Study on the Adsorption of Hydrolyzed Polyacrylamide by Zeolitic Imidazole Framework

Abstract

Three types of Zeolitic imidazolate framework‐8 (ZIF‐8 s), i. e. ZIF‐8(MeOH), ZIF‐8(H2O), and ZIF‐8(NH3.H2O), were synthesized by using different solvents. Influences of the ZIF‐8 type, hydrolyzed polyacrylamide (HPAM) property, and salinity of the solution on their adsorption performance were discussed. The results indicated that ZIF‐8(NH3 ⋅ H2O) showed larger adsorption capacity compared to other counterparts. An increase in the hydrolysis degree of HPAM had a positive influence on the adsorption capacity of ZIF‐8(NH3 ⋅ H2O). With the increase of NaCl concentration in the solution, the adsorption capacity of ZIF‐8(NH3 ⋅ H2O) first increased and then decreased. Adsorption thermodynamics and kinetic investigation showed that the adsorption of HPAM by ZIF‐8 is a spontaneous endothermic chemisorption process. The influences of injection rate, temperature, ZIF‐8 mass and HPAM initial concentration on the dynamic adsorption were investigated. The processing volume per unit mass of ZIF‐8 increased with the increasing temperature, ZIF‐8 mass and HPAM initial concentration, while decreased with the increasing injection rate. Lastly, the adsorption mechanism was analyzed. The results of IR and XPS confirmed that the HPAM adsorption on ZIF‐8 was caused by three interactions, including the electrostatic attraction between ZIF‐8 and HPAM, the coordination interaction between Zn2+ and NH+ with COO−, and the hydrogen bonding between nitrogen and amide group.