MB Solution Research Articles

Methylene Blue Adsorption Isotherm on Spirulina sp. Microalgae Biomass Coated by Silica-Magnetite

In this study, it has been performed modification of Spirulina sp. algae biomass with silica (HAS) coated with magnetite particles (HASM) and its adsorption test on a solution of methylene blue dye (MB) in solution. The identification of functional groups from HASM adsorbent was studied using infra-red (IR) spectrophotometer, the degree of crystallinity of the material was determined by X-ray diffraction (XRD), while the morphology and HASM constituent elements were analyzed by Scanning Electron Microscopy-Energy-Dispersive-X-Ray (SEM-EDX). The HASM adsorption isotherm of MB solution was studied by applying adsorption experiments using the batch method. The concentrations of MB dye in the adsorption process were analyzed by a UV-Vis spectrometer. Adsorption of 100 mg L−1 MB dye solution by HASM adsorbent at pH of 6 with a contact time of 60 minutes resulted in an adsorbed MB amount of 90.90 mg g−1. The adsorption isotherm model of the MB dye solution in the HASM adsorbent tends to follow the model of Freundlich adsorption isotherm. The adsorbent HASM is the effective adsorbent to absorb MB dye in solution.

Hydrogels Loaded with Methylene Blue: Sorption-Desorption and Antimicrobial Photoactivation Study

Cross-linked dextran-graft-polyacrylamide hydrogels with different cross-linking density loaded with methylene blue was prepared as light-activated antimicrobial materials. Sorption/desorption properties of hydrogels were studied by estimating the change in the absorption maximum of MB solutions. The sorption/desorption rate of MB into/out of hydrogel depends on the hydrogel structure. The antibacterial properties of the light-irradiated materials were tested against Staphylococcus aureus. It was shown that irradiation of hydrogels in the presence of methylene blue was able to eliminate the bacteria strains.

PVDF composite membrane with robust UV-induced self-cleaning performance for durable oil/water emulsions separation

Membranes with special wettability (superhydrophobic/superoleophilic or superhydrophilic/superoleophobic) had been introduced to separate oil/water emulsions. Nevertheless, the surface or pore canals of membrane easily fouled by oily wastewater are the tough challenges towards longtime application. In this work, a PVDF@PDA@ZnO membrane was firstly fabricated via growth of ZnO nanoparticles from ZnO seeds planted on the PVDF@PDA membrane. This PVDF@PDA@ZnO membrane showed good separation capability for various emulsions (which the separation efficiencies and fluxes were up to 99.1% and 654 L m − 2h − 1, respectively). The degradation rate of MB solution treated by the composite membrane was almost 100% attributing to the excellent photocatalytic ability of ZnO. Moreover, the composite membrane could maintain high efficiency (above 99.27%) after long-time emulsions separation/UV-light irradiation, which displayed superior UV-driven self-cleaning and oxidation resistance performance. This self-cleanable composite membrane possessed durability and held high promise for long-time oil/water emulsions separation.

Confined crystallization of microporous metal-organic framework within mesoporous silica with enhanced hydrostability: Ultrafast removal of organic dyes from aqueous solutions by MIL-68(Al)@SBA-15 composite

In this study, MIL-68(Al), a metal-organic framework, and SBA-15 (Santa Barbara Amorphous-15), a well-known silica material, were chosen for fabrication of composite material 1 by reflux method. The composite 1 named MIL-68(Al)@SBA-15 was characterized fully. TEM images and BET results confirmed the crystallization of MIL-68(Al) inside SBA-15 channels. Interestingly the BET surface area increased from 797 m2 g−1 for SBA-15 to 947 m2 g−1 for composite 1. Herein for the first time, we synthesized and used composite 1 for the adsorption of dye pollutants from water. The adsorption ability of composite 1 was investigated towards different dye solutions and was compared with the ability of bare MIL-68(Al) and SBA-15. The results revealed that the composite 1 adsorbed 100 % of MB solution in 0.5 min with a maximum adsorption capacity of 68.93 mg g−1. Furthermore, the composite 1 was used for adsorption of binary, ternary, and quaternary mixed dye solutions and showed high adsorption efficiency for removal of all the mixed dye solutions in short time. The kinetics of the adsorption process follows the pseudo-second-order model, and the Langmuir isotherm model provides the best fitting for the adsorption of MB onto composite 1. Also, for investigation of the effect of synthesis route on the prepared composite material, the composite 2 named MIL-68(Al)/SBA-15 was synthesized by solid-state grinding and its adsorption ability toward dye solutions was compared with composite 1.

