Methyl Orange Removal Efficiency Research Articles

Development of novel reduced graphene oxide/metalloporphyrin nanocomposite with photocatalytic and antimicrobial activity for potential wastewater treatment and medical applications.

This research investigates a novel nanocomposite material composed of reduced graphene oxide (rGO) and nickel-5,15-bisdodecylporphyrin (Ni-BDP) nanoparticles for the effective removal of methyl orange (MO), a harmful synthetic dye, from water. The structure and composition of the synthesized rGO/Ni-BDP nanocomposite were characterized using high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and ultraviolet-visible (UV-Vis) spectroscopy. The study demonstrates the material's efficacy as both a catalyst and adsorbent for MO removal. Optimal performance was observed at pH 3.0, where the positively charged nanocomposite surface facilitated strong interactions with negatively charged MO molecules, leading to enhanced photocatalytic activity. Under these conditions, 0.01g of the nanocomposite achieved an impressive 86.2% MO removal efficiency. Furthermore, the study explored the reusability of the rGO/Ni-BDP nanocomposite in repeated cycles of photocatalytic MO degradation under visible light irradiation. While exhibiting some decrease in efficiency over five cycles, the nanocomposite maintained a respectable degradation rate even after multiple uses. Finally, the antimicrobial properties of the nanocomposite were evaluated against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria exhibiting a zone of inhibition measuring 23mm and 26, respectively. The minimum inhibitory concentration (MIC) values of 2.50µg/ml and 1.25µg/ml for Escherichia coli and Staphylococcus aureus, respectively. The results revealed significant antibacterial activity, demonstrating the broad-spectrum efficacy of the rGO/Ni-BDP nanocomposite. This research underscores the potential of the rGO/Ni-BDP nanocomposite as a versatile material for environmental remediation and antibacterial applications.

Photoluminescence and photocatalytic activity of sol gel synthesized Mg doped TiO2 nanoparticles

The influence of magnesium doping on the optical properties, structural characteristics, and photocatalytic performance of TiO2 nanoparticles was investigated. Pure and Mg-doped TiO2 nanoparticles with varying weight percentages of magnesium were synthesized via the sol–gel method, followed by calcination at 100 °C for 12 h and annealing at 400 °C for 2 h to promote crystallization. X-ray diffraction (XRD) analyses confirmed the formation of crystalline mixed phases of anatase and rutile TiO2 nanoparticles, exhibiting their crystalline nature upon synthesis. Scanning electron microscopy (SEM) images were employed to study the morphological features of the samples, while energy dispersive spectroscopy (EDS) provided insights into their elemental composition. Photoluminescence (PL) emission spectra revealed ultraviolet (UV) to visible region emission for both pure and doped TiO2 samples. The photocatalytic activity was evaluated by monitoring the degradation of methyl orange under natural sunlight irradiation, elucidating the impact of visible light exposure. Furthermore, investigations were conducted to assess the influence of catalyst loading, initial dye concentration, and pH of the dye solution on the methyl orange removal efficiency. The 3 wt% Mg doped TiO2 exhibited 95 % of decolorization of Methyl Orange. X-ray photoelectron spectroscopy measurements was performed to verify the elemental composition and chemical valence states of each element. The scavenger test in photodegradation mechanism revealed that the main reactive species was superoxide species. The electron species resonance (ESR) measurement demonstrate that the synthesized sample shows the low spin state of Mg2+ in TiO2. The correlation between Mg doping on photocatalytic activity and crystal structure were studied. Theoretical calculations were performed to gain insights into the potential mechanism underlying the tuning of luminescent and photocatalytic properties of Mg-doped TiO2 nanoparticles, enabling a comprehensive discussion.

Mesoporous TiO2@nitrogen-doped carbon nanosheets implanted in flexible and robust chitosan membrane with dual-function for efficient adsorption of iodide and methyl orange from aqueous solution

