Methylene Blue Adsorption Process Research Articles

Methylene Blue Adsorption Using Boric Acid Functionalized Activated Carbon: Kinetics, Isothermal, and Thermodynamic Studies

AbstractIn this study, the activated carbon (AC) was prepared from Sesbania sesban plant stem. Boric acid (H3BO3) was used as an activating agent. During calcination, the optimized temperature was kept upto 500 °C for 2 h. The prepared adsorbents were characterized using various techniques such as FT‐IR, scanning electron microscopy, energy dispersive x‐ray spectroscopy, and thermogravimetric analyzer. The prepared adsorbents were used for the removal of methylene blue (MB) dye adsorption. The adsorption experiments were conducted at different pHs such as (2–11), doses (0.0025–0.020 mg), times (30–300 min), MB initial concentrations (100–600 mg L−1), and temperatures (298–318 K), respectively. The maximum MB uptake capacity of the prepared adsorbent was 1380 mg g−1 under optimized adsorption conditions. Furthermore, the kinetic study is well described by pseudo‐second order, whereas the isothermal study showed the Freundlich isotherm was better followed by the equilibrium data. Based on thermodynamic studies, the negative values of ΔG° and ΔH° revealed that the MB adsorption process is spontaneous and exothermic in nature. However, the negative ∆Sxg° value indicates that solid‐solute interaction decreased randomness in the adsorption systems. The overall studies of AC showed that it was better to remove MB from an aqueous solution.

Effective adsorptive removal of heavy metal anion Cr(Ⅵ) and dye cation methylene blue by the novel 2D material TiVCTx MXene

With the increasingly serious industrial pollution, the effective removal of heavy metal ions and organic pollutants from wastewater has become a key issue of environmental protection. In this paper, a new MXene material, TiVCTx, was prepared by in situ etching, and its adsorption capacity of heavy metal anion Cr(Ⅵ) and methylene blue (MB) dye cation was studied. The effect of adsorption time, pH values, temperatures, initial concentrations of adsorbent and adsorbate, interfering ions on the Cr(Ⅵ) and MB adsorption of TiVCTx was systematically investigated. It is found that TiVCTx has excellent Cr(Ⅵ) and MB adsorption property, the adsorption capacity can be as high as 600mg/g and 1430mg/g, respectively. The adsorption experiments revealed that the adsorption process of Cr(Ⅵ) conformed to the Langmuir isotherm model and the Pseudo-second-order kinetic model, which indicated that the Cr(Ⅵ) adsorption was a heat-absorbing monolayer chemisorption. In contrast, the adsorption process of MB is in accordance with the Freundlich isotherm model and the Pseudo-second-order kinetic model, suggesting that the MB adsorption was an exothermic multilayer chemisorption. The results of X-ray electron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis further confirmed that the reductive adsorption and electrostatic adsorption can account for the outstanding Cr(VI) and MB adsorption capacity of TiVCTx, respectively.

A sustainable lignin-clay nano-absorbent for highly efficient methylene blue removal

Water pollution caused by toxic dyes such as methylene blue (MB) has become a bottleneck for recycling or reusing enormous industrial wastewater. Designing a green and cost-effective bio-absorbent for the highly efficient removal of MB from wastewater is crucial but remains a great challenge. In this study, abundant, inexpensive, and environmentally benign lignin and bentonite were used as starting materials, and quaternary and amphiphilic lignin as a network macromolecule was designed to be inserted into the galleries of the stacked bentonite clay to prepare lignin-bentonite nanohybrids. The specific surface area of the modified nano-absorbent was significantly increased to 45.60 m2/g and owned a type II-like isothermal mechanism. The absorbent showed a maximum removal of MB of 99.7 % at neutral pH and room temperature with a maximum adsorption capacity of 822.22 mg/g, demonstrating the potential of an excellent adsorbent. The MB adsorption process fits well with both Langmuir and Freundlich isotherm models, the adsorption mechanism includes strong electrostatic attraction between absorbent and MB, and physical adsorption in a complicated monolayer and multiple macroporous structures. This study leverages the economic and environmental benefits of lignin and bentonite clay to prepare a cost-effective bio-absorbent for efficient removal of MB from aqueous solutions.

