Study on Removal of Humic Acid by Polyurethane Foam/Activated Carbon Composites in Boiler Feedwater

A new type and high efficiency adsorbent was prepared with powder activated carbon and polyurethane vesicant and surfactant, which being used to adsorb humic acid (HA) in boiler feedwater. The batch adsorption experiments were carrid at different pH value, different adsorbent dosage and different initial concentration to investigate HA removal rate and adsorption capacity by as-produced adsorbent. Their adsorption kinetics experiments data was fitted with pseudo-second-order rate model, its quation was 1/q(t)=0.094+5.51/t, and equilibrium adsorption capacity obtained from fitting curve was 10.6mg/g, consistent with the experimental results(11.5mg/g).The adsorption isotherm test was carried at 25 degrees C-50 degrees C, the equilibrium adsorption capacity was 10.9mg/g by Langmuir model, which being similar with experiment results, the free energy (Delta G), enthalpy(Delta H) and entropy (Delta S) were obtanined with Clapeyron-Clausius and Gibbs-Helmholtz equation in the adsorption isotherm, which all were negative, indicated that HA adsorbed by as-produced adsorbent was an exothermic process of entropy reduction.