Accessible Eco-Friendly Method for Wastewater Removal of the Azo Dye Reactive Black 5 by Reusable Protonated Chitosan-Deep Eutectic Solvent Beads

A novel approach to enhance the utilization of low-cost and sustainable chitosan for wastewater remediation is presented in this investigation. The study centers around the modification of chitosan beads using a deep eutectic solvent composed of choline chloride and urea at a molar ratio of 1:2, followed by treatment with sulfuric acid using an impregnation accessible methodology. The effectiveness of the modified chitosan beads as an adsorbent was evaluated by studying the removal of the azo dye Reactive Black 5 (RB5) from aqueous solutions. Remarkably, the modified chitosan beads demonstrated a substantial increase in adsorption efficiency, achieving excellent removal of RB5 within the concentration range of 25-250 mg/L, ultimately leading to complete elimination. Several key parameters influencing the adsorption process were investigated, including initial RB5 concentration, adsorbent dosage, contact time, temperature, and pH. Quantitative analysis revealed that the pseudo-second-order kinetic model provided the best fit for the experimental data at lower dye concentrations, while the intraparticle diffusion model showed superior performance at higher RB5 concentration ranges (150-250 mg/L). The experimental data were successfully explained by the Langmuir isotherm model, and the maximum adsorption capacities were found to be 116.78 mg/g at 298 K and 379.90 mg/g at 318 K. Desorption studies demonstrated that approximately 41.7% of the dye could be successfully desorbed in a single cycle. Moreover, the regenerated adsorbent exhibited highly efficient RB5 removal (80.0-87.6%) for at least five consecutive uses. The outstanding adsorption properties of the modified chitosan beads can be attributed to the increased porosity, surface area, and swelling behavior resulting from the acidic treatment in combination with the DES modification. These findings establish the modified chitosan beads as a stable, versatile, and reusable eco-friendly adsorbent with high potential for industrial implementation.

Fabrication of biopolymeric sheets using cellulose extracted from water hyacinth and its application studies for reactive red dye removal

Driven by the imperative need for sustainable and biodegradable materials, this study focuses on two pivotal aspects: cellulose extraction and dye removal. The alarming repercussions of non-biodegradable food packaging materials on health and the environment necessitate the exploration of viable alternatives. Herein, we embark on creating easily degradable biopolymer substitutes, achieved through innovative crafting of a biodegradable cellulose sheet sourced from extracted cellulose. Concurrently, the significant environmental and health hazards posed by textile industry discharge of wastewater laden with persistent dyes demand innovative treatment strategies. This study extensively investigated four distinct methods of cellulose extraction from water hyacinth, a complex aquatic weed. The functional groups, crystallinity index, thermal stability, thermal effects, and morphology of the extracted cellulose were characterized by FTIR, XRD, TGA, DSC, and SEM. This exploration yielded a notable outcome, as the most promising yield (39.4 ± 0.02% w/w) emerged using 2% sodium chlorite and 2% glacial acetic acid as bleaching agents, surpassing other methods. Building on this foundational cellulose extraction process, the extracted fibers were transformed into highly biodegradable cellulose sheets, outlining conventional packaging materials. Moreover, these cellulose sheets exhibit exceptional efficacy in adsorbing reactive red dye, with the adsorption capacity of 71.43 mg/g by following pseudo-second kinetics. This study establishes an economically viable avenue for repurposing challenging aquatic weeds into commercially valuable biopolymers. The potential of these sheets for dye removal, coupled with their innate biodegradability, opens auspicious avenues for broader applications encompassing commercial wastewater treatment procedures.

Amino-Functionalized Titanate Nanotubes: pH and Kinetic Study of a Promising Adsorbent for Acid Dye in Aqueous Solution

This work reports the functionalization of sodium titanate nanotubes with amine groups obtained from the reaction of titanate nanotubes with [3-(2-Aminoethylamino)propyl]trimethoxysilane, NaTiNT-2NH, and 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane, NaTiNT-3NH. It was verified that the crystalline and morphological structures of NaTiNT were preserved after the functionalization, spectroscopies showed that aminosilane interacted covalently with the surface of NaTiNT, and the incorporation of the aminosilane groups on the surface of NaTiNT can be confirmed. The adsorbent matrices NaTiNT-2NH and NaTiNT-3NH were used to remove the anionic dye from remazol blue R (RB) in aqueous medium, and the highest adsorption capacity was around 365.84 mg g-1 (NaTiNT-2NH) and 440.70 mg g-1 (NaTiNT-3NH) in the range of pH 5.0 to 10.0 and the equilibrium time was reached in 210 min (NaTiNT-2NH) and 270 min (NaTiNT-3NH). Furthermore, the Elovich model, which reports the adsorption in heterogeneous sites and with different activation energies in the chemisorption process, was the most appropriate to describe the adsorption kinetics. Thus, these adsorbent matrices can be used as an alternative potential for dye removal RB in aqueous solution.

