Adsorption Of Methylene Blue Dye Research Articles

Carboxyl functionalized covalent organic framework material for selective adsorption of methylene blue in aqueous solutions

In this paper, M-TzDha-COF composed of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl) trianiline (Tz) and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde (Dha) was synthesized by grafting carboxyl groups onto COF framework via the solvent-free esterification. M-TzDha-COF retains the porous structure and has good crystallinity and high thermal stability. M-TzDha-COF exhibits selective adsorption and efficient removal of methylene blue dye with the maximum adsorption capacity of 95 mg·g−1. M-TzDha-COF can adsorb methylene blue rapidly and maintain high adsorption efficiency after several cyclic applications. The adsorption of methylene blue on M-TzDha-COF is consistent with the pseudo-second-order adsorption kinetic model and Langmuir adsorption model. Adsorption is caused by three interactions: π-π stacking between the triazine group and methylene blue, electrostatic interaction between the carboxyl group and the methylene blue cationic portion, and hydrogen bonding interaction. Fast kinetics, high adsorption capacity and good reusability make carboxyl functionalized COF have great potential in removing methylene blue dye from water.

Selective adsorption of methylene blue dye by a flocculation sludge-derived adsorbent prepared by carboxymethyl chitosan-based flocculants

The flocculation of dyeing wastewater generated a large amount of sludge that was often disposed as refractory hazardous waste. The resource utilization of flocculation sludge was of great significance in terms of low treatment cost of sludge, low environmental risk and high usage efficiency of reactive dyes. Herein, a flocculation sludge-derived (FSD) adsorbent was prepared via cross-linking of flocculation sludge yielding by carboxymethyl chitosan-based flocculants and dyes. FSD adsorbent had excellent selective adsorption performance for methylene blue (MB) treatment. The highest removal rate of MB and adsorption capacity of FSD adsorbent were 96.48 % and 354.7066 mg/g, attributing to its rich functional groups, negative charges and special micropore structure. FSD adsorbent owned the favorable regeneration efficiency and stability. Its removal rate of MB was still above 71.8 % after 6 regeneration-adsorption cycles. Its leaching rate of dyes was only 0.0016 mg/mg that was rather lower than common dried flocculation sludge. The adsorption processes of FSD adsorbent were complex in accordance with its characteristics, adsorption isotherms, adsorption kinetics and theoretical calculation. Multiple adsorption mechanisms were present in the treatment of dyeing wastewater by FSD adsorbent. The resource utilization of flocculation sludge, as adsorbents, was a potential candidate in field application.

Dynamic intercalation of methylene blue in BC-MgFe-HT composite: Unveiling adsorption mechanisms for efficient wastewater treatment

Developing efficient and eco-friendly adsorbents for removing dye from wastewater presents a significant challenge. In this study, by combining MgFe-hydrotalcite (MgFe-HT) with bamboo charcoal (BC) we report the synthesis of a composite material named BC-MgFe-HT to achieve rapid and effective adsorption of methylene blue (MB) dye. The novelty of our work lies in the distinctive intercalation arrangement of the MB dye post-adsorption within the BC-MgFe-HT layers, which was quantitatively measured and found to be at an intercalation angle of approximately 44.26° rather than the conventional vertical positioning. This unique phenomenon indicates a dynamic rearrangement of the composite structure upon MB adsorption, significantly enhancing its adsorption capacity and efficiency. Comprehensive characterization of the BC-MgFe-HT composite was performed using the following techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis, and thermogravimetric analysis (TGA). The adsorption studies demonstrated a maximum adsorption capacity of 194.09 mg/g within 20 min, attributed to the composite's high surface area, porous architecture, and dye intercalation capacity. Kinetic studies revealed that the pseudo-second-order (PSO) kinetics model best describes the adsorption process, while the Langmuir isotherm model provided the most accurate fit for the adsorption equilibrium data. These findings offer novel insights into the adsorption mechanisms of MB onto the BC-MgFe-HT composite, highlighting its potential for the design and optimization of composite materials for effective wastewater remediation.

