Amphoteric gellan gum-based terpolymer–montmorillonite composite: synthesis, swelling, and dye adsorption studies

An Overview of Potential Applications of Environmentally Friendly Hybrid Polymeric Materials

The applications of polymeric materials are being constantly reviewed and improved. In the present world, the word hybrid, and the general idea of combining two or more inherently different approaches, designs, and materials is gaining significant attention. The area of sustainable materials with a low environmental impact is also rapidly evolving with many new discoveries, including the use of materials of a natural origin and countless combinations thereof. This review tries to summarize the current state of knowledge about hybrid polymeric materials and their applications with special attention to the materials that can be considered "environmentally friendly". As the current application field is quite broad, the review was limited to the following topics: packaging, medical applications, sensors, water purification, and electromagnetic shielding. Furthermore, this review points out the new prospects and challenges for the use of the mentioned materials in terms of creating novel solutions with different nano and micro-materials of mostly natural and renewable origin.

Removal of diclofenac sodium from aqueous solution using different ionic liquids functionalized tragacanth gum hydrogel prepared by radiation technique

Diclofenac sodium (DCF) was reported as an important emerging environmental pollutant and its removal from wastewater is very urgent. In this study, different alkyl substituted ionic liquids (1-alkyl -3-vinyl- imidazolium bromide [CnVIm]Br, n = 4, 6, 8, 10, 12) functionalized tragacanth gum (TG-CnBr) are prepared by radiation induced grafting and crosslinking polymerization. The adsorption behaviors of ionic liquids functionalized tragacanth gum for diclofenac sodium from aqueous solutions are examined. The adsorption capacity of TG-CnBr for diclofenac sodium increases with the increasing of alkyl chain length of the imidazolium cation and the hydrophobicity of the hydrogels. The maximum adsorption capacity by TG-C12Br for diclofenac sodium at 30, 40 and 50 °C were 327.87, 310.56 and 283.29 mg/g, respectively. The adsorption of TG-C12Br towards diclofenac sodium was little decreased with NaCl increasing. The removal efficiency was still remained 94.55 % within 5 adsorption-desorption cycles by 1 M HCl. Also, the adsorption mechanism including electrostatic attraction, hydrophobic interaction, hydrogen bonding, and π - π interaction was proposed.

Methylene blue removal from aqueous solutions using a biochar/gellan gum hydrogel composite: Effect of agitation mode on sorption kinetics

Hydrogel membranes are prepared by casting a mixture of gellan gum (associated with PVA) and biochar produced from a local Egyptian plant. The mesoporous material is characterized by a specific surface area close to 134 m² g^-1, a residue of 28 % (at 800 °C), and a pH_PZC close to 6.43. After grinding, the material is tested for Methylene Blue sorption at pH 10.5: sorption capacity reaches 1.70 mmol MB g^-1 (synergistic effect of the precursors). The sorption isotherms are fitted by both Langmuir and Sips eqs. MB sorption increases with temperature: the sorption is endothermic (∆H°: 12.9 kJ mol^-1), with positive entropy (∆S°: 125 J mol^-1 K^-1). Uptake kinetics are controlled by agitation speed (optimum ≈200 rpm) and resistance to intraparticle diffusion. The profiles are strongly affected by the mode of agitation: the equilibrium time (≈180 min) is reduced to 20-30 min under sonication (especially at frequency: 80 kHz). The mode of agitation controls the best fitting equation: pseudo-first order rate agitation for mechanical agitation contrary to pseudo-second order rate under sonication. The sorption of MB is poorly affected by ionic strength (loss <6 % in 45 g L^-1 NaCl solution). Desorption (faster than sorption) is completely achieved using 0.7 M HCl solution. At the sixth recycling, the loss in sorption is close to 5 % (≈ decrease in desorption efficiency). The process is successfully applied for the treatment of MB-spiked industrial solution: the color index decreases by >97 % with a sorbent dose close to 1 g L^-1; a higher dose is required for maximum reduction of the COD (60 % at 3 g L^-1).

Structural and Thermal Characteristics of Buriti Tree Gum (Mauritia flexuosa)

A polysaccharide was isolated from the exudate of a buriti tree trunk (Mauritia flexuosa). The molecular structure, thermal stability, morphology, crystallinity, and elemental composition of the product were investigated through spectroscopic techniques, such as Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR 1H and 13C), and energy-dispersive X-ray spectroscopy (EDS); thermogravimetric analysis (TG), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In addition to NMR molecular modeling studies, were performed to confirm the 1H and 13C chemical shifts to Gal and Xyl conformers. Buriti tree gum (BG) is an arabinogalactan, containing Rha, Ara, Xyl, and Gal, and degrades almost completely (98.5%) at 550 °C and has a maximum degradation peak at 291.97 °C, with a mass loss of 56.33%. In the temperature range of 255–290 °C, the energy involved in the BG degradation process was approximately 17 J/g. DSC indicated a glass transition temperature of 27.2 °C for BG, which had an irregular and heterogeneous morphology, with smooth or crumbling scaly regions, demonstrating the amorphous nature of BG that was confirmed by the XRD standard. EDS revealed the presence of carbon and oxygen, as well as calcium, magnesium, aluminum, silicon, chlorine, and potassium, in the BG composition.

