Competitive adsorption of Pb(II) and Zn(II) from aqueous solution by modified beer lees in a fixed bed column

Continuous fixed-bed column studies for Pb(II) and Zn(II) simultaneous removal from aqueous solutions were carried out by using the modified beer lees as an absorbent. The effects of weight of adsorbent in each depth of the bed, flow rate and initial concentration were examined. The results show that the adsorption capacity of Pb(II) and Zn(II) both increase with the increase in the influent concentration, and decrease with the increasing of the packing weight of adsorbent and flow rate. Under the optimum conditions with Pb(II) and Zn(II) concentration of 30 mg/L and 15 mg/L, the adsorbent's packing weight of 4 g, and the flow rate of 1.0 mL/min, the adsorption capacity of Pb(II) and Zn(II) can reach 29.6 mg/g and 5.43 mg/g, respectively. The coefficients of Bed Depth Service Time and Yoon-Nelson models are all above 0.95, which is suitable to describe the continuous adsorption process of Pb(II) and Zn(II) by the modified beer lees and to predict effluent data in column operation under different experimental conditions. The results of EDX confirm that the Pb(II) and Zn(II) ions presence on the surface of the modified beer lees after adsorption process and the FTIR analysis identifies the hydroxyl, aliphatic acids and carboxyl functional groups as the active binding sites for Pb(II) and Zn(II) ions adsorption.