Effectiveness of Porous Durian Shell-based Activated Carbon for Methylene Blue Adsorption

In this study, durian shell-based activated carbon (DAC) was produced via chemical activation method by utilising durian shell and sulphuric acid (H2SO4) as the starting material and activating agent, respectively. The incorporation of H2SO4 in the DAC production process resulted an improvement in the surface properties and adsorption capacity of the produced DAC adsorbent. Field emission scanning electron microscopy analysis further showed that the produced DAC possessed a porous structure which was beneficial for dye adsorption application. Under operating conditions of 500°C and 3 hours carbonisation temperature and time, the Brunauer–Emmett–Teller (BET) surface area, total pore volume and BET average pore diameter were measured to be 242.03 m2/g, 0.028 cm3/g and 2.28 nm, respectively. The adsorption performance of the produced DAC was then investigated using methylene blue (MB) as the model adsorbate. The optimum MB dye removal and adsorption capacity were found to be 92.05% and 0.767 mg/g, respectively, with 0.6 g of DAC dosage, 10 ppm of initial MB dye concentration and 15 min of contact time.

A green solution for eliminating methylene blue and crystal violet dyes using eco-friendly zinc oxide nanoparticles synthesized from Dracaena trifasciata

Modern technological development has unavoidably resulted in more pollution, especially in aquatic environments. While extensively utilized in various industries, cationic dyes pose a significant threat to both the environment and human health, ranking among the most hazardous pollutants. When exposed to these dyes, one may experience skin irritation and allergic dermatitis because they are frequently mutagenic, toxic, carcinogenic, and resistant to biodegradation. The continued release of these dyes into the environment exacerbates human health and ecosystem concerns. This work investigates the possibility of eco-friendly zinc oxide nanoparticles, which are produced by the co-precipitation method from leaf extracts of the Dracaena trifasciata plant, also referred to as snake plant, for the elimination of the cationic dyes methylene blue and crystal violet. This work presents a novel approach for synthesizing eco-friendly zinc oxide nanoparticles using leaf extract from Dracaena trifasciata. To examine the eco-friendly zinc oxide nanoparticles, characterization studies were carried out using various instrumental methods. The best conditions for removing methylene blue and crystal violet were found through batch adsorption investigations, which produced removal percentages of 86 % and 88 %, respectively, under specific conditions. The eco-friendly zinc oxide nanoparticles achieved maximum adsorption capacity and effective removal of methylene blue and crystal violet dyes under the following conditions: a pH value of 10, nanoparticle concentration of 0.06 g, reaction time of 50 min, dye concentration of 50 mg/L, and reaction temperature of 40 °C. Isotherm investigations demonstrated that the adsorption of methylene blue dye by eco-friendly zinc oxide nanoparticles followed the Temkin isotherm model, whereas the adsorption of crystal violet dye followed the Freundlich isotherm model. The kinetic parameters describing the adsorption of methylene blue and crystal violet dye onto eco-friendly zinc oxide nanoparticles were identified as pseudo-first-order and Elovich models, respectively. Following the above-mentioned studies, eco-friendly zinc oxide nanoparticles were subjected to additional characterization in order to assess their potential for wastewater treatment.

Enhanced methylene blue dye sequestration by carbon-embedded mesoporous zinc oxide nanoparticles fabricated utilizing Aloe barbadensis miller biowaste: Batch optimization, simulation modeling, and textile effluent feasibility

