Xanthated chitosan/cellulose sponges for the efficient removal of anionic and cationic dyes

A novel sponge composite of chitosan-sodium tripolyphosphate-melamine for anionic dye Orange II removal

Since the potential carcinogenic, toxic and non-degradable dyes trigger serious environmental contamination by improper treatment, developing novel adsorbents remains a major challenge. A novel high efficiency and biopolymer-based environmental-friendly adsorbent, chitosan‑sodium tripolyphosphate-melamine sponge (CTS-STPP-MS) composite, was prepared for Orange II removing with chitosan as raw material, sodium tripolyphosphate as cross-linking agent. The composite was carefully characterized by SEM, EDS, FT-IR and XPS. The influence of crosslinking conditions, dosage, pH, initial concentration, contacting time and temperature on adsorption were tested through batch adsorption experiments. CTS-STPP-MS adsorption process was exothermic, spontaneous and agreed with Sips isotherm model accompanying the maximum adsorption capacity as 948 mg∙g-1 (pH = 3). Notably, the adsorption performance was outstanding for high concentration solutions, with a removal rate of 97 % in up to 2000 mg∙L-1 OII solution (100 mg sorbent dosage, 50 mL OII solution, pH = 3, 289.15 K). In addition, the adsorption efficiency yet remained 97.85 % after 5 repeated adsorption-desorption cycles. The driving force of adsorption was attributed to electrostatic attraction and hydrogen bonds which was proved by adsorption results coupled with XPS. Owing to the excellent properties of high-effective, environmental-friendly, easy to separate and regenerable, CTS-STPP-MS composite turned out to be a promising adsorbent in contamination treatment.

Removal of direct dyes from wastewater using chitosan and polyacrylamide blends

This study investigated the feasibility of employing neat chitosan powder, polyacrylamide, and chitosan micro-beads as adsorbents for the rapid and efficient removal of Direct Blue 78 dye from textile industrial wastewater. A series of batch experiments were conducted to examine the impact of adsorbent dose, contact time, and pH on the adsorption process. The physicochemical analysis, including FTIR, zeta potential analysis, and SEM were performed to identify the adsorption mechanism of chitosan powder and micro-beads. It was found that increasing the powder chitosan dose to 4.5 g/L and contact time up to 40 min resulted in achieving a significant increase in dye removal efficiency up to 94%. The highest removal efficiency of 94.2% was achieved at an initial dye concentration of 50 mg/L, a chitosan dosage of 4.5 g/L, and an optimized contact time of 60 min. Utilizing a polyacrylamide gel dose of 45 mL/L reduced the sedimentation time of chitosan from 8 h to 5 min. Equilibrium studies showed an initial L-shaped equilibrium curve, indicating that the adsorption process primarily arises from electrostatic interactions between dye molecules and adsorbent particles (physical forces). The Langmuir isothermal model demonstrated the best fit to the equilibrium data. Combining chitosan powder with polyacrylamide gel emerges as an economically viable choice for dye removal in industrial wastewater effluents, offering a cost-effective alternative to pricey commercial adsorbents. The results of the study revealed that the presence of polyacrylamide dye enhanced the removal efficiency and settling time of DB78 dye using chitosan.

NaBiS2 decorated polysaccharide sponges for adsorption-photocatalytic degradation of dye under visible light illumination

Dye is emissions aggravating aquatic ecosystem pollution, and photocatalysis is considered the most appealing option to remove dyes by degradation. However, the current photocatalysts suffer from agglomeration, large bandgaps, high mass transfer resistance, and high operation cost. Herein, we present a facile hydrothermally induced phase separation and in situ synthesis strategy for fabrication of sodium bismuth sulfide (NaBiS₂)-decorated chitosan/cellulose sponges (NaBiCCSs). The NaBiCCSs demonstrate unique polysaccharide cellular structure (150-500 μm), uniformly immobilized NaBiS₂ nanoparticles (70-90 nm), narrow bandgap (1.18 eV), high photocurrent (0.74 μA/cm²), and outstanding compressibility. Benefiting from the characteristics and the high affinity to dyes, the NaBiCCSs provide innovative synergistic adsorption-photocatalytic degradation model for dye removal, attaining a superior methylene blue removal rate of 98.38 % under visible light illumination and offering good reusability. This study offers a sustainable technical solution for dye contaminant removal.

