Boron separation by adsorption and flotation with Mg–Al-LDHs and SDBS from aqueous solution

Abstract

Layered double hydroxides (LDHs) have been shown to be effective adsorbents for boron. However, solid–liquid separation is still a problem when separating boron from industrial radioactive waste liquid. In this research, three types of Mg–Al-LDHs including Mg–Al-LDH(NO3–), Mg–Al-LDH(Cl–) and Mg–Al-LDH(SO42–) were applied to adsorb boron, and moreover sodium dodecylbenzenesulfonate (SDBS) was used to float the LDH particles from aqueous solution after boron adsorption. The results showed that 60 min was sufficient for the equilibrium adsorption of the three LDHs. The boron adsorption capacity of three LDHs was determined as follows: Mg–Al-LDH(NO3–) > Mg–Al-LDH(Cl–) > Mg–Al-LDH(SO42–), and was 2.0, 0.98 and 0.2 mmol·g−1, each ranging from 0 to 80 mmol·L–1 with the initial boron concentration. The efficiency of boron removal by Mg–Al-LDH(NO3–) and SDBS can reach up to 89.7%. Furthermore, the boron flotation mechanism of SDBS and LDHs has been studied, since SDBS as a flotation agent can react with LDHs and penetrate into the interlayer of LDHs in addition to electrostatic attraction. Therefore, LDHs in solution can be floated onto the foam layer to be separated from the solution, and the clarified solution was obtained. The method is simple and promising for boron removal from aqueous solution.