Initial Methylene Blue Concentration Research Articles

High biosorption of cationic dye onto a novel material based on paper mill sludge

The valorization of paper mill sludge (PMS) is the main goal of this study. The emissions of PMS continue to increase at global scale, especially from packaging paper and board sectors. The raw sludge was used to prepare an adsorbent to remove toxic pollutants from wastewater, the methylene blue (MB), an organic dye. Firstly, the physico-chemical characterization of PMS was done determining the crystalline phases of PMS fibers, the content of main elements, and the pH zero point charge, which was determined at around pH 7. The adsorption of MB on PMS powder was studied at 18 °C with an agitation of 200 rpm, being the best operating conditions 30 min of contact time, 250 mg L−1 of initial MB concentration and 0.05 g in 25 mL of adsorbent dose. Experimental data of MB adsorption was fitted to Langmuir and Freundlich isotherm equations. The Langmuir model was more accurate for the equilibrium data of MB adsorption at pH 5.1. The PFOM and PSOM were adjusted to experimental adsorption kinetics data, being PSOM, which describes better the MB adsorption by PMS powder. This was confirmed by calculating the maximum adsorption capacity with PSOM, which was 42.7 mg g−1, being nearly similar of the experimental value of 43.5 mg g−1. The analysis of adsorption thermodynamics showed that the MB was adsorbed exothermically with a ΔH0 = − 20.78 kJ mol−1, and spontaneously with ΔG0 from − 0.99 to − 6.38 kJ mol−1 in the range of temperature from 291 to 363 K, respectively. These results confirm that the sludge from paper industry can be used as biosorbent with remarkable adsorption capacity and low cost for the treatment of wastewater. PMS can be applied in the future for the depollution of the effluents from the textile industry, which are highly charged with dyes.

Preparation of Bamboo-Based Activated Carbon via Steam Activation for Efficient Methylene Blue Dye Adsorption: Modeling and Mechanism Studies.

Dye pollution has long been an ecological and human health issue. Activated carbon is considered to be the most promising material for dye adsorption. In this study, bamboo was used as a biomass precursor to produce activated carbon with a high specific surface area by the steam activation method. The physical activation reaction between water vapor and bamboo promotes the carbonization product to have a rich porous structure. The prepared activated carbon was investigated from the perspectives of surface morphology, elemental change, surface porosity, and surface functional groups using a variety of techniques. According to the Brunauer-Emmett-Teller analysis, the activated carbon has a high surface area (1273 m2/g) and a mesoporous structure (average pore size 3.1 nm). On this basis, the effect of activated carbon on the removal of methylene blue (MB) dye from aqueous environments was evaluated and optimized by response surface methodology (RSM). Key adsorption parameters include initial MB concentration (150-200 mg/L), adsorption time (5-120 min), adsorbent dosage (30-50 mg), adsorption temperature (5-50 °C), and solution pH (3-11). Box-Behnken design (BBD) was used for modeling and analysis. Kinetic and isotherm model studies show that pseudo-second-order model kinetics and Langmuir isotherm can better describe the process of MB dye adsorption. This study will provide new ideas for the preparation of bamboo-activated carbon and provide a model prediction basis for dye adsorption research.

Intensified photocatalytic degradation of methylene blue over Fe supported on dendritic fibrous SBA-15: Optimisation, kinetic, isotherm, and reusability

A novel photocatalyst, Fe supported on dendritic fibrous SBA-15 (Fe/DFSBA-15), is synthesised and employed for methylene blue (MB) photocatalytic degradation. The DFSBA-15 was synthesised by applying a microemulsion technique and SBA-15 crystal-seed crystallisation approach. The TEM and FESEM of Fe/DFSBA-15 revealed the revolution of rod-typed SBA-15 into dendritic fibrous-structured (DFSBA-15). The characterisation analyses using FTIR, XRD, BET, PL and UV-Vis DRS, confirmed favourable properties of Fe/DFSBA-15 compared to Fe/SBA-15. Fe/DFSBA-15 exhibits superior properties, attributed to its unique dendritic fibrous morphology that increases the surface area, pore accessibility, and mass transfer. These exceptional features establish it as a highly promising and efficient photocatalyst for diverse applications. Optimisation of MB degradation (Y, %) by using Fe/DFSBA-15 was conducted by employing response surface methodology (RSM) of independent parameters such as catalyst loading (X1, 0.5 – 2.0 g/l), pH (X2, 6 – 10) and initial MB concentration (X3, 10 – 50 mg/l). The model was significant, and MB degradation was optimised at 99.54% (X1 = 1.66 g/l, X2 = 9, and X3 = 27.5 mg/l) along with validation experiments (3.62% error). The research outcome was in agreement with the Langmuir second-order (R2 ≥ 0.99), indicating a predictable trend of the MB degradation process. Interestingly, the excellent degradation and reusability performance of Fe/DFSBA-15 offered a prospective approach for industrial wastewater treatment.

Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Graphite as Methylene Blue Adsorbents

Methylene blue (MB) is one of the toxic synthetic dyes that are being discharged heavily into water supplies. Hence, MB removal is one of the most important tasks for a cleaner water supply. By using inexpensive, abundant, and easy-to-synthesize materials, superparamagnetic iron oxide nanoparticles, which were synthesized using the co-precipitation method with polyvinyl alcohol and graphite (SPION/PVA/GR), can be used to adsorb MB. The adsorbent was characterized using FE-SEM, FTIR, XRD, VSM, and BJH. The entrapment efficiency of MB on SPION/PVA/GR after 12 days was 33.96 ± 0.37–42.55 ± 0.39%, at 333.15, 310.15, and 298.15 K, and the initial concentration of MB was 0.017–0.020 mg/mL. The adsorption process can be considered spontaneous, endothermic, chemisorption, heterogeneous, or multilayer adsorption. When releasing MB at 298.15 K and a pH of 3.85 after 7 days, the release percentage ranged from 11.56 ± 0.33 to 22.93 ± 5.06 depending on the initial loading conditions and mainly the releasing temperature following the Higuchi kinetic model. Since this is a novel SPION-based MB adsorbent, optimization, and different forms of adsorbent (i.e., thin film composite) should be further researched.

Enhancing sonocatalytic dye pollutant degradation using MoS2/RGO nanocomposites: An optimization study

This research focuses on the synthesis of MoS2/RGO nanocomposite, which serves as an efficient sonocatalyst, using a simple one-step hydrothermal method. The MoS2/RGO was characterized through various techniques including X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), Raman spectrometry, diffuse reflectance spectroscopy (DRS), and Fourier transform infrared (FTIR) spectroscopy. A comprehensive investigation into the sonocatalytic degradation efficiency of methylene blue (MB) dye was conducted under different conditions using design of experiment (DOE) approach. Response surface methodology (RSM) based on central composite design (CCD) was employed to optimize the key operational parameters, namely initial dye concentration, catalyst dosage, ultrasonic power, sonication time, and pH. The reliability of the model was assessed using analysis of variance. Under the optimal conditions of 20 mg/L initial MB concentration, catalyst dosage of 0.5 g/L, 67 W ultrasonic power, sonication time of 28 min, and pH of 7, a remarkable MB degradation efficiency of 99% was achieved. Hydroxyl radical (●OH) were identified as the main radical species in the sonoluminescence reaction. Additionally, the sonocatalyst demonstrated an excellent reusability, with approximately 95% retention of the degradation efficiency observed over five sonocatalysis cycles.

Development of carboxymethyl cellulose-graphene oxide biobased composite for the removal of methylene blue cationic dye model contaminate from wastewater