Novel polyamide/silica/chitosan covalent hybrid: One-step BIC/sol-gel preparation at room temperature and dual applications in Hg2+ electrochemical probing and dye adsorption

Room-temperature preparation of polymer-based covalent hybrids, which with multiple functional characteristics, is instrumental to overcome the performance shortcomings of single-polymer materials and broaden their applications thus. Herein, by introducing chitosan (CS) as a starting substrate into benzoxazine-isocyanide chemistry (BIC)/sol-gel reaction system, a novel polyamide (PA)/SiO₂/CS covalent hybrid (PA-Si-CS) was successfully prepared in-situ at 30 °C. PA-Si-CS's chemical structure and elementary properties were characterized here. The introduction of CS combining with the presence of diverse N, O-containing segments (amide, phenol -OH, Si-OH, etc.) in PA-Si-CS provided its synergistic adsorption for Hg²⁺ and anionic dye Congo red (CR). The capture of PA-Si-CS for Hg²⁺ was rationally applied to the "enrichment"-type electrochemical probing of Hg²⁺. Relevant detection range, detection limit, interference, and probing mechanism were systematically analyzed. Compared with the experimental results of control electrodes, the electrode modified with PA-Si-CS (PA-Si-CS/GCE) showed a significantly enhanced electrochemical response to Hg²⁺, with a detection limit up to ~2.2 × 10^-8 mol/L. In addition, PA-Si-CS also exhibited the specific adsorption for CR. Systematic analyses of dye adsorption selectivity, kinetics, isothermal models, thermodynamics, and adsorption mechanism told that PA-Si-CS can be used as an efficient CR adsorbent, with a maximum adsorption capacity of ~348 mg/g.

Recent advances in biopolymer-based advanced oxidation processes for dye removal applications: A review

Over the past few years, synthetic dye-contaminated wastewater has attracted considerable global attention due to the low biodegradability and the ability of organic dyes to persist and remain toxic, causing numerous health and environmental concerns. As a result of the recalcitrant nature of those complex organic dyes, the remediation of wastewater using conventional wastewater treatment techniques is becoming increasingly challenging. In recent years, advanced oxidation processes (AOPs) have emerged as a potential alternative to treat organic dyestuffs discharged from industries. The most widely employed AOPs include photocatalysis, ozonation, Fenton oxidation, electrochemical oxidation, catalytic heterogeneous oxidation, and ultrasound irradiation. These processes involve the generation of highly reactive radicals to oxidize organic dyes into innocuous minerals. However, many conventional AOPs suffer from several setbacks, including the high cost, high consumption of reagents and substrates, self-agglomeration of catalysts, limited reusability, and the requirement of light, ultrasound, or electricity. Therefore, there has been significant interest in improving the performance of conventional AOPs using biopolymers and heterogeneous catalysts such as metal oxide nanoparticles (MONPs). Biopolymers have been widely considered in developing green, sustainable, eco-friendly, and low-cost AOP-based dye removal technologies. They inherit intriguing properties like biodegradability, renewability, nontoxicity, relative abundance, and sorption. In addition, the immobilization of catalysts on biopolymer supports has been proven to possess excellent catalytic activity and turnover numbers. The current review provides comprehensive coverage of different AOPs and how efficiently biopolymers, including cellulose, chitin, chitosan, alginate, gelatin, guar gum, keratin, silk fibroin, zein, albumin, lignin, and starch, have been integrated with heterogeneous AOPs in dye removal applications. This review also discusses the general degradation mechanisms of AOPs, applications of biopolymers in AOPs and the roles of biopolymers in AOPs-based dye removal processes. Furthermore, key challenges and future perspectives of biopolymer-based AOPs have also been highlighted.

Mycosynthesis of Hematite (α-Fe2O3) Nanoparticles Using Aspergillus niger and Their Antimicrobial and Photocatalytic Activities

Nanoparticles (NPs) and nanomaterials (NMs) are now widely used in a variety of applications, including medicine, solar energy, drug delivery, water treatment, and pollution detection. Hematite (α-Fe₂O₃) nanoparticles (Hem-NPs) were manufactured in this work by utilizing a cost-effective and ecofriendly approach that included a biomass filtrate of A. niger AH1 as a bio-reducer. The structural and optical properties of Hem-NPs were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV-visible and Fourier-transform infrared (FTIR) spectroscopies. The results revealed that all of the studied parameters, as well as their interactions, had a significant impact on the crystallite size. The average diameter size of the biosynthesized Hem-NPs ranged between 60 and 80 nm. The antimicrobial and photocatalytic activities of Hem-NPs were investigated. The antimicrobial results of Hem-NPs revealed that Hem-NPs exhibited antibacterial activity against E. coli, B. subtilis, and S. mutans with MICs of 125, 31.25, and 15.62 µg/mL, respectively. Moreover, Hem-NPs exhibited antifungal activity against C. albicans and A. fumigatus, where the MICs were 2000 and 62.5 µg/mL, respectively. The efficiency of biosynthesized Hem-NPs was determined for the rapid biodegradation of crystal violet (CV) dye, reaching up to 97 percent after 150 min. Furthermore, Hem-NPs were successfully used more than once for biodegradation and that was regarded as its efficacy. In conclusion, Hem-NPs were successfully biosynthesized using A. niger AH1 and demonstrated both antimicrobial activity and photocatalytic activity against CV dye.

