Lead ion removal characteristics of poly(lactic acid)/hydroxyapatite composite foams prepared by supercritical CO 2 process

We have prepared a series of poly(lactic acid)/hydroxyapatite (PLA/HAp) composite foams by a supercritical CO 2 foaming process and investigated the lead ion (Pb 2+ ) removal performances of the foam samples in batch aqueous solutions (foam sample of 5 g, aqueous solution of 500 ml, initial Pb 2+ ion concentration of 275 mg/l, pH values of 2.0–6.0) at 25°C. It is characterized that the porosity of the foams decreases from 96.3% to 50.3% as the HAp content increases from 0 to 40 wt%, although all the foam samples exhibit well‐developed open porous structures. The maximum capacity of Pb 2+ ions removed by the composite foams increases from 81.2 to 140.5 mg/g with increasing the HAp content from 10 to 40 wt%, due to the increased adsorption sites of HAp for Pb 2+ ions. However, the removal kinetic analysis based on the pseudo‐second order model demonstrates that the Pb 2+ ion removal rate is slightly faster for the composite foams with higher porosity (i.e., lower HAp content). The maximum Pb 2+ ion removal capacity of a given composite foam increases from 20.2 to 140.5 mg/g with increasing the initial pH value from 2.0 to 5.0 but it decreases slightly to 111.7 mg/g at the initial pH value of 6.0. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers