Adsorption of copper ions onto acid-modified Aframomum africanum shell: Isotherm and kinetic studies Scientific paper

Abstract

In this work, copper ions were successfully removed from aqueous solution using the acid-modified Aframomum africanum shell (MAAS) as an adsorbent. The adsorbent was characterized using Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM). The A. africanum shells were also characterized before and after acid modific­ation to determine their pH at the point of zero charge (pH_PZC). MAAS was found to have a pH_PZC value of 4.77. In batch experiments, the adsorption cap­acity of MAAS was investigated as a function of solution pH, adsorbent dosage, contact time, initial copper ion concentration and agitation speed. The results revealed that at a solution pH of 9, an adsorbent dosage of 5 g/L, a contact time of 30 min, an initial Cu(II) ion concentration of 50 mg/L and at an agitation speed of 250 rpm, the maximum Cu(II) ion adsorption capacity of MAAS was 31.25 mg/g. The adsorption kinetic data and isotherm data were also studied to find the suitable models of Cu(II) removal. The kinetic data and the isotherm data of Cu(II) removal by MAAS were found to follow the pseudo-second order kinetics model (R² = 0.999) and the Langmuir isotherm model (R² = 0.990), respectively. Therefore, the outcome suggested that A. africanum shells can be utilized as an economical and efficient adsorbent for the removal of Cu(II) from aqueous solution.