Preparation and Characterisation of Biosorbent from Local Robusta Spent Coffee Grounds for Heavy Metal Adsorption

Abstract

In this study, the removal of lead heavy metal pollutants from artificially lead-contaminated water was carried out using biosorbent prepared from local Robusta spent coffee grounds. The effects of temperature of carbonisation and concentration of HCl solution as activating agent on biosorbent characteristics and lead- adsorption capabilities were investigated. Characterisation of the resulting biosorbent included functional groups by Fourier Transform Infra-Red Spectrophotometer (FTIR) and morphological properties by scanning electron microscope (SEM). Lead-adsorption capabilities were studied using a synthetic wastewater containing 50 ppm of lead. All adsorption processes were carried out for 30 min at room temperature with the ratio of spent coffee grounds biosorbent mass to lead solution volume of 1:10. Concentrations of lead solution before and after adsorption were measured using an atomic absorption spectrophotometer. Result showed that fixed carbon content of biosorbent prepared from spent local-coffee grounds was 97.1 %, it is fulfilled the requirement of Standar Industri Indonesia (SII) as potential activated carbon. Carbonisation and activation processes have altered the functional groups of spent coffee grounds. The prepared biosorbent showed a rougher and more porous surface morphology following the treatments. Adsorption process using spent coffee grounds biosorbent carbonised at 400 °C and activated using 0.2 M HCl solution gave the highest lead-removal percentage of 51.6% and adsorption capacity of 8.6683 mg/g.