Porous graphene oxide-based carbon artefact with high capacity for methylene blue adsorption

A three-dimensional porous graphene oxide (PGO) material prepared by hydrothermal method was selected to adsorb methylene blue (MB), which demonstrates a high MB adsorption capacity, up to 1100 mg g^?1 in alkaline solution at room temperature. The influences of different pore structures and different contents of oxygen-containing functional groups on MB adsorption behaviors were studied in detail, which indicated that the high MB adsorption capacity is mainly ascribed to the synergistic effect of the large number of oxygen-containing functional groups and the interconnected 3D porous network. Moreover, based on the investigation on the adsorption kinetics and the effect of pH value on MB adsorption, we propose a two-step adsorption kinetics for PGO, which involved in two interactions between MB molecular and porous graphene oxide-based carbon: electrostatic force and π-π stacking. Besides, the calculation of the activation energies indicates that chemisorption dominates the adsorption for PGO in comparison with physisorption for three-dimensional porous graphene materials which has low adsorption capacity because of the removal of functional groups. The results are of great significance for the design and environmental applications of PGO as a promising adsorbent material for water purification.     

Super-assembled highly compressible and flexible cellulose aerogels for methylene blue removal from water

Physical adsorption is a common method to solve the contamination of methylene blue in dyeing wastewater. As a kind of adsorption material, cellulose aerogels with high porosity and surface areas have great potential application in methylene blue removal. However, the week hydrogen bonding between cellulose nanofibers making the cellulose aerogels with the poor mechanical properties and can be easily destroyed during adsorption. Hence, the preparation of cellulose aerogels with high mechanical strength is still a great challenge. Here, we report a robust super-assembly strategy to fabricate cellulose aerogels by combining cellulose nanofibers with PVA and M-K10. The resulting cellulose aerogels not only has a robust chemically cross-linked network, but also has strong H-bonds, which greatly enhance the mechanical properties. The resulting cellulose aerogels possess a low density of 19.32 mg/cm3.Furthermore, the cellulose aerogel shows 93% shape recovery under 60% strain(9.5 k Pa under 60% strain)after 100 cycles, showing excellent mechanical property. The adsorption capacity of cellulose aerogel to methylene blue solution of 20 mg/L is 2.28 mg/g and the adsorption kinetics and adsorption isotherms have also been studied. Pseudo-second-order kinetic model and Freundlich isotherm model are more acceptable for indicating the adsorption process of methylene blue on the cellulose aerogel. Thus, this compressible and durable cellulose aerogel is a very prospective material for dyeing wastewater cleanup.     

Facile synthesis of magnetic hybrid metal–organic frameworks with high adsorption capacity for methylene blue

A magnetic hybrid material (Fe₃O₄‐COOH/HKUST‐1) was easily synthesized via a two‐step simple solvothermal method. Through adding sodium acrylate directly into the synthesis of Fe₃O₄ spheres, the surface has more carboxyl groups. It is notable that the reactions proceed without use of organic surfactants. The magnetic hybrid material was characterized using various techniques. The magnetic hybrid material has a high specific surface area (430.15 m² g⁻¹) and excellent magnetism (23.65 emu g⁻¹). It is an efficient adsorbent for removing organic dyes like methylene blue (MB) from aqueous solution. It also can be easily recovered from liquid media using an external magnetic field. Adsorption experiment shows the magnetic hybrid material possesses a high adsorption capacity (118.6 mg g⁻¹), and has high adsorption efficiency (94.3%) after five adsorption cycles with ethanol (0.2% HCl) as eluent. The sorption kinetics and isotherm analysis indicate these sorption processes are better fitted to the pseudo‐second‐order and Langmuir equations. Thermodynamic study shows the sorption processes are spontaneous and endothermic.     