Magnetized Tectona grandis sawdust as a novel adsorbent: preparation, characterization, and utilization for the removal of methylene blue from aqueous solution

In the submitted research work, adsorption characteristic of magnetized Tectona grandis sawdust for methylene blue from aqueous media was explored. The prepared adsorbent was characterized by SEM/EDXS, TEM, BET, XRD, FTIR, TGA-DTG/DTA, VSM, and point of zero charge. To investigate the adsorption capacity and mechanisms prevailing for the adsorption of methylene blue, batch adsorption studies were performed by changing adsorbate/adsorbent contact time, pH, initial dye concentration, and temperature. The removal efficiency was found to be 90.8% under the optimized adsorption conditions. The optimal process parameters were 1 g/L of magnetized adsorbent, 60 min contact time, pH 8, and temperature of 30 °C for 100 mg/L MB solution. The laboratory generated adsorption data was best conformed by pseudo-second-order kinetics and Langmuir adsorption isotherm models. The maximum monolayer adsorption capacity was determined to be 172.41 mg/g. The adsorption process was established to be thermodynamically feasible and accompanying with the absorption of heat and escalation of entropy. Regeneration study revealed that magnetized Tectona grandis sawdust could be reused efficaciously up to four repeated adsorption–desorption cycles using HCl as the best desorbing agent. The magnetized Tectona grandis sawdust has been proved to be novel, efficient, and cost-effective adsorbent. The combined advantages of easy preparation, good affinity towards dyes, excellent separability, reusability, and cost-effectiveness of magnetized Tectona grandis sawdust make it a novel adsorbent.

Kinetics and thermodynamics of methylene blue adsorption on the Fe-oxide nanoparticles embedded in the mesoporous SiO2

Fe-oxide nanoparticles with a diameter of ~10 nm embedded into the porous structure of mesoporous SiO2 particles using temperature regulated chemical vapor deposition and a subsequent annealing process. The kinetics and thermodynamics of MB adsorption on bare SiO2 and Fe-oxide/SiO2 particles were investigated. MB adsorption kinetics of both SiO2 particles can be described by pseudo first order and intra particle diffusion plot. Thermodynamic parameters were calculated based on the modified Langmuir isotherm model. Equilibrium constant and spontaneity of MB adsorption was increased with the presence of Fe-oxide nanoparticles inside the SiO2 pores, which can be ascribed to the more negative values of ΔH of Fe-oxide/SiO2 particles compared to bare SiO2. A higher affinity of Fe-oxide nanoparticles for MB adsorption facilitated the intra particle diffusion of MB molecules at a longer time of MB adsorption and improve the maximum MB adsorption capacities of Fe-oxide/SiO2 compared to bare SiO2. The maximum MB adsorption capacities of bare SiO2 and Fe-oxide/SiO2 particles reduced as the initial pH of MB solution increased, however, Fe-oxide/SiO2 particles always exhibited the higher capacity of MB adsorption than bare SiO2.

In situ self-assembly of molybdenum disulfide/Mg–Al layered double hydroxide composite for enhanced photocatalytic activity

In this work, in situ growth of thin layer and highly catalytic activity molybdenum disulfide (MoS2) was successfully synthesized by spatial confinement effect of Mg–Al layered double hydroxide (Simplified as LDH below). Due to the unique spatial confinement effect and electropositivity of the LDH layer, MoS2 will controllable in situ grows along the surface of LDH layer, the MoS2 synthesized in LDH tends to monolayer or thin layer instead of growing into a flower-like structure, this new strategy is different from vapor deposition, exfoliation and laser irradiation to prepare thin layer MoS2. Meanwhile, the conglomerate structure of LDH is opened and converted to thin layer by the growth of MoS2, too. The rich defects carried by thin layer LDH also help to improve the catalytic ability of MoS2. MoS2/LDH can absorb the light from ultraviolet to visible light region, The prepared MoS2/LDH composite was used as a photocatalytic material, and was found to be the best photocatalyst degrading about 96% of the MB solution (20 mg/L) after 180 min.

