Facile construction of lignin-based network composite hydrogel for efficient adsorption of methylene blue from wastewater

Preparation of chitosan derivatives/oxidized carboxymethyl cellulose hydrogels by freeze-thaw method: Synthesis, characterization, and utilization in dye absorption

This study successfully synthesized hydrogels by modifying chitosan with water-soluble and carboxyethyl groups, followed by crosslinking with oxidized carboxymethyl cellulose (OCMC). Structural analyses substantiated the establishment of robust imine linkages between the amino and aldehyde groups, affirming the hydrogel's architecture. Using scanning electron microscopy and texture analysis, it was observed that incorporating water-soluble chitosan significantly increased the hydrogel's porosity and hardness. Simultaneously, the addition of carboxyethyl groups enhanced the network structure, rendering it more compact and thereby improving the hydrogel's mechanical strength. The adsorption performance of the carboxyethyl chitosan (CEC)/OCMC hydrogel towards methylene blue was meticulously evaluated, demonstrating a substantial enhancement in adsorption capacity from 7.74 mg/g to 39.57 mg/g following the carboxyethyl modification of chitosan. Adsorption kinetics and isotherm analysis indicated that the adsorption behavior of the hydrogel followed the pseudo-second-order kinetic model and the Langmuir isotherm model. Furthermore, the maximum adsorption capacity of the hydrogel for methylene blue was predicted to be 111.60 mg/g using the Langmuir isotherm model.

Highly efficient removal of adsorbed cationic dyes by dual-network chitosan-based hydrogel

This research presents the effective preparation of a novel dual network chitosan-based hydrogel (CMAPP) for the adsorption of methylene blue (MB), malachite green (MG), crystalline violet (CV), and basic fuchsin (BF) using the sol-gel method to address the escalating issue of dye pollution. FTIR, XRD, SEM, EDS, XPS, TGA, and zeta potential study examined hydrogel production and physicochemical properties. To ascertain the maximum adsorption capacity, the influences of pH, temperature, initial dye concentration, contact time, and adsorbent dosage on adsorption were systematically analyzed. It was observed that CMAPP demonstrated significant removal efficiencies (97.62%, 96.67%, 98.12%, and 99.32%) for the dyes MB, MG, CV, and BF at a concentration of 500 mg/L under optimal conditions. The findings from the adsorption kinetics and isotherm studies indicated that pseudo-second-order kinetics and the Langmuir model were the most appropriate for characterizing the adsorption process of hydrogels. The thermodynamic findings demonstrated that the adsorption process was exothermic and spontaneous. After five cycles of adsorption, the hydrogel demonstrated a consistent dye removal efficiency of around 80%, indicating commendable recyclability. In the interference studies, CMAPP exhibits superior anti-interference capability against CV and BF, which is advantageous for its practical application. The findings from XPS and FTIR investigations indicate that electrostatic attraction, hydrogen bonding, and n-π interactions are the primary forces between the adsorbent and the dyes. The synthesis of CMAPP offers an innovative approach for the effective elimination of cationic dyes and demonstrates significant potential in the treatment of complicated wastewater.

Multifunctional property of N,N-bis (carboxymethyl) glutamic acid modified biomass material: adsorption and degradation removals of cationic dyes in wastewater