Artificial Neural Network Modeling of the Removal of Methylene Blue Dye Using Magnetic Clays: An Environmentally Friendly Approach

In this study, the effectiveness of Fe3O4-based clay as a cost-effective material for removing methylene blue (MB) dye from aqueous solutions was evaluated. The structural properties of the clay and Fe3O4-based clay were analyzed using SEM, XRF, BET, XRD, FTIR, and TGA techniques. In this research, the effects of various aspects, such as adsorbent amount, contact time, solution pH, adsorption temperature, and initial dye concentration, on the adsorption of Fe3O4-based clay are investigated. The experiments aimed at understanding the adsorption mechanism of Fe3O4-based clay have shown that the adsorption kinetics are accurately described by the pseudo-second order kinetic model, while the equilibrium data are well represented by the Langmuir isotherm model. The maximum adsorption capacity (qm) was calculated as 52.63 mg/g at 25 °C, 53.48 mg/g at 30 °C, and 54.64 mg/g at 35 °C. All variables affecting the MB adsorption process were systematically optimized in a controlled experimental framework. The effectiveness of the artificial neural network (ANN) model was refined by modifying variables such as the quantity of neurons in the latent layer, the number of inputs, and the learning rate. The model’s accuracy was assessed using the mean absolute percentage error (MAPE) for the removal and adsorption percentage output parameters. The coefficient of determination (R2) values for the dyestuff training, validation, and test sets were found to be 99.40%, 92.25%, and 96.30%, respectively. The ANN model demonstrated a mean squared error (MSE) of 0.614565 for the training data. For the validation dataset, the model recorded MSE values of 0.99406 for the training data, 0.92255 for the validation set, and 0.96302 for the test data. In conclusion, the examined Fe3O4-based clays offer potential as effective and cost-efficient adsorbents for purifying water containing MB dye in various industrial settings.

Adsorption Behavior of Methylene Blue Onto Activated Coconut Shells: Kinetic, Thermodynamic, Mechanism and Regeneration of the Adsorbent.

Adsorption techniques are widely used to remove some classes of pollutants from waters, especially those which are not easily biodegradable. The removal of Methylene blue (MB), as a pollutant, from waste waters of textile, paper, printing and other industries has been addressed by the researchers. The aim of this study is to eliminate MB by Activated Coconut Shells (ACS) produced at low cost by adsorption in batch mode. The ACS was characterized by the FTIR spectroscopy and point of zero charge (pHpzc: 5.06). Some examined factors were found to have significant impacts on the MB uptake of ACS like the initial dye concentration Co (40-120mg/L), solution pH (2-8), ACS dose (1-12g/L), agitation speed (50-500 r/min), particles size (1.0-1.2mm) and temperature (298-333K). The best capacity was found at pH 6 with an adsorbent dose 8g/L, an agitation speed 200 r/min and a contact time of 60 min. Modeling Kinetics and Isotherms shows that the pseudo-second-order kinetic model with R 2 (0.935 -0.998) and Langmuir adsorption isotherm model provide better fitness to the experimental data with the maximum adsorption capacity of 30.30mg/g at 25°C. The separation factor RL (0.933-0.541) in the concentration range studied (10-120mg/L) shows a favorable adsorption. The isotherms at different temperatures have been used for the determination of the free energy ΔG° (198-9.72kJ/mol); enthalpy ΔH° (82.082kJ/mol) and entropy ΔSo (245.689J/K mol) to predict the nature of MB adsorption process. The positive values of (ΔGo) and (ΔHo) indicate a non-spontaneous and endothermic MB adsorption with a chemisorption. The adsorbent elaborated from Coconut Shells was found to efficient and suitable for the removal of MB dye from aqueous solutions, due to its availability, low cost preparation and good uptake capacity.