Utilizing Glutaraldehyde crosslinked sodium carboxymethyl cellulose (CMC-GA) hydrogel and its nanographene oxide composite (CMC-GA-GOx), an effective carboxymethyl cellulose-graphene oxide biobased composites adsorbent was developed for the adsorption removal of methylene blue (MB) cationic dye contaminate from industrial wastewater. The CMC-GA-GOx composites developed were characterized using FTIR, RAMAN, TGA, SEM, and EDX analysis instruments. Through batch experiments, several variables affecting the removal of MB dye, including the biocomposites GO:CMC composition, adsorption time, pH and temperature, initial MB concentration, adsorbent dosage, and NaCl concentration, were investigated under different conditions. The maximum dye removal percentages ranged between 93 and 98%. They were obtained using biocomposites CMC-GA-GO102 with 20% GO weight percent, adsorption time 25 min, adsorption temperature 25 °C, MB concentrations 10–30 ppm, adsorption pH 7.0, and 0.2 g adsorbent dose. The experimental data of the adsorption process suit the Langmuir isotherm more closely with a maximal monolayer adsorption capacity of 76.92 mg/g. The adsorption process followed the kinetic model of pseudo-second order. The removal of MB was exothermic and spontaneous from a thermodynamic standpoint. In addition, thermodynamic results demonstrated that adsorption operates most effectively at low temperatures. Finally, the reusability of the developed CMC-GA-GO102 has been proved through 10 successive cycles where only 14% of the MB dye removal percentage was lost. These results suggest that the developed CMC-GA-GO102 composite may be an inexpensive and reusable adsorbent for removing organic cationic dyes from industrial wastewater.

Valorization of spent Aureobasidium pullulans for the removal of toxic pollutant in wastewater treatment

Textile industries are growing rapidly due to increased demand for textile products worldwide. The discharge of textile effluent containing synthetic dyes, chlorides, pigments, aromatic compounds, and heavy metals contributes substantially to water pollution due to its toxicity and chemical composition. This work is focused on the potential usage of treated Aureobasidium pullulans biomass (TAPB) to remove the toxic chemical pollutant, Methylene Blue (MB), from an aqueous solution. Experimental results found that maximum MB removal of 76.5% was observed using TAPB dosage of 3 ​g/L, initial pH 8.0, temperature 30 ​°C, and initial MB concentration of 50 ​mg/L. The maximum biosorption capacity of TAPB was found to be 113.75 ​mg/g using the Langmuir non-linear approach. Successive biosorption and desorption experiments showed better regeneration capacity of TAPB until the fourth trial. These results demonstrated that maximum MB removal (%) could be possible with a small quantity of biomass, consequently offering a minimum size of the contactor and less capital cost requirement for biosorption. It also showed a greater regeneration capacity biosorbent for removing MB. Hence, the feedstock consumption for MB removal could be considerably decreased in large-scale processes.

Study on methylene blue adsorption using cashew nut shell-based activated carbon

Adsorption is a widely used technique for the treatment of wastewater containing dyes, which are pollutants that can have serious impacts on the aquatic ecosystems. In this work, activated carbon (AC) was prepared from cashew nut shell (CNS) and used to adsorb methylene blue (MB) from solution. The CNS AC was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption isotherms. The adsorption behavior of MB on CNS AC was investigated by varying the initial solution pH, adsorbent dosage, and initial MB concentration. The results showed that the CNS AC was effective for MB removal, with an adsorption capacity of 24.8 mg/g. The adsorption nature of MB onto the CNS AC surface was explored by analyzing the experimental data using isotherm and kinetic models. The Freundlich and Dubinin-Radushkevich (D-R) isotherm models showed good agreement with the experimental adsorption equilibrium results. The mean adsorption energy was found to be 22.4 kJ/mol, indicating chemical adsorption. The adsorption of MB on the CNS AC followed pseudo-second-order kinetics. This study demonstrates the potential application of CNS AC for MB removal.

Valorization of Peanut and Walnut Shells through Utilisation as Biosorbents for the Removal of Textile Dyes from Water

The present research focuses on the application of peanut and walnut shells, in their natural state, for the removal of methylene blue (MB) from water solutions in batch and dynamic (flow-through) conditions. Under batch conditions, at a 100 mg/L MB concentration of aqueous solution, the optimum dose of the studied biosorbents was determined to be 2.5 g/L, reaching about 95–97% efficiency of MB removal for both materials. Langmuir and Freundlich isotherms were used to model and evaluate the experimental data under different initial concentrations of MB (25 to 100 mg/L). The determined maximum adsorption capacities are 41.50 mg/g for walnut shells and 46.80 mg/g for peanut shells. Under flow-through conditions, breakthrough curves are determined for three sizes of fractions (<0.25 mm, 0.315–0.5 mm, and 0.8–1.6 mm). For peanut shells, the smaller the particle size, the higher the adsorption capacity and the column breakthrough time. For walnut shells, however, the particle size seems to have a more complex influence on the adsorption process parameters, and this phenomenon deserves future investigation. The adsorption capacity for one and the same fraction size of 0.315–0.5 mm and initial MB concentration of 50 mg/L is higher under dynamic flow conditions, i.e., 51 mg/g compared to 20 mg/g for walnut shells and 46 mg/g compared to 17.5 mg/g for peanut shells.

