Methylene Blue Adsorption Capacity Research Articles

Preparation of versatile lignin-based adsorbent for the removal of organic dyes and its application in wound healing

In this work, a lignin-based adsorbent with high positive charge and excellent biocompatibility was prepared by grafting quaternary ammonium groups. Firstly, the structure of quaternized lignin (QL) was characterized by 1H NMR, FT-IR, GPC, TGA, zeta potential etc. Then, the effects of adsorbent dosage, ambient temperature, stirring frequency, contact time and initial concentration on the adsorption capacity were studied in detail. The results showed that QL exhibited efficient adsorption for rhodamine B (RB), methylene blue (MB), acid blue 92 (AB-92) and congo red (CR) dyes. All adsorption processes followed the pseudo-second order and Langmuir models. The maximum adsorption capacities of RB, MB, AB-92 and CR were 41.85, 49.47, 110.53 and 134.61 mg/g, respectively. Finally, antimicrobial activity assays and cellular viability assays demonstrated the excellent biocompatibility of QL with no cytotoxic effect. In a murine wound model, QL remarkably accelerated the re-epithelialization formation and dermal closure, indicating that it could promote cell proliferation. The finding of this study provides a facile and eco-friendly strategy to construct hydrophilic and biocompatible versatile lignin-based adsorbent for removing of cationic and anionic dyes, and the adsorbent could also be applied as an effective wound dressing, protecting the organisms in water during the adsorption.

Response Surface Modelling of Methylene Blue Adsorption onto Seaweed, Coconut Shell and Oak Wood Hydrochars

Adsorption of methylene blue (MB) dye from an aqueous solution onto hydrochars produced from brown seaweed (Fucus Serratus) (FS-HC), coconut shell (CS-HC), and oak wood (Oak-HC) at different temperatures (200–250 °C) was investigated in a batch system. Response surface modelling (RSM) was used to investigate the effect of initial MB concentration (50–300 mg/L), contact time (0–240 min), and solution pH (2–12) on the adsorption process. RSM was also used to model and optimise these parameters for efficient adsorption. Kinetic and isotherms studies were carried out to study the adsorption mechanism onto the hydrochars. It was found that the best adsorbent from the RSM model was FS-HC200, and the optimal conditions for greater MB dye uptake were lower initial MB concentration (50 mg/L), pH 6 and contact time of 84 min; removing >99% of MB. Langmuir and Redlich–Peterson isotherm models fitted the adsorption of MB onto hydrochars prepared at 200 and 250 °C. Freundlich and Redlich–Peterson isotherms were suitable for hydrochars produced at 220 °C. FS-HCs have the highest maximum adsorption capacity of MB of about (8.60–28.57) mg/g calculated from the Langmuir isotherm. The adsorption process for all the hydrochars followed a pseudo-second-order model (R2 = 0.96–1.00), and film diffusion and intraparticle diffusion were the rate-determining steps. Therefore, this work identifies cheap adsorbents from biowaste that are effective for the removal of cationic pollutants from wastewater.

Influence mechanism of sucrose on phase change of K-feldspar during hydrothermal decomposition

AbstractSucrose was added to the hydrothermal decomposition reaction of calcium oxide and K-feldspar to improve the adsorption performance of the hydrothermal product tobermorite. The effects of the sucrose concentrations on the decomposition rates of K-feldspar were studied based on the extraction rates of potassium oxide, and the influence mechanism of sucrose on the phase change of K-feldspar during the hydrothermal decomposition was elucidated. It was shown that when n(Su)/n(Ca)=0.1:1, the extraction rate of potassium oxide was 83.83%, and the decomposition of K-feldspar was inhibited with the increase of the sucrose concentration. The increase in the viscosity of the reaction system and the formation of calcium complexes during the hydrothermal process were the main reasons for the inhibition of the decomposition of K-feldspar. Moreover, the enhancement mechanism of the methylene blue adsorption capacity of the sucrose-modified tobermorite was explained from the perspective of the microstructure.

