Adsorption characteristics of gallic acid on fresh calcium phosphate

The adsorption characteristics of gallic acid on fresh calcium phosphate were discussed. Three kinetic models, including pseudo-first-order model, pseudo-second-order model and intraparticle diffusion model, were selected to follow the adsorption processes. The results showed that the pseudo-second-order equation provided the best correlation to the experimental data ( R2= 0. 9943 ~ 0. 9946) , under the initial gallic acid concentration were 25, 50, 75mg/L. pH value was an important factor for affecting adsorption. The amount of adsorbed gallic acid reached maximum when pH value was between 7.2 and 7.5. The results showed that the adsorption isotherm could be described by Langmuir model (R2=0.9965) , and the saturated adsorption capacity reached 8.4317mg/g.