Chitosan membranes filled with biomimetic mineralized hydroxyapatite for enhanced proton conductivity

Hydroxyapatite (BMHA) particles, using Ca(OH)(2) and H(3)PO(4) as the reactants and chondroitin sulfate as the template/catalyst, are synthesized through a biomimetic mineralization approach. The BMHA particles are then incorporated into chitosan (CS) matrices to prepare the CS/BMHA hybrid membranes. Thermal stability of the hybrid membranes is enhanced owing to the formation of strong hydrogen bonds between the BMHA surface and CS molecules. The methanol crossover of the CS/BMHA membranes is decreased due to their prolonged methanol transfer pathways and the improved hydrophilicity. The hybrid membranes exhibit at most 127% higher proton conductivity than the pure CS membrane because of the high intrinsic proton conductivity of the BMHA particles, the strong hydrophilicity and the large free volume of the membranes. In particular, the hybrid membrane with BMHA content of 8 wt% exhibits 1.8 times higher selectivity of proton to methanol than the pure CS membrane. (C) 2011 Elsevier B.V. All rights reserved.