Synthesis and characterization of clay-biochars produced with facile low-temperature one-step in the presence of air for adsorbing methylene blue from aqueous solution

A facile and low-energy approach for biochar-supported clay preparation was developed at a low temperature (250°C) in the presence of air. A new type of engineered biochar by implanting clay particles on carbon surfaces had been successfully exploited as a low-priced adsorbent for environmental application. Two biomass feedstocks (tea and coffee wastes) were pretreated with kaolinite or montmorillonite suspension and then clay-biochars were synthesized using the facile one-step method. The adsorption performance, influencing factors, and mechanism of clay-biochars for methylene blue (MB) were investigated with adsorption experiments. The characterization results confirmed that clay exited on the biochar’s surface and the adsorption results revealed that biochar-supported clay had excellent methylene blue adsorption capacities (>20 mg/g) at unadjusted solution pH and room temperature (25°C ± 1°C). Batch adsorption experiments showed that initial solution pH, ionic strength, and competing compounds affected methylene blue adsorptions. The biochar-supported clay also had a potential of recycle and reusability for methylene blue removal. The methylene blue adsorption was predominately controlled by cation exchange (with both biochar and clay) and electrostatic interaction (with biochar only) mechanisms. This study provides a simple and environmental-friendly technology for creating high-efficiency clay-biochar adsorbent for removing cationic contaminants.

The selective and enhanced adsorptive behaviors of supramolecular recrystallized 1,3,5-benzenetricarboxylic acid assembled nano-bacterial cellulose

The effluent discharge produced in the textile printing and dyeing, leather and other fields, will cause the irreversible environmental pollution and extremely threatening safety of living organisms. The appropriate and efficient disposal method of dyestuff originated wastewater has been widely concerned in the past decades. In this study, the recrystallization of 1,3,5-benzene tricarboxylic acid (RCTMA) was put forward via a hydrothermal method to form the supramolecular RCTMA-based hexamer and thereafter assembled into the porous nano-bacterial cellulose (NBC) to construct the RCTMA@NBC composite. The morphology and surface properties of RCTMA@NBC were examined by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy. This RCTMA@NBC was employed to adsorb methylene blue (MB) adjusting the pH, temperature, and dosage of adsorbent. The result showed the maximal absorption capacity of RCTMA@NBC appeared under pH = 7.1 and higher temperature will hinder the adsorption of dyes. Moreover, the adsorption isotherms and kinetics were evaluated which was more confirmed to Langmuir model and quasi-second-order kinetic equation, and the simulated maximum adsorption capacities of MB was 1162.12 mg/g. Moreover, cationic golden XGL and anionic brilliant crocein were selected to further verify the distinct adsorptive behavior. The excellent affinity towards cationic dyes proved the easy combination was based on the chemical force originated from mutual attraction between opposite charges, π–π interactions, and H-bonding, whereas the poor attraction for brilliant crocein was due to the electrostatic repulsion between sulfonic and carboxyl groups. The synthesized RCTMA@NBC possesses higher efficiency and selective adsorption, which exhibits the promising potential in the field of precise treatment of organic dye wastewater.

Valorization of food waste digestate to ash and biochar composites for high performance adsorption of methylene blue

The valorization and appropriate treatment of food waste digestate (FWD) is a critical issue for facilitating the sustainable development of anaerobic digestion and actualizing a circular economic. The FWD contains high ash contents and is conventionally considered as an inappropriate feedstock for producing high-value products such as biochar. However, this ash content may also have a chance to enhance the application performance of biochar as an adsorbent if positive synergic effect is identified. This study used industrial FWD as a widely obtainable feedstock for producing ash-biochar composites (ABCs) for methylene blue (MB) contaminated wastewater abatement. The obtained ABCs performed a maximum MB adsorption capacity of 1123.5 mg/g. Mechanism and modeling assessments demonstrated that the ash components on the surface of ABC adsorbent enhanced MB removal by providing alkaline adsorption environment and more oxygen-based n-π interaction sites. In addition, increasing pyrolysis temperature enlarged the biochar surface area and homogenously rearranged the carbon structure to strength the π-π interaction between MB and ABC adsorbent. This research suggests that FWD is principally an ideal feedstock that can be directly used for making high-performance absorbents for wastewater treatment.

