Ecofriendly Synthesis of Magnetic Composites Loaded on Rice Husks for Acid Blue 25 Decontamination: Adsorption Kinetics, Thermodynamics, and Isotherms.

Addressing the growing need for methods for ecofriendly dye removal from aqueous media, this study explores the potential of rice husks coated with iron oxide (Fe2O3@RH composites) for efficient Acid Blue 25 decontamination. The adsorption potential of Acid Blue 25 is analyzed using raw rice husks and Fe2O3 nanoparticles in the literature, but their enhanced removal capacity by means of Fe2O3@RH composites is reported for the first time in this study. Fe2O3@RH composites were analyzed by using analytical techniques such as TGA, SEM, FTIR, BET, and the point of zero charge (pH(PZC)). The Acid Blue 25 adsorption experiment using Fe2O3@RH composites showed maximum adsorption at an initial concentration of Acid Blue 25 of 80 ppm, a contact time of 50 min, a temperature of 313 K, 0.25 g of Fe2O3@RH composites, and a pH of 2. The maximum percentage removal of Acid Blue 25 was found to be 91%. Various linear and nonlinear kinetic and isothermal models were used in this study to emphasize the importance and necessity of the adsorption process. Adsorption isotherms such as the Freundlich, Temkin, Langmuir, and Dubinin-Radushkevich (D-R) models were applied. The results showed that all the isotherms were best fitted on the data, except the linear form of the D-R isotherm. Adsorption kinetics such as the intraparticle kinetic model, the Elovich kinetic model, and the pseudo-first-order and pseudo-second-order models were applied. All the kinetic models were found to be best fitted on the data, except the PSO model (types II, III, and IV). Thermodynamic parameters such as ΔG° (KJ/mol), ΔH° (KJ/mol), and ΔS° (J/K*mol) were studied, and the reaction was found to be exothermic in nature with an increase in the entropy of the system, which supported the adsorption phenomenon. The current study contributes to a comprehensive understanding of the adsorption process and its underlying mechanisms through characterization, the optimization of the conditions, and the application of various models. The findings of the present study suggest practical applications of this method in wastewater treatment and environmental remediation.

Adsorption Behavior and Dynamic Interactions of Anionic Acid Blue 25 on Agricultural Waste.

In this study, adsorption characteristics of a negatively charged dye, Acid Blue 25 (AB25), on pomelo pith (PP) was studied by varying the adsorption parameters, with the aim of evaluating the adsorption mechanism and establishing the role of hydrogen bonding interactions of AB25 on agricultural wastes. The kinetics, intraparticle diffusion, mechanism, and thermodynamics of the AB25 adsorption were systematically evaluated and analyzed by pseudo-first-order and pseudo-second-order kinetic models, the Weber-Morris intraparticle and Boyd mass transfer models, the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models, and the Van't Hoff equation. It was found that AB25 adsorption followed pseudo-second-order kinetics, governed by a two-step pore-volume intraparticle diffusion of external mass transfer of AB25 onto the PP surface. The adsorption process occurred spontaneously. The adsorption mechanism could be explained by the Langmuir isotherm model, and the maximum adsorption capacity was estimated to be 26.9 mg g-1, which is comparable to many reported adsorbents derived from agricultural wastes. Changes in the vibrational spectra of the adsorbent before and after dye adsorption suggested that AB25 molecules are bound to the PP surface via electrostatic and hydrogen bonding interactions. The results demonstrated that the use of pomelo pith, similar to other agricultural wastes, would provide a basis to design a simple energy-saving, sustainable, and cost-effective approach to remove negatively charged synthetic dyes from wastewater.

Removal of Acid Blue25 from aqueous solutions using Bengal gram fruit shell (BGFS) biomass.

