Selective Extraction of Salt Ions from Groundwater by Polyamide Membranes

Abstract

In this work, problems related to qualitative description and number of parameters of diffusion selective extraction of salt ions in polymer membranes were solved, taking into account the size of membrane pores and pH solutions. The dependence of diffusion coefficient of aqueous solution of salt ions (pH 6.5-7.5) in a range of polyamide membranes with dominant pore radius of less than 6-7 nm has been investigated. The characteristic features of the diffusion coefficient change are compared with the salt ion content within the pH range of the solution. The diffusion coefficients of salt ions in membranes with pore radii of 5 to 8 nm at pH = 6.5-7.5 are generally comparable for salt ions. In the wrong interval between membrane regeneration operations, the efficiency of membrane regeneration operations was reduced, and changes in membrane characteristics could be avoided. The duration of the inter-regeneration period depends on the composition of the source water and its preparation before reverse osmosis. The quality of the water preparation is considered good if the stability of the operation of the desalination apparatus is achieved by perio-dipping them not more than once a month. Features of diffusion of salt ions in PA membranes (exponential dependence of diffusion coefficient on radius of pores of membranes, v lysine pH) and comparison of the obtained data with the available salts allow to determine prospects and conditions of their separation in PA membranes.