DEIONIZATION OF WATER WITH A RECOVERABLE REGENERANT
Abstract
A methodology for choosing the most suitable pair of cation and anion exchangers, a UF membrane, and an organic regenerant was developed to achieve the objective of these investigations, i.e. deionization of water with a recoverable regenerant. Based on the results of preliminary investigations, single resin ion exchange column studies, and mixed-bed resin column tests, it was thus concluded that the operation of a mixed-bed resin (Amb-200/IRA-900) DI system in conjunction with a recoverable organic regenerant (sodium gluconate), via ultrafiltration membrane (Sepa-97 CA) process, was technically feasible. The proposed process would have three advantages compared with the conventional mixed-bed deionization process. First, all the cations (Ca('++) and Mg('++)) and anions (SO(,4)('=), Cl('-), and HCO(,3)('-)) retained in the exhausted mixed-bed resin column would be replaced by introducing one organic regenerant, (Sodium Gluconate) to the column. Secondly, the process would not require separation of the resins in a mixed-bed resin column before regeneration. Thirdly, the organic regenerant (Sodium Gluconate) discharged from the column, during the service cycle, can be recoverable and recyclable through use of a UF process. For a service cycle feed solution containing 392 mg/l Ca('++), 98 mg/l Mg('++), 390 mg/l SO(,4)('=), and 760 mg/l Cl('-), it would produce an effluent Sodium Gluconate concentration of 1500-6000 mg/l and column utilization ratio for Amb-200 and IRA-900 resin of approximately 51.3% and 88.6%, respectively. Additional studies utilized Purdue Cold Tap Water as a service cycle feed and resulted in a column effluent with 875-7250 mg/l of Sodium Gluconate and column utilization for Amb-200 and IRA-900 resin of 30% and 56.7%, respectively. In these investigations, the most effective regeneration results (97.3% to 99.8%) were achieved while feeding 8% sodium Gluconate to the mixed-bed resin column at 0.5 gpm/ft('2) down-flow rate. The UF/RO Sepa-97 CA membrane was found to be successful for recovery (97%) of an organic regenerant, i.e. Sodium Gluconate, discharging from the column during the service cycle.
Degree
Ph.D.
Subject Area
Civil engineering
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