Synthesis And Properties Of Two Polymeric Adsorbents With Amide Groups

Adsorption and separation using polymeric adsorbents,is a new technology developed in the late 1960s after the occurance of ion-exchange resins.The adsorption properties of polymeric adsorbents are mainly determined by the pore structure,surface characteristics of the adsorbents and the property of adsorbents.To obtain larger adsorption capacity and higher selectivity for a specific organic compound,chemical modification of the ordinary macroporous crosslinked polymeric adsorbents is frequently adopted by introducing some special functional groups into the matrix of the adsorbents. These introduced functional groups will modify the chemical composition of the adsorbents' surface and hence improve their adsorption behaviors for organic compounds.In the study,two amide group functionlization polymeric adsorbents,poly(N-methyl-N-p-vinylbenzy-ε-caprolactam)(PStCH₂-ε-CLt) and poly(N-methyl-N-p-vinylbenzyurea)(PStCH₂-Ur)were synthesized from macroporous crosslinked chloromethylated polystyrene(PStCH₂Cl),and their adsorption properties for phenol,tea polyphenols and tannic acid were investigated.1.Poly(N-methyl-N-p-vinylbenzy-ε-caprolactam)(PStCH₂-ε-CLt)and poly(N-methyl-N-p-vinylbenzyurea)(PStCH₂-Ur)were obtained from the chemical modification of PStCH₂Cl withε-caprolactam and urea in the presence of base.The molecular structures of these two adsorbents were evaluated through analysis of the residual chlorine content,BET specific surface area,and FT-IR spectrum.All the experimental results indicated that PStCH₂Cl had been functionalized successfully.2.Adsorption behaviors of phenol on PStCH₂-ε-CLt and PStCH₂-Ur were tested both in aqueous solution and heptane.Through comparing the adsorption capacities of phenol on PStCH₂Cl with that on PStCH₂-ε-CLt and PStCH₂-Ur, it was found that the adsorption capacities of phenol on PStCH₂-ε-CLt and PStCH₂-Ur were greatly improved.Further research on the adsorption mechanism indicated that hydrogen bonding,hydrophobic interaction,andÏ€-Ï€staking were the main driving forces for the adsorption of phenol onto these two modified adsorbents in aqueous solution,while the adsorption in heptane was primarily due to hydrogen bonding.3.Adsorption properties of tea polyphenols(TP)and tannic acid(TA)onto PStCH₂-ε-CLt and PStCH₂-Ur were also studied in aqueous solution.By comparing the adsorption capacity of TP and TA onto PStCH₂Cl with PStCH₂-ε-CLt and PStCH₂-Ur at the same equilibrium concentration and temperature,it was shown that the adsorption TP and TA onto these two synthesized adsorbents were enhanced with respect to that of PStCH₂Cl.This comes to a conclusion that the adsorption capacity of polymeric adsorbents can be enhanced using functionlization technology.