Hydrothermal synthesis of phosphorylated chitosan and its adsorption performance towards Acid Red 88 dye

A comparison of freeze- and air-dried chitosan salicylaldehyde/calcium oxide biocomposites for optimized removal of acid red 88 dye

Chitosan salicylaldehyde/calcium oxide nanoparticle (CS-SL/CaO) was synthesized by hydrothermal process and isolated via different drying processes, namely, air-drying (AD) and freeze-drying (FD). The physicochemical properties of freeze-dried CS-SL/CaO nanoparticle (CS-SL/CaO-FD) and air-dried CS-SL/CaO nanoparticle (CS-SL/CaO-AD) were compared. In particular, the adsorption properties reveal that the specific surface area of CS-SL/CaO-FD increased by ca. 6 times (BET SA = 7.28 m2/g) greater than CS-SL/CaO-FD (BET SA = 1.26 m2/g). Also, the adsorptive removal of acid red 88 dye (AR88) from aqueous media was optimized by employing the Box-Behnken design (BBD). The optimal adsorption conditions obtained from desirability functions test for the removal of AR88 dye employed a dosage of 0.09 g/100 mL of adsorbent dosage at a solution pH of 5.6 and 25 °C. The best AR88 dye removal was found for the adsorbents CS-SL/CaO-AD (38.2 %) and CS-SL/CaO-FD (86.1 %), which concur with differences in the adsorbent surface areas. Moreover, the adsorption kinetics and isotherm profiles for CS-SL/CaO-FD were described by the pseudo second order (PSO) and Temkin models, where the maximum adsorption capacity of AR88 by CS-SL/CaO-FD 175.4 was mg/g. These findings reveal the potential application of the CS-SL/CaO-FD towards removal of toxic cationic dye (AR88) from an aqueous environment.

Efficient removal of crystal violet and acid red 88 dyes from aqueous environments using easily synthesized copper ferrite nanoparticles

This study details the synthesis and application of magnetic copper ferrite (CuFe2O4) nanoparticles for the efficient removal of acid red 88 and crystal violet dyes from aqueous solutions. Utilizing a combustion method, nanoparticles were synthesized with succinic and malic acids as fuels, yielding samples with crystallite sizes of 28.54 ± 0.90 nm for the sample synthesized with malic acid and 19.79 ± 0.75 nm for the sample synthesized with succinic acid. Optimum removal conditions were found at a pH of 2 for acid red 88 and pH 10 for crystal violet, with a contact time of 80 min and an adsorbent dosage of 0.05 g in a 100 mL solution. Under these conditions, the sample synthesized using succinic acid achieved sorptive capacities of 452.49 mg/g for acid red 88 and 446.43 mg/g for crystal violet, while the sample synthesized using malic acid reached 408.16 mg/g and 374.53 mg/g, respectively. Both adsorption processes followed the pseudo-second-order kinetic model and aligned with the Langmuir isotherm. Thermodynamic analysis confirmed the process as exothermic and spontaneous. Practical trials demonstrated removal efficiencies above 95% for both dyes in real wastewater samples, underscoring the method's practical potential in water purification applications.

Chitosan-Polyaniline (Bio)Polymer Hybrids by Two Pathways: A Tale of Two Biocomposites

Previous research highlights the potential of polyaniline-based biocomposites as unique adsorbents for humidity sensors. This study examines several preparative routes for creating polyaniline (PANI) and chitosan (CHT) composites: Type 1-in situ polymerization of aniline with CHT; Type 2-molecular association in acidic aqueous media; and a control, Type 3-physical mixing of PANI and CHT powders (without solvent). The study aims to differentiate the bonding nature (covalent vs. noncovalent) within these composites, which posits that noncovalent composites should exhibit similar physicochemical properties regardless of the preparative route. The results indicate that Type 1 composites display features consistent with covalent and hydrogen bonding, which result in reduced water swelling versus Type 2 and 3 composites. These findings align with spectral and thermogravimetric data, suggesting more compact structure for Type 1 materials. Dye adsorption studies corroborate the unique properties for Type 1 composites, and 1H NMR results confirm the role of covalent bonding for the in situ polymerized samples. The structural stability adopts the following trend: Type 1 (covalent and noncovalent) > Type 2 (possible trace covalent and mainly noncovalent) > Type 3 (noncovalent). Types 2 and 3 are anticipated to differ based on solvent-driven complex formation. This study provides greater understanding of structure-function relationships in PANI-biopolymer composites and highlights the role of CHT as a template that involves variable (non)covalent contributions with PANI, according to the mode of preparation. The formation of composites with tailored bonding modalities will contribute to the design of improved adsorbent materials for environmental remediation to versatile humidity sensor systems.