Investigating mixed biosolids and cardboard for methylene blue adsorption: Activation, adsorption modelling and thermodynamics

Ongoing global population boom has led to the rise in waste and related research on increasing its economic value. In such an attempt, this study aims to activate gas-to-liquids (GTL) derived biosolids (BS) and cardboard (CB) and mixed samples (50:50) using potassium carbonate to produce three activated carbons (ACs): KBS, KCB and KM respectively. The characterization of the samples revealed surface areas of 156, 515, and 527 m2/g for KBS, KCB, and KM, respectively based on Brunauer–Emmett–Teller (BET) analysis, with increased porosity and metal content after activation evident from the Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) results, as well as the presence of magnetite in the KBS and KM samples apparent from the X-ray powder diffraction (XRD) results. Additionally, Fourier Transform Infrared Spectroscopy (FTIR) results indicate increased C–O–C stretches and O–H bonds after activation of the samples.The ACs were used for methylene blue (MB) removal process which is a rapid for all three samples, reaching equilibrium after 9 h, and optimal at neutral pH and maximum at the highest temperature, 40 °C. The MB adsorption capacity was highest for KM (191.07 mg/g), followed by the KCB and KBS samples. Isotherm modelling of the samples showed best fits for KBS, KCB and KM as Langmuir-Freundlich (LF), Langmuir and Toth models respectively. On the contrary, kinetic modelling using contact time study data for all samples exhibited best fits by the Diffusion-chemisorption (DC) model. Finally, the thermodynamic calculations of the mixed sample disclosed the adsorption process to be exothermic and spontaneous, with potential mechanisms being electrostatic attraction, ion exchange, π-π interactions, and hydrogen bonding. Multiple cycles of KM regeneration was also achieved with good adsorption capacities. Future work will explore other activation methods and examine the magnetic properties of KBS and KM for real water treatment.

Removal of cationic dyes from a synthetic effluent using a calcium surfactant

Abstract The present study aimed to evaluate the removal efficiency of two types of cationic dyes of different classes – methylene blue (MB) and malachite green (MG) – from a synthetic effluent using a calcium surfactant (CaSF) originated from used frying soybean oil. The Fourier Transform Infrared Spectroscopy (FTIR) spectra showed that the functional groups present on the surface of CaSF can form surface complexes or bonds with the dye molecules and, consequently, promote their adsorption. The adsorption kinetics studies indicated that the equilibrium point of the process is reached in 90 min for both dyes. Equilibrium studies indicated that the adsorption isotherm models that best fit MB and MG were the Langmuir and the Dubinin–Radushkevich models, respectively. The maximum adsorption capacities of MB and MG, according to the Langmuir model, were 199 and 123 mg·g−1, respectively. In the sight of the high MB and MG removal efficiency (84 and 100%, respectively), the use of CaSF is an excellent alternative for the treatment of effluents contaminated by cationic dyes. The adsorption–desorption cycle studies showed that CaSF maintains a good dye removal efficiency for up to three cycles.

Multifunctional pH-responsive carbon-based hydrogel adsorbent for ultrahigh capture of anionic and cationic dyes in wastewater

An environmental friendly hydrogel adsorbent (DEC@GEL) was successfully manufactured by a facile free-radical polymerization method. Multiple characterizations demonstrated that the adsorbent was rich in functional groups and porous structures. The batch and multisystem adsorption experiments were applied to systematically investigate the adsorption properties of methylene blue (MB), malachite green (MG), indigo sodium dimethyl sulfonate (IC) and tartrazine (TR) in wastewater. The experimental results proved that the kinetic and isotherms of four dyes were more consistent with the pseudo-second-order and Langmuir model, respectively. Notably, the maximum adsorption capacities of MB, MG, TR and IC at 318 K were 2186.85, 2302.53, 1766.13 and 2301.75 mg/g, respectively, which were higher than many adsorbents that had been reported. Recycle experiment demonstrated the high reusability of the DEC@GEL. The selectivity and adsorption column experiments proved that DEC@GEL was not only widely applicable to various dyes, but also provided a positive start for the industrial application. Moreover, the simulated adsorption experiments further demonstrate that DEC@GEL had the prospect of application in real industrial conditions. Finally, four adsorption mechanisms had been proposed. Various adsorption experiments had shown that DEC@GEL was not only efficient in processing dyes, but also had great potential for practical industrial applications.

