Evaluation of experimental and economic potential of industrial borax aqueous solution by eutectic freeze crystallization method

Abstract

In industry, various compounds are derived from boron minerals, and the production and processing of these minerals produce various waste materials. Boron production and the discharge of boron waste streams pose a significant threat to the environment. The goal of future process technologies is to recover water and boron minerals from process effluents and minimize waste. The eutectic freeze crystallization (EFC) method stands out as a promising candidate to offer an alternative solution to this problem. This study evaluates the possibility of using EFC technology for an industrial borax system for the first time. The eutectic point of Na2B4O7–H2O is determined. Moreover, the study delves into the crystal sizes, appearances, growth rates, and impurities of both ice and borax (Na2B4O7·10H2O) salt crystals. The successful application of the EFC method for the recovery of water and Na2B4O7·10H2O salt from an industrial waste solution has been achieved. Finally, a treatment facility dedicated to borax, employing EFC for the separation of industrial waste borax solution, has been designed. Additionally, an economic evaluation has been conducted. The analysis showed that the payback time for this investment is 9.2 years, and 78% conversion of liquid waste from the industrial borax waste stream to pure borax and water is possible. Thus, attractive EFC technology succeeds in approaching a zero-waste stream by converting waste into raw materials.