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The introduction of active groups from biomass is currently the most promising alternative method for increasing the adsorption effect of dyes. In this study, modified aminated lignin (MAL) rich in phenolic hydroxyl and amine groups was prepared by amination and catalytic grafting. The factors influencing the modification conditions of the content of amine and phenolic hydroxyl groups were explored. Chemical structural analysis results confirmed that MAL was successfully prepared using a two-step method. The content of phenolic hydroxyl groups in MAL significantly increased to 1.46 mmol/g. MAL/sodium carboxymethylcellulose (NaCMC) gel microspheres (MCGM) with enhanced methylene blue (MB) adsorption capacity owing to the formation of a composite with MAL were synthesized by a sol-gel process followed by freeze-drying and using multivalent cations Al 3+ as cross-linking agents. In addition, the effects of the MAL to NaCMC mass ratio, time, concentration, and pH on the adsorption of MB were explored. Benefiting from a sufficient number of active sites, MCGM exhibited an ultrahigh adsorption capacity for MB removal, and the maximum adsorption capacity was 118.30 mg/g. These results demonstrated the potential of MCGM for wastewater treatment applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The detoxification of dye-contaminated water by photocatalysis has become a research priority. Here, a novel hybrid material, cuprous oxide/sunflower stem pith (Cu 2 O/SSP), was successfully synthesized in situ, using copper hydroxide gel, prepared by ion exchange, as the precursor to Cu 2 O. The presence of Cu 2 O nanoparticles on the SSP was confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction analyses. Using methylene blue (MB) as the target pollutant, Cu 2 O/SSP delivered excellent adsorption-photocatalytic degradation and was readily photoregenerated. Cu 2 O/SSP removed 72.7% of MB after 60 min under visible light irradiation, an increase of 15.6 % compared with unmodified SSP. SSP plays three roles in the removal of MB: it acts as an adsorbent for the MB, a carrier for the Cu 2 O nanoparticles and it also inhibits photocorrosion of Cu 2 O. The mechanism of adsorption-photocatalysis by Cu 2 O/SSP was investigated and a description of the mechanism is provided. This study paves the way for the detoxification of dye-containing wastewater using hybrid biomass materials.

In this study, we report the development of physically cross-linked hydroxyethyl cellulose grafted polyacrylic acid-co-polyacrylamide/silver nanocomposite [Ag@HEC-g-P(AA-co-AM)-Fe 3+ ] possesses excellent antimicrobial and enhanced MB adsorption. A green in-situ reduction process was used to prepare silver nanoparticles. UV-Vis spectroscopy, TEM, ATR-IR, XRD, SEM-EDS were used to analyze the green produced silver nanoparticles and Ag@HEC-g-P(AA-co-AM)-Fe 3+ . The swelling ratio of Ag@HEC-g-P(AA-co-AM)-Fe 3+ is dependent on AgNPs content and pH. The swelling kinetics fitted with Pseudo-second order. The cumulative release#% of AgNPs was 29.63 ± 1.7%, respectively up to 10 h and its kinetics obey Korsmeyer-Peppas model. The grafting to HEC and incorporation of AgNPs into HEC-g-P(AA-co-AM)-Fe 3+ enhances the thermal stabilities and increases total activation energies from 19,122.2 to 66,287.1 KJ mol. Ag@HEC-g-P(AA-co-AM)-Fe 3+ has powerful antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Micrococcus leutus, Staphyllococus aureus. The maximum adsorption capacity of MB was 133.38 ± 1.25 mg/g at nanocomposite concentration (300 mg/L), pH (9.0), and MB concentration (5 mg/L). To anticipate the adsorption mechanism, Pseudo-first and second-order models, as well as three isotherm models (Langmuir, Freundlich, and Temkin) were used to model adsorption kinetics. The nonlinear Langmuir models and second-order kinetics were the most appropriate., (Copyright © 2021. Published by Elsevier B.V.)