Functionalization effect of Fe-type MOF for methylene blue adsorption

Water pollutant such as dyes had danger the water quality. Todays, porous materials are great potential for dye adsorption from water bodies. In this study, the iron-based metal–organic framework (MOF-Fe) of MIL-101 is synthesized through a facile solvothermal method. The amine-functionalization effect of the MOF-Fe (amine-MOF-Fe) is evaluated for the adsorptive removal of methylene blue (MB) from aqueous solution. The adsorption behaviour had shown a rapid MB adsorption within the first hour of the process due to the pore-filling mechanism of the porous MOF-Fe structure. The electrostatic interaction between the amino group of amine-MOF-Fe and MB had contributed to the high adsorption capacity. The amine-functionalization effect also found the amine-MOF-Fe is having two times higher adsorption capacity when used with the loading two times lower than non-functionalized MOF-Fe. The maximum equilibrium adsorption capacities were measured at 149.25 and 312.5 mg/g with optimum MOFs loading of 0.8 and 0.4 g/L for MOF-Fe and amine-MOF-Fe, respectively. The adsorption mechanism proposed includes the electrostatic interaction, pore filling, hydrogen bonding, and π–π stacking. The regeneration study showed the MOFs could be recycled without interfering with the removal efficiency. Hence, the results indicate that the MOFs had desirable reusability for the practical adsorption of cationic dyes with its features of fast adsorption and high capacity.     

Amino modified mesostructured silica nanoparticles for efficient adsorption of methylene blue

In this work, mesostructured silica nanoparticles (MSN(AP)) with high adsorptivity were prepared by a modification with 3-aminopropyl triethoxysilane (APTES) as a pore expander. The performance of the MSN(AP) was tested by the adsorption of MB in a batch system under varying pH (2-11), adsorbent dosage (0.1-0.5gL(-1)), and initial MB concentration (5-60mgL(-1)). The best conditions were achieved at pH 7 when using 0.1gL(-1) MSN(AP) and 60mgL(-1)MB to give a maximum monolayer adsorption capacity of 500.1mgg(-1) at 303K. The equilibrium data were evaluated using the Langmuir, Freundlich, Temkin, and Harkins-Jura isotherms and fit well to the Freundlich isotherm model. The adsorption kinetics was best described by the pseudo-second order model. The results indicate the potential for a new use of mesostructured materials as an effective adsorbent for MB.     

Novel alkylimidazolium/vanadium pentoxide intercalation compounds with excellent adsorption performance for methylene blue

Novel alkylimidazolium-intercalated V₂O₅ compounds were synthesized by a redox reaction between iodide ion and V₂O₅. The X-ray photoelectron spectroscopy and the diffuse reflectance UV-vis spectrometry experiments reveal that the vanadium in the intercalated V₂O₅ products was partially reduced by an iodide ion and the resultant iodine can be removed in the final products. The transmission electron microscope observation and X-ray diffraction analysis testify that the prepared alkylimidazolium/V₂O₅ intercalation compounds have typical lamellar structure with different d₁₀₀ interlayer spacing values and the special straw-like nanofiber morphology with the length of 0.5-10 μm. Systematic investigation indicates that new intercalation compounds possess the extraordinary adsorption performance for methylene blue in an aqueous solution.     

Heterogeneous photocatalysis of methylene blue over titanate nanotubes: effect of adsorption

Titanate nanotubes were synthesized with hydrothermal reaction using TiO(2) and NaOH as the precursors and subsequent calcination at 400°C for 2h. The products were characterized with SEM and XRD. Adsorption and photocatalysis of methylene blue over titanate nanotubes and TiO(2) were investigated. The results indicated that titanate nanotubes exhibited a better photocatalytic degradation of methylene blue in a simultaneous adsorption and photodegradation system than that in equilibrium adsorption followed by a photodegradation system, whereas TiO(2) showed no significant differences in photocatalytic activity in the two systems. The methylene blue overall removal efficiency over TNTs in the first system even exceeded that over TiO(2). The different catalytic performances of titanate nanotubes in the two systems were tentatively attributed to different effects of adsorption of methylene blue, i.e., the promoting effect in the former and the inhibition effect in the latter. Decantation experiments showed that the titanate nanotube photocatalyst could be easily separated from the reaction medium by sedimentation. Thus titanate nanotubes with high sedimentation rates and concurrent adsorption represent a new catalyst system with a strong potential for commercial applications.     

