본 연구에서는 붕소함유 인공염수(간수)를 수산화칼슘으로 포화시켜 calcium borate를 합성하는 반응에서, 첨가하는 황산이 미치 는 영향을 알아보았다. 다양한 조건(반응온도, 반응시간, 가열반응 후 방랭온도)에서 calcium borate 합성을 시도하였고, 각 조건에서 황산 첨 가유무에 따른 calcium borate의 회수율과 순도 변화를 알아보았다. XRD 분석을 통해 황산의 첨가유무에 상관없이 calcium borate(Ca2B2O5·H2O)가 생성되었음을 확인하였고, 황산을 첨가하면 부산물로 황산칼슘(CaSO4·0.5H2O)이 생성되었다. 황산을 첨가하지 않았 을 때, 실험한 모든 반응온도와 반응시간 조건에서 calcium borate의 회수율과 순도가 황산을 첨가했을 때보다 더 높았다. 황산을 첨가하면 수산화칼슘의 용해도는 높아지지만, 부산물로 생성되는 황산칼슘이 calcium borate의 생성을 방해하여 그 회수율과 순도가 낮아진다고 판단 된다. 본 연구에서는 붕소함유(500 mg-B/L) 인공염수(간수)에 황산을 첨가하지 않고 수산화칼슘으로 포화시켜서 80-105 ℃에서 10분 이내로 가열하여 calcium borate를 합성하였고, 그 회수율과 순도는 각각 최대 80 %, 96 %로 매우 높았다.

To investigate the usability of the bitterns produced during salt manufacture, the characteristics of soybean curdscoagulated with bitterns like solar salt bitterns (SSB), dehydrated salt bitterns (DSB), concentrated sea water (CSW) and bitterns produced during the storage of solar salt (BSS) were measured. The Mg contents of all the bitterns were the same, but the Na content of the BSS was 1.0-2.0 times as high as that of the other bitterns. The yield of the soybean curds did not differ with the addition of coagulants, except for the CSW. However, the soybean curds were acquired in large quantities by the DSB and CSW. The mg and Na contents of the soybean curds that were made with the bitterns were higher than those of MgCl2. The heavy metals were below 3 ppm in the curds, especially those produced by the CSW, but Pb was not detected. Among the mechanical characteristics of the soybean curds, their adhesiveness was not affected by the coagulants, but the mechanical hardness of the curds produced by the DSB and CSW was lower. The sensory evaluation showed that the curds that were produced by the bitterns were more highly preferred than those produced by MgCl2. In particular, the soybean curd that was made with the CSW was favored due to its soft texture. The results of this study, particularly the high yield of the curds that showed a soft texture, showed that the bitterns, especially the CSW, could be used safely and economically.

The characteristics of precipitation separation and solvent extraction separation of magnesium from the waste bittern were studied experimentally. In the result of precipitation separation, the size of magnesium hydroxide precipitated was not affected on pH, but decreased with increasing the precipitation temperature. The purity of magnesium oxide precipitated was increased with pH beyond pH 11. From the solvent extraction separation, the equilibrium extraction ratio of magnesium was increased with pH and temperature of extraction phase, the concentration of stripping phase, and with decreasing pH of stripping phase. The extractant of Aliquat 336 and Acid 810 mixture was more effective than that of DCH18C6 and D2EHPA mixture in the extraction separation of magnesium.