Developing a sustainable, efficient and recyclable heterogeneous Fenton-like catalyst is important to wastewater treatment. Herein, well-dispersed MnO 2 and Fe 3 O 4 nanoparticles inlaid in chitosan beads (MnO 2 -Fe 3 O 4 /CH) was firstly fabricated and employed in the degradation of methylene blue (MB). The bead was prepared via a facile one-step method by dropwise addition of chitosan-metal salt solution into alkaline solution. Comparing with monometallic chitosan beads (MnO 2 /CH, Fe 3 O 4 /CH) and naked MnO 2 -Fe 3 O 4 , MnO 2 -Fe 3 O 4 /CH displayed significantly higher activity for MB degradation with the assistance of hydrogen peroxide (H 2 O 2 ), finally removing 96.8% MB under the optimal conditions (50 mg L -1  MB, 4.0 g L -1 catalyst, 30 g L -1 H 2 O 2 , pH = 7, 60 min). Based on a series of characterizations, the large surface area (60.1 m 2  g -1 ), well-developed porosity (0.3 cm 3  g -1 ), and intensified electron transport of MnO 2 -Fe 3 O 4 /CH consequently enhanced the catalytic performance via a synergistic effect. Because the specific porous structure of MnO 2 -Fe 3 O 4 /CH facilitated the adsorption/diffusion of reactants and exposure of active sites. Meanwhile, the electron transfer from Mn 3+ to Fe 3+ accelerated the Fe 3+ /Fe 2+ cycle, which favored the production of dominant reactive species hydroxyl radical for MB degradation. Besides, the magnetic beads could be easily collected from the solution and reused for five times with a negligible leaching., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this work, lignin fractionation is proposed as an effective approach to reduce the heterogeneity of lignin and improve the adsorption and recycle performances of lignin as a cationic dye adsorbent. By stepwise dissolution of enzymatic hydrolysis lignin in 95% and 80% ethanol solutions, three lignin subdivisions (95% ethanol-soluble subdivision, 80% ethanol-soluble subdivision, and 80% ethanol-insoluble subdivision) were obtained. The three lignin subdivisions were characterized by gel permeation chromatography (GPC), FTIR, 2D-NMR and scanning electron microscopy (SEM), and their adsorption capacities for methylene blue were compared. The results showed that the 80% ethanol-insoluble subdivision exhibited the highest adsorption capacity and its value (396.85 mg/g) was over 0.4 times higher than that of the unfractionated lignin (281.54 mg/g). The increased adsorption capacity was caused by the enhancement of both specific surface area and negative Zeta potential. The maximum monolayer adsorption capacity of 80% ethanol-insoluble subdivision by adsorption kinetics and isotherm studies was found to be 431.1 mg/g, which was much higher than most of reported lignin-based adsorbents. Moreover, the 80% ethanol-insoluble subdivision had much higher regeneration yield (over 90% after 5 recycles) compared with the other two subdivisions. Consequently, the proposed fractionation method is proved to be a novel and efficient non-chemical modification approach that significantly improves adsorption capacity and recyclability of lignin.

Adsorption behaviors of methylene blue (MB) from aqueous solution using sunflower stem pith (SSP) as adsorbent were investigated. The effects of adsorption conditions such as adsorption time, initial concentration of MB and dosage of SSP on the detoxification of MB were examined. The equilibrium adsorption data were analyzed using three well-known isotherms: Langmuir, Freundlich and Temkin. The results indicated that the Langmuir isotherm fitted well to the data as compared with another isotherm model. The maximum adsorption capacity calculated by the Langmuir isotherm model was 277 mg/g at 338 K. Kinetic analyses were conducted using pseudo first order, pseudo second order and the Elovich model. The regression results showed that the MB adsorption was described by the pseudo second order model. Different thermodynamic parameters such as Gibb's free energy (ΔG o ), standard enthalpy change (ΔH o ) and standard entropy change (ΔS o ) were also evaluated. The results showed that the detoxification of MB using SSP as adsorbent was feasible, non-spontaneous and exothermic under experimental conditions.