Comparative study for the removal of methylene blue via adsorption and photocatalytic degradation

Physically and chemically activated carbons were prepared from date pits and olive stones. Titania and WO(x)-TiO(2)/MCM-41 were prepared as photoactive catalysts. Surface characterizations were investigated from ash content, pH, base neutralization capacities and FT-IR techniques. The textural characteristics, namely specific surface area (S(BET)) and pore texture, were determined from low temperature adsorption of N(2) at 77 K. The decolorization of aqueous solution of methylene blue was performed by means of two alternative methods. Steam-activated carbons own higher surface area compared with ZnCl(2)-activated carbons, and the micropore surface area represents the major contribution of the total area. Steam-activated carbons were the most efficient decolorizing adsorbents owing to its higher surface area, total pore volume and the basic nature of the surface. The calculated values of DeltaG(0), DeltaH(0) and DeltaS(0) indicate the spontaneous behavior of adsorption. The photocatalytic degradation is more convenient method in decolorizing of methylene blue compared with the adsorption process onto activated carbons.     

Ionic polyacrylamide hydrogel improved by graphene oxide for efficient adsorption of methylene blue

Research on Chemical Intermediates - The ionic polyacrylamide/graphene oxide (PAM/GO) hydrogel as an excellent methylene blue (MB) adsorbent was prepared by an improved one-step radical...     

Wavelet method to film-pore diffusion model for methylene blue adsorption onto plant leaf powders

In this paper, we have developed an accurate and efficient Haar wavelet method to solve film-pore diffusion model. Film-pore diffusion model is widely used to determine study the kinetics of adsorption systems. To the best of our knowledge, until now rigorous wavelet solution has been not reported for solving film-pore diffusion model. The use of Haar wavelets is found to be accurate, simple, fast, flexible, convenient, and computationally attractive. The power of the manageable method is confirmed. It is shown that film-pore diffusion model satisfactorily describes the kinetics of methylene blue adsorption onto three low-cost adsorbents, Gauva, teak and gulmohar plant leaf powders, used in this study.     

Localized hydrogels based on cellulose nanofibers and wood pulp for rapid removal of methylene blue

Access to clean water has become increasingly difficult, motivating the need for materials that can efficiently remove pollutants. Hydrogels have been explored for remediation, but they often require long times to reach high levels of adsorption. To overcome this limitation, we developed a rapid, locally formed hydrogel that adsorbs dye during gelation. These hydrogels are derived from cellulose—a renewable, nontoxic, and biodegradable resource. More specifically, we found that sulfated cellulose nanofibers or sulfated wood pulps, when mixed with a water-soluble, cationic cellulose derivative, efficiently remove methylene blue (a cationic dye) within seconds. The maximum adsorption capacity was found to be 340 ± 40 mg methylene blue/g cellulose. As such, these localized hydrogels (and structural analogues) may be useful for remediating other pollutants.     

Carbon black: a promising electrode material for sodium-ion batteries

The reactions of sodium with non-porous carbon blacks have been studied. These materials show a high reversible capacity in sodium-ion batteries. The presence of disordered layers and the low density of the carbon black materials favor the reversibility of the process. A maximum amount of 0.0155 mole of sodium by cm³ of carbon is achieved. The performance of a sodium-ion cell using Na_0.7CoO₂ as the positive electrode and carbon black as the negative is described.     