Carboxymethyl cellulose/sodium alginate beads incorporated with calcium carbonate nanoparticles and bentonite for phosphate recovery

Although anionic polyelectrolyte hydrogel beads offer attractive adsorption of cationic dyes, phosphate adsorption is limited by electrostatic interactions. In this work, carboxymethyl cellulose (CMC)/sodium alginate (SA) hydrogel beads were modified with calcium carbonate (CaCO3) and/or bentonite (Be). The compatibility between CaCO3 and Be was proven by the homogeneous surface, as shown in the scanning electron microscopic images. Fourier-transform infrared and X-ray diffraction spectra further confirmed the existence of inorganic filler in the hydrogel beads. Although CMC/SA/Be/CaCO3 hydrogel beads attained the highest methylene blue and phosphate adsorption capacities (142.15 MB mg/g, 90.31 P mg/g), phosphate adsorption was significantly improved once CaCO3 nanoparticles were incorporated into CMC/SA/CaCO3 hydrogel beads. The kinetics of MB adsorption by CMC/SA hydrogel beads with or without inorganic fillers could be described by the pseudo-second-order model under chemical interactions. The phosphate adsorption by CMC/SA/Be/CaCO3 hydrogel beads could be explained by the Elovich model due to heterogeneous properties. The incorporation of Be and CaCO3 also improved the phosphate adsorption through chemical interaction since Langmuir isotherm fitted the phosphate adsorption by CMC/SA/Be/CaCO3 hydrogel beads. Unlike MB adsorption, the reusability of these hydrogel beads in phosphate adsorption reduced slightly after 5 cycles.

One-step preparation of coal-based magnetic activated carbon with hierarchically porous structure and easy magnetic separation capability for adsorption applications

Coal-based magnetic activated carbons (CMACs) were prepared from Zhundong coal in the presence of various Fe-based additives by fast one-step physical activation method. The roles of types and doses of Fe sources for pore structures and magnetic properties of the resulting CMACs were systematically investigated. Fe species in coal promoted the development of mesopore structures, and AC-FC-3 derived from FeCl3-loaded coal (3% Fe content) possessed hierarchical pore structure with highest micropore and mesopore volumes up to 0.282 cm3·g−1 and 0.222 cm3·g−1, respectively. Considering the minimum dose of additives, the CMACs loaded a trace amount of reduced iron powder (0.5% and 1% weight ratios of coal) were prepared, and had improved micropore and mesopore structures compared with AC derived from the demineralized coal. Meanwhile, strong magnetic iron oxides (Fe3O4 and γ-Fe2O3) were generated during CO2 activation process. The CMACs derived from different Fe sources loaded coal samples with same Fe content (3% weight ratio of coal) had saturation magnetizations of 0.55–14.26 emu·g−1. Evaluated as adsorbents for Methylene Blue (MB) removal, the CMACs with hierarchical pore structure exhibited better MB adsorption capacities up to 120.3 mg·g−1. Furthermore, the magnetic properties of CMAC could accelerate the solid–liquid separation with an applied magnetic field and improve recovery efficiency of the adsorbent.

Conversion of cassava rhizome into efficient carbonaceous adsorbents for removal of dye in water