Kinetics and Thermodynamics of Sorption of Methylene Blue Dye Onto Raw Groundnut Shell Biosorbent

Dyes are one of the hazardous chemicals found in wastewater produced by textile and allied industries that need to be removed from the wastewater before it is released into water bodies. The sorption efficiency of raw groundnut shell (RGS), an agricultural waste, was tested on methylene blue (MB) dye through a batch adsorption experiment. Physicochemical analysis of the RGS indicated good biosorbent properties. Fourier transform infrared (FTIR) spectroscopy analysis of the RGS revealed the presence of heterofunctional groups. The effect of various biosorption parameters such as initial dye concentration, contact time, and biosorbent dosage was systematically investigated. The quantity of MB adsorbed increased as the initial concentration and contact time increased and decreased with an increase in biosorbent dose. A maximum uptake capacity of 29.3 mg/g was recorded for 50 mg/L MB initial concentration. The equilibrium data from the batch adsorption experiments were fitted well into Freundlich isotherm and pseudo-second-order kinetic models. The results from this study indicate that RGS can serve as an alternative, low-cost, eco-friendly and efficient adsorbent for the removal of MB dye from wastewater.

Optimization of methylene blue removal from aqueous solutions using activated carbon derived from coffee ground pyrolysis: A response surface methodology (RSM) approach for natural and cost-effective adsorption

This study aimed to examine the impact of operational factors on the adsorption capacity of methylene blue (MB) using a natural and cost-effective adsorbent, activated carbon from coffee grounds (CAP). The three-factor Box-Behnken design of the response surface methodology (RSM) was employed to optimize this economically viable process with maximum efficiency. Through extensive experiments, the factors influencing the adsorption process were identified, their interactions were measured, and a mathematical model was developed. The experiment evaluated the quantity of MB adsorbed by CAP based on pH (2.5–10), initial MB concentration (10–100 mg/L), and CAP adsorbent amount (0.05–0.1 g/L). The results revealed that both concentration and mass significantly influenced the decoloration enhancement. Optimal conditions for achieving a 91 % degradation efficiency were determined as 0.05 g/L adsorbent weight, 100 mg/L dye concentration, and pH 2.5, with a desirability score of approximately 0.986, aligning closely with the predictions of the BBD model. In conclusion, this research addresses a research gap by demonstrating the high effectiveness of the CAP adsorbent in removing dyes from textiles.

Synthesis and application of Fe3O4/GO/PVP composite material for methylene blue adsorption

In this study, Fe3O4/GO/PVP (FGP) was successfully synthesized and efficiently applied for absorbing methylene blue. First, GO was synthesized by Hummer’s method from waste home-batteries. The chemical co-precipitation method was used to fabricate Fe3O4/GO from a mixture solution of GO, Fe3+, Fe2+. Polyvinylpyrrolidone PVP was selected to functionalize Fe3O4/GO and form Fe3O4/GO/PVP for improving dispersibility purpose in aqueous solution. The obtained Fe3O4/GO/PVP was characterized by XRD, FT-IR, BET, FE-SEM, UV-Vis techniques. Moreover, the effecting factors as pH, time adsorption, initial concentration of methylene blue were conducted. Adsorption isotherm models were also identified. The results showed that specific surface area of FGP-3 was 70.0 m2.g-1, the Freundlich isotherm model was suitable and the Dubinin - Radushkevich isotherm model showed that the process was physical adsorption. The maximum capacity (qmax) was 30.4 mg.g-1. These findings prove Fe3O4/GO/PVP as an inexpensive and efficient adsorbent for removal of cationic dyes.

