Lead Ion Removal Characteristics of Polyflactic acid)/Hydroxyapatite Composite Foams Prepared by Supercritical CO2 Process

摘要

We have prepared a series of polyflactic acid)/hydroxy-apatite (PLA/HAp) composite foams by a supercritical CO? foaming process and investigated the lead ion (Pb ) 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 + 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.