As a common type of pollutants in industrial wastewater, cationic dyes have attracted great attentions. Using biodegradable N,N-di (carboxymethyl) glutamic acid (GLDA) as ligand and corn stalk (CS) as matrix, a novel and green biomass modified material GLDA-CS was successfully prepared. The multifunctional property of GLDA-CS for removing methylene blue (MB), malachite green (MG) and alkaline red 46 (R-46) from wastewater was evaluated. The dyes were removed by the electrostatic adsorption based on the cationic adsorption properties of GLDA-CS. The removal rates of MB, MG and R-46 can quickly reach 90.4%, 96.8% and 94.8% in short time. especially for MG and R-46 even only 20 min. The adsorption capacities of the dyes still remain more than 86.5% of the initial values after 5 cycles. In a heterogeneous system, the dyes were removed by Fenton-like degradation based on the metal chelating property of GLDA-CS. 100% degradation rates of the dyes can be achieved in 35 min under the acidic region. Even if at pH 7, degradation rates are 44.1%, 47.1% and 56.6% higher than those under the conventional homogeneous system, and the degradation rate remained at 83.7% after 5 cycles. Regardless of the adsorption or degradation, GLDA-CS shows strong anti-anion interference ability. The potential mechanisms of adsorption and degradation for the dyes by GLDA-CS were deduced by quantization calculation. It is concluded that the adsorption removal of the dyes by GLDA-CS follows MG > R-46 > MB, and mainly depends on the electrostatic interaction between -COOH in GLDA-CS and -N- in the dye molecules. Based on the degradation mechanism of Fenton-like reaction, the possible active sites of the dyes attacked by free radicals and their possible degradation intermediates were predicted by the calculations of Fukui function.

Methylene blue sorption performance of lignocellulosic peach kernel shells modified with cellulose derivative chitosan as a new bioadsorbent

In this study, adsorption isotherms (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and thermodynamic properties of cationic methylene blue (MB) dye adsorption onto chitosan-coated peach kernel shell waste (CTS-PKSh) from wastewater were investigated. CTS was cross-linked with citric acid (CA) and glutaraldehyde (GA). The adsorbents were characterized by FE-SEM/EDS, FTIR, and particle size distribution. MB adsorption behavior onto the biosorbents was investigated concerning parameters such as adsorbent dosage (0.8-8 g/L), time (0-540 min), pH (3-10), initial dye concentration (50-700 mg/L), and temperature (25-55 °C). The Langmiur qmax and experimentally qe MB adsorption capacities of the new adsorbents were found to be 227.27 and 201 mg/g for CA cross-linked CTS-PKSh (CA@CTS-PKSh) and 111.12 and 96.5 mg/g for GA cross-linked CTS-PKSh (GA@CTS-PKSh), respectively. The results of thermodynamic analysis showed that adsorption was feasible, exothermic, and spontaneous. According to adsorption and recyclability results, CA@CTS-PKSh was more effective for MB removal at a 2 g/L adsorbent dose for an initial dye concentration of 100 mg/L, 25 ± 1 °C, contact time 60 min, and pH 7.

Double network self-healing hydrogels based on carboxyethyl chitosan/oxidized sodium alginate/Ca2+: Preparation, characterization and application in dye absorption

This paper presents the formation of a self-healing hydrogel prepared by carboxyethyl modification of chitosan and crosslinking with oxidized sodium alginate. Concurrently, the incorporation of Ca2+ facilitated the formation of "calcium bridges" through intricate coordination with carboxyl moieties, bolstering the attributes of the hydrogel. Various characterization methods, including scanning electron microscopy, texture analysis, and rheological measurements, demonstrated that the introduction of carboxyethyl groups resulted in a more compact hydrogel network structure and improved the hardness and elasticity. The addition of Ca2+ helped to further enhance the mechanical performance of the hydrogel and increase its thermal stability. Then, the adsorption capacity was also investigated, showing adsorption capacities of 46.17 mg/g methylene blue and 46.44 mg/g congo red for carboxyethyl chitosan/oxidized sodium alginate hydrogel, a four-fold increase for congo red versus chitosan/oxidized sodium alginate hydrogel. In addition, the adsorption behavior of CEC/OSA/2%Ca2+ hydrogel can be well described by pseudo-second-order kinetic model and Langmuir adsorption isothermal model. Compared to traditional hydrogels, CEC/OSA/2%Ca2+ hydrogel shows superior mechanical strength, enhanced thermal stability, and improved adsorption capacity, which can effectively adsorb not only methylene blue but also congo red. These advancements demonstrate our hydrogel's innovative properties.