Facile synthesis of eco-friendly alginate-chitosan bio-adsorbent for critical raw materials adsorption: A comprehensive study

Sustainable management of critical raw materials is of paramount importance to ensure a steady supply and reduce environmental impact. The application of newly synthesized and environmentally friendly ALG@CS material as a bio-adsorbent for the effective rare earth elements removal from aqueous solution has been presented. The synthesized material underwent FTIR, XPS, EDX, and SEM analysis to determine its suitability for metal uptake. To evaluate the adsorption capacity of ALG@CS for rare earth elements several factors were taken into consideration. These factors included alginate:chitosan ratios, bead size, pH level, composite mass, interaction time, metal ion concentration, and temperature, being all varied during the batch mode evaluation process. Under the optimal conditions, the maximum adsorption capacities were found to be 145.90 mg La(III)/g, 168.44 mg Ce(III)/g, 132.51 mg Pr(III)/g, 128.40 mg Nd(III)/g, 154.36 mg Sm(III)/g, and 165.10 mg Ho(III)/g. The equilibrium data fits well with non-linear three-parameter Sips and Redlich-Peterson isotherm models. The PSO model finds the highest process suitability. The synthesized ALG@CS bio-adsorbent showed excellent regenerative capacity in ten cycles, making it a suitable adsorbent for rare earth elements uptake. The unique bio-adsorbents combination allows for efficient critical raw materials adsorption providing a promising solution for their recovery and recycling.

Opportunity for a greener recovery of dysprosium(III) from secondary sources by a novel Mannich reaction-modified phosphorylated chitosan hydrogel

The depleting supply of natural sources of rare earth elements (REE) is a concern to many nations as demand for advanced technology is becoming vital for national security. In this communication, the recovery of dysprosium(III) from aqueous systems was exemplified by a modified phosphorylated chitosan (PCs/MB) prepared by the C-Mannich reaction of phosphorylated chitosan, glutaraldehyde, and 4-hydroxycoumarin in ethanolic solution. Batch adsorption studies achieved a maximum adsorption capacity (qmax) of 34 mg/g at 25 °C and pH = 5.4 for 2 h. Fourier Transform-Infrared Spectroscopy, elemental mapping, and quantitative analyses revealed ion-exchange mechanism with C6-phosphate and a synergistic complexation with the amino group between two hexose units of the chitosan chain confirming the correlation provided by the pseudo-second order kinetics (R2 = 0.9996), extrapolated mean free energy of adsorption (Eads) of 12.9 kJ/mol from the corrected Dubinin-Radushkevich isotherm, and the extrapolated enthalpy of adsorption (ΔH0ads) of -42.4 kJ/mol from the linearized Van't Hoff plot. Competitive adsorption with iron(II), cerium(III), and neodymium(III) demonstrated preferential removal of dysprosium(III) and complete exclusion of iron(II), which illustrates potential application in the separation of REE from electronic wastes.

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.

Development of a chitosan/nanosilica biocomposite with arene functionalization via hydrothermal synthesis for acid red 88 dye removal

Herein, the polymer nanomatrix of chitosan/SiO2 (CHI/n-SiO2) was enriched with a π-π electron donor-acceptor system using diaromatic rings of benzil (BEZ) assisted via a hydrothermal process to obtain an effective adsorbent of chitosan-benzil/SiO2 (CHI-BEZ/n-SiO2). The polymer nanomatrix (CHI/n-SiO2) and the resulting adsorbent (CHI-BEZ/n-SiO2) were applied to remove the anionic acid red 88 (AR88) dye from aqueous media in a comparative mode. Box-Behnken design (BBD) was adopted to optimize AR88 adsorption onto CHI/n-SiO2 and CHI-BEZ/n-SiO2 with respect to variables that influence AR88 adsorption (adsorbent dose: 0.02-0.1 g/100 mL; pH: 4-10; and time: 10-90). The adsorption studies at equilibrium were conducted with a variety of initial AR88 dye concentrations (20-200 mg/L). The adsorption isotherm results reveal that the AR88 adsorption by CHI/n-SiO2 and CHI-BEZ/n-SiO2 are described by the Langmuir model. The kinetic adsorption profiles of AR88 with CHI/n-SiO2 and CHI-BEZ/n-SiO2 reveal that the pseudo-first-order model provides the best fit results. Interestingly, CHI-BEZ/n-SiO2 has a high adsorption capacity (261.2 mg/g), which exceeds the adsorption capacity of CHI/n-SiO2 (215.1 mg/g) that relates to the surface effects of SiO2 and the functionalization of chitosan with BEZ. These findings show that CHI-BEZ/n-SiO2 represents a highly efficient adsorbent for the removal of harmful pollutants from water, which outperforming the CHI/n-SiO2 system.

