(A) study on the separation of boric acid in liquid waste with membrane extractor

Abstract

The chemical and physical characteristics of boric acid were investigated. Especially the behavior of borate ions in aqueous solution was focused and the computer programs were developed to calculate the distribution of borate ions at various conditions. The programs were used to analyze the diffusion phenomena of aqueous boric acid. In order to determine an economical and simple separation method of boric acid in aqueous solution, some possible technologies were investigated. Membrane extractor without dispersion and density differences was selected and its theory was established. Separation experiments using membranes such as Celgard 3401 hydrophilic microporous and $AFN^\circledR$ anion exchange membrane were made at boric acid concentrations up to 2.0 M and cobalt concentration of $5.0\times10^{-4}M$ as cobalt chlorides ($CoCl_2$), pH of 7.0, temperatures of 25, 40, and $55\,^\circ\!C$, and flow rates of 100, 300, 400, 500, and 800 $cm^3$/min. The membrane extractor was simulated with the theory established. For the simulation of membrane extractor some parameters such as the differential diffusion coefficients (DDC) and the mass transfer coefficients of boric acid in AFN membrane were measured. Diffusion coefficient for aqueous boric acid without pH control or with pH of 7.0 have been measured at 25, 40, and $55\,^\circ\!C$ and at concentrations up to 2.0 M. The mass transfer coefficients in charged membrane were estimated with the same device at $55\,^\circ\!C$. Diluent and concentrate streams flow rate were 27 and 42 $cm^3$/min., respectively. Diffusion coefficients were measured by Stokes diaphragm cell method and the experimental results were analyzed with the newly developed method using regression analysis. The experimental and data analysis method was checked with HCl. The following relationship for the estimation of the DDC of HCl in aqueous solution was obtained: $D(10^5\,cm^2/\sec) = 3.3390 + 1.397362C - 0.086295C^2 - 1.2149445C^{1/2}$. This coef...