Adsorption Properties of Keggin-Type Cr(III) Substituted Heteropolytungstates on the D301R Resin

The adsorption behaviors of Cr(Ⅲ)-substituted heteropolyanion PW11O39Cr(Ⅲ)(H2O)4-(PW11Cr) on the D301R resin were investigated.Influences of pH and temperature upon PW11Cr adsorption capacity and adsorption rate were also examined,respectively.The adsorption thermodynamic and kinetic equations were simulated and the corresponding parameters were calculated on the basis of adsorption kinetic curves and adsorption isotherms determined at different temperatures.The results showed that the adsorption capacities of PW11Cr on the resin increased with pH increasing from 2 to 8 in the aqueous solution,and decreased with the increase of temperature.The adsorption kinetics followed the pseudo-second-order regime controlled by a surface process.The rate constant k2 that decreased with the increase of temperature was determined to be 1.54×10-3 g·mg-1·min-1 at 298 K.The adsorption isotherms were consistent with Freundlich model and the adsorption enthalpy calculated was about-37 kJ·mol-1,indicating a physical adsorption process.