Results of in Vitro Electroregeneration Test of Multi-bed Resin

In 1992, Millipore, an American company, designed and patented an EDI technology using bipolar membranes. Reports indicate that under conditions where the conductivity of the raw water is 1 μS/cm, the voltage drop at the bipolar membrane interface is greater than 1 V, the measured current efficiency is less than 30%, and the concentration of H+ and OH- ions generated by water dissociation from the bipolar membrane can reach over 104 mg/L, while the concentration of impurity ions in the raw water is only 10⁻² to 10⁻⁵ mg/L, a difference of 10⁶ to 10⁹ times. This ratio is 2 to 5 orders of magnitude higher than traditional chemical regeneration; therefore, the resin regeneration rate should be higher than that of chemical regeneration.

Inspired by the author's invention of resin electroregeneration, several young teachers at Hebei University of Architecture and Technology completed experimental research on the electroregeneration of mixed-bed ion exchange resins. They then collaborated with engineers from Hebei Electric Power Equipment Factory and teachers from Taiyuan University of Technology to conduct experiments on the electroregeneration of mixed-bed resins using bipolar membranes (Hebei Province 2000 Science and Technology Research and Development Program Project 00213093). They used domestically produced bipolar membranes and other materials, and manufactured an EDI device with anion and cation resins respectively filled on both sides of the bipolar membrane, following Millipore's EDI technology using bipolar membranes. Experimental results of the electroregeneration of multi-bed ion exchange resins showed that when the regeneration voltage was 60 V and the regeneration time was 60 min, the electroregeneration effect of the device was close to that of chemical regeneration, demonstrating good technical feasibility. Cao Liancheng and Deng Yongnan of Huazhong University of Science and Technology also conducted electroregeneration experiments on multi-bed resins using bipolar membranes (1999 Hubei Provincial Science and Technology Commission Key Science and Technology Project 992P1202), reaching the same conclusions as the above experiments.

Beijing Guodian Longyuan Environmental Engineering Co., Ltd. and North China Electric Power University focused on developing multi-bed resin electroregeneration using bipolar membranes as a key technology for resin electroregeneration. Their work on resin electroregeneration technology was initiated by the author of this paper as the inventor of the resin electroregeneration patent, and applied for by Beijing Guodian Longyuan Environmental Engineering Co., Ltd., and listed as a 2001 State Power Corporation Science and Technology Fund project (SP-2001-02-25). The experimental results showed that the regeneration effect of anion resin was very good, reaching or exceeding the effect of alkali regeneration, while the regeneration effect of cation resin was slightly worse [8]. They did not conduct further in-depth research to find the reasons and improve the regeneration effect of cation resin, but abandoned the research on direct electro-regeneration of resin using bipolar membranes. Instead, they conducted experiments on preparing acids and bases using bipolar membranes, and used the prepared acids and bases to regenerate the cation and anion beds in the composite bed, respectively. They believed that this was the most suitable method for regenerating composite bed resins. There are still many problems to be solved in the topic of preparing acids and bases using bipolar membranes. It seems simple, but it is actually difficult to implement. Therefore, the preparation of acids and bases using bipolar membranes may not reach the practical stage until after the industrialization of composite bed electro-regeneration. On the other hand, they have abandoned the research on direct electro-regeneration of resin using bipolar membranes, and their research in this regard is later than that of others. However, they applied for an invention patent for "method and device for regenerating ion exchange resin by bipolar membrane water dissociation method", claiming that the bipolar membrane water dissociation method is superior to the chemical regeneration method, and attempted to obtain the patent right for regenerating resin using bipolar membranes. This raises the question: is this a commercial stunt, or is there some other reason?