Effective adsorption of polycyclic aromatic Congo red dye by modified garlic peel

Abstract

To evaluate the competence of garlic peel (GP) as a low-cost bio-adsorbent, GP was chemically modified with sodium carbonate (Na2CO3) and hydrochloric acid, and used to adsorb Congo red (CR). The surface morphology, chemical characterization and structural information of the adsorbents were studied by scanning electron microscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. The impact of different adsorption settings on the removal effectiveness of CR by sodium carbonate-treated garlic peel (Na2CO3-GP) was also studied. The optimum conditions for effective adsorption of CR by Na2CO3-GP is found to be pH of 7, 90 minutes of equilibrium contact duration, 50 mg/L of initial CR concentration, 200 revolutions per minute of stirring (RPM), 0.10 g/mL of adsorbent dosage, and temperature of 298 K. As indicated by Langmuir isotherm, monolayer adsorption occurs at a maximum capacity of 52.6 mg/g for Na2CO3-GP. Adsorption kinetic studies suggest chemisorption, the process follows a pseudo-second-order model and thermodynamics of adsorption specifies that the process is spontaneous. The results explicitly show that Na2CO3-GP can be an effective bio-adsorbent for the removal of CR.