Ternary‐Grafted Starch‐Based Hydrogel with Improved Adsorption Capacity for Dyes

AbstractBiomass‐based hydrogels can be used as the adsorbents in sewage water, as they have good adsorption capacity for heavy ions and dyes. A ternary‐grafted starch‐based hydrogel, St1.0/CMC0.5/P(AM3.0‐AA5.0‐AMPS1.0), was prepared using cornstarch (St) and sodium carboxymethyl cellulose (CMC) as raw materials, with acrylamide (AM), acrylic acid (AA), and 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) as graft monomers. Due to the introduction of CMC and AMPS, the number and type of effective adsorption functional groups in the St1.0/CMC0.5/P(AM3.0‐AA5.0‐AMPS1.0) hydrogel increased, leading to an improved adsorption capacity and removal rate for methylene blue (MB). The maximum adsorption capacity and removal rate for MB could be 1624.49 mg/g and 91.8 %, respectively, at 25 °C. According to the adsorption isotherm and adsorption kinetics, the MB adsorption process on the hydrogel occurs according to the Langmuir isotherm model and quasi‐second‐order kinetics via a chemisorption process occurring on the adsorbent monolayer. Moreover, the St1.0/CMC0.5/P(AM3.0‐AA5.0‐AMPS1.0) hydrogel displayed good regeneration performance. The removal rate for MB could still achieve 84.3 % after the hydrogel was reused four times.

Application of sewage sludge derived hydrochar as an adsorbent for removal of methylene blue

Hydrothermal pretreatment (HTP) is used to convert biomass into hydrochar (HC) through the application of heat and pressure in a water-based medium. The HC has emerged as a promising material for various environmental applications including wastewater treatment, soil amendment, and carbon sequestration. In this study, the applicability of sewage sludge (SS) derived HC was tested as an adsorbent for methylene blue (MB) dye removal from wastewater. The HC was also subjected to chemical activation with KOH before the adsorption study. The HC samples were characterized for structural morphology and molecular functionalities using instrumental analysis. All the HC samples exhibited almost similar adsorption capacity (∼190 mg/g) for MB after 24 h of contact time (MB concentration = 200 mg/L, solution pH = 7 and adsorbent dose = 1 g/L). The equilibrium data could be adequately fit in Langmuir model equation. The negative value of free energy indicated favorable MB adsorption process. The study demonstrated that the SS derived HC can be recycled as adsorbent in wastewater treatment plant which is not only an environment-friendly approach but also may reduce cost of tertiary treatment at sewage treatment plant often required to remove emerging contaminants.

Novel Efficient and Eco‐Friendly Biosorbent Derived from Ditax (Detarium senegalense) Fruit Hulls for Removal of Cationic Dyes: Adsorption Modeling and Statistical Optimization

AbstractRemediation of wastewater laden with dyes using optimized and less expensive techniques remains a challenge for environmental protection. In the current research work, alkaline activation approach was employed to derive a biosorbent from ditax fruit hulls (DS‐FHB), and its sorption performance was tested on Methylene blue (MB) dye biosorption with optimizing adsorption parameters. Structural and chemical properties of DS‐FHB including crystallinity, morphology, and surface functionality were analysed using XRD, SEM, FTIR technics, and pHPZC determination. Optimization of adsorption parameters using a centered composite design (CCD) from response surface methodology led to achieving a peak dye removal rate of 98.97 %. The optimal conditions were determined as DS‐FHB mass of 0.23 g, pH 7.12, contact time 39.00 min, and initial MB concentration of 69.35 mg/L. The findings demonstrated a strong alignment with both the Langmuir isotherm and pseudo‐second order kinetic model, suggesting their appropriateness in describing the adsorption process of MB onto DS‐FHB. According to the Langmuir isotherm model, the sorption of MB dye onto DS‐FHB occurred by monolayer formation with a maximum dye sorption capacity of 96.453 mg/g. Based on the structural and physico‐chemical properties of DS‐FHB biosorbent, and its adsoption applicability evaluated in the experimental conditions, detax derived‐biosorbent can be proposed as a successful and effective low‐cost biosorbent for removing cationic dyestuffs from aqueous solutions.