Water remediation using activated montmorillonite/metal-organic framework nanocomposites: Response surface methodology, kinetic, and thermodynamic studies

The presence of dye pollutants in effluents is a significant concern due to their adverse effects on many life forms. For the purpose of removing Methylene Blue (MB) from an aqueous solution through the adsorption process, the H-MMT/MOF-5 and H-MMT/MOF-199 composites (MMT = montmorillonite, MOF = metal-organic framework) were produced. Composites made with diverse H-MMT: MOF (w/w %) ratios were used for the MB dye removal to study their adsorption characteristics over a 0–30 min time range. The 60 % H-MMT/40 % MOF-5 % and 70 % H-MMT/30 % MOF-199 composites showed the greatest amounts of MB removal. The effects of contact time, adsorbent dose, pH, and initial MB concentration on the removal of MB were studied using the central composite design (CCD) method. The process was studied using Response Surface Methodology (RSM) technique to optimize the adsorption process, and the optimum conditions were identified. For 60 % H-MMT/40 % MOF-5 % and 70 % H-MMT/30 % MOF-199, optimum MB removals of 97.52 % and 98.73 % with maximum adsorption capacities (qmax) of 192.3 and 238.09 mg g−1 were obtained. The experimental data of MB adsorption on H-MMT/MOF-5 and H-MMT/MOF-199 composites followed the Langmuir isotherm and pseudo-second-order kinetic model. Thermodynamic study demonstrated exothermic and spontaneous characters of the adsorption process. Also, MB adsorption by H-MMT/MOF-5 and H-MMT/MOF-199 composites was happened by electrostatic attraction, π-π interactions, and hydrogen bonding. The H-MMT/MOF-5 and H-MMT/MOF-199 composites based on a clay mineral H-MMT with greater specific surface area and reactive -OH groups are effective materials for developing low-cost and ecologically friendly adsorbents. According to the leaching test, H-MMT/MOF-5 and H-MMT/MOF-199 adsorbents presented good stability at pH values above 5. Therefore, the synthesized H-MMT/MOF-5 and H-MMT/MOF-199 composites could be effectively used to remove MB from water.

Biosorption of methylene blue by lentil shell on activation with sulfuric acid, formaldehyde, and calcination: kinetic, isotherm, and thermodynamic study

Lentil shell (LS) on modification with sulfuric acid (LSAC), formaldehyde (LSFM), and on calcination (LSCL) were used for the adsorption of methylene blue dye in the present study. The sulfuric acid treated LS adsorbent has shown maximum adsorption. The batch adsorption experiments were studied with the effect of adsorbent dose (10–60 mg), pH (4–10), dye concentration (10–80 mg/L), contact time (10–60 minutes), and temperature (303–333 K). The maximum removal of methylene blue was found at pH 10 with adsorption time 60 minutes. The maximum adsorption capacity is measured for LSAC, LSCL, LSFM, and LS untreated (LSUN) are 49.56, 45.79, 42.24, and 42.09 mg/g respectively for 60 mg adsorbent dose with 60 mg/L of initial methylene blue dye concentration. The biosorbents were characterized with Fourier Transform Infrared spectra, Scanning Electron Microscopy, Transmission Electron Microscopy, BET-N2 adsorption, and Energy Dispersive X-ray analysis. The adsorption isotherm was studied at the temperature of 303, 313, 323, and 333 K. It was found that the higher temperature suitable for maximum adsorption. Langmuir model and Freundlich model were studied from the obtained results for adsorption mechanism. The pseudo second order kinetic model was found suitable for the present adsorption study in comparison with pseudo first order model and intraparticle diffusion model. The data obtained from the present work showed that LS could be employed as an efficient adsorbent for the adsorption of the dye.

The Removal of Methylene Blue from Aqueous Solutions Using Zinc Oxide Nanoparticles With Hydrogen Peroxide

Industrial effluents produce vast amounts of pollutants and account for 20% of industrial wastewater annually. Methylene blue (MB) is one of the most widely used dyes in the medical, pharmaceutical, and textile industries. However, it is toxic to living organisms, and even a short-time exposure to it can be potentially harmful. Therefore, the purpose of this study was to investigate the efficiency of zinc oxide nanoparticles in removing MB from aqueous solutions in the presence of hydrogen peroxide. The effects of various parameters such as pH (3-10), ZnO nanoparticle dose (0.01-0.08 g/L), reaction time (5-50 minutes), initial concentration of MB (20-200 mg/L), and the hydrogen peroxide concentration (0.5-5 mg/L) were studied. The wavelength of maximum absorption (λmax) was 665 nm. The optimal pH value was 5, zinc oxide nanoparticle dose was 0.05 g/L, the initial concentration of MB was 40 mg/L, the concentration of hydrogen peroxide was 2 mg/L, and the contact time was 20 minutes. The efficiency of MB removal was 97.99%. The results showed that zinc oxide nanoparticles in the presence of hydrogen peroxide could remove the MB from aqueous solutions with high efficiency.

