Evaluating the decolorization potential of methylene blue by indigenous Bacillus tequilensis BS007 biofilm isolated from industrial wastes

An investigation of transition metal doped TiO2 photocatalysts for the enhanced photocatalytic decoloration of methylene blue dye under visible light irradiation

<abstract> <p>Nanostructured titanium dioxide (TiO<sub>2</sub>) among other oxides can be used as a prominent photocatalytic nanomaterial with self-cleaning properties. TiO<sub>2</sub> is selected in this research, due to its high photocatalytic activity, high stability and low cost. Metal doping has proved to be a successful approach for enhancing the photocatalytic efficiency of photocatalysts. Photocatalytic products can be applied in the building sector, using both building materials as a matrix, but also in fabrics. In this study undoped and Mn-In, Mn-Cu, In-Ni, Mn-Ni bimetallic doped TiO<sub>2</sub> nanostructures were synthesized using the microwave-assisted hydrothermal method. Decolorization efficiency of applied nanocoatings on fabrics and 3-D printed sustainable blocks made from recycled building materials was studied, both under UV as well as visible light for Methylene Blue (MB), using a self-made depollution and self-cleaning apparatus. Nanocoated samples showed high MB decolorization and great potential in self-cleaning applications. Results showed that the highest MB decolorization for both applications were observed for 0.25 at% Mn-In doped TiO<sub>2</sub>. For the application of 3-D printed blocks Mn-In and In-Ni doped TiO<sub>2</sub> showed the highest net MB decolorization, 25.1 and 22.6%, respectively. For the application of nanocoated fabrics, three samples (Mn-In, In-Ni and Mn-Cu doped TiO<sub>2</sub>) showed high MB decolorization (58.1, 52.7 and 47.6%, respectively) under indirect sunlight, while under UV light the fabric coated with Mn-In and In-Ni doped TiO<sub>2</sub> showed the highest MB decolorization rate 26.1 and 24.0%, respectively.</p> </abstract>

Optimization of decolorization of methylene blue by lignin peroxidase enzyme produced from sewage sludge with Phanerocheate chrysosporium

Oxidative decolorization of methylene blue using pelagite

Novel 2D layered g-C3N4 nanocomposite materials for sustainable wastewater treatment by catalytic degradation of toxic dye

The presence of methylene blue (MB) dye in wastewater has raised concern about human health and environmental ecology due to potential carcinogenic, and mutagenic effects. Therefore, this work aims to remove MB dye from wastewater using γ-Al2O3 nanoparticles synthesized from aluminum scrap via simple electrolytic method. The successful synthesis of the adsorbent was confirmed by a range of spectroscopy and microscopy techniques, including XRD, SEM, FTIR, and BET. The central composite design (CCD) of the response surface methodology (RSM) method was used to optimize the processing parameters such as solution pH, contact time, initial MB concentration, and adsorbent dose. The ANOVA results clearly shows that the quadratic model (p < 0.0001) was sufficient to the best predicting of the removal performance of MB dye (R2 = 0.9862). The optimum condition for the maximum MB dye removal (98.91%) was achieved at solution pH of 8.298, initial MB concentration of 31.657 mg/L, adsorbent dose of 0.387 g/L, and contact time of 46.728 min. Nano-γ-Al2O3 was shown to have a good surface area of 59 mg2/g by BET analysis. The adsorption kinetics follows the pseudo-second-order model (R2 = 0.997). With a maximum adsorption capacity of 137.17 mg/g, the Langmuir isotherm model (R2 = 984) provides the best fit to the adsorption isotherm data, indicating a monolayer adsorption process. Furthermore, thermodynamic analysis demonstrated that the adsorption of MB dye was an endothermic and spontaneous process. The reusability study showed that γ-Al2O3 nano-adsorbent retained 85.08% of its original removal efficiency after five cycles. According to the findings of the study, MB dye molecules were taken up by γ-Al2O3 nano-adsorbent via hydrogen bond formation, Van der Waals interaction, and electrostatic attraction. Therefore, γ-Al2O3 nanoparticles can be used as a potentially eco-friendly and low-cost adsorbent for the removal of MB dye from aqueous solutions.