Fabrication of magnetic chitosan-grafted salicylaldehyde/nanoclay for removal of azo dye: BBD optimization, characterization, and mechanistic study

Herein, a novel nanohybrid composite of magnetic chitosan-salicylaldehyde/nanoclay (MCH-SAL/NCLA) was hydrothermally synthesized for removal of azo dye (acid red 88, AR88) from simulated wastewater. Response surface methodology combined with the Box-Behnken design (RSM-BBD) was applied with 29 experiments to assess the impact of adsorption variables, that include A: % NCLA loading (0-50), B: MCH-SAL/NCLA dose (0.02-0.1 g/100 mL), C: pH (4-10), and time D: (10-90 min) on AR88 dye adsorption. The highest AR88 removal (75.16 %) as per desirability function was attained at the optimum conditions (NCLA loading = 41.8 %, dosage = 0.06 g/100 mL, solution pH = 4, and time = 86. 17 min). The kinetic and equilibrium adsorption results of AR88 by MCH-SAL/NCLA reveal that the process follows the pseudo-first-order and Temkin models. The MCH-SAL/NCLA composite has a maximum adsorption capacity (173.5 mg/g) with the AR88 dye. The adsorption of AR88 onto the MCH-SAL/NCLA surface is determined by a variety of processes, including electrostatic, hydrogen bonding, n-π, and n-π interactions. This research revealed that MCH-SAL/NCLA can be used as a versatile and efficient bio-adsorbent for azo dye removal from contaminated wastewater.

Design of separable magnetic chitosan grafted-benzaldehyde for azo dye removal via a response surface methodology: Characterization and adsorption mechanism

In this study, a magnetic chitosan grafted-benzaldehyde (CS-BD/Fe₃O₄) was hydrothermally prepared using benzaldehyde as a grafting agent to produce a promising adsorbent for the removal of acid red 88 (AR88) dye. The CS-BD/Fe₃O₄ was characterized by infrared spectroscopy, surface area analysis, scanning electron microscopy-energy dispersive X-ray, vibrating sample magnetometry, powder X-ray diffraction, CHN elemental analysis, and point of zero charge (pH_PZC). The Box-Behnken design (BBD) was adopted to study the role of variables that influence AR88 dye adsorption (A: CS-BD/Fe₃O₄ dose (0.02-0.1 g), B: pH (4-10), and time C: (10-90 min)). The ANOVA results of the BBD model indicated that the F-value for the AR88 removal was 22.19 %, with the corresponding p-value of 0.0002. The adsorption profiles at equilibrium and dynamic conditions reveal that the Temkin model and the pseudo-first-order kinetics model provide an adequate description of the isotherm results, where the maximum adsorption capacity (qmax) with the AR88 dye was 154.1 mg/g. Several mechanisms, including electrostatic attraction, n-π interaction, π-π interaction, and hydrogen bonding, regulate the adsorption of AR88 dyes onto CS-BD/Fe₃O₄ surface. As a result, this research indicates that the CS-BD/Fe₃O₄ can be utilized as an effective and promising bio-adsorbent for azo dye removal from contaminated wastewater.

Study of phenobarbital removal from the aqueous solutions employing magnetite-functionalized chitosan

Due to its wide use in anticonvulsant pharmacotherapy, phenobarbital (PHEN) is an aquatic contaminant with a high prevalence in the environment. In this adsorption study, chitosan and chitosan-based magnetic adsorbents containing different amounts of incorporated magnetite (CS, CS·Fe₃O₄ 1:1, CS·Fe₃O₄ 1:5, and CS·Fe₃O₄ 1:10) were used for phenobarbital removal. The magnetic adsorbents were synthesized by co-precipitation method and characterized through FTIR, XRD, MEV, and VSM analysis. In PHEN adsorption, the equilibrium and adsorption kinetic were better adjusted by the Sips and pseudo-second-order model, respectively. Among the four nanoadsorbents used, the maximum phenobarbital adsorption capacity was 94.60 mg g^-1 using 25 mg of CS·Fe₃O₄ 1:5, with a concentration of PHEN (50 mg L^-1), pH 7.0 at room temperature. The parameters of pH, adsorbent dosage, ionic strength, and thermodynamic study were tested for the adsorbent with the highest performance (CS·Fe₃O₄ 1:5). The nanoadsorbent demonstrates efficiency in the removal of the contaminant for diverse adsorption cycles. Finally, the protocol employing magnetic adsorbents dispenses the subsequent steps of filtration and centrifugation.

