Separation of Boric Acid in Liquid Waste with Anion Exchange Membrane Contractor

Abstract

In order to separate boric acid in liquid waste, some possible technologies were investigated and the membrane contactor without dispersion and density differences was selected. The separation experiments on a Celgard 3401(R) hydrophilic microporous membrane contactor were first performed to obtain the basic data and to determine the properties of the contactor. The experimental conditions were as follows: boric acid concentrations up to 2.0 M, pH 7.0, temperatures of 25 and 55 degrees C, and flow rates of 100, 300, 500, and 800 cm(3)/min. Secondly, an AFN(R) anion exchange membrane contactor was tested at temperatures of 40 and 55 degrees C and how rate 400 cm(3)/min. Boric acid solutions were prepared by the same method as that for Celgard 3401(R) but contained 5.0 x 10(-4) M cobalt chloride (CoCl2). To simulate membrane contactors, parameters such as the differential diffusion coefficients of boric acid and the mass transfer coefficients in the AFN membrane were measured, and regression models estimating the diffusion coefficient at several conditions were developed. The Celgard 3401(R) membrane contactor was simulated and compared with experimental data. Simulation results agreed with the experimental data well when a proper correction factor was utilized. The correction factor was independent of the solution temperature and was 8.75 at the flow rates of 300-800 cm(3)/min. This correction factor was also applied to simulate the AFN(R) contactor. The simulation on the AFN(R) resulted in a good agreement with experiment at 40 degrees C, but not 55 degrees C. The retention on cobalt was also better at 40 degrees C than 55 degrees C. The simulating computer program was also applied to a life size contactor designed conceptually.