Radioactive iodide (I−) and methyl orange (MO) are two leading pollutants in wastewater, posing significant health risks. Crosslinked chitosan membranes (CCM) combined with TiO2@nitrogen-doped carbon nanosheets (CCM/TiO2@NC) were prepared as efficient I− and MO adsorbents in wastewater. These membranes leverage multiple interactions between I−/MO and functional groups (−NH2, nitrogen-doped carbon, and TiO2) within the membrane. As expected, CCM/TiO2@NC exhibited high I− removal efficiencies of nearly 82 % across a wide pH range (pH 3 − 11) and an exceptional MO removal efficiency of 96.1 % at a neutral condition. The adsorption behaviors followed the Langmuir isotherm and pseudo-second order kinetic model for both species, achieving maximum adsorption capacities of 1.383 mmol/g (175.6 mg/g) for I− and 661.4 mg/g for MO, respectively. Additionally, CCM/TiO2@NC maintained a high absorption efficiency for both I− and MO through five regeneration cycles. The I− adsorption mechanism of CCM/TiO2@NC involves electrostatic attraction, anion-π interaction, and hydrogen bonding, while MO adsorption involves electrostatic attraction, n/π-π interactions, and hydrogen bonding. This study offers feasible guidance on developing chitosan/nanomaterial composites as promising adsorbents for removing I− and MO from wastewater.

Magnetic activated carbon for the removal of methyl orange from water via adsorption and Fenton-like degradation

Water pollution caused by organic dyes is a critical environmental issue. Although activated carbon (AC) is commonly used for dye adsorption, its effectiveness is limited by challenges in separation and regeneration. To address these limitations, a convenient recyclable magnetic activated carbon (MAC) was fabricated via co-precipitation and calcination method, serving as adsorbent and catalyst for methyl orange (MO) removal through a Fenton-like degradation process. Characterization techniques, including XRD, FTIR, SEM and TEM, confirmed that Fe3O4 nanoparticles (10–20 nm) were uniformly dispersed on AC surface. The MAC maintaining a high surface area (997 m2/g) and pore volume (0.795 cm3/g) and exhibited superparamagnetic properties with a saturated magnetization of 5.52 emu/g, enabling effective separation from aqueous solutions by magnet. Batch adsorption studies revealed that MO adsorption onto MAC followed pseudo-second-order kinetic and Freundlich isotherm model, with a maximum adsorption capacity of 205 mg/g at 25 °C. Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic. Simultaneous degradation of MO and in-situ regeneration of MAC were achieved via Fenton-like reaction using sodium persulfate (PS). Under a PS concentration of 9 mmol/L, the MO removal efficiency near 95% after 60 min, with a total organic carbon (TOC) reduction of 83.1%. The reaction of Fe3O4 and oxygen functional groups on AC surface with PS facilitated the generation of SO4•-, thereby enhancing catalytic degradation of MO. The degradation efficiency improved as the temperature increased from 25 °C to 45 °C. Cycle tests demonstrated that the MO removal efficiency of MAC remained above 90% after 5 cycles of regeneration. Overall, this study highlights the potential of MAC for efficient removal of organic dyes from water through the coupling of adsorption and Fenton-like degradation, providing a promising solution for addressing water pollution challenges.

S-type Bi2S3/BiOBr heterojunction with robust piezo-photocatalytic dye removal activity: Degradation performance and mechanism investigation

In this work, an efficient S-type Bi2S3/BiOBr piezo-photocatalysts was prepared by the decoration of Bi2S3 nanorods on the surface of BiOBr nanosheets. The piezo/photo/piezo-photocatalytic performance of samples were evaluated under the irradiation of ultrasonic and/or simulated-sunlight employing methyl orange (MO) as a target reactant, indicating that above catalytic activity of BiOBr is able to be elevated after Bi2S3 attachment. Particularly, the 10%Bi2S3/BiOBr sample exhibits the optimal catalytic performance. It is worth noting that the 10%Bi2S3/BiOBr sample achieves much higher piezo-photocatalytic MO removal efficiency than its photocatalysis and piezocatalysis, demonstrating a remarkable synergistic improvement between piezocatalysis and photocatalysis with a synergistic enhancement factor (SF) of ∼1.29. The formation of S-type heterojunction in the Bi2S3/BiOBr composite was directly confirmed by the combination of density functional theory (DFT) calculation and in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) measurement, elevating the surface separation of generated charges. Meanwhile, the ultrasonic-excited piezoelectric polarization field in BiOBr nanosheets excited by ultrasonic irradiation promotes the bulk segregate of generated charges. Benefiting from above two aspect effects, the overall separation of generated charges can be effectively achieved, leading to outstanding piezo-photocatalytic degradation activity of Bi2S3/BiOBr composite.