Performance Evaluation of Gum Gellan-Based Hydrogel as a Novel Adsorbent for the Removal of Cationic Dyes: Linear Regression Models

In this work, the suitability and efficacy of the previously reported biodegradable gellan gum (GG)-based hydrogel have been thoroughly investigated with respect to the adsorption mechanisms of malachite green (MG) and methylene blue (MB) dyes. The dyes' removal from aqueous solutions using GG-cl-poly(AA) as an adsorbent material has been studied in a discontinuous system with respect to contact time, dose, pH, and temperature. The synthesized hydrogel was characterized by FT-IR, TGA, XRD, ¹H NMR, and FE-SEM. The adsorption capacity of GG-cl-poly(AA) hydrogel was investigated at different pH solutions (3, 7, and 10), and it was found that neutralized charge plays a crucial role in the enhancement of dye removal. To better understand the behavior of the GG-cl-poly(AA) hydrogel in adsorbing model dyes, adsorption kinetics, isotherms, and thermodynamics were also investigated. The values of qmax for MG and MB were obtained to be 552.48 and 531.9 mg g^-1. In addition, the influence of NaCl concentration on adsorption efficiency was investigated, and it was found that as the ion concentration increased, the effectiveness of the adsorption process dropped. Moreover, the synthesized hydrogel's potential application in the adsorption and separation of dyes from wastewater is enhanced by the reusability investigations conducted in convenient conditions. As a result, it is possible to conclude that reusing GG-cl-poly(AA) hydrogel as a low-cost, easy-to-handle, nontoxic material in an industrial wastewater treatment plant's adsorption process can provide a number of advantages, including high efficiency for MG and MB removal and cost savings on overall treatment plant operations.

Grafted Microparticles Based on Glycidyl Methacrylate, Hydroxyethyl Methacrylate and Sodium Hyaluronate: Synthesis, Characterization, Adsorption and Release Studies of Metronidazole

Three types of precursor microparticles based on glycidyl methacrylate, hydroxyethyl methacrylate and one of the following three crosslinking agents (mono-, di- or triethylene glycol dimethacrylate) were prepared using the suspension polymerization technique. The precursor microparticles were subsequently used to obtain three types of hybrid microparticles. Their synthesis took place by grafting sodium hyaluronate, in a basic medium, to the epoxy groups located on the surface of the precursor microparticles. Both types of the microparticles were characterized by: FTIR spectroscopy, epoxy groups content, thermogravimetric analysis, dimensional analysis, grafting degree of sodium hyaluronate, SEM and AFM analyses, and specific parameters of porous structures (specific surface area, pore volume, porosity). The results showed that the hybrid microparticles present higher specific surface areas, higher swelling capacities as well as higher adsorption capacities of antimicrobial drugs (metronidazole). To examine the interactions between metronidazole and the precursor/hybrid microparticles the adsorption equilibrium, kinetic and thermodynamic studies were carried out. Thus, it was determined the performance of the polymer systems in order to select a polymer-drug system with a high efficiency. The release kinetics reflect that the release mechanism of metronidazole in the case of hybrid microparticles is a complex mechanism characteristic of anomalous or non-Fickian diffusion.

Gellan gum/bacterial cellulose hydrogel crosslinked with citric acid as an eco-friendly green adsorbent for safranin and crystal violet dye removal

In this study, ex-situ crosslinked gellan gum (GG)/bacterial cellulose (BC) hydrogels have been investigated as good absorbents for the removal of safranin and crystal violet dye pollutants. The preparation involves a cost-effective and easy-to-perform crosslinking procedure, using citric acid (CA) as a green crosslinker. The physicochemical and mechanical properties of the crosslinked hydrogels were examined by FTIR, TGA, SEM, XRD, and unconfined compression analyses. The swelling capacity of the hydrogels as a function of pH was investigated. CA depicted to improve structural stability as a crosslinker. The dye removal capacity of the hydrogels as good adsorbents was explored and showed higher efficiency in the removal of safranin dye as compared to crystal violet with optimum adsorption capacities obtained as 17.57 and 13.49 mg/g, respectively. Adsorption kinetics and isotherm models as well as thermodynamics examined. Results showed the adsorption process well fitted the pseudo 2nd-order kinetic and Langmuir-Freundlich models while temperature dependence study depicted to be exothermic. Furthermore, no significant loss of removal efficiency of the hydrogel adsorbent was observed even after five adsorption-desorption cycles. Based on the revealed results, the prepared hydrogel may serve as an effective adsorbent for the removal of dyes from the aqueous phase.

