Competitive Adsorption Of Cu(â…¡) And Pb(â…¡) Ions From Aqueous Solutions By Calcium Alginate Immobilized Saccharomyces Cerevisiae And Activated Carbon

In this paper, some immobilized beads were produced, which was prepared byimmobilizing the powdered activated carbon and Saccharomyces cerevisiae usingsodium alginate. As a novel biosorbent, the immobilized beads were used to adsorbCu²⁺and Pb²⁺from aqueous solutions. And then the adsorption properties of theimmobilized beads for Cu²⁺and Pb²⁺were studied with regard to the experimentconditions of the adsorption process, the reusability of the immobilized beads, theadsorption kinetics and adsorption isotherms, competitive adsorption of Cu²⁺and Pb²⁺by the immobilized beads and so on.Using static adsorption method, the effect of the main factors, such as initial pH,temperature, adsorbent dosage, contact time and initial metal ions concentration onthe adsorption process have been systematically investigated and optimized. Theresults showed that the optimum pH for Cu²⁺and Pb²⁺adsorption was determined as5.0, the effect of temperature on the adsorption process was not obvious, theabsorption equilibrium was reached within3hours, the adsorption capacity of Cu²⁺and Pb²⁺by the immobilized beads decreased with increasing the immobilized beadsdosage and increased with increasing initial metal concentration. Therefore,considering from the two aspects of economic and removal efficiency, the optimaldosage of the adsorbent is2g when the solution volume was100mL and the initialmetal concentration was100mg/L.The reusability of the immobilized beads was investigated though a consecutiveadsorption-desorption cycles. The experiment result indicates that the adsorptioncapacity of the immobilized beads did not noticeably change after sixadsorption-desorption cycles. So, the immobilized beads produced in this study can berepeatedly used.The kinetic studies showed that the adsorption process of Cu²⁺and Pb²⁺by theimmobilized beads can be well described by the pseudo-second-order model. Thisindicates that the adsorption rate of Cu²⁺and Pb²⁺by the immobilized beads was notonly influenced by the external liquid film diffusion velocity, but also influenced bythe intra-particle diffusion velocity.The isotherm studies showed that the equilibrium adsorption data of Cu²⁺andPb²⁺adsorption on the immobilized beads in single system are formed to be best represented by the Langmuir isotherm model; and the experimental adsorption data ofCu²⁺and Pb²⁺adsorption on the immobilized beads in binary system are bestdescribed by the extended Freundlich isotherm and the extended Langmuir isothermrespectively.There is a antagonistic competitive relationship between Cu（Ⅱ） and Pb（Ⅱ） ions ina binary system, the existence of one heavy metal ions in the solution will influencethe adsorption of the immobilized beads for another heavy metal ions, and theremoval of Cu（Ⅱ） ions was more significantly influenced by the presence of thecoexistent Pb（Ⅱ） species, while the interference of Cu（Ⅱ） in the sorption of Pb（Ⅱ） wasconsiderably less intense.