The present study reports novel carbon-embedded mesoporous zinc oxide nanoparticles (ZnO/C NPs) utilizing Aloe barbadensis miller (Aloe vera) biowaste extract as size-reducing agent and bio-stabilizer via a one-pot green fabrication approach. The fabricated nanoparticles were carbonized at 250 °C and characterized using FTIR, UV-Vis, ZPA, TEM, SEM/EDX, XRD, BET, and TGA techniques. Using Brunauer, Emmett, and Teller's theory, the ZnO/C NPs specific surface area was determined to be 63.25 m2/g, and the average pore diameter (3.46 nm) was in the mesoporous range. Fabricated ZnO/C NPs have an un-uniform size distribution, with an average crystallite size of 17.37 nm. The methylene blue (MB) dye adsorption of mesoporous ZnO/C NPs was studied in batch mode experiments at 37 °C using an aqueous solution. Detailed isotherms and kinetics modeling were performed, and it established that the Langmuir isotherm and Pseudo second order kinetic correctly fit the optimized MB dye adsorption data due to their higher correlation coefficients than other analyzed models. The Langmuir isotherm-based monolayer adsorption was found to be 105.26 mg/g. The pseudo second order kinetic best explains the adsorption reaction, indicating that the chemisorption mechanism is more likely to regulate the MB dye adsorption. Further, thermodynamics parameters showed that the MB dye adsorption onto ZnO/C NPs was spontaneous, endothermic, and accompanied by increased entropy. The ZnO/C NPs demonstrated remarkable MB dye sequestration from aqueous solution upto four reusability cycles, with regenerability of ≥84.52 %. Furthermore, feasibility study revealed an outstanding decolorization efficacy of MB dye upto 58.18 % from textile effluent, establishing mesoporous ZnO/C NPs as viable, environment-friendly, and cost-effective remedies for textile wastewater treatment.

BMIM][X] Ionic Liquids Supported on a Pillared-Layered Metal-Organic Framework: Synthesis, Characterization, and Adsorption Properties.

Combining ionic liquids (ILs) and metal-organic frameworks (MOFs) can be an intriguing opportunity to develop advanced materials with different adsorption capabilities for environmental applications. This study reports the preparation and characterization of a 3D pillared-layered compound, namely, [Zn2(tz)2(bdc)] (CIM91), formed by 1,2,4-triazole (Htz) and 1,4-benzenedicarboxylic acid (H2bdc) ligands. Then, various loadings of the water-stable and hydrophobic IL, 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and the water-soluble 1-n-butyl-3-methylimidazolium chloride ([BMIM][Cl]) were incorporated into CIM91. Detailed characterization by X-ray powder diffraction (XRD), FT-IR spectra, scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) analysis, N2 adsorption measurements, and thermogravimetric analysis confirmed the formation of [BMIM][X]/CIM91 composites and the structural stability of the MOF after the incorporation of the ionic liquids. CO2 adsorption-desorption analysis was experimentally carried out for all the materials at 298 K and 318 K, demonstrating a great enhancement in the CO2 adsorption properties of the sole MOF CIM91, particularly by including [BMIM][PF6] species in its structure with a double isosteric heat of CO2 adsorption. The composites were also tested for the adsorption of methylene blue (MB) dye. The results indicate that the incorporation of [BMIM][X] into CIM91 can substantially modify the adsorption properties of the MOF. The influence of the nature of the [BMIM][X] anions on these properties has also been analyzed.

Agricultural low-cost waste adsorption of methylene blue and modelling linear isotherm method versus nonlinear prediction

AbstractThis study shows that geographically marked wheat hull, named Siyez, rice hull Sarı Kılçık, and Taşköprü Garlic stalk were used as agricultural waste to potential adsorbent materials for removing methylene blue from aqueous solution. Experimental data were evaluated in both equilibrium batch process and kinetic studies. In addition, the factors that affect the adsorption capacities, such as pH solutions, methylene blue concentration, contact time, and temperatures, were also investigated. Obtained data were subject to two constant adsorption models of Langmuir, Freundlich, Temkin, and Dubinin−Radushkevich. The kinetic models (pseudo-first-order, pseudo-second-order, intra-particle diffusion and film diffusion) and thermodynamic parameters were evaluated. The adsorption isotherms, characterized by an excellent fit with the Langmuir model (R2 = 0.99) across all adsorbents, underscore the prevalence of monolayer adsorption of methylene blue, in contrast to the Freundlich equation. Adsorption kinetics of the methylene blue onto the adsorbents followed pseudo-second-order kinetic model. According to high regression coefficient (R2) and minimal values of nonlinear error functions like RMSE; the maximum monolayer adsorption capacities of wheat hull, rice hull and garlic stalk were found to be 62.50 (mg/g), 54.94 (mg/g), and 370.37 (mg/g), respectively. The results indicated that these proposed adsorbents could be low-cost and effective adsorbents for water purification and have adsorption capacity as much as comparable with the literature. In batch equilibrium studies, the adsorption of methylene blue dye onto the wheat hull, rice hull, and garlic stalk exhibited a significant correlation with temperature, contact time, and initial concentration of methylene blue dye and Adaptive Neuro-Fuzzy Inference System algorithm for forecasting overall the system parameter well fitted with these findings with the accuracy of outputs (R2 about 0.99 for each). Consequently, the thermodynamic analysis revealed that the adsorption process takes place in bulk diffusion by liquid phase mass transfer and occurred spontaneously with endothermically except garlic stalk. Adsorption thermodynamic studies show that the adsorption of methylene blue onto the garlic stalk was spontaneous and exothermic. Graphical Abstract