Silica Gel From Bagasse Ash for Methylene Blue Adsorption

Most silica sources are from non-renewable natural sand or rock materials, which affect the element's diminishing availability in the environment. Because bagasse ash has a relatively high silica concentration, it can be used as a silica source to manufacture silica gel. HCl is added during the sol-gel process of silica gel synthesis. The silica gel's characterization employs FTIR, XRD, and SEM instruments. Characterization results showed that silica gel contains silanol groups identified by the appearance of vibrations at the wavenumber of 3383,93 cm-1 and 1635,17 cm-1. Vibrations of the siloxane group appear at the wavenumber of 1020,83 cm-1 and 579,88 cm-1. Silica gel diffractogram showing dilated diffraction peaks at 2q = 22,90ᵒ. Silica gel has potential as an adsorbent in adsorbing methylene blue dye. The ideal parameters for the methylene blue adsorption process are pH 10 and 45 minutes of contact time., silica gel weight of 0.1 g, and methylene blue concentration of 100 mg/L. Using the Langmuir isotherm rule, the silica gel of bagasse ash has a high adsorption capacity of 56.818 mg/g.

Methylene blue removal using nano-TiO2/MWCNT/Chitosan hydrogel composite beads in aqueous medium

Dyestuff, one of the most hazardous compounds in terms of threats to people and the environment, is found in wastewater from industrial usage. The removal of Methylene Blue (MB) from a water-based medium has been studied by numerous researchers using a variety of adsorbents. To remove MB from aqueous solution, nano-TiO2/MWCNT/Chitosan hydrogel composite beads (n-TiO2/MWCNT/Cht) were developed in this study using a sol-gel method. This research discusses the characterisation of a new adsorbent substance using Infrared Spectroscopy (FT-IR) analysis and scanning electron microscopy (SEM). The optimal pH, adsorbent dosage, duration, and starting concentration were ascertained by analyzing the removal efficiencies of MB using the batch adsorption method. Adsorption behaviour at the equilibrium state has been investigated using a variety of adsorption isotherms, including Freundlich, Langmuir, and Dubinin-Radushkevich. The Langmuir adsorption isotherm has been useful to clarify adsorption behaviors. nTiO2-Cht/MWCNT had an adsorption capacity of 80.65 mg/g for MB. The pseudo-second-order kinetic model offered the best agreement to the experimental data for the adsorption of MB. Kinetic models of pseudo-first-order and pseudo-second-order were employed to explore the adsorption processes of MB on the n-TiO2/MWCNT/Cht. This study demonstrated the efficiency of n-TiO2/MWCNT/Cht for the removal of MB from a water-based solution.

Production of Low-Cost Adsorbents within a Circular Economy Approach: Use of Spruce Sawdust Pretreated with Desalination Brine to Adsorb Methylene Blue.

A sustainable low-cost activated carbon substitute was produced based on pretreated lignocellulosic biomass, especially spruce sawdust. A harmful liquid waste, desalination brine, was used for the treatment of a solid wood industry waste, spruce sawdust. This approach is in the circular economy theory and aims at the decarbonization of the economy. Pretreated sawdust was tested as an adsorbent appropriate for the removal of a commonly used pollutant, methylene blue, from industrial wastewater. The adsorption capacity of the pretreated material was found to have increased four times compared to the untreated one in the case that the Freundlich equation was fitted to the isotherms' data, i.e., the one with the best fit to the isotherm's experimental data of the three isotherm models used herein. The treatment experimental conditions with desalination brine that gave maximum adsorption capacity correspond to a 1.97 combined severity factor in logarithmic form value. Moreover, a kinetic experiment was carried out with regard to the methylene blue adsorption process. The desalination brine-pretreated sawdust adsorption capacity increased approximately two times compared to the untreated one, in the case when the second-order kinetic equation was used, which had the best fit of the kinetic data of the three kinetic models used herein. In this case, the pretreatment experimental conditions that gave maximum adsorption capacity correspond to -1.049 combined severity factor in logarithmic form. Industrial scale applications can be based on the kinetic data findings, i.e., spruce sawdust optimal pretreatment conditions at 200 °C, for 25 min, with brine solution containing 98.12 g L-1 NaCl, as they are related to a much shorter adsorption period compared to the isotherm data.

