Permselectivities of monovalent anions through pyridine-modified anion-exchange membranes

摘要

The permselectivities of three new series of anion-exchange membranes were evaluated by using anions such as fluoride,chloride,bromide,iodide,hydroxyl,nitrate,and nitrite ions.The membranes were prepared,respectively,via(i)quaternary amination of 100% bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide)(BPPO)with n-butanol/pyridine solutions(A series),(ii)cross-linking of BPPO with ammonia and subsequent reaction with pyridine(B series),(iii)cross-linking of BPPO with ammonia,subsequent reaction with pyridine,and final quaternary amination of the residual bromomethyl groups with trimethylamine(C series).A stronger hydrophobicity was imparted on the anion-exchange membranes after modification with pyridine.The permselectivity tests indicate that anions with lower Gibbs free energies of hydration are more easily to permeate through a hydrophobic anion-exchange membrane generally and in the case of anions with similar Gibbs free energies of hydration,smaller Stokes radii of the anions are in favor of permeation.According to the experimental results,the B series of anion-exchange membranes have the best performances as in separation of monovalent anions.