Comparative Study on the Ni2+ Biosorption Capacity and Properties of Living and Dead Pseudomonas putida Cells

Abstract

<em>Microbial cells ha</em><em>ve</em><em> been successfully used as biosorbent</em><em>s</em><em> to remove heavy metal</em><em>s</em><em> from wastewater. </em><em>In some cases, dead cells </em><em>appear to</em><em> offer more advantages than living cells in the removal and recovery of heavy metal ions from industrial wastewater. Maintaining higher biosorption capability and understanding the biosorption properties of dead cells are the keys </em><em>to</em><em> heavy metal removal and recovery from wastewater using dead cells as biosorbent</em><em>s</em><em>. The present experiment showed that the dead Pseudomonas putida 5-x cells killed by dilute HCl had a higher Ni²⁺ biosorption capacity due to </em><em>the </em><em>ret</em><em>ention of</em><em> a complete cell structure during the </em><em>acid </em><em>treat</em><em>ment</em><em> process. The biosorption process of the dead cell</em><em>s</em><em> was faster than </em><em>that </em><em>of the living cell</em><em>s</em><em>. Metabolic-independent physical adsorption played a major role in the Ni²⁺ sorption by the dead cells.</em><em>The </em><em>pH </em><em>obviously </em><em>affected </em><em>the</em><em> biosorption capacity </em><em>of the dead cells,</em><em> because of the variation of </em><em>the </em><em>hydrogen ion concentration and cell surface property, as well as occurrence of micro-precipitation</em><em> along with the change of solution pH. Considering both biosorption capacity and desorption efficiency, pH 6.5-7.0 is a suitable condition for Ni²⁺ biosorption by dead P. putida 5-x cells killed with dilute HCl.</em>