A Novel Approach to Recycle Waste Serpentine Tailing for Mg/Al Layered Double Hydroxide Used as Adsorption Material.

In China, there are about a thousand million tons of waste serpentine tailings (WSTs) that cause serious environmental problems. So it is urgent to treat WSTs. In this work, the MgO in WSTs was extracted to synthetize a high value-added Mg(II)Al(III) layered double hydroxide (LDH) by an alkali fusion process, and the purified SiO2 can be obtained by the precipitation of Na2SiO3. The results indicated that the MgO extraction rate increased with the increase of Na2CO3 content and calcination temperature. The serpentine structure was destroyed and the MgO extraction rate increased rapidly to reach 91.4% when the temperature reached 750°C and the ratio of WSTs and Na2CO3 was 1:2. However, when the temperature was over 800°C, the serpentine completely transformed into forsterite with higher crystal strength, which was difficult to react with Na2CO3. The Mg-Al-LDH synthesis was carried out using a chemical precipitation method. It was not conducive to synthesis of Mg-Al-LDHs for using the rich magnesium solution that was obtained under low MgO extraction rate. The structure and surface morphology of the LDHs were characterized by an X-ray diffraction, FT-IR, and scanning electron microscopy (SEM). Finally, the Mg(II)Al(III)LDHs property of adsorbing Pb and P was investigated. The removal rate of Pb could reach about 99% and there was good adsorption capacity for P. This indicates that it is possible to synthetize high value-added Mg(II)Al(III) LDH by WSTs that could be recycled. [ABSTRACT FROM AUTHOR]