Application of Polyampholytes

Abstract

Water-soluble and water-swelling polyampholytes are used in a wide number of applications including desalination of water, sewage treatment, flocculation, coagulation, drilling fluids, enhanced oil recovery etc. The desalination of water by crosslinked polyampholytes can be regulated by changing of the temperature.¹ Such polyampholytes are called as thermoregenerable resins (TRR). To perform the thermoregeneration the next equilibrium should take place in dependence of temperature (Scheme 7.1). In principle the function of TRR is as follows: the absorbed at room temperature salts (for instance NaCl) can easily be regenerated by hot water, e.g. the exchange equlibrium is shifted at room temperature to the right and at high - to the left. At room temperature the proton is transferred from the acid to the base forming charged ion-exchanging zones (COOH → NR₂ → COO^- N⁺HR₂). The heating of water from 298 K to 358 K leads to the accumulation of H⁺ and OH^- owing to the ionization of water molecules; the concentration of H⁺ and OH^- increases approximately 30 times. Hydrogen and hydroxyl ions suppress the degree of ionization of amphoteric resin and the equilibrium shifts to the left side. Thus hot water serves as “reservoir” of H⁺ and OH^- ions.