Mussel-inspired polydopamine functionalized recyclable coconut shell derived carbon nanocomposites for efficient adsorption of methylene blue

Relatively cheap or at no cost, easily available, renewable agricultural waste has been given a new purpose. Using coconut shells as the raw material, and being obtained from agricultural, industry by-products, or even waste materials were used as carbon resource. Acid etching coconut shells carbon (AC) rendered micro/nanoscale hierarchical structures and made the surface available for further modification. Then, the surface of acidified coconut shell carbon was engineered via mussel inspired chemistry. The polydopamine functionalized AC composites (AC-PDA) were applied for efficient removal of methylene blue (MB) dye. Further, the surface morphology, and chemical structure were evaluated by means of scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). Through the combination of acid etching and mussel inspired chemistry, organic functional groups can be successfully introduced onto the surface of the coconut shells carbon. The improvement of adsorption capacity of AC-PDA compared with AC is probably due to the increased number of active binding sites resulting from surface modification and formation of new functional groups.     

Synthesis,characterization of palygorskite supported zero-valent iron and its application for methylene blue adsorption

In this work, natural palygorskite impregnated with zero-valent iron (ZVI) was prepared and characterized. The combination of ZVI particles on surface of fibrous palygorskite can help to overcome the disadvantage of ultra-fine powders which may have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. There is a significant increase of methylene blue (MB) decolourized efficiency on acid treated palygorskite with ZVI grafted, within 5 min, the concentration of MB in the solution was decreased from 94 mg/L to around 20 mg/L and the equilibration was reached at about 30–60 min with only around 10 mg/L MB remained in solution. Changes in the surface and structure of prepared materials were characterized using X-ray diffraction (XRD), infrared (IR) spectroscopy, surface analysing and scanning electron microscopy (SEM) with element analysis and mapping. Comparing with zero-valent iron and palygorskite, the presence of zero-valent iron reactive species on the palygorskite surface strongly increases the decolourization capacity for methylene blue, and it is significant for providing novel modified clay catalyst materials for the removal of organic contaminants from waste water.     

A new decavanadate polyoxovanadate nanocluster: synthesis,characterization and rapid adsorption of methylene blue

A new decavanadate polyoxovanadate nanocluster, [2-ampH]₆[V₁₀O₂₈]?2H₂O (1), was synthesized through reaction between ammonium vanadate and 2-aminopyridine at pH = 2. Nanocluster 1 was characterized by IR, elemental analysis, and X-ray crystallography. 1 was found to adsorb and desorb dyes and may have widespread application in wastewater treatment. The utility of 1 for adsorption of methylene blue was studied. The adsorbed dyes can be easily desorbed, and 1 has full efficiency after five cycles.     

Radiation-induced grafting of cellulose for adsorption of hazardous water pollutants: A review

This review paper briefly introduces the radiation chemistry of cellulose, the different grafting techniques used, and the methods of characterization of the grafted material. It shows the application of the grafted polymer for the removal of water pollutants and also the regeneration of the adsorbent.     

Determination of adsorptive properties of clay/water system: methylene blue sorption

In this study, adsorption of methylene blue onto clay was investigated. The effect of adsorption time and temperature on the adsorption process was studied. To reveal the adsorptive characteristics of the clay studied, porosity and BET surface area measurements were made. It was observed that the adsorption capacity decreases with increasing temperature, and adsorption equilibrium was attained within 1 h. It was found that the data fit well to Langmuir, Halsey, Henderson, and Harkins-Jura models but experimental data deviate significantly from BET and Freundlich models at especially high concentrations. Furthermore, isosteric adsorption enthalpy and entropy are calculated as -7.99 kJ mol(-1) and 25.41 JK(-1)mol(-1), respectively.     

Chemical modification of a cellulose-based material to improve its adsorption capacity for anionic dyes

A cellulosic material was modified to enhance its anionic dye adsorption capacity. The chemically modified cucumber peel was characterized by FTIR, SEM, TGA, XRD, proximate and ultimate analyses, and pH_zpc measurements, and was used for the removal of toxic textile dyes. The kinetic data followed the pseudo-first-order model. The isotherm data fitted to the Langmuir model giving maximum capacities of 95.24 and 129.87 mg g^?1 for Reactive Black 5 and Direct Blue 71, respectively. Thermodynamic parameters suggest that the process is spontaneous and endothermic. The recovery of the adsorbed dyes was achieved by NH₃ and NaOH solutions.