Adsorption of Methyl Orange from Water Using Chitosan Bead-like Materials

Efficient encapsulation of a model drug in chitosan cathodic electrodeposition: Preliminary analysis using FTIR, UV-vis, and NMR spectroscopy

This study investigates the preliminary efficacy of drug encapsulation in chitosan hydrogels by cathodic electrodeposition for the encapsulation of the aromatic dye methyl orange to enhance drug delivery in biological systems. Chitosan, a biocompatible and transparent polymer, is known for its ability to effectively encapsulate and transport therapeutic agents, which is critical for sustained and targeted drug release. Methyl orange was selected as a model drug to study the effects of deposition and immersion times on encapsulation efficiency. The effects of deposition and immersion times on encapsulation efficiency were analyzed by synthesizing multilayer hydrogels via electrochemical oxidation. Characterization techniques, including UV-visible spectroscopy, FTIR, and NMR, were employed; FTIR indicated an effective absorption of 4.34 % for Td50Ti60, while UV-Vis showed 46.41 % at Td60Ti50. NMR analysis revealed effective concentrations of 0.47 mM for Td70Ti60 and 0.38 mM for Td60Ti50, indicating that longer immersion times enhance absorption. These findings provide a foundation for further studies aimed at optimizing drug delivery strategies and improving the therapeutic efficacy of encapsulated agents in biological applications.

Tailoring of carboxymethyl guar gum hydrogels via gamma irradiation for remarkable removal of cationic and anionic dyes from simulated solutions

Green hydrogels were synthesized from carboxymethyl guar gum (CMGG)-polyacrylic acid (PAAc) via gamma irradiation at doses of 10-40 kGy, they were codes as (CMGG/PAAc). FTIR spectroscopy was applied to confirm the chemical transformation of GG into the hydrogel formulations while the 1HNMR was employed to confirm the successful preparation of CMGG. TGA, XRD, and AFM were used to compare the improved formulation to native and CMGG. The investigated hydrogels were then applied comparatively to remove methylene blue (MB) and methyl orange (MO) dyes from aqueous solution under various operating parameters. In addition, the AFM was used comprehensively to address the adsorption process by comparing the surface topographies, height and roughness measurements between the dry and dye-loaded hydrogel. Four adsorption isotherms were investigated in order to go deep through the adsorption mechanism. These are Langmuir Freundlich, Redlich-Peterson and Jovanovich isotherms. Based on the values of R2 for all the models, it can be assumed that the Langmuir model is best appropriate for the adsorption process and that the dyes were adsorbed onto a homogenous surface. Kinetic tests showed that the pseudo-second-order model best fitted the adsorption process, with R2 values of 0.9999 for both dyes, confirming chemisorption as the rate-limiting step. The thermodynamic data indicates spontaneous, exothermic adsorption processes, with Gibbs free energy changes (∆G) for MB ranging from -11.265 to -10.82 kJ/mol and MO from -3.221 to -3.323 kJ/mol. Negative enthalpy changes (∆H) of -17.892 kJ/mol for MB and - 17.005 for MO show the exothermic nature of adsorption. The data proved effective removal of MB and MO dyes onto CMGG/PAAc hydrogels with better affinity for MB dye, making them excellent wastewater treatment adsorbents.

Preparation of ultra-light, highly compressible, and biodegradable chitosan porous materials for heavy metal adsorption, dye adsorption and oil-water separation

Chitosan materials are much important in adsorption, separation and water treatment due to their hydrophilicity, biodegradability and easy functionalization. However, they were difficult to form structural materials, which limited its application in engineering. In this paper, a new type of chitosan porous materials was prepared with two-step strategy involving the freezing crosslinking of chitosan with glutaraldehyde to form cryogels, and their subsequent reduction with NaBH4 to transform CN bonds into CN bonds, resulting in remarkable improvement of mechanical property. That is, the strength remained almost unchanged after 80 % deformation. The abundant -NH2 and -OH on the surface of materials, as well as the unique pore structure from cryogels, gave relatively high adsorption capacity for metals and dyes (88.73 ± 4.25 mg·g-1 for Cu(II) and 3261.05 ± 36.10 mg·g-1 for Congo red). The surface hydrophilicity of materials made it possible for selective water permeation with over 95 % separation efficiency for oil-water mixtures. In addition, simple hydrophobic modification using bromotetradecane achieved selective oil permeation with over 96 % separation efficiency for oil-water mixtures. This study not only provides a new strategy to endow chitosan materials with excellent mechanical property, large adsorption capacity and good oil-water separation performance, but also offers environmentally friendly materials for sewage treatment applications.