Fabrication, characterization, and photocatalytic activity of anatase/rutile/SnO2 nanocomposites

Anatase/rutile/SnO2 nanocomposites have been synthesized through a sol–gel method. The crystal structure, surface morphology, chemical valence, specific surface area, and optical property of the samples were investigated by XRD, Raman, SEM, TEM, HRTEM, XPS, BET, DRS, and PL analyses. The addition of Sn promotes the phase transition from anatase to rutile. The formed anatase/rutile/SnO2 three-phase coexistence structure is beneficial to the separation of photogenerated pairs and the decrease of band gap. The photocatalytic behavior of photocatalysts was studied via the photodegradation of MB solution under xenon lamp irradiation. With the increase of Sn concentration, the photocatalytic performance of TiO2/SnO2 is improved, and all TiO2/SnO2 photocatalytic activities are higher than pure TiO2. 32%Sn–TiO2 (32%ST) exhibits the highest photocatalytic activity and the MB has been completely photodegraded in 30 min.

Carbon nanotubes-based polymer nanocomposites: Bio-mimic preparation and methylene blue adsorption

The effective removal of environmental pollutants using nanomaterials and their composites has attracted great attention over the past few decades. Among them, carbon nanotubes (CNTs) have been extensively applied as adsorbents to remove various environmental pollutants for their small size, large surface areas and unique chemical structure. However, the adsorption performance of pristine CNTs is largely limited for their poor dispersibility and lack of functional groups. In this work, CNTs based composites (CNTs@poly(S-co-MA-DA)) have been successfully synthesized through combination of ring-opening reaction and mussel inspired chemistry. The pristine CNTs and as-prepared CNTs@poly(S-co-MA-DA) were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The influence of various experimental factors on the adsorption process, such as contact time, initial MB concentration, solution pH and temperature, was studied. Experimental results show that adsorption capacity of CNTs@poly(S-co-MA-DA) is about 4 times that of pristine CNTs in same experimental conditions. The kinetics and isotherms studies suggest that pseudo-second-order kinetic and Freundlich isotherm models could well fit with the adsorption data. The thermodynamic studies imply that the adsorption process of MB onto CNTs@poly(S-co-MA-DA) is endothermic and spontaneous. The adsorption mechanism might be the synergistic action of physical adsorption of CNTs@poly(S-co-MA-DA) particles and electrostatic interaction between the MB and functional groups on the surface of CNTs@poly(S-co-MA-DA) composites, including carboxyl, acylamino, hydroxyl and aromatic moieties. These obtained results and facts indicate that the as-prepared CNTs@poly(S-co-MA-DA) could be utilized as high-performance adsorbents with great potential applications in environmental treatment.

Development of activated carbon from Eichhornia Crassipes via chemical activation and its application to remove a synthetic dye

Dyes wastewater is listed as one of the largest water polluter in this world and cause problems to the environment as well as human health. The present study aims to investigate the adsorption of methylene blue, a cationic dye commonly used in industries by activated carbon derived from the water hyacinth stem (Eichhornia crassipes (Mart.) Solms). The removal of MB solution was affected by some parameters such as dosage, contact time, pH, and initial dye concentration. The present study showed that the optimum condition for the adsorption process was pH 7, the adsorbent dosage at 0.8 g with the equilibrium was reached at 100 minutes. However, there is no significant adsorption in the effect of pH. It was found that the best correlation of kinetic with the MB adsorption was the pseudo-second-order model, while the isotherm study was well represented with the Freundlich model. The porosity of adsorbent was enhanced after carbonization process. The functional group presence on the surface of adsorbent including alcohols, carboxyl and carbonyl were also contributed to the effectiveness of adsorption process.

Low-cost, biodegradable and highly effective adsorbents for batch and column fixed bed adsorption processes of methylene blue

This work reports the preparation of low-cost and ecological bioadsorbents and study of their adsorption properties in the elimination of methylene blue dye (MB) from wastewater Unmodified citrus peels (UCP) and unmodified citrus peels encapsulated with calcium alginate (UCP/A) were characterized by elementary analysis, FTIR, DRX, SEM. Isotherm studies in the batch system were investigated and the maximum adsorbed amounts were found to be 185.83 and 964.54 mg/g respectively for UCP and UCP/A. The Langmuir model fitted well experimental data of isotherms with high coefficient correlation R2, low RMSE and χ2. Fixed bed adsorption was studied with operational conditions such as the bed height, MB flow rate and MB inlet concentration to test the performance of column. The breakthrough curves and the break time increase with the decrease of the rate flow and with the increased bed height. The highest bed capacity of 31.45 mg/g and highest percentage of MB solution treated (93.6%) was obtained using 2 mL/min rate flow, 200 mg/L inlet MB concentration and 3.5 cm (4 g) bed height. The breakthrough curves were fitted using Thomas and Yoon and Nelson models. The behaviors of the breakthrough and the R2 founded by these models are high (R2>0.97) which shows good applicability of models.