Fabrication of maleic anhydride-acrylamide copolymer based sodium alginate hydrogel for elimination of metals ions and dyes contaminants from polluted water

The study explores the synergy of biobased polymers and hydrogels for water purification. Polymer nanomaterial's, synthesized by combining acrylamide copolymer with maleic anhydride, were integrated into sodium alginate biopolymer using an eco-friendly approach. Crosslinking agents, calcium chloride and glutaraladehyde, facilitated seamless integration, ensuring non-toxicity, high adsorption performance, and controlled capacity. This innovative combination presents a promising solution for clean and healthy water supplies, addressing the critical need for sustainable environmental practices in water purification. In addition, the polymer sodium alginate hydrogel (MAH@AA-P/SA/H) underwent characterization via the use of several analytical procedures, such as FTIR, XPS, SEM, EDX and XRD. Adsorption studies were conducted on metals and dyes in water, and pollutant removal methods were explored. We investigated several variables (such as pH, starting concentration, duration, and absorbent quantity) affect a material's capacity to be adsorbed. Moreover, the maximum adsorption towards Cu2+ is 754 mg/g while for Cr6+ metal ions are 738 mg/g, while the adsorption towards Congo Red and Methylene Blue dye are 685 mg/g and 653 mg/g correspondingly, within 240 min. Adsorption results were further analyzed using kinetic and isothermal models, which showed that MAH@AA-P/SA/H adsorption is governed by a chemisorption process. Hence, the polymer prepared from sodium alginate hydrogel (MAH@AA-P/SA/H) has remarkable properties as a versatile material for the significantly elimination of harmful contaminants from dirty water.

In-situ preparation of lignin/Fe3O4 magnetic spheres as bifunctional material for the efficient removal of metal ions and methylene blue

In this paper, magnetic composite of lignin/Fe3O4 spheres were synthesized via a straightforward one-step in-situ solvothermal method showing good capacity for adsorbing heavy metal ions and dyes. The physicochemical properties of lignin/Fe3O4 spheres are analyzed using a range of techniques such as SEM, XRD, FTIR, VSM, TG, and BET. Lignin/Fe3O4 spheres exhibited high adsorption capacities of 100.00, 353.36 and 223.71 and 180.18 mg/g for Cu (II), Ni (II) and Cr (VI) metal ions and methylene blue (MB) with equilibrium attained within 60 min. After the recycling experiments, lignin/Fe3O4 spheres still possesses excellent superparamagnetic properties and displays high adsorption capacity. The lignin/Fe3O4 spheres are an efficient and continuous adsorbent to remove heavy metal ions of Cu (II), Ni (II), Cr (VI) and cationic dyes of methylene blue in wastewater, which proves the great potential in practical pollutants treatment applications for water systems.

Recent advances and future perspective on lignocellulose-based materials as adsorbents in diverse water treatment applications

The growing shortage of non-renewable resources and the burden of toxic pollutants in water have gradually become stumbling blocks in the path of sustainable human development. To this end, there has been great interest in finding renewable and environmentally friendly materials to promote environmental sustainability and combat harmful pollutants in wastewater. Of the many options, lignocellulose, as an abundant, biocompatible and renewable material, is the most attractive candidate for water remediation due to the unique physical and chemical properties of its constituents. Herein, we review the latest research advances in lignocellulose-based adsorbents, focusing on lignocellulosic composition, material modification, application of adsorbents. The modification and preparation methods of lignin, cellulose and hemicellulose and their applications in the treatment of diverse contaminated water are systematically and comprehensively presented. Also, the detailed description of the adsorption model, the adsorption mechanism and the adsorbent regeneration technique provides an excellent reference for understanding the underlying adsorption mechanism and the adsorbent recycling. Finally, the challenges and limitations of lignocellulosic adsorbents are evaluated from a practical application perspective, and future developments in the related field are discussed. In summary, this review offers rational insights to develop lignocellulose-based environmentally-friendly reactive materials for the removal of hazardous aquatic contaminants.