Preparation of modified rice straw-based bio-adsorbents for the improved removal of heavy metals from wastewater

Abstract

Economical wastewater treatment can be achieved by using locally available and degradable material which has the low cost. Rice straw is a cheap and easily available substrate which has the potential to be converted into bio-adsorbent for heavy metal removal from the wastewater. The proposed experiment was designed to form a novel rice straw-based bio-sorbent to investigate their adsorption potential for removing heavy metal ions from wastewater. Three bio sorbents, namely, raw (RRS), alkali (ARS), and biochar (BRS) based adsorbents, were prepared, and their potential for adsorption of Cd(II) and Zn(II) was analyzed. The adsorption process was optimized for pH, contact time, metal concentration, and adsorption dose. The adsorbents were characterized using Fourier-transform infrared spectroscopy and Scanning electron microscopy, and the metal adsorption was quantified using atomic adsorption spectroscopy. In the batch study, all three adsorbents showed higher Cd(II) ion adsorption than the Zn(II) ion, with the highest recorded for RRS i.e. 20.9% and 8.4% respectively. For all adsorbents, the optimum pH for Cd(II) and Zn(II) was found as 5 and 4, respectively. The optimum dose of adsorbent for Cd(II) was 0.1, 0.1, and 0.55 g, while for Zn(II), it was 0.55, 0.1, and 0.1 g for RRS, ARS, and BRS, respectively. The adsorption capacity was best fitted for Freundlich isotherm for all adsorbents, which reflect heterogeneous property and favorable adsorption process. The prepared adsorbent was found excellent in heavy metal removal from wastewater and could be used for its commercial applications.