Methylene blue dye elimination from synthetic wastewater by modified adsorbent produced from Foeniculum vulgare waste: Thermodynamic, equilibrium, and kinetic studies

In the current investigation, seeds of the Foeniculum vulgare plant were acquired from the KSA, Tabuk City, and its powder was chemically modified by four different reagents. The four resulting samples were identified by SEM and IR techniques and inspected for methylene blue (MB) dye adsorption. The influence of MB concentration, adsorbent dose, solution pH, temperature, and contact time on adsorption performance was examined. This adsorption's kinetic, isothermal, and thermodynamic parameters were correspondingly studied. The idyllic adsorbent was established to be the modified sample with oxalic acid, which removed 90.15 % of the MB dye. It was also shown that the MB adsorption matched well with the kinetically 2nd -order model. The findings of the experiment fit better with the model of Langmuir isotherm than the other models. The negative values of each ΔG°, ΔH°, and ΔS° indicate the adsorption of MB is an exothermic and spontaneous process. The very law value of adsorption enthalpy proves the physisorption adsorption. The very high maximum adsorption capacity (qmax) values of this adsorption (892.857, 684.932, 487.805 mg g−1), the stability and availability and of this oxalic acid modified adsorbent suggest it will be highly valued in the field of water decontamination.

Effect of KOH- and NaOH-modified fly ash on the adsorption of methylene blue and crystal violet dyes: a Box-Behnken design study

ABSTRACT Coal Fly Ash (FA) and modified fly ash (mFA), treated with either KOH or NaOH, were used to remove methylene blue (MB) and crystal violet (CV) dyes from aqueous solution. Several techniques, including Thermogravimetric analysis, X-Ray diffraction analysis, Fourier-transform infrared spectroscopy, Brunauer-Emmett-Teller, and Scanning Electron Microscopy, were used to characterise both FA and mFA. To optimise the adsorption process, the Response Surface Methodology (RSM) with the Box – Behnken design (BBD) was applied. Key parameters such as solution pH (4–10), initial dye concentration (200–300 mg/L), contact time (15–180 minutes), and temperature (30–50°C) were varied to assess their impact on adsorption efficiency. The adsorption followed the Langmuir model and pseudo-second-order (PSO) kinetic model. The adsorption capacity of mFA for MB dye was 49.5 mg/g at 50°C, while for CV dye, it was 495.5 mg/g at the same temperature. The adsorption mechanism involved electrostatic attraction, n-π interaction, Yoshida hydrogen bonding, and hydrogen bonding. These results highlight the effectiveness of mFA as a high-capacity adsorbent for treating MB and CV dyes in water solutions.

Electrolytic synthesis of γ-Al2O3 nanoparticle from aluminum scrap for enhanced methylene blue adsorption: experimental and RSM modeling

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.