Adsorption study of methylene blue dye using activated carbon prepared from waste palm fiber.

The study investigated the utilization of waste palm fiber as an adsorbent for methylene blue (MB) removal. The waste palm fiber was treated by a series of steps to prepare an activated charcoal adsorbent. The adsorption process of MB on the activated charcoal was modeled using the Box-Behnken design (BBD) in the response surface methodology (RSM). Adsorbent mass, solution pH, temperature, and time were selected as factors, while removal efficiency and adsorption capacity were chosen as responses. Both models were significant with correlation factors of 0.85 and 0.99 for removal efficiency and adsorption capacity, respectively. Optimal conditions for MB removal were achieved at an initial pH of 7, an adsorbent dose of 0.05 g/L, and a contact time of 30 min, resulting in a 99% removal efficiency. The adsorption of MB using the activated charcoal indicates the physical nature of the reaction.

Cellulose Acetate Supported MOF-5/Crystalline Nanocellulose Composite Film as an Adsorbent Material for Methylene Blue Removal from Aqueous Solutions.

In this study, a novel, low-cost, and efficient adsorbent film was fabricated by a solvothermal method. The adsorbent film was developed to be hydrolytically stable, not vulnerable to aggregation in aqueous environments, and not prone to secondary contamination. The adsorbent consists of cellulose acetate (CA) as a support embedded with a MOF-5/crystalline nanocellulose (CNC) composite material. The CA-supported MOF-5/CNC film was characterized using a variety of techniques, including X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, which revealed hydroxyl and carbonyl functional groups on the adsorbent film. The film was evaluated for the adsorptive removal of methylene blue (MB) from an aqueous solution. Adsorption was characterized by a rapid increase in MB adsorption during the first hour with equilibrium achieved within 4-5 h into the adsorption process. The maximum adsorption capacity was determined to be 4.29 mg/g and the maximum dye removal efficiency was 77%. The MB adsorption process best fitted the Freundlich isotherm and pseudo-second-order kinetic models. Thermodynamic studies showed that the adsorption was exothermic and feasible. The adsorbent film showed admirable regeneration ability, demonstrating its cost-effectiveness and its potential as a promising material for wastewater treatment.

Novel sulfonic groups grafted sugarcane bagasse biosorbent for efficient removal of cationic dyes from wastewater

In this research, we reported the synthesis of effective sulphonated sugarcane bagasse (SCB@SA) biosorbent based on agriculture waste materials via a simple diazotization strategy for the removal of methylene blue (MB) and Bismarck Brown R(BB) dyes from waste water samples. First, the sugarcane bagasse (SCB) waste was collected, grinded, and sieved to obtain the desired size. Secondly, the SCB powder is modified with sulfanilinic acid (SA) via the formation of its diazonium salt to introduce sulfonic groups on the SCB surface. Different advanced techniques were applied to characterize the prepared materials before and after the adsorption process viz. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS) and Thermogravimetric analysis (TGA). Different parameters affecting the adsorption process of both MB and BB were studied. Because of the higher correlation coefficient (R2 ≥ 0.999) and lower error functions, the equilibrium MB and BB adsorption isotherms for a single-dye system fit Langmuir with maximum adsorption capacity reaching to 127.48 and 166.75 mg/g for MB and BB, respectively. Moreover, the RL values obtained for both dyes lie between 0 and 1, indicating that MB and BB adsorption by SCB@SA is a favorable process. Besides, the error functions’ values of the pseudo-2nd-order are significantly lower than those of the pseudo-1st-order, implying that the adsorption MB and BB onto SCB@SA biosorbent fitted the pseudo-2nd-order kinetic model in a chemosorption manner. In the thermodynamic studies, the adsorption process is spontaneous, exothermic, and has less randomness. In addition, the SCB@SA biosorbent could be reused in five cycles maintaining on suitable adsorption efficiency. Finally, the MB and BB dyes could be adsorbed on the SCB@SA biosorbent via three mechanisms including π-π stacking, columbic attraction, and hydrogen bonding.