The development of sustainable adsorbent materials for removing pollutants from water is of great interest for environmental remediation and human safety. This work presents the beneficial use of cassava rhizome (CR) to produce economical and efficient carbonaceous adsorbents for dye removal. CR derived activated carbons (AC) and magnetic AC were fabricated by one-pot hydrothermal carbonization in the presence of ZnCl2 and ZnCl2/FeCl3 respectively, followed by pyrolysis at 800 °C. Porosity tuning and degree of magnetization of as-prepared carbons were achieved by varying the amount of ZnCl2 and FeCl3 as an activating agent and source of magnetic particles respectively. The result indicated that the optimal condition to obtain ACs with a high SBET (1405 m2/g) and the largest mesopore volume (0.54 cm3/g) was using the weight ratio of ZnCl2 to CR of 3 (3AC). While, the magnetic mesoporous carbon with the highest SBET (554 m2/g) was yielded when addition of FeCl3 into the reaction mixture with a FeCl3 to ZnCl2 weight ratio of 1(3AC-1M). 3AC and 3AC-1M were tested as adsorbents to investigate the adsorption efficiency of methylene blue (MB) in water. The adsorption behavior of MB on 3AC and 3AC-1M were monolayer adsorption based on the Langmuir isotherm model with R2 of 0.9993 and 0.9953, respectively. 3AC showed the MB adsorption capacity of 274 mg/g which is comparable to that of commercial ACs. 3AC-1M that adsorbs MB with the maximum capacity of 102 mg/g, was separated from aqueous solution easily using an external magnet. This study demonstrates that the carbon precursors from biomass waste as CR can be conveniently converted into efficient carbonaceous adsorbents and functionalized for example by adding magnetic properties into the carbon structure to enable manipulations in industrial operations.

Synthesis of adsorbent from rubberwood sawdust (Hevea brasiliensis)

This study describes the synthesis of adsorbent from rubber wood sawdust. The adsorbent is the activated carbon here. Temperature and activation time were used to investigate the effects of process factors on the pore structure of activated carbons. The adsorbent were prepared from char using muffle furnace at temperature of 400 °C. In this work, we showed two types of activation, namely before pyrolysis activation (AC-01), and after pyrolysis activation (AC-02). The adsorption capacity of (AC-01) obtained was 12.139 dye adsorbed (mg of dye/g of adsorbent) in 500 PPM of initial methylene blue concentration and adsorption capacity of (AC-02) obtained was 12.14 dye adsorbed (mg of dye/g of adsorbent) in 500 PPM of initial methylene blue concentration.

Halloysite-Magnesium Silicate Composites as Adsorbent for Removal of Methylene Blue and Heavy Metals from Aqueous Solution

Objectives : The thermal stability of halloysite and magnesium silicate is discussed in terms of microstructural change and adsorption behavior to optimize their composite as an absorbent for methylene blue (MB) and heavy metal ions removal from an aqueous solution.Methods : Halloysite-magnesium silicate tubular composites with high adsorption capacity of methylene blue and heavy metal ions were prepared with extrusion and consequent firing. To define the firing temperature of the tubular media, the microstructure and the adsorption equilibrium characterized the thermal stability of halloysite and magnesium silicateResults and Discussion : The magnesium silicate used in this study shows broad peaks in x-ray diffraction; however, the treatment of 750℃ induces its crystallization. The specific surface area of the magnesium silicate is also gradually decreased along with the firing temperature increase. No significant degradation in methylene blue adsorption capacity for magnesium silicate is observed until 500℃-treatment. However, the higher firing temperature reduces the capacity: 6.9%P, 27.3%P, and 91.2%P decrease for 600℃, 700℃, and 750℃, respectively. Regardless of heat treatment, the Langmuir isotherm equation represents the adsorption equilibria well compared to the Freundlich model. The tubular media of the halloysite – 30 wt% of magnesium silicate fired at 600℃ exhibits a high specific surface area of 115 m<sup>2</sup> g<sup>-1</sup> and a relative porosity of 43.5%. Compared to the halloysite-only tubular media, the adsorption capacity of the composites is significantly improved with the incorporation of magnesium silicate. The adsorption capacity of 168h for methylene blue is more than tripled, 29.8 mg g<sup>-1</sup>, and the adsorption capacity of Cr(III), Cu(II), and Zn(II) is also greatly enhanced by more than 4.8 times.Conclusion : The thermal stability of magnesium silicate is investigated for use as an additive adsorbent in terms of the microstructure and the adsorption capacity. Even at 600℃ of the firing temperature, magnesium silicate shows a higher specific surface area and higher adsorption capacity of MB compared to those of the halloysite; the adsorption fits well into Langmuir behavior. The addition of magnesium silicate into the halloysite media significantly enhances its adsorption capacity for MB and heavy metal ions such as Cr(III), Cu(II), and Zn(II).