Valorization of toxic methylene blue dye adsorption by sodium alginate/carboxymethyl cellulose/activated carbon ternary composites

In the present study, the performance of the sodium alginate/carboxymethyl cellulose/activated carbon (SA/CMC/AC) ternary composite microbeads containing different weight ratios of AC for the adsorptive removal of hazardous methylene blue (MB) from aqueous solutions. Firstly, the composite beads were prepared by adding AC with weight ratios of 10%, 20%, and 30% concerning the polymer amount. Then the composite beads were prepared by crosslinking in 2 wt. % CaCl2 solution. Initially, adsorption studies were carried out to determine the optimum properties, and the highest performance was obtained at pH = 7 and 298 K by using the composite containing 30% AC. Adsorption data were applied to several isotherms, and the Langmuir isotherm was found to be the best isotherm model for adsorption. The highest adsorption capacity was calculated as 308.6 mg/g at 298 K using this isotherm. Studies on adsorption kinetics revealed that the process followed a quasi-second-order kinetic model. FTIR-ATR analyses showed the interactions between dye molecules and the adsorbent and also indicated that the hydroxyl and carboxyl groups functioned as active adsorption sites. Furthermore, SEM analyses proved the presence of the dye particles on the surface of the adsorbent. This study demonstrated that the produced composite microbeads may be employed as a promising adsorbent for removing cationic contaminants from aqueous solutions.

Sulphonated date palm (Phoenix dactylifera) stone via microwave‑assisted H2SO4 activation: optimisation with desirability function for methylene blue adsorption

ABSTRACT In this work, a sulphonated date palm (Phoenix dactylifera) stone (SDPS) was produced as a cost-effective and renewable adsorbent for the removal of a cationic dye called methylene blue (MB). The production process involved the use of microwave irradiation combined with H2SO4 activation under the condition of 600 W microwave radiation for 15 min. The physicochemical characteristics of SDPS were evaluated using various analytical techniques, including XRD, BET, FTIR, pHpzc, and SEM. The Box-Behnken design (BBD) was employed to optimise key adsorption variables, including A: SDPS dosage (0.02–0.1 g/100 mL), B: pH (4–10), and C: contact time (5–25) min. According to the BBD model, the most effective removal of MB (98.4%) occurred with a dosage of 0.06 g/100 mL of SDPS, a pH of 10, and a contact time of 25 min. The rate of adsorption of the MB dye followed a pseudo second order (PSO) model, whereas the equilibrium adsorption was described by the Langmuir and Temkin models. The maximum adsorption capacity (q max ) of SDPS for MB dye was found to be 122.3 mg/g at 25°C. Several contributions to the MB dye adsorption process include electrostatic interactions, H-bonding, pore filling, and π-π stacking onto the SDPS adsorbent surface.

Immobilization of EPS-modified sodium alginate microcapsule by co-polymerization for methylene blue dye adsorption and kinetics

Exopolysaccharide (EPS) was extracted from Bacillus sp. and purified by ethanol precipitation method. This work mainly examines the dye removal efficiency of biopolymer beads (sodium alginate microcapsules) encapsulated with EPS extracted from Bacillus sp. Encapsulation of EPS-modified sodium alginate microcapsule was done by co-polymerization method. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the co-polymerization of sodium alginate and EPS in the microcapsule. The adsorption capacity of the microcapsule was found to be 0.58682 mg/mL which can be attributed to the larger surface area and increased surface sites in the microcapsule adsorbent. Increased dye removal efficiency of 83% was observed for the microcapsule with 50 mg/mL of EPS. The results of the methylene blue dye adsorption experiment show that the adsorption fitted into the Freundlich isotherm and followed pseudo-second-order reaction with correlation coefficients of 0.939 and 0.9673, respectively. The prepared sodium alginate biopolymer is biodegradable, and numerous studies have documented its biodegradability. Overall, these results evidenced that dye adsorption from textile effluent can be easily managed using the biodegradable polymer materials. Hence, this immobilization approach can be effectively used in textile dye removal process.

Synthesis of chitosan-graphene oxide (GO) composite using the sol-gel method and its application in the adsorption of methylene blue dye