Steric and energetic investigations of adsorption isotherms of methylene blue on new polymeric multi-layered material-based k-carrageenan and alginate

In this research study, we examined the adsorption behavior of methylene blue (MB) on a novel biosorbent made of polyelectrolyte multilayers (PEM) biopolymeric material at three different temperatures. Various models derived from statistical physics formalism were employed to analyze the adsorption isotherms. An alternative approach based on the application of multilayer models from statistical physics theory was used to better investigate the adsorption mechanisms of MB on the PEM grafting material. We adjusted various parameters within this model across temperatures of 295K, 313 K, and333K, and these parameters played a crucial role in comprehending the adsorption mechanism. In addition, this approach revealed that the MB dye is linked through a multilayer process on the PEM grafting material with ‘non-parallel’ configurations and multimolecular process. The PEM grafting material showed maximum adsorption capacities ranging from 632.23 mg⁄g to 463.76 mg⁄g for the removal of MB over a pH of 6. The calculated adsorption energies ranged from 11.6 to 18.65kJ/mol, indicating that the MB adsorption process was primarily of a physisorption nature influenced by both hydrogen bonding and van der Waals interactions. Thus, the theoretical analysis indicated that this low-cost adsorbent material (PEM grafting) is a promising material for the removal of MB dye from the solution. Additionally, we examined the adsorption behavior by calculating the entropy, the free energy and the internal energy which govern the adsorption process of MB onto the PEM grafting material.

Effect of dissolution for black carbon on the adsorption capacity for methylene blue: Equilibrium, kinetics and thermodynamics

Black carbon was widely researched due to its significant role on the global carbon cycle and contaminant transport, and most people were concerned about the property of the dissolved black carbon from black carbon. In this work, we focused on the research of the residual those of black carbon. Two kinds of black carbon originated from peanut shell and bamboo were prepared and the corresponding residual black carbons were also obtained by the ultrasonic dissolution process. It was found the chemical and structure properties of residual black carbon changed a lot compared to black carbon. Using methylene blue as a target contaminant, the adsorption capacity of methylene blue by the residual black carbon was greater than that of black carbon. The adsorption capacity of black carbon-bamboo for methylene blue increased from 11.1 mg/g to 16 mg/g after the dissolution process, and the adsorption capacity of black carbon-peanut shell for methylene blue increased from 14 mg/g to 23 mg/g. The various influencing factors, such as the pH, initial concentration, temperature and adsorbent dosage, were systematically studied. The black carbons derived from peanut shell before and after the ultrasonic dissolution process both showed greater adsorption capacities for methylene blue. To further elucidate the methylene blue adsorption process, different kinds of isotherm and kinetics models were applied to simulate the experimental data. The results indicated that the Langmuir isotherm model was suitable to all the carbons before and after the ultrasonic dissolution process, and the pseudo-second-order model showed great simulation for the adsorption of methylene blue. In addition, the analysis of the thermodynamic study revealed that the adsorption processes of methylene blue were endothermic and spontaneous. Overall, results obtained from this work revealed the black carbon after been dissolved showed better adsorption capacity for contaminant.

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.

Preparation magnetic graphene oxide/diethylenetriamine composite for removal of methylene blue from aqueous solutions