Facile preparation of micro-porous biochar from Bangladeshi sprouted agricultural waste (corncob) via in-house built heating chamber for cationic dye removal

Herein, in-house built heating chamber aided facile preparation of biochar was carried out using Bangladeshi sprouted corncob as the precursor for removing methylene blue (MB). The corncob biomass (CCB) was pyrolyzed at 700 °C for 2hrs (heating rate: 10 °C/min) using the in-house built heating chamber in a muffle furnace, eliminating the necessity of pyrolytic chamber. The prepared corncob biochar (CCBC) was characterized for elemental composition, crystallinity (XRD), functional groups (ATR-FTIR), surface morphology-elemental composition (SEM-EDX), surface area (BET), surface charge (point of zero charge), particle size-stability (DLS-zeta potential) and thermal stability (STA). Adsorption efficacy of CCBC was investigated in batch experiment with MB dye as well as effect of various factors such as contact time (5–120 min), initial MB concentration (7–15 mg/L), pH (2–10) and adsorbent dosage (10–35 mg). Without any chemical treatment for activation, CCBC produced maximum adsorption capacity (Qmax) of 20.42mgg−1 at 25 °C. The adsorption behavior of MB by CCBC could be better understood by Langmuir isotherm and Pseudo-second order kinetic model as they were the best fitted isotherm and kinetic models. Thus, waste to treat waste, meaning agricultural wastes like corncob can easily be converted into effective adsorbent for treating dye bearing wastewater.

Advanced oxidation process using cobalt-based metal-organic frameworks via operating Co(II)/Co(III) redox cycling for efficient organic contaminant degradations

Cobalt-terephthalate metal-organic frameworks (Co-BDC MOFs), is a well-known-designed inorganic-organic hybrid polymeric material. Because of its oxo-cluster, it has a durable and potent capability for cyclic-redox applications particularly when synthesis gives cobalt in mixed valency conditions, Co(II) and Co(III). The mixed valency condition offers a fast redox cycling progression due to the intimate localization of both Co(II) and Co(III) within the Co-BDC structure (the oxo-cluster) and consequently should accelerate H2O2 decomposition. Hence, in this work, Co-BDC MOF has been synthesized by the typical solvothermal method and has been characterized via SEM/EDX, XRD, FTIR, and XPS analyses. The most important result of characterizations is that cobalt presents pristinely with mixed valency states Co(II)/Co(III). To assess its heterogenous catalysis performance, Co-BDC has been applied in combination with H2O2 for an advanced oxidation process (AOP) against a test dye methylene blue (MB). According to kinetic studies, H2O2 decomposition was found to obey the regular second-order model with rate constant = 0.3649 mM−1 min−1, while, MB degradation obeyed the pseudo-first-order model with rate constant ranges from 0.1116 to 0.0716 min−1 depending on MB initial concentration. Hence, it has been concluded that MB degrades by relatively highly abundant oxidative radicals for the applied H2O2 concentration. Also, a catalytic system where the effects of initial MB concentration (2, 5, and 10 ppm), and dosage of 10, 20, 50, and 100 mg of Co-BDC were investigated. According to the results, MB degrades well at different doses of Co-BDC. Because Co(II) and Co(III) coexist in the Co-BDC matrix, a single-catalyst synergistic catalysis mechanism may be proposed.

