‎Application of Box-Behnken Design and Response Surface Methodology of Acid Red 18 Adsorption onto PAC‎ (Synthesized Carrot Waste) Coated with Fe3O4 Nanoparticles from Aquatic Solution: Kinetic and Isotherm Studies

Background & Aims of the Study: The dyes present in the effluent from the textile industry are among the most polluted and hazardous wastewater discharged, causing severe changes in water quality and the environment. The use of agricultural residues as inexpensive organic adsorbents is very suitable for removing industrial dyes from aquatic solutions, especially in developing countries. This study aimed to investigate the effectiveness of activated carbon synthesized from carrot waste as an inexpensive and available organic adsorbent in the removal of Acid Red 18 (AR18) dye. Materials and Methods: In this study, response surface methodology (RSM) was discussed as an efficient method for the optimization of AR18 adsorption onto PAC‎ (obtained from waste carrot) coated with Fe3O4 nanoparticles. ANOVA analysis based on the Box-Behnken design-RSM was applied to investigate the correlation coefficient of PAC (Synthesized Carrot Waste). Adsorbent dose, initial dye concentration, and pH were optimized and evaluated using RSM with respect to contact time on adsorption of AR18. Moreover, X-ray diffraction, transmission electron microscopy, Brunauer–Emmett–Teller, Fourier-transform infrared, and field emission scanning electron microscopy techniques were used to study the adsorbent properties and characteristics of PAC‎. Isotherm data were modeled with both Langmuir and Freundlich isotherm. Results: The results obtained from Langmuir isotherm showed the best fit to experimental data proposing homogeneous dispersion of adsorption sites. Moreover, the compatibility of the adsorbent was examined by fitting the adsorption data with a pseudo-second-order kinetic model. The results of ANOVA analysis showed a good fit between quadratic model predictions with experimental values, resulting in R2 of 0.997 for PAC. The results showed 99.7% of dye AR18 was removed after 80 min, pH at 3, and the adsorbent dose of 1.5 g. Conclusion: It can be concluded that PAC‎ (Synthesized Carrot Waste) has great potential applications for the removal of AR18 dye from the textile industry. Large-scale applications of adsorbent and adsorbate, due to their recuperation and reusability characteristics, are proposed by observations and experimental results of this study.