Ag/LDH-itaconic acid-gellan gam nanocomposites: Facile and green synthesis, characterization, and excellent catalytic reduction of 4-nitrophenol

The catalytic reduction reaction is one of the most commonly used solutions to convert high-risk contaminants into safe or low-risk materials. Today, with the increasing water pollution, the urgent need for efficient and effective catalysts is felt more than ever. For this purpose, for the first time, a green catalyst composed of silver nanoparticles anchored on itaconic acid-modified Ca-Al layered double hydroxide/gellan gum nanocomposite (Ag/LDH-ITA-GG NC) was prepared from a green approach without the use of any toxic organic solvents. To gain an in-depth insight into the physicochemical properties of the catalyst, different techniques including nitrogen adsorption-desorption isotherms, FESEM/mapping, FTIR, TGA, and XRD were used. The catalytic performance of the Ag/LDH-ITA-GG NC toward 4-nitrophenol reduction by NaBH₄ was investigated. The calculated values of the apparent rate constant for this reaction are 0.2142 min^-1 (for 1.0 mg of the catalyst), 0.2375 min^-1 (for 3.0 mg of the catalyst), and 0.2550 min^-1 (for 5.0 mg of the catalyst), indicating that the catalytic conversion of 4-nitrophenol to 4-aminophenol on the Ag/LDH-ITA-GG NC catalyst follows the pseudo-first-order kinetics and is comparable to the previous findings in the literature. The results of this study indicated that Ag/LDH-ITA-GG NC can potentially be utilized as an auspicious high efficient green catalyst for the reduction of pollutants like 4-nitrophenol.

Adsorption Method for the Remediation of Brilliant Green Dye Using Halloysite Nanotube: Isotherm, Kinetic and Modeling Studies

The first-ever use of halloysite nanotube (HNT), a relatively low-cost nanomaterial abundantly available with minor toxicity for removing brilliant green dye from aqueous media, is reported. The factors affecting adsorption were studied by assessing the adsorption capacity, kinetics, and equilibrium thermodynamic properties. All the experiments were designed at a pH level of around 7. The Redlich-Peterson isotherm model fits best amongst the nine isotherm models studied. The kinetic studies data confirmed a pseudo model of the second order. Robotic investigations propose a rate-controlling advance being overwhelmed by intraparticle dispersion. The adsorbent features were interpreted using infrared spectroscopy and electron microscopy. Process optimization was carried out using Response Surface Methodology (RSM) through a dual section Fractional Factorial Experimental Design to contemplate the impact of boundaries on the course of adsorption. The examination of fluctuation (ANOVA) was utilized to consider the joined impact of the boundaries. The possibilities of the use of dye adsorbing HNT (“sludge”) for the fabrication of the composites using plastic waste are suggested.

Application of a modified biological flocculant in total nitrogen treatment of leather wastewater

Leather wastewater harms the ecological environment and human health. In this study, a modified bio-flocculant was prepared to facilitate treatment of leather wastewater. A bio-flocculant produced by Bacillus cereus was combined with amphoteric starch and modified using a cerium ammonium nitrate initiator. Single factor optimization and orthogonal optimization were used to determine the optimal preparation conditions as follows: amphoteric starch-to-flocculant ratio = 22:30; reaction temperature = 64 °C; initiator dosage = 2.00%; reaction time = 15 min; stirring speed = 600 rpm; and flocculation system pH = 8.0. At a dosage of 1 g/L added to simulated leather industry wastewater, the flocculation efficiency (98.17%) and the total nitrogen removal efficiency (100.00%) of modified bio-flocculant was superior to that achieved by 1 g/L of unmodified bio-flocculant (72.16% and 50.00%, respectively), amphoteric starch (8.50% and 0.00%) and polyacrylamide (95.55% and 75.00%). Analysis of natural and flocculated precipitates in the wastewater showed that the modified bio-flocculant significantly changed several characteristics of the flocculated particles; in addition, it promoted the removal of nitrogenous substances in the process of denitrification. These changes helped explain the material's flocculating ability. The results confirmed that the modified bio-flocculant was an effective additive for treating leather wastewater.