The feasibility for the removal of Acid Blue25 (AB25) by Bengal gram fruit shell (BGFS), an agricultural by-product, has been investigated as an alternative for high-cost adsorbents. The impact of various experimental parameters such as dose, different dye concentration, solution pH, and temperature on the removal of Acid Blue25 (AB25) has been studied under the batch mode of operation. pH is a significant impact on the sorption of AB25 onto BGFS. The maximum removal of AB25 was achieved at a pH of 2 (83.84%). The optimum dose of biosorbent was selected as 200 mg for the removal of AB25 onto BGFS. Kinetic studies reveal that equilibrium reached within 180 minutes. Biosorption kinetics has been described by Lagergren equation and biosorption isotherms by classical Langmuir and Freundlich models. Equilibrium data were found to fit well with the Langmuir and Freundlich models, and the maximum monolayer biosorption capacity was 29.41 mg g-1 of AB25 onto BGFS. The kinetic studies indicated that the pseudo-second-order (PSO) model fitted the experimental data well. In addition, thermodynamic parameters have been calculated. The biosorption process was spontaneous and exothermic in nature with negative values of ΔG° (-1.6031 to -0.1089 kJ mol-1) and ΔH° (-16.7920 kJ mol-1). The negative ΔG° indicates the feasibility of physical biosorption process. The results indicate that BGFS could be used as an eco-friendly and cost-effective biosorbent for the removal of AB25 from aqueous solution.

Highly Electroactive Frozen-State Polymerized Polypyrrole Nanostructures for Flexible Supercapacitors.

The polymerization of pyrrole in the frozen state with the presence of organic dyes (methyl orange (MO) and Acid Blue 25 (AB)) has proven to produce polypyrrole (PPy) nanostructures. Herein, we explore the electrochemical properties of PPy prepared under frozen-state conditions (-24 °C) with and without the presence of organic dyes. The electroactivity of PPy prepared with MO and AB significantly increased in all electrolytic media with a capacitance higher than this of the PPy prepared at room temperature. The highest capacitance (1914 F g-1) was obtained for PPy-MO in 0.2 M HCl solution. The impedance spectra of PPy showed a decrease in charge transfer resistance when the dyes were present. This indicates a conductivity increase of PPy. Improved electrochemical stability was observed for PPy, PPy-MO, and PPy-AB prepared at -24 °C, wherein a steady gain of capacitance was maintained during 5000 potential cycling. In addition, a PPy-based supercapacitor device was fabricated to demonstrate the energy storage characteristics of PPy, where it showed good capacitive behavior and stability. Overall, frozen-state polymerized PPy posed an impressive capacitive performance for flexible supercapacitors.

Enhanced adsorption of acid Blue-25 dye onto chitosan/porous carbon composite modified in 1-allyl-3-methyl imidazolium bromide ionic liquid.

In this study, chitosan/porous carbon composite (C-PC) modified in 1-Allyl-3-methyl imidazolium bromide [AMIM][Br] under airtight condition was prepared for the removal of Acid Blue-25 dye (AB-25) from aqueous medium. For comparison of adsorption efficiency of C-PC, chitosan-activated carbon composite (C-AC) was also prepared in 1% acetic acid. The adsorbents were characterised using SEM, EDX, XRD, BET, TGA and FTIR. The micrograph of C-PC revealed cavities and slightly rough surfaces dominated with similar sized and irregular shaped stone-like materials which differ from the precursors' micrograph. BET analysis revealed the domination of mesopores on the C-PC and C-AC surfaces, as the hydroxyl and amino group on C-PC are the main active sites for AB-25 dye uptake. The dye was better adsorbed onto C-PC at pH 2 and C-AC at pH 4. The adsorption capacity obtained for C-PC, C-AC, activated carbon (AC) and chitosan (CH) using Langmuir isotherm model are 3333.33 mg/g, 909.90 mg/g, 909.09 mg/g and 833.33 mg/g, respectively. The experimental data are well described by Langmuir and Fruendlich isotherms for adsorption of the dye onto C-PC, AC and CH. C-AC fitted into Langmuir isotherm only. The kinetics of the adsorption fitted into pseudo-second order indicating the possibility of chemical interactions in the adsorption process.

Preparation of novel chitosan polymeric nanocomposite as an efficient material for the removal of Acid Blue 25 from aqueous environment.