Methylene blue (MB) dye is a common colorant used in numerous industries, particularly the textile industry. When methylene blue is discharged into water bodies without being properly treated, it may seriously damage aquatic and human life. As a result, a variety of methods have been established to remove dyes from aqueous systems. Thanks to their distinguishing features e.g., rapid responsiveness, cost-effectiveness, potential selectivity, portability, and simplicity, the electrochemical methods provided promising techniques. Considering these aspects, a novel quartz crystal microbalance nanosensors based on green synthesized magnesium ferrite nanoparticles (QCM-Based MgFe2O4 NPs) and magnesium ferrite nanoparticles coated alginate hydrogel nanocomposite (QCM-Based MgFe2O4@CaAlg NCs) were designed for real-time detection of high concentrations of MB dye in the aqueous streams at different temperatures. The characterization results of MgFe2O4 NPs and MgFe2O4@CaAlg NCs showed that the MgFe2O4 NPs have synthesized in good crystallinity, spherical shape, and successfully coated by the alginate hydrogel. The performance of the designed QCM-Based MgFe2O4 NPs and MgFe2O4@CaAlg NCs nanosensors were examined by the QCM technique, where the developed nanosensors showed great potential for dealing with continuous feed, very small volumes, high concentrations of MB, and providing an instantaneous response. In addition, the alginate coating offered more significant attributes to MgFe2O4 NPs and enhanced the sensor work toward MB monitoring. The sensitivity of designed nanosensors was evaluated at different MB concentrations (100 mg/L, 400 mg/L, and 800 mg/L), and temperatures (25 °C, 35 °C, and 45 °C). Where a real-time detection of 400 mg/L MB was achieved using the developed sensing platforms at different temperatures within an effective time of about 5 min. The results revealed that increasing the temperature from 25 °C to 45 °C has improved the detection of MB using the MgFe2O4@CaAlg NCs nanosensor and the MgFe2O4@CaAlg NCs nanosensor exhibited high sensitivity for different MB concentrations with more efficiency than the MgFe2O4 NPs nanosensor.

In the current study, the mechanistic understanding of the adsorption isotherm and thermodynamic aspects of cationic methylene blue (MB) dye adsorption onto cellulosic olive stones biomass from wastewater were investigated. The batch adsorption of MB onto the olive stones (black and green olive stones) was tested at a variety of pH, dye concentrations, temperatures, and biomass particle sizes. The adsorption thermodynamics such as Gibbs free energy, enthalpy, and entropy changes were also calculated. Moreover, the desorption studies of MB from the spent olive stones were studied to explore the re-usability of the biomasses. The results revealed that under the optimum pH of 10, the maximum MB uptake was achieved i.e. 80.2% for the green olive stones and 70.9% for the black olive stones. The green olive stones were found to be more efficient in remediating higher MB concentrations from water than the black olive stones. The highest MB removal of the green olive stones was achieved at 600 ppm of MB, while the highest MB removal of the black olive stones was observed at 50 ppm of MB. Furthermore, for almost all the concentrations studied (50–1000 ppm), the MB adsorption was the highest at the temperature of 45 °C (P value < 0.05). It was shown by the Fourier transform infrared that the electrostatic interaction and hydrogen bonding were proposed as dominant adsorption mechanisms at basic and acidic pH, respectively. While the hydrophobic-hydrophobic interaction was a dominant mechanism at neutral pH. The thermodynamic studies revealed that the adsorption process was endothermic, spontaneous, and favorable. Moreover, the real wastewater experiment and the desorption studies showed that the green and black olive stones were a cost-effective and promising adsorbents for MB remediation from wastewater on account of their high adsorption and desorption removal capacities.

A novel system of MnO2-mullite-cordierite composite particle with NaClO for Methylene blue decolorization

Algerian Eucalyptus Leaves (AEL), a natural biodegradable adsorbent abundantly available, was used for the removal of methylene blue (MB) dye. The AEL properties for the removal of MB were investigated under different conditions by varying the AEL amount, MB concentration, pH of the solution and the reaction temperature. Scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) techniques have been used to characterize AEL biosorbent. Experimental results showed that the adsorption of MB dye at the concentration of 50 mg L−1 reached to 91 % at pH 10 with a stirring speed of 200 rpm and after 180 min of reaction time. The experimental data were analyzed using the linear forms of different kinetic models (pseudo-first order kinetic model, pseudo-second order kinetic model, and intra-particle diffusion models). The results demonstrated that the adsorption kinetics of MB was consistent with the pseudo-second order model with R 2 value of 0.9969. The isotherm models Langmuir, Freundlich, Dubinin, Elovich, Brunaut Emmet Teller and Temkin models were also investigated to describe the adsorption equilibrium. The results show that the AEL adsorption is in accordance with Temkin isotherm. The thermodynamic study revealed that the adsorption is spontaneous and exothermic. Therefore, as a cheap green adsorbent with high MB adsorption performance, AEL is expected to become one of the best candidate materials for future industrial wastewater treatment.

