Adsorption of Congo Red Dye from Aqueous Solutions Using an Eco-Friendly Adsorbent Derived from Buckthorn Fruits

Abstract

Dyes are used in the textile, paper, plastics, leather, foodstuff, and artificial fiber industries. Congo red dye (CR) is one of the dyes found in industrial wastewater. The present study investigates the Congo red dye removal from aqueous solutions using low-cost adsorbents that are eco-friendly and highly efficient, such as activated carbon prepared from Buckthorn fruit (BT) under various experimental conditions, as an ideal alternative to the current expensive methods for removing dyes from aqueous solutions. X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET),  scanning electron microscope (SEM), and Fourier-transformed infrared (FTIR) analyses were used for the fabricated-activated carbon characterization. Based on batch system experiments, various variables affecting the adsorption process were studied, including the solution’s pH, adsorbent dose, contact time, initial dye concentration, and mixing speed. The results showed that the highest dye removal efficiency was 63% at pH = 5, the contact time was 80 minutes, the dose of adsorbent was 3 g/l, and the mixing speed was 150 rpm. The data from the experiments were analyzed using the Langmuir and Freundlich model and showed a high agreement with the Langmuir model (R2 = 0.989). When studying the adsorption kinetics, the results agreed with the Pseudo-second order, where the values of K2 and R2 were 0.083g/mg. min and 0.992, respectively. The adsorption was endothermic and spontaneous, as shown by the thermodynamic parameters study at 25, 35, and 45 °C, where the ∆H was 13.709 kJ/mol and ∆G values were negative values. The study also showed the possibility of using Buckthorn fruit as a low-cost adsorbent in CR removal.