Removal of both anionic and cationic dyes from wastewater using pH-responsive adsorbents of L-lysine molecular-grafted cellulose porous foams

High adsorption efficiency, active to both anionic and cationic dyes and simple desorption are three main challenges of the existed adsorbents for decolorization of the dye-contained wastewaters. Porous foams based on L-lysine (Lys) molecular-grafted cellulose were firstly designed and fabricated to overcome those challenges. Cellulose were grafted with Lys in 1-butyl-3-methylimidazolium chloride (BMIMCl) via a chemical connection resulted from glycidyl methacrylate (GMA). The synthesized cellulose derivative (Cell-g-PGMA-Lys) was regenerated in the morphology of foam by non-solvent induced phase inversion from the BMIMCl-based solutions. The presence of Lys moieties and porous structure of Cell-g-PGMA-Lys were confirmed with a series of instrumental analysis. Both anionic reactive brilliant red X-3B (RBR X-3B) and cationic methylene blue (MB) were effectively adsorbed on and desorbed from Cell-g-PGMA-Lys by adjusting the solution pH value. Cell-g-PGMA-Lys had higher adsorption capacities than most of the reported adsorbents and was easy to separate from the decolorized water. It could be reused many times with little reduction of the adsorption capacity, which remained 86.9% and 92.5% for RBR X-3B and MB respectively after six adsorption-desorption cycles. The isothermal and kinetic adsorption proved that dyes were adsorbed single-layered on Cell-g-PGMA-Lys depending upon the electrostatic interaction between adsorbent and adsorbate.

Review on effect of different type of dyes on advanced oxidation processes (AOPs) for textile color removal

The textile industry is one of the most valuable industries, especially in developing countries, because it employs a large portion of the workforce. However, the development of the textile industry has led to increasing concern about environmental issues. Wastewater from the textile industry has a high COD and an undesirable color. Color is one of the problems with the wastewater due to its toxicity and low biodegradability. Color in textile wastewater mainly originates from the dyestuff used during the dyeing or printing process. Amongst all of available technology for color removal, advanced oxidation processes (AOPs) are considered one of the best and the most potential technology. However, the understanding of AOPs reaction mechanism to degrade dyestuff is still limited. In general, dyes degradation mechanism will vary and mainly depend on the chemical structure of the dyes itself. Some reaction pathway that seems less favorable thermodynamically can still happen during the process. Understanding the mechanism will be beneficial for future dyes improvement, especially on developing the moiety of the aromatic compound in order to produce easily degraded dyes while maintaining the fastness quality.

Synthesis and Characterization of Novel Uracil-Modified Chitosan as a Promising Adsorbent for Efficient Removal of Congo Red Dye

Novel Uracil-modified chitosan (UCs) adsorbent has successfully been synthesized through a four-step method during which the amino groups of chitosan have been protected, then epoxy nuclei have been incorporated, afterwards the latter have been opened using 6-amino-1,3-dimethyl uracil, and finally the amino groups have been regained via removing the protection. Its structure was checked using FTIR, XRD and SEM techniques. The adsorption capacity of UCs for anionic Congo Red (CR) dye was studied under various conditions. It decreased significantly with increasing the solution pH value and dye concentration, while increased with increasing temperature. The adsorption of UCs for CR dye at different temperatures, solution pH and dye concentrations fitted to the kinetic model of pseudo-second order and Elovich model. The intraparticle diffusion model showed that the adsorption process involves multi-step process. The isotherm of CR dye adsorption by UCs conforms to the Langmuir isotherm model indicating the monolayer nature of adsorption. The maximum monolayer coverage capacity, q_max, was 434.78 mg g⁻¹. Studying the thermodynamic showed that the adsorption of CR dye onto UCs was endothermic as illustrated from the positive value of enthalpy (21.37 kJ mol⁻¹). According to the values of ΔG°, the adsorption process was spontaneous at all selected temperatures. The value of ΔS° showed an increase in randomness for the adsorption of CR dye by UCs. The value of activation energy was 18.40 kJ mol⁻¹.