In this study, the nano-spinel CoMn2O4 was synthesized by coprecipitation pyrolysis and employed to heterogeneously activate hypochlorite (NaClO) for the oxidative decolorization of methylene blue (MB). The crystal structure, elemental composition, surface morphology, and microstructure of the prepared CoMn2O4 nano-spinel were analyzed using a series of characterization techniques. The pyrolysis temperature was screened on the basis of MB decolorization efficiency and the leaching of metal ions during the reaction. The MB decolorization efficiency was compared using different catalysts and process. The impacts of CoMn2O4 dosage, effective chlorine dose, MB concentration, and initial pH on MB decolorization were explored. The catalytic mechanism of MB oxidation was elucidated through quenching experiments combined with radical identification. The degradation pathway of MB was preliminarily proposed based on the detection of the intermediates. The reusability of recycled CoMn2O4 was finally investigated. The results revealed that maximal MB oxidation efficiency and minimal leaching of Co and Mn ions were achieved at the calcination temperature of 600 °C. Complete oxidative decolorization of MB within 40 min was obtained at an initial MB concentration of 50 mg/L, a CoMn2O4 dosage of 1 g/L, an effective chlorine dose of 0.1%, and an initial pH of 4.3. Superoxide radical (O2•-) was found to be dominantly responsible for MB decolorization according to the results of radical scavenging experiments and electron paramagnetic resonance. The CoMn2O4 spinel can be recycled for five cycles with the MB removal in the range of 90.6~98.7%.

Copper oxide incorporated fly ash-derived zeolite X (CuO/FAZ-X) was synthesized from solid waste coal fly ash by ion exchange with Cu2+ followed by calcination process. The synthesized materials were characterized by XRF, FTIR, SEM, EDX, and BET methods. In the application of the catalysts for wet peroxide oxidative decolorization of the model dye MB (Methylene Blue), the e ects of major parameters, such as CuOloading, initial H2O2 concentration, initial dye concentration, catalyst dosage, and pH, were investigated to assess the activity of the catalysts. In comparison with the activity of either fly ash-derived zeolite X (FAZ-X) or CuO, the combined catalyst (CuO/FAZ-X) showed an enhanced wet catalytic activity. Under the optimal condition (catalyst dose 250 mg/L, 100 ppm dye, pH = 6.8, 1 ml H2O2, and room temperature or 30C), the decolorization of MB was about 100% in 120 min by CuO/FAZ-X and only 31% and 44% by FAZ-X andCuO, respectively. Based on the decolorized products identi ed by HPLC-(-ESI)-TOFMS, the decolorization pathway of MB was proposed. Consequently, incorporation of CuO remarkably improved the catalytic activity of FAZ-X, such that CuO/FAZ-X emerged as a novel, reusable heterogeneous Fenton-like catalyst for oxidative decolorization of model dye MB. Thus, the present work demonstrates a simple and facile route for the conversion of waste coal fly ash into a valuable catalyst.

Performance of wastewater sludge modified with zinc oxide nanoparticles in the removal of methylene blue from aqueous solutions

Mechanical alloying is one of the popular, simple, and easy powder metallurgy methods to prepare nanostructured high entropy alloys (HEA). HEAs are modern-day alloys that exhibit significantly improved properties and are used in many unique applications. One such application is using HEA powders for determining the methylene blue dye in wastewater using cyclic voltammetry. We have successfully synthesized the HEA powder of composition 25Fe-19Cr-19Ni-18Ti-19Mn by planetary ball mill and studied their phases, surface morphology, and particle sizes by x-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) respectively. We have fabricated the HEA-modified carbon paste electrode (HEA-MCPE) to study the electrochemical oxidation of methylene blue (MB) dye present in the wastewater. MB is a cationic dye that is toxic, and carcinogenic in high doses; generally used in textile, paper, and leather industries for coloring purposes and discharged into the water sources and thus creating a threat to aquatic animals and humans. Therefore, we must determine the MB dye in waste water regularly. Our fabricated electrode can detect MB dye in wastewater over a pH range of 6 to 7.6 with a significant current response. We have found that, the 4 mg HEA-MCPE and pH 6 are the optimal experimental conditions for achieving a higher rate of electro-oxidation of MB dye. The calculated active surface area for bare and HEA-MCPE is found to be 0.180 and 0.918 cm2 respectively. We have found out that, increase in the concentration of MB from 1 mM to 5 mM increases the anodic peak current linearly due to the increased molecular interaction and the mobility of electrons between the analyte and the electrode surface.

Optimization of the column studies into the adsorption of basic dye using tartaric acid-treated bagasse