Synthesis and adsorption performance of fly ash/steel slag‐based geopolymer for removal of Cu (II) and methylene blue

AbstractIn order to realize the value‐added resource utilization of solid waste, geopolymer particle adsorbents were prepared at low temperatures using silica‐aluminum‐rich fly ash and steel slag powders as raw materials. In order to investigate the mechanism of their adsorption of dyes and heavy metal ions from wastewater, the effects of steel slag/fly ash ratio, adsorbent dosage, initial concentration of methylene blue (MB) and Cu2+ solution, adsorption time and temperature on the adsorption performance of the fly ash/steel slag‐based geopolymer adsorbents were investigated, systematically. Results presented that the adsorption capacities of MB and Cu2+ were 33.30 and 24.15 mg/g, and the removal efficiencies were 99.90% and 96.59% with the dosages of 3 and 4 g/L geopolymer adsorbents (steel slag/fly ash ratio of 20 wt.%), respectively. The adsorption processes of MB and Cu2+ on the adsorbents were in accordance with the proposed pseudo‐second‐order and Langmuir isotherm models, which mainly included physical and chemical adsorption mechanisms. The adsorption was a spontaneous endothermic process. The fly ash/steel slag‐based geopolymer had good removal ability for dyes and heavy metal ions, and it could maintain good adsorption performance after three cycles of regeneration. It had potential application in wastewater treatment.

Novel dye removing agent based on CTS-g-P(AA-co-NIPAM)/GO composite

A novel composite Chitosan graft poly (acrylic acid-co-N-isopropylacrylamide)/graphite oxide (CTS-g-P(AA-co-NIPAM/GO) is synthesized and used to remove methylene blue (MB) and fuchsin basic (FB) from aqueous solutions by adsorption. Small amount of GO brings about great improvement of the thermostability together with the adsorption amount. Adsorption capacities of MB and FB increase from 842.1 and 633.7 mg/g, respectively, to 1496.3 and 1000.8 mg/g, respectively, with 0.02 g intercalation amount of GO. The interactions between GO and main body of CTS-g-P(AA-co-NIPAM) graft copolymer are hydrogen and amide bonds, whereas that between dye molecules and CTS-g-P(AA-co-NIPAM)/GO composite is hydrogen bond as well as electrostatic interaction. Effect of various conditions on the adsorption capacities is discussed. Adsorption isotherms and thermodynamics are studied. The adsorption of both MB and FB are spontaneous and satisfy the Redlich-Peterson equation. Kinetic study shows that the adsorption of both dyes is in accordance with the Pseudo first-order kinetic model.

Sweet-Potato-Vine-Based High-Performance Porous Carbon for Methylene Blue Adsorption.

In this study, sweet-potato-vine-based porous carbon (SPVPC) was prepared using zinc chloride as an activating and pore-forming agent. The optimised SPVPC exhibited abundant porous structures with a high specific surface area of 1397.8 m2 g-1. Moreover, SPVPC exhibited excellent adsorption characteristics for removing methylene blue (MB) from aqueous solutions. The maximum adsorption capacity for MB reached 653.6 mg g-1, and the reusability was satisfactory. The adsorption kinetics and isotherm were in good agreement with the pseudo-second-order kinetics and Langmuir models, respectively. The adsorption mechanism was summarised as the synergistic effects of the hierarchically porous structures in SPVPC and various interactions between SPVPC and MB. Considering its low cost and excellent adsorption performance, the prepared porous carbon is a promising adsorbent candidate for dye wastewater treatment.

Pyrolysis characteristics, kinetics, and biochar of fermented pine sawdust-based waste.