Kinetics, Isotherm and Thermodynamic Studies for Efficient Adsorption of Congo Red Dye from Aqueous Solution onto Novel Cyanoguanidine-Modified Chitosan Adsorbent

Novel Cyanoguanidine-modified chitosan (CCs) adsorbent was successfully prepared via a four-step procedure; first by protection of the amino groups of chitosan, second by insertion of epoxide rings, third by opening the latter with cyanoguanidine, and fourth by restoring the amino groups through elimination of the protection. Its structure and morphology were checked using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The adsorption capacity of CCs for Congo Red (CR) dye was studied under various conditions. It decreased significantly with the increase in the solution pH value and dye concentration, while it increased with increasing temperature. The adsorption fitted to the pseudo-second order kinetic model and Elovich model. The intraparticle diffusion model showed that the adsorption involved a multi-step process. The isotherm of CR dye adsorption by CCs conforms to the Langmuir isotherm model, indicating the monolayer nature of adsorption. The maximum monolayer coverage capacity, q_max, was 666.67 mg g^-1. Studying the thermodynamic showed that the adsorption was endothermic as illustrated from the positive value of enthalpy (34.49 kJ mol^-1). According to the values of ΔG°, the adsorption process was spontaneous at all selected temperatures. The value of ΔS° showed an increase in randomness for the adsorption process. The value of activation energy was 2.47 kJ mol^-1. The desorption percentage reached to 58% after 5 cycles. This proved that CCs is an efficient and a promising adsorbent for the removal of CR dye from its aqueous solution.

Recent Advances in Biopolymer-Based Dye Removal Technologies

Synthetic dyes have become an integral part of many industries such as textiles, tannin and even food and pharmaceuticals. Industrial dye effluents from various dye utilizing industries are considered harmful to the environment and human health due to their intense color, toxicity and carcinogenic nature. To mitigate environmental and public health related issues, different techniques of dye remediation have been widely investigated. However, efficient and cost-effective methods of dye removal have not been fully established yet. This paper highlights and presents a review of recent literature on the utilization of the most widely available biopolymers, specifically, cellulose, chitin and chitosan-based products for dye removal. The focus has been limited to the three most widely explored technologies: adsorption, advanced oxidation processes and membrane filtration. Due to their high efficiency in dye removal coupled with environmental benignity, scalability, low cost and non-toxicity, biopolymer-based dye removal technologies have the potential to become sustainable alternatives for the remediation of industrial dye effluents as well as contaminated water bodies.

The Development and Characterization of a Cotton-Chitosan Composite for Lead Removal from Water

Heavy metals in water are a serious environmental problem due to their accumulation and toxicity; there are several processes we can use to address this issue, but adsorption is the most popular due to its simplicity and efficiency. Polysaccharides such as cellulose have received attention as adsorbents for heavy metals, and cotton-chitosan composites (CCs) were developed here with nontoxic reagents such as carboxylic acids as crosslinkers and NaH2PO4 as a catalyst to achieve chitosan covalent crosslinkage into oxidized cotton textiles with H2O2. The composites were characterized by fourier-transform infrared spectroscopy (FTIR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), atomic-force and scanning electron microscopy (AFM and SEM), and tensile strength; the adsorption of lead ions (Pb) was evaluated with cotton-chitosan composites and quantified by microwave plasma atomic emission spectroscopy (MP-AES). The composites showed a maximum incorporation of chitosan of 27.62 mg per gram of cotton textile. A tensile strength analysis of the composite showed a Young's modulus approximately 1 MPa higher than that of cotton textile. The adsorption of lead ions with composites in an aqueous solution at pH 5 and 25 °C was circa 74% after 6 h of contact, as determined by MP-AES. This work is an approach to demonstrate the potential of these polysaccharides, modified by "green" procedures to remove pollutants from water.

Chitosan-based hybrid materials for adsorptive removal of dyes and underlying interaction mechanisms

Environmental pollution by dyes molecules has become a subject of intensive research in recent years due to their hazardous effects on human health, organisms, and animals. Effective treatment and removal of dye molecules from the environmental matrices and water sources are of supreme concern. The deployment of cheap, safe, green, sustainable, and eco-friendly materials to remove these pollutants from water is the main challenge during the last decades. Chitosan and its derivatives/composites, as a cheap, easily available, and environmentally friendly sorbent, have attracted increasing attention for the removal of dye molecules. This review article focuses on the application of chitosan and chitosan-based smart adsorbents for the removal of dyes. Recent methods for the preparation of chitosan-based composites and their application in the removal of dyes are discussed. Moreover, the possible mechanisms for the interaction of chitosan and chitosan-based adsorbents with dyes molecules were evaluated. Finally, future prospects of using chitosan as an adsorbent for the removal of dye molecules are directed.