This study prepared a carboxylate-functionalized sugarcane bagasse (CF-SCB) from sugarcane bagasse (SCB) via a simple and low-toxicity chemical modification to enhance its capacity for adsorbing methylene blue (MB) from aqueous solutions. The success of chemical modification was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), the pore area and porosity, and zeta potential measurement analysis. The adsorption capacity of CF-SCB was investigated at different pHs, ionic strengths, temperatures, contact times and initial dye concentrations. Equilibrium data were best described by the Langmuir isotherm model, and the maximum monolayer adsorption capacity of CF-SCB (296.74 mg g -1 ) was greatly improved compared with SCB (77.16 mg g -1 ) at 30 °C. The thermodynamic study indicated that MB adsorption onto CF-SCB was a spontaneous, endothermic and entropy increased process. Adsorption kinetics followed a pseudo-second-order mode, and the adsorption mechanism was based on electrostatic interactions. The reusability study showed that CF-SCB had reasonably good reuse potential. All the results suggested that CF-SCB has high potential to be used as an effective and renewable adsorbent for MB removal from wastewater.

Cellulose grafted with soy protein isolate (SPI), sustainable and cost effective material, was investigated as a bioactive material for calcium phosphate mineralization. The formation of hydroxyapatite rod-like nanocrystals with ∼50nmdiameter was confirmed by different characterization tools. Cellulose grafted SPI/hydroxyapatite hybrid was evaluated as recyclable adsorbent for methylene blue (MB) from aqueous solutions using batch adsorption technique. The new sustainable material exhibited adsorption capacity up to 454mg/g. Adsorption data were examined using different kinetics and isotherms to investigate the adsorption mechanism. After four adsorption-desorption cycles, the efficiency of MB removal is ∼95%. These results present new sustainable, cost effective and reusable hybrid material as a promising adsorbent for organic dyes removal from waste water., (Copyright © 2016 Elsevier Inc. All rights reserved.)

In this article, the use of low-cost adsorbents for the removal of methylene blue (MB) from solution has been reviewed. Adsorption techniques are widely used to remove certain classes of pollutants from waters, especially those which are not easily biodegradable. The removal of MB, as a pollutant, from waste waters of textile, paper, printing and other industries has been addressed by the researchers. Currently, a combination of biological treatment and adsorption on activated carbon is becoming more common for removal of dyes from wastewater. Although commercial activated carbon is a preferred adsorbent for color removal, its widespread use is restricted due to its relatively high cost which led to the researches on alternative non-conventional and low-cost adsorbents. The purpose of this review article is to organize the scattered available information on various aspects on a wide range of potentially low-cost adsorbents for MB removal. These include agricultural wastes, industrial solid wastes, biomass, clays minerals and zeolites. Agricultural waste materials being highly efficient, low cost and renewable source of biomass can be exploited for MB remediation. It is evident from a literature survey of about 185 recently published papers that low-cost adsorbents have demonstrated outstanding removal capabilities for MB., (Copyright (c) 2009 Elsevier B.V. All rights reserved.)

Anionic groups (AGs) on different cellulosic fiber surfaces were investigated by methylene blue (MB) and polyelectrolyte (PE) sorption, X-ray photoelectron spectroscopy (XPS), and total attenuated reflectance infrared spectrometry (FTIR-ATR). The MB sorption isotherms fitted well the Langmuir equation that gave consistent estimations of sorption capacities. FTIR-ATR showed that MB molecules had extensive accessibility to the fiber wall pores. Estimation of surface AGs by PE sorption gave much higher values than a new method combining MB sorption and XPS measurements (MB-XPS). The surface AGs in different cellulosic fibers accounted for 1-3% of the total AG content as revealed by MB-XPS. It was suggested that PE molecules can penetrate the fiber wall and form loops or unattached segments at external fiber surfaces that disrupt the PE sorption stoichiometry. The competition of MB and PE for the anionic sites in papermaking was assessed and it was shown that MB ions have a much stronger affinity to AGs than PE molecules.