Hybrid Chitosan Biosorbents: Tunable Adsorption at Surface and Micropore Domains

Herein, we report a study that provides new insight on the knowledge gaps that relate to the role of biopolymer structure and adsorption properties for chitosan adsorbents that are cross-linked with glutaraldehyde. The systematic modification of chitosan cross-linked with glutaraldehyde (CG) and its quaternized forms (QCG) was studied in relation to the reaction conditions: mole ratios of reactants and pH conditions. Complementary adsorbent characterization employed 13C NMR/FTIR spectroscopy, TGA and DSC, point-zero-charge (PZC), solvent swelling, and sorption studies using selected dye probes. The spectral and thermal techniques provide complementary evidence that affirm the key role of cross-linker content and quaternization on variation of the physicochemical properties of chitosan. The PZC results reveal a neutral surface charge for the modified materials between pH 6.0 to 6.3 ± 0.3, as compared with pH 8.7 ± 0.4 for pristine chitosan. Solvent swelling in water decreased with greater cross-linking, while the QCG materials had greater swelling over CG materials due to enhanced hydration. The adsorption results reveal variable dye uptake properties according to the cross-linker content. Similarly, surface versus micropore adsorption was demonstrated, according to the nature and ionization state of the dye for the modified adsorbents, where the CG and QCG materials had tunable sorption properties that exceeded that of unmodified chitosan. A key step in tuning the structure and surface chemical properties of cross-linked chitosan involves pH control during synthesis. The facile tunability of the physicochemical properties of the modified biopolymers reported herein means that they possess features of biomimetics that are relevant to advanced drug delivery, antimicrobial materials for wound healing, biosensors, and biosorbents for biomedical applications.

Development of Variable Charge Cationic Hydrogel Particles with Potential Application in the Removal of Amoxicillin and Sulfamethoxazole from Water

Cationic hydrogel particles (CHPs) crosslinked with glutaraldehyde were synthesized and characterized to evaluate their removal capacity for two globally consumed antibiotics: amoxicillin and sulfamethoxazole. The obtained material was characterized by FTIR, SEM, and TGA, confirming effective crosslinking. The optimal working pH was determined to be 6.0 for amoxicillin and 4.0 for sulfamethoxazole. Under these conditions, the CHPs achieved over 90.0% removal of amoxicillin after 360 min at room temperature, while sulfamethoxazole removal reached approximately 60.0% after 300 min. Thermodynamic analysis indicated that adsorption occurs through a physisorption process and is endothermic. The ΔH° values of 28.38 kJ mol-1, 12.39 kJ mol-1, and ΔS° 97.19 J mol-1 K-1, and 33.94 J mol-1 K-1 for AMX and SMX, respectively. These results highlight the potential of CHPs as promising materials for the removal of such contaminants from aqueous media.

Engineering a sustainable cadmium sulfide/polyethyleneimine-functionalized biochar/chitosan composite for effective chromium adsorption: optimization, co-interfering anions, and mechanisms

A novel eco-friendly adsorbent was fabricated by mixing mushroom-derived cadmium sulfide and polyethyleneimine-functionalized biochar that was fabricated from coffee waste with a chitosan biopolymer. The green-synthesized CdS/PEI-BC/CTS composite was analyzed using several characterization methods to identify its morphological, compositional, and structural characteristics. In addition, the adsorption property of the composite was investigated for hexavalent chromium as a model for anionic heavy metals. The best adsorption conditions to efficiently adsorb Cr(vi) onto CdS/PEI-BC/CTS were scrutinized in the batch mode. The experimental results elucidated that the higher adsorption efficacy for Cr(vi) was 97.89% at pH = 3, Cr(vi) concentration = 50 mg L-1, CdS/PEI-BC/CTS dose = 0.01 g, and temperature = 20 °C. The impact of co-interfering anionic species on Cr(vi) adsorption was identified in simulated wastewater. The recycling property of the CdS/PEI-BC/CTS composite was assessed for ten runs to ensure the applicability of the green composite. The adsorption mechanism and interaction types were proposed on the basis of kinetic and isotherm studies, along with analysis tools. The mechanistic study proposed that the Cr(vi) adsorption onto CdS/PEI-BC/CTS occurred via chemical and physical pathways, including protonation, electrostatic interactions, reduction, and coordination bonds.

Harnessing the power of polyethyleneimine in modifying chitosan surfaces for efficient anion dyes and hexavalent chromium removal

In this investigation, synthesis of a surface-functionalized chitosan known as amino-rich chitosan (ARCH) was achieved by successful modification of chitosan by polyethyleneimine (PEI). The synthesized ARCH was characterized by a specific surface area of 8.35 m2 g-1 and a microporous structure, with pore sizes predominantly under 25 nm. The Zeta potential of ARCH maintained a strong positive charge across a wide pH range of 3-11. These characteristics contribute to its high adsorption efficiency in aqueous solutions, demonstrated by its application in removing various anionic dyes, including erioglaucine disodium salt (EDS), methyl orange (MO), amaranth (ART), tartrazine (TTZ), and hexavalent chromium ions (Cr(VI)). The adsorption capacities (Qe) for these contaminants were measured at 1301.15 mg g-1 for EDS, 1025.45 mg g-1 for MO, 940.72 mg g-1 for ART, 732.96 mg g-1 for TTZ, and 350.15 mg g-1 for Cr(VI). A significant observation was the rapid attainment of adsorption equilibrium, occurring within 10 min for ARCH. The adsorption behavior was well-described by the Pseudo-second-order and Langmuir models. Thermodynamic studies indicated that the adsorption process is spontaneous and endothermic in nature. Additionally, an increase in temperature was found to enhance the adsorption capacity of ARCH. The material demonstrated robust stability and selective adsorption capabilities in varied conditions, including different organic compounds, pH environments, sodium salt presence, and in the face of interfering ions. After five cycles of adsorption, ARCH maintained about 60% of its initial adsorption capacity. Due to its efficient adsorption performance, simple synthesis process, low biological toxicity, and cost-effectiveness, ARCH is a promising candidate for future water treatment technologies.