Improving the Photo Electro Catalytic Degradation of Methylene Blue by Modified TiO2/ITO Photo Anodes

TiO2 photoanodes have gained significant attention for the removal of organic pollutants through photoelectrocatalytic processes, with the aim of developing a cost-effective and efficient method for improving the degradation of pollutants in surface water. This study investigated the effects of adding titanium nanooxide (Degussa P25) containing 70% anatase and 30% rutile phases on the properties of nanostructured TiO2 photoanodes prepared on glass substrates (indium tin oxide (ITO)) using sol–gel/dip coating techniques The results obtained from ultraviolet–visible transmittance spectroscopy, electrochemical (EC) impedance spectroscopy, photocurrent, and atomic force microscopy analyses revealed that the addition of Degussa P25 improved the electrical conductivity of the TiO2/ITO anode and reduced the optical bandgap from 3.50 to 3.35 eV, while the size of the titanium oxide particles decreased to about 75 nm. The EC impedance spectra measurement confirms that the addition of titanium nanooxide Degussa P25 improved the electrical conductivity for TiO2/ITO anode. The photoelectrocatalysis (PEC) performance of the TiO2 photoanodes was investigated via the degradation of methylene blue (MB) under UVA light irradiation. The AB photoanode (with the addition of Degussa P25) exhibited excellent PEC performance, with 95.9% color removal efficiency and 63% total organic carbon (TOC) removal efficiency, compared to 92% color removal efficiency and 56% TOC removal efficiency for the A photoanode (without the addition of Degussa P25). The kinetic constants (k) were 134 × 10−4, 110 × 10−4 (min−1) for A and AB anodes, respectively, and the degradation of MB followed first-order kinetics for all anodes. The A and AB anodes were compared as electrodes for the degradation of MB using PEC, photocatalysis (PC), and EC technologies. Subsequently, The A and AB anodes were utilized as electrodes to compare the performance of PEC, PC, and EC technologies for the degradation of MB. The results showed that the AB anode exhibited higher efficiency in all PC technologies, with color removal (%) efficiencies of 95.9% (PEC), 33% (PC), and 21% (EC) compared to 92% (PEC), 28% (PC), and 19% (EC) for the A anode. Additionally, the photooxidation process had a 2.1% effect on the degradation of the initial MB concentration.

Red mud-derived iron carbon catalyst for the removal of organic pollutants in wastewater

In order to reduce the environmental hazards of red mud (RM) and realize its resource utilization, in this study, RM-based iron-carbon micro-electrolysis material (RM-MEM) were prepared by a carbothermal reduction process using RM as raw material. The influence of the preparation conditions on the phase transformation and structural characteristics of the RM-MEM were investigated during the reduction process. The ability of RM-MEM to remove organic pollutants from wastewater was evaluated. The results showed that RM-MEM prepared at a reduction temperature of 1100 °C, a reduction time of 50 min and a coal dosage of 50% had the best removal effect for the degradation of methylene blue (MB). When the initial MB concentration was 20 mg L−1, the amount of RM-MEM material was 4 g L−1, the initial pH was 7, and the degradation efficiency reached 99.75% after 60 min. When RM-MEM is split into carbon free and iron free parts for use, the degradation effect becomes worse. Compared to other materials, RM-MEM has lower cost and better degradation. X-ray diffraction (XRD) analysis showed that hematite was transformed to zero-valent iron with the increase in the roasting temperature. Scanning electron microscopy (SEM) and energy spectroscopy (EDS) analysis showed that micron-sized ZVI particles were formed in the RM-MEM, and increasing the carbon thermal reduction temperature was beneficial to the growth of zero-valent iron particles.

Microcrystalline cellulose/graphene oxide aerogel for adsorption of cationic dye from aqueous solution

Today, the increasing growth of industrial activities has caused the entry of large amounts of pollutants into water resources. Owing to the toxicity of these pollutants, their removal from water sources is essential. An adsorbent based on microcrystalline cellulose/graphene oxide (MCC/GO) aerogel was synthesised and its efficiency was investigated to remove methylene blue (MB) dye from aqueous solutions. Various factors such as concentration of GO in microcrystalline cellulose/graphene oxide (MCC/GO-x) aerogel, pH solution, adsorbent dosage, initial concentration of MB and contacting time were optimised on the adsorption capacity. The outcomes displayed that the maximum adsorption capacity could get to 645 mg g−1. The batch adsorption tests confirmed the pseudo-second-order and Langmuir isotherms as the best-fitted models to describe the adsorption of the adsorbent.