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.

This study aims to purify water from hazardous dyes and for this purpose, a novel adsorbent is developed that was synthesized by using sodium alginate, guar gum and iron coated activated alumina (SA@GG@ICAA Composites) with the Ion Gelation Method. The novel composites were characterized by using SEM, XRD, DSC, FTIR, BET, EDX, zeta potential and zeta sizer. These novel composites were used for the removal of Direct Blue 86 (DB86). The surface area of the adsorbent was found to be 5.606 m²/g. Zeta size and zeta potential was found to be 169.9 nm and −47.7 mV, respectively. Optimized parameters were achieved for best adsorption of the selected dye. For DB86, the removal efficiency was found to be 97% at 40 ppm (dye concentration), 150 min (contact time), 3 (pH) and 150 mg (adsorbent concentration) at λmax of 620 nm. Linear and non-linear forms of adsorption isotherms are applied on the experimental data to check the adsorption methodology and its chemistry. The non-linear form of the Freundlich isotherm was found to be best fitted for the current work (0.942) as compared with the linear form (0.76). The first order kinetics model and second order kinetics model are applied in both linear and non-linear forms, and results with a high R² value were obtained for the non-linear form of pseudo-first order kinetics. The adsorption mechanism was found to be electrostatic based on the interaction of the adsorbent and dye. Synthesized adsorbent can be successfully applied for the removal of DB86 dye from waste water.