A novel, sustainable chitosan polymeric nanocomposite (CS-PVA@CuO) was synthesized and subjected to the removal of acid blue 25 (AB25) from the aqueous environment. The influence of different variables such as pH, contact time, initial dye concentration, temperature, and adsorption kinetics has been examined in the batch adsorption process. The CS-PVA@CuO composite was systematically characterized by XRD, FTIR, SEM, and EDX analysis. The pseudo-first order (PFO), pseudo-second order (PSO), and intra-particle diffusion kinetics equations were used to examine the kinetic data of the adsorption process. The adsorption kinetics confirms that the PSO model was a more exact fit. Thermodynamics study typically revealed that the uptake of AB25 by the adsorbent is spontaneous and endothermic in nature. Remarkably, the results reveal the highest adsorption capacity of the CS-PVA@CuO was 171.4 mg/g at 313 K. To be specific, CS-PVA@CuO polymer nanocomposite can be effectively used as a suitable adsorbent material for the potential elimination of anionic AB25 dye from the aqueous solutions.

Synthesis, characterization, and assessment of cationic and anionic dye adsorption performance of functionalized silica immobilized chitosan bio-polymer.

The functionalization of polymers is still an efficient scheme to provide materials with new properties. In this paper, 4-methyl-2-(naphthalen-2-yl)-N-propylpentanamide-functionalized ethoxy-silica was successfully immobilized onto chitosan bio-polymer spherical beads to improve their adsorption characteristics. The interaction between the polymer and the functionalized silica was analyzed using FT-IR spectroscopy and SEM analysis. FT-IR investigation suggested that the interaction between chitosan and functionalized silica occurred through hydrogen bonding. The morphology of the prepared composite gel beads exhibited a spherical shape surface covered by silica particles. The unfunctionalized and functionalized beads were studied for the adsorption of methylene blue (MB) and Acid blue 25 (AB25) from water. The influence of pH, time, dye concentration, and temperature on the adsorption characteristics was investigated. The results showed that the highest adsorption amount of dyes was reached using the functionalized chitosan beads under the following conditions; pH = 5 for AB25 and pH = 6 for MB, time = 120 min, and T = 20 °C. The adsorbed yield of MB using the composite beads increased three times more than the capacity of chitosan beads and it was improved 1.4 times in the case of AB25. The mean free energy values (74.53-223.61 kJ mol-1), computed from the Dubinin-Radushkevich model suggested the chemi-sorption nature of the adsorption phenomenon.

[λ­Carrageenan­calcium phosphate] and [sodium alginate­calcium phosphate] modified with dimethyl diallyl ammonium chloride and diallylamin co-polymer as efficient adsorbents of anionic dyes.

Alginate and carrageenan bio-polymers have been proved to be, only, good sorbents of cationic dyes. In this study, we reported the synthesis of [λ­carrageenan­calcium phosphate] and [sodium alginate­calcium phosphate] modified with dimethyl diallyl ammonium chloride and diallylamin co-polymer, which could be used as effective adsorbents of anionic dyes. Evidence of chemical modification was proved through Fourier Transform Infrared Spectroscopy (FT-IR) band shifting, peaks broadening in X-Ray Diffraction (XRD) and the change in thermal event (TGA). The sorption process was studied using acid blue 25 as representative anionic dye. The adsorbed quantity reached, at equilibrium, 446 mg/g and 195 mg/g using cationized [sodium alginate­calcium phosphate] and cationized [λ­carrageenan­calcium phosphate], respectively. However, it does not exceed 3.4 mg/g in the case of the unmodified [sodium alginate­calcium phosphate]. The sorption of acid blue 25 using cationized hybrid materials complied well with the pseudo-second-order suggesting a chemi-sorption. Freundlich isotherm described well the adsorption mechanism of the three studied adsorbents. In summary, the high sorption capacities of the cationized hybrid materials obtained in this study suggest their use as effective adsorbents of acid dyes from wastewaters.