Adsorption studies on brilliant green dye in aqueous solutions using activated carbon derived from guava seeds by chemical activation with phosphoric acid

Abstract

In this research, brilliant green dye (BG) has been removed from synthetic wastewater using activated carbon derived from guava seeds (AGSC) which was collected as a waste product from factories producing juice concentrates. A single-stage batch adsorber was designed for adsorption of BG by AGSC based on some experimental parameters such as contact time (5–40 min), adsorbent mass (0.01–0.08 g), temperature (25°C–95°C), pH (3–10), and initial dye concentration (10–100 ppm). The maximum adsorption capacity of AGSC was found to be 80.5 mg/g using the Langmuir isotherm model which is the best-fitted model for the process. The experimental data were fitted well with the pseudo-second-order kinetic model. The changes in functional groups, surface morphology, and chemical composition of AGSC before and after adsorption were identified by Fourier transform infrared spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, respectively. The specific surface area of AGSC was measured to be 605.1 m2 /g using Brunauer– Emmett–Teller analysis. Pore volume and pore diameter were found to be 0.57 cm3 /g and 3.78 nm, respectively. The thermodynamic study proved that adsorption of BG on AGSC was physiosorptive (ΔG = –7.7 kJ/mol) and spontaneous at high temperature (ΔH = 13.4 kJ/mol, ΔS = 0.07 kJ/mol K).