Monte Carlo Simulation, Artificial Intelligence and Machine Learning-based Modelling and Optimization of Three-dimensional Electrochemical Treatment of Xenobiotic Dye Wastewater

The present study investigates the synergistic performance of the three-dimensional electrochemical process to decolourise methyl orange (MO) dye pollutant from xenobiotic textile wastewater. The textile dye was treated using electrochemical technique with strong oxidizing potential, and additional adsorption technology was employed to effectively remove dye pollutants from wastewater. Approximately 98% of MO removal efficiency was achieved using 15 mA/cm2 of current density, 3.62 kWh/kg of energy consumption and 79.53% of current efficiency. The 50 mg/L MO pollutant was rapidly mineralized with a half-life of 4.66 min at a current density of 15 mA/cm2. Additionally, graphite intercalation compound (GIC) was electrically polarized in the three-dimensional electrochemical reactor to enhance the direct electrooxidation and.OH generation, thereby improving synergistic treatment efficiency. Decolourisation of MO-polluted wastewater was optimized by artificial intelligence (AI) and machine learning (ML) techniques such as Artificial Neural Networks (ANN), Support Vector Machine (SVM), and random forest (RF) algorithms. Statistical metrics indicated the superiority of the model followed this order: ANN > RF > SVM > Multiple regression. The optimization results of the process parameters by artificial neural network (ANN) and random forest (RF) approaches showed that a current density of 15 mA/cm2, electrolysis time of 30 min and initial MO concentration of 50 mg/L were the best operating parameters to maintain current and energy efficiencies of the electrochemical reactor. Finally, Monte Carlo simulations and sensitivity analysis showed that ANN yielded the best prediction efficiency with the lowest uncertainty and variability level, whereas the predictive outcome of random forest was slightly better.Highlights• In-depth analysis of various artificial intelligence optimization techniques.• Prediction efficiency of artificial intelligence and machine learning algorithms.• 98% dye removal and 100% regeneration of graphite intercalation compound.• Advanced statistical analysis of targeted responses and data fitting techniques.• Analysis of uncertainties and variability using Monte Carlo simulation.

Synthesis of bare and modified zerovalent iron nanoparticles and their use in porous polylactic acid composites for methyl orange removal

The main objective of this study was to assess the efficacy of two types of immobilised zerovalent iron nanoparticles (nZVI) incorporated into a porous biopolymer matrix of polylactic acid (PLA) as a novel multifunctional composite system for potential use in dye wastewater treatment. The study involved the preparation of unmodified and 2,6-pyridinedicarboxylic acid (PDCA) modified nZVI material using liquid phase reduction method. Zeta potential measurement and UV-Vis spectrophotometry revealed that the ligand-modified nZVI particles exhibited better dispersion stability in aqueous media than bare particles. SEM-EDS analysis showed a higher oxidation state of the ligand-modified nZVI particles and good dispersion and adhesion of nZVI particles in the mesoporous structure of PLA matrix. The removal efficiency of methyl orange was determined spectrophotometrically where a high efficiency (above 90 %) for high concentration of bare nZVI was detected. Its composites also showed an efficiency of 75 – 100 %. However, modified nZVI showed much lower efficiency, especially after embedding in the PLA matrix.

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

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

Chitosan/polyvinyl acetate/manganese ferrite as a eco-friendly adsorbent for separation of methyl orange dye from aqueous solution

This study presents a novel approach in the field of wastewater treatment, focusing on the development of an eco-friendly magnetic adsorbent, CS/PVAc/MnFe2O4, for the efficient removal of methyl orange (MO) from aqueous solutions. The combination of chitosan, polyvinyl acetate, and manganese ferrite demonstrated a remarkable MO removal efficiency of 96.7% in just 75 min at a pH = 3, utilizing only 0.03 g of adsorbent and 50 mg/L of MO. The material was thoroughly characterized using FT-IR, XRD, SEM, and VSM techniques, confirming its effectiveness. The study successfully applied the Langmuir isotherm and pseudo-second-order kinetics models to describe the adsorption isotherms and kinetics, revealing a maximum adsorption capacity of 80.58 mg/g. The findings underscore the potential of CS/PVAc/MnFe2O4 as a cost-effective and efficient solution for wastewater treatment, particularly in the removal of organic contaminants. This research contributes to the advancement of adsorbent materials and recommends further exploration for industrial applications and development.

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.