Enhanced Pb(II) removal by algal-based biosorbent cultivated in high-phosphorus cultures

This study developed a novel strategy for phosphorus and Pb(II) removal sequentially from water by Chlorella sp. QB-102, in which algae was firstly cultivated in high-phosphorus culture and then the biomass was harvested as biosorbents for Pb(II) removal. Biomass production and biosorption performances of biosorbents from different concentrations of phosphorus cultures were investigated. The optimal biomass production was found at high P culture of 280 mg L-1. The biomass obtained from different P cultures were evaluated for their Pb(II) sorption performances. The results showed that pH 6.0 was the optimal for sorption. Biosorption kinetics and isotherms were fitted to the pseudo-second order and Langmuir models, respectively for all the biosorbents. Biosorbents under 280 mg L-1 phosphate concentration achieved the largest Pb(II) biosorption capacity of 635.8 mg g(-1). The changes in these values of standard Gibb's free energy (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees) demonstrated the feasible, endothermic, spontaneous and random nature of biosorption process for the adsorbent from 280 mg L-1 P culture. The regeneration experiments indicated that the adsorbent was easy to recycle and of high efficiency. FT-IR, XPS and potentiometric titration analysis showed that the surface phosphoryl functional groups dominated the Pb(II) biosorption and showed a positively linear relationship with the biosorption capacity. It was suggested that high phosphorus cultivation for microalgae is a good method for enhancing the surface phosphoryl functional groups for higher Pb(II) removal and the biosorbent from high P cultures was promising for heavy metal removal.