Experimental study and theoretical statistical modeling of acid blue 25 remediation using activated carbon from Citrus sinensis leaf

Abstract

In this study, Citrus Sinensis Leaf Activated Carbon (CSLAC), as adsorbent for acid blue 25 (AB25) dye removal from water, was synthesized from Citrus Sinensis Leaf (CSL) by using sulfuric acid (H2SO4) activation procedure. The obtained adsorbent was thereafter characterized by various methods such as FTIR, BET-BJH, and SEM-EDX. Further, the adsorption of AB25 on CSLAC was performed under different operating conditions. High CSLAC surface area of 485.16 m2 g–1 was obtained, affirming that the prepared adsorbent is permeable, which is an advantage for the efficient removal of contaminants. Moreover, optimal conditions for the batch removal process of the dye from water were investigated. It was found that for 100 mg L–1 AB25 dye initial concentration, the CSLAC achieved almost complete removal of 98.64% within 60 min at a temperature of 25 °C, by using only 0.4 g L–1 of the adsorbent dose. In addition, the Langmuir theoretical model efficiently agreed with the experimental data, and it has led to a maximum equilibrium adsorption capacity of 543.47 mg g–1at 25 °C. Kinetic studies, on the other hand, were in favor of pseudo-second-order (PSO) model to describe the dye removal from water. Others features of the CSLAC adsorbent resulted in its good regeneration and reusability. The results of theoretical statistical modeling at temperatures varied from 25 to 40 °C showed a monolayer adsorption of AB25 with two energy sites of CSLAC. Various characterization methods show that the mechanism of adsorption for CSLAC towards AB25 including electrostatic attraction, hydrogen bond, and π-π interactions. Finally, the AB25 adsorption appeared to be an endothermic spontaneous process as evidenced by the determined thermodynamic parameters. The obtained overall data suggest that the CSLAC is an inexpensive adsorbent which has promising potential for dye removal from wastewater.