Atmospheric pressure helium plasma jet and its applications to methylene blue degradation

The optical and electrical characteristics of atmospheric pressure He plasma are investigated. The optical emission at the plasma-solution interface confirms the existence of active radicals such as O⋅H, O⋅ and H⋅. The dissipated power was estimated with Lissajous figure. The plasma plume length reaches a maximum length at flow rate of 7.5 L/min, which is accompanied by a peak value of dissipated power and currents. The Trot and Tvib decrease as He flow rate increases at a fixed discharge voltage. The degradation efficiency and decolorization of MB solution were found to be strongly dependent on the He flow rate.

A novel Cu2O@HNbWO6 heterojunction photocatalyst with enhanced photocatalytic performance

A novel Cu2O@HNbWO6 p-n heterojunction photocatalyst was synthesized via solution redox method, which showed excellent photocatalytic activity and stability for the degradation of MB solution under simulated solar irradiation. The enhanced photocatalytic activity can be attributed to the p-n heterojunction formed between Cu2O and HNbWO6, which can improve the separation and migration of the photo-induced electron-hole pairs and provide enriched active sites. Further, in order to explore the relationship between the structure and properties of the photocatalyst, the compositions and structures of the photocatalyst were characterized in detail by SEM, XRD, Raman and UV–vis DRS, etc. Finally, the possible photocatalytic enhancement mechanism was proposed.

Synthesis, Crystal Structures, and Photocatalytic Activity of Two Nickel(II) Coordination Polymers with Flexible Bis(benzimidazol-1-yl)alkane and Polycarboxylate Ligands

Two ternary Ni(II) coordination polymers (CPs) named as: {[Ni2(L1)2(1,8-NDC)2(H2O)2]·2H2O}n (1), {[Ni2(L2)1.5(FA)(H2O)3]·3.75H2O}n (2), (L1 = 1,6-bis(5,6-dimethylbenzimidazol-1-yl)hexane, L2 = bis(5,6-dimethylbenzimidazol-1-yl)methane, 1,8-H2NDC = 1,8-naphthalenedicarboxylic acid, H4FA = 4,4′-(hexafluoroisopropylidene)diphthalic acid) were hydrothermally synthesized and characterized through physicochemical and spectroscopic methods. CP 1 features a 1D double straight-line chain and further extends into a 2D layers via π–π stacking interactions, while CP 2 shows a unique 2D (5,4,4)-connected network. The thermal stabilities, luminescence properties and photocatalytic activities of CPs 1–2 for methylene blue decomposition were also presented in detail. Two luminescent Ni(II) coordination polymers (CPs) were synthesized under hydrothermal condition. The crystal structure of CP 1 features a 1D double straight-line chain and further extends into a 2D layers via π–π stacking interactions, while CP 2 shows a unique 2D (5,4,4)-connected network. The photocatalytic experiments in the presence of catalysts CP 1 indicated higher degradation efficiency for MB solution than CP 2, and ·OH radical plays a key effect in the efficient degradation of MB.

Recycling of pre-consumer viscose waste fibers for the removal of cationic dye from aqueous solution

Recycling of textile waste materials has attracted significant attention for fabrication low-cost dye adsorbent from aqueous solutions. Viscose cellulosic waste fibers are supposed to give an answer to the finding low-cost adsorbent materials. In this research work, viscose waste fibers (VF) were modified by selective oxidation to improve the ability to absorb cationic dyes during wastewater treatment. For this purpose, different treatment parameters were investigated such as sodium periodate concentration, and time of selective oxidation with sodium chlorite. Then, unmodified and oxidized viscose fibers (OVF) were ball milled to produce viscose powder (VP) and oxidized viscose powder (OVP), respectively. The morphology of obtained viscose powders was characterized by scanning electron microscopy. Furthermore, methylene blue adsorption onto viscose cellulose fiber waste (VF) and oxidized viscose fibers (OVF) was studied as a function of contact time (0–80 min), adsorbent dosage (1–9 g/L), MB solution initial pH (3–9) and MB initial concentration (20–80 mg/L). The results showed that MB adsorption onto VF and OVF is a rapid favorable chemisorption process that can be well described by the Langmuir model. The higher adsorption capacity of OVF than VF was related to the increase of the carboxylic group. The oxidized viscose fiber can be used as a potential adsorbent for water treatment.