Graphene oxide (GO) and its derivatives have several applications in many areas such as environmental and energy materials, water treatment and biomedical technologies. Because of having various polar groups on its surface, GO is considered as an excellent adsorbent. However, for many applications such as adsorption of pollution from aqueous solutions, chemical functionalization of graphene oxide is often a necessary requirement. In the present study, a new composite from graphene oxide, diethylenetriamine (DETA) and silica coated MnFe2O4 nanoparticles (GO/DETA/MnFe2O4@SiO2) was prepared. The structure, thermal stability and magnetic properties of the composite were studied by FT-IR, XRD, SEM, EDS, VSM and TGA spectroscopic methods. The prepared composite showed magnetic property with a saturation magnetization of 3.0 emu/g. The adsorption properties of GO/DETA/MnFe2O4@SiO2 composite for methylene blue (MB) in aqueous solution were studied using batch method. The effects of important parameters on the surface adsorption process of MB, including pH, contact time, adsorbent dosage and initial dye concentration were investigated. The adsorption isotherm was in accordance with Langmuir model showing surface homogeneity of the adsorbent. According to the Langmuir analysis, the maximum adsorption capacity (qm) of GO/DETA/MnFe2O4@SiO2 composite for MB was found to be 243.91 mg/g. The kinetic studies showed that the adsorption was pseudo first-order process. In addition, the thermodynamic studies indicated the adsorption was spontaneous and endothermic process.

Adsorption behaviors and mechanisms of porous polyvinyl alcohol/xanthan gum hydrogel for methylene blue and Pb2+

Faced with extensive water pollution caused by dyes and heavy metals, it is imperative to create cost-effective adsorbents that can effectively eliminate residual pollutants in wastewater. The synthesis of polyvinyl alcohol/xanthan gum (PVA/XG) hydrogels involved a combination of freeze-thaw cycling technique and the adsorption characteristics and mechanisms of methylene blue (MB) and heavy metal ions Pb2+ were investigated. In comparison to pure PVA hydrogels, the swelling behavior of PVA/XG3 hydrogel exhibited a 185 % increase in swelling rate. The adsorption test results suggested that PVA/XG3 hydrogel was effective in absorbing MB (27.39 mg/g) and Pb2+ (17.07 mg/g) from a 50 mg/L pollutant solution. The adsorption process of MB and Pb2+ by PVA/XG3 hydrogel followed Langmuir adsorption isotherm and the QFO models, indicating a preference for homogeneous physical adsorption. Specifically, the Langmuir isothermal model predicted that the qmax of MB and Pb2+ by PVA/XG3 hydrogel were 94.47 and 58.50 mg/g, respectively. Therefore, this essay has created a cost-effective and environmentally friendly method for producing versatile PVA/XG hydrogels specifically intended for water treatment purposes.

Effect of citric acid modification on the properties of hydrochar and pyrochar and their adsorption performance toward methylene blue: crucial roles of minerals and oxygen functional groups.

Modification is widely used to enhance the adsorption performance of pristine hydrochar (HBC) and pyrochar (BC). However, comparisons between modified HBC and BC toward pollutant removal have rarely been reported. In this study, pristine HBC and BC derived from rice straw were first produced, and then citric acid (CA) was used as a modifier to synthesize CA-modified HBC (CAHBC) and CA-modified BC (CABC). Furthermore, the adsorption performance of biochars toward methylene blue (MB) was investigated. The results showed that BC exhibits relatively rough surfaces and contains more minerals (ash), whereas HBC has plentiful O-containing functional groups and fewer minerals. CA modification partially removed minerals from the surface of BC, which weakened the ion exchange, surface complexation, and n-π interaction, resulting in a lower adsorption ability toward MB. By contrast, CA produced more O-containing functional groups on the surface of HBC, which strengthened the hydrogen bonding and electrostatic interaction, thus increasing the adsorption capacity toward MB. The two-compartment model showed a good fit to the adsorption process of MB on CAHBC, and the isotherm data for MB adsorption by HBC and CAHBC are suitable for the Freundlich model. The highest adsorption amount of MB using CAHBC was 80.13mg·g-1, which was 27.66% higher than that for CABC. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis indicated that the carboxyl groups in the surface functional groups of CAHBC played a crucial role in the MB adsorption process. In addition, CAHBC showed a good performance for a wide range of pH values (4.0-10.0) and under the interference of coexisting ions, and also presented a recycling ability. Furthermore, the adsorption of MB on CAHBC biochar was a spontaneous, exothermic, degree-of-randomness-increasing process. Consequently, CA modification of HBC is a promising strategy and could be used for MB removal from aquatic environments.