Chemical modifications in the structure of marine polysaccharide as serviceable food processing and preservation assistant: A review

Marine polysaccharides are a kind of natural polysaccharides which isolated and extracted from marine organisms. Now some marine polysaccharides, such as chitosan, sodium alginate and agar, have been proven to exhibit antibacterial, antioxidant functions and biocompatibility, which are often used to preserve food or improve the physicochemical properties of food. However, they still have the defects of unsatisfactory preservation effect and biological activity, which can be remedied by its modification. Chemical modification is the most effective of all modification methods. The advances in common chemical modification methods of chitosan, sodium alginate, agar and other marine polysaccharides and research progress of modified products in food processing and preservation were summarized, and the influence of additional reaction conditions on the existence of chemical modification sites of polysaccharides was discussed. The modification of functional groups in natural marine polysaccharides leads to the change of molecular structure, which can improve the physical, chemical and biological properties of marine polysaccharides. Chemically modified products have been used in various fields of food applications, such as food preservatives, food additives, food packaging, and food processing aids. In general, chemical modification has excellent potential for food processing and preservation, which can improve the function of marine polysaccharides.

Ultrahigh efficient and selective adsorption of U(VI) with amino acids-modified magnetic chitosan biosorbents: Performance and mechanism

Exploiting eco-friendly, highly controlled preparation and convenient solid-liquid separation adsorbent to separate uranium from aquatic medium is of importance and in demand. In this study, magnetic ferroferric oxide nanoparticles synthesized through a facile hydrothermal reaction was cross-linked with chitosan. The intermediate product was subsequently chemically grafting with four amino acids such as alanine, serine, glycine or L-cysteine to produce Ala-MCS, Ser-MCS, Gly-MCS and Cys-MCS. The resultants were verified by SEM, EDS, XRD, VSM, FT-IR and XPS. Adsorption of uranium with amino acids-modified magnetic chitosans were carried out. The parameters that affected the adsorption ability, selectivity toward uranium, and reusability have been illustrated. pH 6.5 was the most beneficial for the adsorption. The saturation adsorption capacity of Ala-MCS, Ser-MCS, Gly-MCS, Cys-MCS were found as 658.88 mg/g ± 1.0 %, 616.10 ± 0.3 % mg/g, 646.38 ± 1.8 % mg/g, 653.96 ± 3.4 % mg/g and 409.15 ± 4.6 % mg/g, respectively. The adsorption process was analyzed using kinetics (pseudo-first-order, pseudo-second-order and intraparticle diffusion models) and isotherms models (Langmuir and Freundlich models). The adsorption of uranium on Ala-MCS, Ser-MCS, Gly-MCS and Cys-MCS happened on monolayer and were controlled by chemisorption. The certified high adsorption amount and efficient solid-liquid separation proved amino acids-modified magnetic chitosan are promising adsorbents for removal of uranium from wastewater.

Chitosan as a Tool for Sustainable Development: A Mini Review

New developments require innovative ecofriendly materials defined by their biocompatibility, biodegradability, and versatility. For that reason, the scientific society is focused on biopolymers such as chitosan, which is the second most abundant in the world after cellulose. These new materials should show good properties in terms of sustainability, circularity, and energy consumption during industrial applications. The idea is to replace traditional raw materials with new ecofriendly materials which contribute to keeping a high production rate but also reducing its environmental impact and the costs. The chitosan shows interesting and unique properties, thus it can be used for different purposes which contributes to the design and development of sustainable novel materials. This helps in promoting sustainability through the use of chitosan and diverse materials based on it. For example, it is a good sustainable alternative for food packaging or it can be used for sustainable agriculture. The chitosan can also reduce the pollution of other industrial processes such as paper production. This mini review collects some of the most important advances for the sustainable use of chitosan for promoting circular economy. Hence, the present review focuses on different aspects of chitosan from its synthesis to multiple applications.