Solar-Light-Driven Efficient ZnO–Single-Walled Carbon Nanotube Photocatalyst for the Degradation of a Persistent Water Pollutant Organic Dye

An efficient photocatalyst, ZnO–single-walled carbon nanotube (ZnO–SWCNT) nanocomposite was successfully fabricated through a straightforward one-pot–two-chemical recrystallization technique followed by thermal decomposition. The photocatalytic efficiency of the prepared ZnO–SWCNT composite was investigated by assessing the degradation of a persistent water-pollutant dye (methylene blue, MB) under visible-light irradiation. We found that the synthesized photocatalyst is an effective and recyclable agent for the decomposition of an MB solution. Its photocatalytic performance was substantially better than that of pristine ZnO nanorods or pristine SWCNTs. The reusability of the photocatalyst was also examined, affirming that it could be used repeatedly for five cycles without conspicuous loss of morphology or catalytic performance.

Facile hydrothermal synthesis of NaTaO3 with high photocatalytic activity

Orthorhombic perovskite structure NaTaO3 with cube shape was successfully synthesized by hydrothermal reaction. The as-prepared NaTaO3 behaves a great photocatalystic activity on degradation of MB solution not only under UV but also visible light irradiation.

Characteristics and Photocatalytic Activity of Sm Doped ZnO Nanoparticles

Sm2O3/ZnO nanoparticles were prepared via microwave-assisted hydrothermal and sol-gel combustion synthesis. Characteristics of obtained samples were compared in dependence of Sm2O3 content and calcination temperature. Prepared nanostructures were characterized with scanning electron microscopy and X-ray diffraction. Nanoparticles prepared via microwave-assisted hydrothermal and sol-gel method have flower-like and spherical shape respectively. The photocatalytic activity of samples under solar light simulated illumination was found to be affected by content of Sm2O3, calcination temperature and preparation method. The first-order rate constant of MB solution degradation of samples prepared via microwave-assisted hydrothermal method approximately three times exceeds that of sol-gel samples.

Iron based metal organic framework for efficient removal of methylene blue dye from industrial waste

The present investigation assesses the applicability of Fe-BDC metal organic framework for the removal of the toxic dye methylene blue from industrial waste. The adsorption characteristics and dye removal efficiency of Fe-BDC MOF has been determined by investigating factors such as effect of contact time, concentration of the dye, amount of adsorbents, and temperature. Upto 94.74% dye removal was attained by increasing the dose of adsorbent and temperature. Maximum 94.74% dye removal was achieved after 24 h, on adding 25 mg of Fe-BDC MOF to dye solution of MB having concentration 5 mg/L. Langmuir, Freundlich and Tempkin, isotherm models have been used to evaluate the ongoing adsorption. Freundlich adsorption isotherm was found to be best fitted for the adsorption process. On the basis of pseudo-first-order, pseudo-second-order and intra particle diffusion kinetic equations, different kinetic parameters have been obtained. Pseudo second order kinetic model with rate constant (k2) 4.9 × 10−2 g/mg·min, is found to be best fitted for adsorption of methylene blue on Fe-BDC MOF indicating that removal of dye takes place dominantly through chemisorption process.

Zn-assisted synthesis of high-performance adsorbent for methylene blue

The rapid removal of organic dyes from water under low temperature environment offers significant advantages when water purification is required in cold regions. In this work, porous lanthanum hexaboride (LaB6) nanoparticles were fabricated via a facile low-temperature molten metal (LTMM) method in Zn media under argon atmosphere. As is evidenced by the characterization results, porous LaB6 can be prepared at 400 °C. Elevated reaction temperature led to the growth of nanoparticles, serious aggregation and the residue of Zn element in the final product. Notably, LaB6 nanoparticles prepared at 600 °C by such a LTMM method presented ultrafast adsorption, with a maximum MB sorption capacity of 606.2 mg·g−1, which was competitive with most of reported sorbents. Owing to the photothermal conversion property, LaB6 powder not only accelerated the melting of iced MB solution, but also achieved the efficient adsorption of MB in cold weather. LaB6 nanoparticles could be used as an attractive sorbent for dye removal from contaminated water, because of its facile synthesis process, excellent sorption performance and photothermal conversion property.