Utilization of Adsorbent Based on Rice Straw (<i>Oryza sativa</i>) for Cr(VI) Ions Reduction in Aqueous Solutions

Abstract

In this study, we utilized an adsorbent based on rice straw for reducing hexavalent chromium ions (Cr (VI)) in an aqueous solution. The rice straw as adsorbent raw material was washed, dried, and powdered. Rice straw powder was heated at 450°C for 2 hours to obtain rice straw adsorbent. The adsorbent was activated with 1M H3PO4 for 4 hours. Characterization of the adsorbent was done using Fourier Transform Infra-Red (FTIR) method. FTIR spectra showed the presence of hydroxy, carboxylic, aromatic, and ether groups on the surface of the rice straw and the made adsorbent. The reduction of Cr (VI) ions in aqueous solutions was carried out using the adsorption batch method. The adsorption process was conducted in various the Cr (VI) solutions pH for 1-5 and variations in contact time for 5-720 minutes. The highest percentage reduction of Cr (VI) reached 66.90%. It has occurred at pH 2 and equilibrium at 600 minutes of contact time.