Improved method for precipitation of insoluble salts in divalent ion-form materials

摘要

Selected polyvalent anions or cations are removed from a liquid sample stream as a pretreatment for the analysis of the liquid sample stream. A stream containing anions of interest, precipitable anions (e.g. sulfate ions) to be removed and an added displacing salt flow through a first cation exchange resin bed having precipitable exchangeable polyvalent ions (e.g. barium ions). Displacing polyvalent cation (e.g. calcium) displaces the exchangeable polyvalent ion from the cation exchange resin into the liquid sample at sufficient concentration to cause the precipitable anion and exchangeable cation to form a precipitate which remains in the resin bed and is thus is removed from the sample stream. Then the anions of interest in the soluble portion of the liquid sample stream are separated and detected. The invention is also applicable to the removal of precipitable cations (e.g. barium ions) by reversing the roles of the anions and cations.