Synthesis of chitosan-GO composites using the sol-gel method and its application to methylene blue adsorption has been carried out. This study aims to determine the ability of chitosan-GO composites to adsorb methylene blue. Chitosan-GO composites were made with mass ratios (1:1), (1:3), and (1:5) and characterized by XRD. Material with a ratio (1:1) was chosen to be characterized using BET, SEM-EDS, and used as methylene blue adsorption. Methylene blue adsorption process with several variables including contact time, concentration, and temperature of methylene blue dye. The results of the XRD characterization of the chitosan-GO composite (1:1), (1:3), and (1:5) showed a diffraction peak at an angle of 2θ, namely 25.1°; 26.29° and 19.54°. The surface area of the chitosan-GO composite (1:1) with BET was 145.3505 m2/g. Characterization using SEM showed that the chitosan-GO (1:1) composite had a porous structure and was not homogeneous. Optimum conditions for the adsorption of the chitosan-GO composite on methylene blue were obtained at 50 minutes contact time, concentration of 60 ppm, and at 50°C. The adsorption process of the chitosan-GO composite on methylene blue followed the Freundlich adsorption isotherm with an adsorption capacity of 2.47 mg/g.

Synthesis and characterisation of novel beta-cyclodextrin based Fe3O4 nanocomposite: adsorption behaviour and photocatalytic dye degradation studies

ABSTRACT Novel Beta-Cyclodextrin-based Fe3O4 nanocomposite has been synthesised through copolymerisation by incorporating Fe3O4 nanoparticles into the polymer matrix. Ultraviolet-Visible (UV-Visible) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric (TGA) analysis, Point of Zero Charge, X-ray diffraction (XRD), and Scanning electron microscopy (SEM) analysis have been used to characterise the Fe3O4 Nanoparticles and β-CDHs@Fe3O4 nanocomposite. The synthesised β-CDHs@Fe3O4 nanocomposite has been utilised for the adsorption of methylene blue (MB) dye from aqueous solutions. The maximum percentage removal of MB dye at optimum pH 7 and was found to be 98.51%. The adsorption capacity (qe) of β-CDHs@Fe3O4 nanocomposite has been found to be 268.09 mg/g at optimum dosages 1.2 g/L, pH 7, temperature 25°C, concentration 100 mg/L and an agitation speed of 200 rpm. Adsorption data have been fitted with three isotherm models namely Langmuir, Freundlich, and Temkin, and it was found to be the best fit with the Langmuir isotherm model. Kinetic studies like the pseudo-first order, pseudo-second order, and intra-particle diffusion model were also performed to study the adsorption mechanism. Further, thermodynamic studies demonstrate that the reaction was exothermic and spontaneous. Photocatalytic degradation of MB dye under visible light has also been studied, and 79.01% degradation of the dye was observed. Also, desorption of the nanocomposite was performed, and it was found to be reusable up to 5 times with 90% dye-desorption in the fifth cycle.

Nanoarchitectonics of hydrothermal carbonized sugarcane juice-derived biochar for high supercapacitance and dye adsorption performance

Here, we report the exfoliation of micron-sphere biochar to a few layers using the conventional KOH activation process. Micron-sphere biochar is obtained from hydrothermal carbonization (HTC) of sugarcane juice (Saccharum officinarum). HR-TEM and Raman spectroscopy studies revealed the conversion of micron-sphere biochar (MSB) to a few layers of biochar (FLB) in the activation process. BET characterization revealed FLB with a high surface area of 681.21 m2/g having mesopores. Consequently, an electrochemical study demonstrated excellent supercapacitor performance with a specific capacitance of 964.5 F/g and an energy density of 33.11 Wh/kg at a maximum power density of 936 W/kg. Batch adsorption studies showed rapid Methylene blue (MB) dye adsorption in 10 min. The equilibrium data analysis indicated the Langmuir adsorption isotherm with a correlation coefficient of 0.99. Evaluation of the kinetic models suggests that pseudo-second-order kinetics is the most appropriate model, implying that the adsorption of MB dye is primarily due to chemisorption. These findings suggest a Nanoarchitectonics of biochar into a few layers using traditional KOH activation, suitable for various applications.

Application of Optimization Response Surface for the Adsorption of Methylene Blue Dye onto Zinc-coated Activated Carbon.

