOD) was found to be 0.8 μg L−1. The MOF could maintain its adsorption efficiency toward MO in the real samples. The combination of electrostatic attractions, hydrophobic and π–π interactions, and iron‐organic coordination bonding make PorphCat‐Fe able to show the superior MO adsorption capacity. Remarkably, the removal efficiency of MO was nearly unchanged after five regeneration sequences on PorphCat‐Fe. This effort offers the ability for application of MOFs beyond metal‐carboxylate linkers in wastewater remediation.

Light driven Aspergillus niger-ZnS nanobiohybrids for degradation of methyl orange

Inorganic-microbial hybrid systems have potential to be sustainable, efficient and versatile chemical synthesis platforms by integrating the light-harvesting properties of semiconductors with microbial cells. Here, we demonstrate light-driven photocatalytic semiconducting Aspergillus niger cells-ZnS nanoparticles for enhanced removal of the dye methyl orange. Chemically synthesized ZnS nanoparticles exhibited a zinc blende pattern in X-ray diffraction, had a dimension of 20–90 nm with a band gap (Ebg) of 3.4 eV at 1.83 × 1018 photons/second. Biologically synthesized ZnS nanoparticles of 40–90 nm showed a hexagonal pattern in the X-ray powder diffraction spectra with an Ebg 3.7 eV at 1.68 × 1018 photons/second. At a methyl orange (MO) concentration of 100 mg/L, dosage of 0.5 × 105 mol catalyst and pH 4, a 97.5% and 98% removal efficiency of MO was achieved in 90 min and 60 min for, respectively, chemically and biologically synthesized ZnS nanobiohybrids in the presence of UV-A light. The major degradation products of photocatalysis for chemically synthesized ZnS nanobiohybrids were naphtholate (C10H7O m/z 143) and hydroquinone (C9H5m/z 113). For the biologically synthesized ZnS nanobiohybrids, the degradation products were hydroquinone (C9H5m/z 113) and 2-phenylphenol (C12H10O m/z 170).

Persulfate activation by novel iron–carbon composites for organic contaminant removal: Performance, mechanism, and DFT calculations

• Novel Fe–C was prepared that can efficiently degrade organic pollutants. • Effects of important parameters on MO degradation were investigated. • Primary reactive oxygen species examined by quenching experiments and ESR. • Possible pathways proposed based on LC-MS and DFT calculation calculations. Persulfate (PDS) activation is an effective approach for removing organic pollutants from industrial wastewater, but a more cost-effective catalyst is required. In this study, novel iron–carbon (Fe–C) granules were successfully prepared by a facile calcination method and were applied to PDS activation. Radical quenching experiments, electron spin resonance spectroscopy, and electrochemical analyses were performed to investigate the removal efficiency of methyl orange (MO) by the Fe–C/PDS process and the effects of influencing factors such as the Fe–C dosage, PDS concentration, initial pH, and MO concentration. Fe–C was observed to have a pore structure and abundant functional groups that are beneficial for PDS activation and pollutant removal. The MO removal mechanisms of the Fe–C/PDS process included adsorption, degradation, and co-precipitation, among which the degradation process consisted of radical and non-radical pathways involving the formation of SO 4 −· , · OH, O 2 −· , and 1 O 2 as well as electron transfer. Calculations based on density functional theory were used to propose potential degradation pathways of MO. The Fe–C/PDS process exhibited high adaptability to inorganic anions and natural organic matter in aquatic environments and high removal efficiencies of various organic pollutants.