AMF기술을 적용한 SWRO 생산수의 잔류붕소제거 및 해수로부터의 붕소회수에 관한 연구

Abstract

In this study, we have developed an efficient technique to remove boron from SWRO permeate water (1.51 mg B/L) and recover it from seawater (4.5 mg B/L) based on the adsorption membrane filtration (AMF) process. CRB05, a commercial boron selective resin (BSR) produced in Mitsubishi chemical Co., is used as an adsorbent. The commercial BSR (300-850um) is grinded to make fine-grain BSR with diameter 10-3000um. The performance by the fine-grain BSR is compared with that by the commercial BSR without grinding for each process of AMF (boron adsorption by BSR, boron desorption from saturated BSR using acid, and regeneration of BSR using base). In the process of boron adsorption from SWRO permeate water, the optimal performance is achieved at 1 g/L of BSR/solution ratio, 150 rpm of stirring speed, and 10 min of reaction time by using the fine-grain BSR, which results in maximum adsorption capacity of 11.68mg B/g BSR. Particularly the reaction time using the fine-grain BSR is shortened by 6 times compared to the commercial BSR. Furthermore, the adsorption capacity is increased by 3 times. In the process of boron adsorption from seawater, on the other hand, the optimal performance occurs at 0.1 g/L of BSR/solution ratio, 100 rpm of stirring speed, and 5 min of reaction time by using the fine-grain BSR, where the reaction time is 60 times shorter than that by the commercial BSR. In the meantime, there is no noticeable difference between SWRO permeate water and seawater in the efficiency of boron desorption from saturated BSR using sulfuric acid and hydrochloric acid. The optimal concentration and volume of sulfuric acid are 0.05M and 1.6L/kg-BSR, respectively, while those of hydrochloric acid are 0.25M and 2.2L/kg-BSR, respectively. Up to 100% of boron is desorbed under the optimal conditions. It is found that both commercial and fine-grain BSRs can be reused with only ±3% of variance in the efficiency of adsorption. The desorbed boron in acid solution is solidified into B(OH)3 by heating and cooling. In addition, the solid boron is formed as sodium borate and calcium borate by reacting with NaOH and Ca(OH)2, respectively, at 140℃.