Study On The Preparation Of Modified Bentonite/Nano-TiO₂ And The Technology And Mechanism For Advanced Treatment Of Cyanide Barren Solution

Bentonite and Bentonite/TiO₂ are all porous materials having layered structure and higher specific surface area. They both show good adsorption properties, and Bentonite/TiO₂ possesses the characteristics of good photocatalytic performance. In the paper, two kinds of bentonite were analysed based on the properties and chemical analysis. By contrast, bottles bentonite was used in purification operation, and it was also used as the carrier for TiO₂. Bentonite/TiO₂ was modified by the doping of rare earth element lanthanum.In the paper, the optimal adsorption process of cyanide waste water was studied by bentonite: the dosage of bentonite was 10 g/L, the optimum adsorption time was 40 min, the solution temperature was 25oC and the solution pH value was 10. The adsorption isotherms of cyanogen, copper and zinc were drawn. The adsorption isotherms were well represented by Langmuir isotherm and Freundlich isotherm. The maximum adsorption of cyanogen, copper and zinc were 33.95 mg·g^-1, 7.895 mg·g^-1 and 20.35 mg·g^-1 by calculation.Bentonite was used as carrier for TiO₂. By butyl titanate as titanium source, lanthanum was used in modifying the materials. La doped Bentonite/TiO₂ was prepared through acid sol-gel method. By studying on the preparation processing, the optimum conditions for preparing photocatalysts: the molar ratio of lanthanum to titanate of 1%, sintering temperature of 400 oC, sintering time of 2h and aging time of 5h.The effects of sintering temperature on preparation were studied by means of XRD. At the sintering temperature of 400 oC, the content of anatase TiO₂ was higher. The effects of doping amount on prepararion were studied by XRD, FT-IR, EDS and TG analysis. At the molar ratio of lanthan um to titanate of 1%, the TiO₂ had good phase stability, having good photocatalytic activity. By studying the BET, FT-IR, SEM and TG-DTG analysis of bentonite, Bentonite/TiO₂ and 1% La-Bentonite/TiO₂, the doping of lanthanum made the TiO₂ equally distributed on the surface of bentonite and made the structure of Bentonite/TiO₂ more stable.In the paper, the effects of treating cyanide waste water was studied by 1% La-Bentonite/TiO₂. The optimum conditions were adsorption time of 2h, photocatalytic time of 2h, the solution pH value of 10 and the solution temperature of 25oC. The adsorption isotherms of copper and zinc were drawn. The adsorption isotherms were represented by Langmuir isotherm and Freundlich isotherm. The maximum adsorption of copper and zinc were 14.6088 mg·g^-1 and 14.6088 mg·g^-1 by calculation. By studying the photocatalytic mechanism, under the high-voltage mecury lamp, the cyanogens was decomposed into NO₃^- and CO₃^2-.