Adsorption Properties of 2,4-Dihydroxybenzoic Acid on Three Anion Exchange Resins
2,4-二羟基苯甲酸在3种树脂上的吸附特性

The adsorption properties of 2,4-dihydroxybenzoic acid by 717(gel-type,strong base),D201(macroporous-type,strong base) and D301R(macroporous-type,weak base) resins were studied through static and dynamic experiments.The results show that the maximum adsorption ability of 717 and D201 resins occurs at pH=4～11,and D301R resin at pH=3～9.At pH=5,293～313 K and initial concentration of 2,4-dihydroxybenzoic acid of 0.6488～6.488 mmol/L,the adsorption isotherms of 2,4-dihydroxybenzoic acid on D301R,717 and D201 resins obey Freundlich model,and their maximum equilibrium adsorption capacity is 2.98,2.66 and 2.54 mmol/g,respectively(the adsorption has not reached saturation yet).The adsorptions are physical and spontaneous,exothermal processes.Pseudo first-order and pseudo second-order models were applied to correlate the kinetic experimental data.The former was more accordant with the experimental data than the latter.The 2,4-dihydroxybenzoic acid adsorbed on the three resins could be eluted by 100 mL 5%(ω) NaCl+2%(ω) NaOH solution quickly with elution rate reaching 99%.The adsorption performance of 2,4-dihydroxybenzoic acid on D301R resin was better than on that on D201 and 717 resins under the same conditions.