Zeolite modification with cellulose nanofiber/magnetic nanoparticles for the elimination of reactive red 198

In this paper for the first time, a cost-effective reinforced zeolite with cellulose nanofibers and magnetic nanoparticles (MZeo/Cellulose nanofiber) was used for the elimination of reactive red 198 (RR198) dye. The fabricated sorbent was characterized by SEM, FTIR, and XRD. The effect of operational parameters, including pH, RR198 concentration, the mass ratios of zeolite to cellulose nanofiber and zeolite coated cellulose to Fe₃O₄ nanoparticles, contact time, agitation speed, sorbent dosage, and temperature were studied. The prepared sorbent exhibited the maximum removal efficiency of 99% for RR198 removal at 30 °C. The presence of other dyes along with the target dye did not negatively affect the adsorption process and RR198 removal efficiency from actual water samples seemed satisfactory and rational. Equilibrium studies confirmed that both Langmuir and Freundlich models described the RR198 adsorption on MZeo/Cellulose nanofiber indicating physical and chemical interactions between the sorbent and RR198 molecules. Kinetic studies demonstrated that pseudo-second-order fitted best with experimental data. Also, thermodynamic studies showed the endothermic nature of the adsorption process. Compared to zeolite, MZeo/Cellulose nanofiber represented a promising removal efficiency for the elimination of RR198 dye from contaminated water.

Kaolinite/cashew gum bionanocomposite for doxazosin incorporation and its release

Incorporation of drugs in clay minerals has been widely proposed for the controlled-release or increased solubility of drugs. In this context, a bionanocomposite based on kaolinite and cashew gum (Kln/Gum) was synthesized and characterized by X-ray diffraction (XRD), thermal analysis (TG/DTA), and Fourier transform infrared spectroscopy (FTIR). The bionanocomposite was applied to the incorporation and further release of doxazosin mesylate (DB). The influence of solution pH (1-3), adsorbent dose (20-50 mg), initial drug concentration (20.0-70.0 mg L^-1), contact time (15-300 min), and temperature (25, 35, and 45 °C) were systematically evaluated. Equilibrium was reached around 60 min, with a maximum adsorption capacity of 31.5 ± 2.0 mg g^-1 at a pH of 3.0 and 25 °C. Hydrogen bonding contributed to DB incorporation on the Kln/Gum. In addition, DB maximum amounts of 16.80 ± 0.58 and 77.00 ± 2.46% were released at pH values of 1.2 and 7.4, respectively. These results indicated that the Kln/Gum bionanocomposite is an effective and promising material for the incorporation/release of drugs with similar structures to DB.

Potential of Cellulose Functionalized with Carboxylic Acid as Biosorbent for the Removal of Cationic Dyes in Aqueous Solution

In the last decade, adsorption has been used to minimize the pollution caused by dyes, which represents a serious environmental problem. In this context, this work reports the preparation of phthalic anhydride-modified cellulose (PhCel), through the reaction of cellulose (Cel) with phthalic anhydride (Ph). The efficiency of the reaction was observed by elemental analysis, Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermogravimetry/derivative thermogravimetry (TG/DTG). The adsorbent matrix (Cel and PhCel) was used in the removal of crystal violet (CV) and methylene blue (MB) dyes in aqueous medium. In the kinetic study, the experimental data obtained had the best fit to the pseudo-first-order model. In general, the isotherms obtained at different temperatures had a best fit to the model proposed by Langmuir, and the CV and MB adsorption process in adsorbent matrixes can be favored strictly by hydrogen bonds and/or electrostatic interactions for Cel and electrostatic interactions for PhCel.

Direct Modification of Microcrystalline Cellulose with Ethylenediamine for use as Adsorbent for Removal Amitriptyline Drug from Environment

Cellulose derivatives have been widely used as adsorbents for the removal of micropollutants such as drugs, dyes, and metals, due to their abundance, low cost and non-contaminating nature. In this context, several studies have been performed searching for new adsorbents (cellulose derivatives) efficient at contaminant removal from aqueous solutions. Thus, a new adsorbent was synthesized by chemical modification of cellulose with ethylenediamine in the absence of solvent and applied to the adsorption of amitriptyline (AMI) in aqueous solution. The modification reaction was confirmed by X-ray Diffraction (XRD), elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry/Differential Scanning Calorimeter (TG/DSC), solid state Nuclear Magnetic Resonance of ¹H and ¹³C (¹H-NMR and ¹³C-NMR). Moreover, the effectiveness of reaction was confirmed by computational calculations using Density Functional Theory (DFT) at level B3LYP/6-31G(d). This adsorption process was influenced by pH, time, concentration, temperature and did not show significant changes due to the ionic strength variation. Through these experiments, it was observed that the maximum adsorption capacity of AMI by CN polymer at 298 K, 300 min, and pH 7 was 87.66 ± 0.60 mg·g⁻¹.