The activated carbon was produced in the first phase of this investigation by chemically activating hazelnut shell waste with H3PO4. Composite materials were obtained by coating the activated carbon with zinc oxide, whose BET surface area was calculated as 1278 m2 g-1. ZnO-doped ZnO/AC composite was synthesized as an adsorbent for its possible application in the elimination of organic dyestuff MB, and its removal efficiency was investigated. Morphological properties of ZnO/AC were characterized using analytical methods such as XRD, SEM, and BET. The adsorption system and its parameters were investigated and modeled using the response surface method of batch adsorption experiments. The experimental design consisted of three levels of pH (3, 6.5, and 10), initial MB concentration (50, 100, and 150 mg L-1), dosage (0.1, 0.3, and 0.5 g 100 mL-1), and contact time (5, 50, and 95 min). The results from the RSM suggested that the MB removal efficiency was 98.7% under the optimum conditions of the experimental factors. The R2 value, which expresses the significance of the model, was determined as 99.05%. Adsorption studies showed that the equilibrium data fit well with the Langmuir isotherm model compared to Freundlich. The maximum adsorption capacity was calculated as 270.70 mg g-1.

Strong, tough, conductive and transparent nanocellulose hydrogel based on Ca2+-induced cross-linked double-networks and its adsorption of methylene blue dye

A novel multi-performance SHNC/SA/CaCl2 hydrogel with multi-performance was prepared via ultra-low-temperature freeze–thaw cycling and Ca2+ cross-linking for the removal of methylene blue (MB) from industrial wastewater. Various methods were used to characterize the structure and properties of hydrogel, and the internal structure of hydrogel showed a three-dimensional network with hydrogen and ester bonds. The SHNC/SA/CaCl2–15 hydrogel exhibited the highest tensile properties (elongation = 800 %), viscoelasticity (90 kPa), compressive strength (0.45 MPa), tensile strength (0.47 MPa) and ionic conductivity (4.34 S/cm). The maximum adsorption capacity of 2 g SHNC/SA/CaCl2–15 hydrogel was 608.49 mg/g at 40 °C, pH = 8 and adsorption 24 h. The adsorption process of hydrogel toward MB was more consistent with the second-order kinetic model and Langmuir isothermal adsorption model. According to the Langmuir isotherm model, the maximum monolayer adsorption capacity of SHNC/SA/CaCl2–15 hydrogel toward MB can reach 613.88 mg/g. Finally, it was found that the removal rate of SHNC/SA/CaCl2–15 hydrogel for MB was still as high as 90 % after five cycles of the adsorption–desorption test, and it could be reused. The hydrogel can be used as cheap and reusable adsorption material for cationic dyes. Our study provides a new perspective for the development of multifunctional cellulose hydrogel adsorbent materials.

Vibrational, optical, and photocatalytic properties of ZnO/layered carbon nanocomposite synthesized by ball milling

ZnO/layered carbon nanocomposites with varied sizes of ZnO nanoparticles (NPs) were synthesized by mechanical milling of mixture of ZnO NPs and carbon NPs. The NP size of ZnO was controlled with average particle sizes about 19.33, 21.87, 24.21, and 27.89 nm by varying the concentrations of carbon NPs viz 0, 2, 5, and 10 weight percent, respectively, in the mixture. Presence of carbon with ZnO in the form of composite also resulted in the enhanced shift of the band gap of ZnO due to the optical transitions in the impurity states or presence of carbon as compared to the ZnO size change alone. Additionally, the enhancement of absorbance in the visible region with an increase in carbon content was observed. Such an increase in absorbance can enhance the photocatalytic activity of ZnO NPs. Raman bands for ZnO NPs also were found to shift faster in the presence of layered carbon. The quenching of visible photoluminescence emission of ZnO NPs with an increase in concentration of carbon NPs in the composite indicated the phenomenon associated with transfer of electrons from ZnO to layered carbon helping the separation of photo-generated electrons and holes in ZnO and can lead to enhancement of the photocatalytic activity of ZnO NPs. In the photocatalytic studies, it was observed that the degradation of methylene blue (MB) dye was significantly enhanced by the increase of content of layered carbon in the nanocomposite. The sample containing 10% carbon showed the highest adsorption in dark conditions which was up to 60% of the starting strength and this was further enhanced to 88% in the presence of UV radiation. Enhanced adsorption of MB dye and the effective separation of electron–hole pairs due to charge transfer were believed to be the main causes behind such kind of improvement in the photocatalytic effects.