科研之友
微信
新浪微博
Facebook
分享链接
摘要
Biochar, produced by the pyrolysis of pig manure at 800 degrees C, was characterized and investigated as an adsorbent for the removal of Direct Red 23 from aqueous solution. The adsorption kinetics was best described by a modified Freundlich model and intra-particle diffusion models. The value of the apparent adsorption constant k (modified Freundlich model) decreased from 0.133 to.0.076 L/(g.min(1/m)), when the amount of biochar increased from 1 to 8 g/L. Values of effective particle diffusion coefficient (D-p) and liquid film diffusion coefficient (D-f) were calculated to further determine the rate-limiting step of the adsorption process. The value of activation energy 5.558 kcal/mol indicates that the adsorption is a physical process controlled by film diffusion and the adsorption process is endothermic. When pH < pH(zpc) (8.71),the surface of biochar is positively charged; the positive charge promoted the anionic dyes attracted onto the biochar by electrostatic force; and a hydrogen band was formed with the protonated -OH functional groups on the active sites. The adsorption equilibrium study indicates that the adsorption was in a multilayer mode, and the maximum adsorption capacity was 2.19 x 10(-5) mol/g, at pH 2.20 and temperature 25 degrees C. Considering the widely availability and high removal efficiency, biochar is deserved further investigations for applications in more hazardous substances removal.
