Study Of The Electrodeionization Technology In The Production Of Pharmaceutical Water

Electrodeionization(EDI), known as a new technology for water purification, combines electrodialysis(ED) and ion exchange(IE), which is capable of continuous deionization and electroregeneration for ion exchange resin under the influence of a DC electric field. However, it is usually required in EDI process that the hardness of the feed water should be less than1.0mg·L－1, or even lower (as CaCO3). As a result, unstable operation and scaling problem of EDI module frequently occur due to unqualified pretreatment, low qualities feed water, operator error in engineering practice.The EDI modules with domestic materials, modified structure, pure water compartments and concentrate water compartments filled with exchange resins were studied. Results showed that,(1) Operating voltage and current are important factors for EDI modules. Running current should be2-3A for one-stage EDI module and two-stage EDI module.(2) Two-stage EDI module was better than one-stage EDI, in respects of adaptability, stability, the quality of production water, etc.(3) Two-stage EDI could continuously produce high pure water(HPW) with resistivity more than17MΩ·cm after40minutes under the condition of running currents between2-3A and feed water conductivity between4.1-6.5μs/cm.(4) Feed water conductivity of one-stage EDI module and two-stage EDI module should be under10μs/cm for meeting HPW quality requirement and longer service life of EDI modules. The optimal conditions were that feed water pressure was0.35-0.4MPa, concentrate water flowrate should be generally about5%-10%of feed water flowrate, electrolyte water flowrate was18-24L/min, etc.According to the above researches and the specific needs of the pharmaceutical water in xian Aierfu enterprise for the production of artificial skin, the process of "two-stage reverse osmosis(RO)+two-stage EDI+ultrafiltration(UF)+mixed bed(MB)"("2RO+2EDI+UF+MB") was put forward in this paper. The production of four types of water including pure water(PW)/HPW/water for injection(WFI)/ultrapure water(UPW) were sent to different workshops to supply different processes to use. Conclusions were as follows:(1) Generally speaking, the processes of "2RO+2EDI+UF+MB" had unique characteristics such as stablility, high efficiency, energy saving, small footprint, less pollution, etc. The terminal production of water could meet the first grade standard of GB/T11446.1-1997. This combination technology would play an important guiding sense and be worthy of application and generalization.(2) The novel non-distillation process of "2RO+2EDI+UF" could completely replace mixed bed(MB) and multiple effect distillation(MED) for the production of pharmaceutical water, for the reason that its production water conductivity, bacterial endotoxin index and others satisfied all criteria for PW and WFI in the2010edition of Chinese Pharmacopoeia.(3) The novel non-distillation process of "2RO+2EDI+UF" had unique characteristics including stablility, high efficiency, energy saving, small footprint, less pollution, automation, etc. The production water was more suitable for heat-resistant pharmaceutical preparations and injection preparations because of its optimal temperature and uninterrupted production.(4) The non-distillation process of "RO-EDI-UF" had an important reference value and theoretical guidance to Chinese Pharmacopoeia and other counties’on preparation process of WFI.