The objective of current study is to explore the energy recovery potential of fermentation residues. In this perspective, pyrolysis characteristics, kinetics, and modified biochar derived from pine sawdust after fermentation (FPD) were determined, and comparison was established with pine sawdust (PD). The variation range of comprehensive pyrolysis index (CPI) values of FPD was found 6.51 × 10-7-16.38 × 10-7%2·min-2·°C-3, significantly higher than that of untreated samples determined under the same experimental conditions. The average activation energy of FPD was 367.95kJ/mol, 389.45kJ/mol, and 346.55kJ/mol calculated by Flynn-Wall-Ozawa (FWO) method, Kissinger-Akahira-Sonuse (KAS), and Starink method respectively, and importantly, these values are much higher than those of PD. Additionally, fermentation could enhance the adsorption capacity for methylene blue of biochar from 0.76mg/g to 1.6mg/g due to the abundant surface functional groups and three-dimensional internal pore structure. The adsorption pattern of fermented pine wood shifted from chemisorption dominated to the synergetic adsorption of surface functional groups adsorption and intragranular filling. These results show that FPD has favorable pyrolytic properties, and the derived biochar has adsorption properties, which is the basis for designing pyrolysis process and reusing fermentation residues. HIGHLIGHTS: The FPD has higher values of CPI and activation energy than the PD. FPD-derived biochar has higher adsorption capacity than PD-derived biochar. The fermentation improves the pyrolysis performance. The fermentation enhances adsorption capacity due to unique structure of biochar.

Understanding association between methylene blue dye and biosorbent: Palmyrah sprout casing in adsorption process in aqueous phase

Water pollution caused by industrial dyes has become a severe problem in the modern world. Biosorbents can be used in an eco-friendly manner to remove industrial dyes. In this study, five biosorbents were selected: palmyrah sprout casing (PSC), manioc peel, lime peel, king coconut husk, and coconut kernel. Batch adsorption experiments were conducted to identify the best biosorbent with the highest ability to adsorb methylene blue (MB) from wastewater. The detailed mechanisms of PSC used in the adsorptive removal of MB in aqueous phase were investigated. Of the five biosorbents, PSC exhibited the best removal performance with an adsorption capacity at equilibrium (qe) of 27.67 mg/g. The qe values of lime peel, king coconut husk, manioc peel, and coconut kernel were 24.25 mg/g, 15.29 mg/g, 10.84 mg/g, and 7.06 mg/g, respectively. To explain the mechanisms of MB adsorption with the selected biosorbents, the Fourier transform infrared (FTIR) spectrometry and X-ray diffraction (XRD) analyses were performed to characterize functional properties, and isotherm, kinetic, rate-limiting, and thermodynamic analyses were conducted. The FTIR analysis revealed that different biosorbents had different functional properties on their adsorptive surfaces. The FTIR and XRD results obtained before and after MB adsorption with PSC indicated that the surface functional groups of carbonyl and hydroxyl actively participated in the removal process. According to the isotherm analysis, monolayer adsorption was observed with the Langmuir model with a determination coefficient of 0.998. The duration to reach the maximum adsorption capacity for MB adsorption with PSC was 120 min, and the adsorption process was exothermic due to the negative enthalpy change (−9.950 kJ/mol). Moreover, the boundary layer thickness and intraparticle diffusion were the rate-limiting factors in the adsorption process. As a new biosorbent for MB adsorption, PSC could be used in activated carbon production to enhance the performance of dye removal.

Bamboo Nanocellulose/Montmorillonite Nanosheets/Polyethyleneimine Gel Adsorbent for Methylene Blue and Cu(II) Removal from Aqueous Solutions

In recent years, the scarcity of pure water resources has received a lot of attention from society because of the increasing amount of pollution from industrial waste. It is very important to use low-cost adsorbents with high-adsorption performance to reduce water pollution. In this work, a gel adsorbent with a high-adsorption performance on methylene blue (MB) and Cu(II) was prepared from bamboo nanocellulose (BCNF) (derived from waste bamboo paper) and montmorillonite nanosheet (MMTNS) cross-linked by polyethyleneimine (PEI). The resulting gel adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), etc. The results indicated that the MB and Cu(II) adsorption capacities of the resulting gel adsorbent increased with the solution pH, contact time, initial concentration, and temperature before equilibrium. The adsorption processes of MB and Cu(II) fitted well with the fractal-like pseudo-second-order model. The maximal adsorption capacities on MB and Cu(II) calculated by the Sips model were 361.9 and 254.6 mg/g, respectively. The removal of MB and Cu(II) from aqueous solutions mainly included electrostatic attraction, ion exchange, hydrogen bonding interaction, etc. These results suggest that the resulting gel adsorbent is an ideal material for the removal of MB and Cu(II) from aqueous solutions.