Biosorption behaviors of biosorbents based on microorganisms immobilized by Ca-alginate for removing lead (II) from aqueous solution

Multiple microorganisms directly or treated with NaOH were immobilized by using Ca-alginate embedding to form biosorbents I and II, successively. The biosorption behaviors of biosorbents I and II for Pb(II) from aqueous solution were investigated in a batch system. Effects of solution pH, initial metal concentration, biosorbent dosage, contact time, temperature, and ionic strength on the adsorption process were considered to study the biosorption equilibrium, kinetics, thermodynamics, and mechanism of Pb(II) ion adsorption on the 2 types of biosorbents. The results showed that the adsorption capacity of biosorbent II for Pb(II) was higher than that of biosorbent I, and biosorbent II had a faster adsorption rate for Pb(II) ions. According to FTIR spectra, the carboxyl, amine, and hydroxyl groups on the biomass surface were involved in the biosorption of Pb(II). EDX analysis showed that ion exchange may be involved in the biosorption process, and the morphology observed by SEM micrograph of biosorbent I was completely different from that of biosorbent II. Desorption and regeneration experiments showed that the 2 types of biosorbents could be reused for 3 biosorption-desorption cycles without significant loss of their initial biosorption capacities.