Adsorption of Phosphate by Biomass Char Deriving from Fast Pyrolysis of Biomass Waste

Biomass char (BC) deriving from fast pyrolysis of biomass was a potential adsorption material due to its relative high fixed-carbon content and the inherent porous structures. Adsorption of phosphate from aqueous solution by BC was investigated in this paper. The results showed that the adsorption capacity of BC was dependent on pyrolysis conditions, such as temperature and holding time. The maximum adsorption capacity for phosphate was approximately 15.11?mg?g-1 at 298?K. The pseudo-second order model of the adsorption kinetics indicated that the adsorption process was complex and several mechanisms were involved. Equilibrium isotherm was satisfactorily followed the Freundlich isotherm model. The KF value in Freundlich equation gradually increased with elevating temperature. Moreover, the thermodynamic constants: ?G0, ?H0, and ?S0 were evaluated as -6.49?kJ?mol-1 (at 298?K), 13.41?kJ?mol-1, and 66.70 J?mol-1?K-1, respectively. Phosphate adsorption onto BC was spontaneous and endothermic. As a waste, BC was a potentially attractive adsorbent for phosphate removal from aqueous solution with low cost and high capability.