Study On The Catalytic Performance Of Palladium Colloids And The Supported Catalysts In Cr(â…¥) Reducted Reaction

With the industrial and economic development, chromium salt was widely used in all walks of life, which cause large amount of wasterwater with chromium without the suitable treatment, high poisonous Cr(Ⅵ) will enter into our environment including soil and water, and cause serious pollution. This dissertation focus on the catalytic performance of palladium colloid, and their supported catalysts in the reduced reaction of Cr(Ⅵ) to Cr(Ⅲ). Two parts are involved as follows:(1) Catalytic performance of the colloidal palladium nanoparticles (PdNPS) and their magnetic catalyst (Pd-Fe3O4). The colloidal PdNPS were synthesized by the chemical reduction method in the presence of polyvinylpyrrolidone (PVP) as the capping agent, which showed superior catalytic performance in the Cr(Ⅵ) degradation reaction. Over 2.82×10-6 mol PdNPS catalyst,7mL 71.4 mM Cr(VI) was totally reduced into Cr(Ⅲ) in 8 min under the conditions of T= 45℃and pH= 3.98. For recycle and reusing of catalysts, the PdNPS was immobilized on the superparamagnetic support Fe3O4. The Pd-Fe3O4 catalyst had high superparamagnetism and its saturated magnetization was 61.4emu/g, which implied that the catalyst can be easily separated from the reaction system by using a magnetic field. After the recycling of the magnetic catalyst for eight times, the reduction of Cr(Ⅵ) to Cr(Ⅲ) rate had a slight change from0.023mmol/min to 0.018mmol/min which revealed good stability of the catalyst.(2) Catalytic performance of the mesoporous SBA-15 supported Pd-Au bimetallic nanoparticles catalysts. The mesoporous SBA-15 was modified with amino groups and used as carriers for the metallic nanoparticles. The mesoporous support had odered pore structure, which was favorable to the formation of small-sized metallic particles, and the metallic nanoparticles distributed uniformly in the pore and on the surface of the mesoporous silica. The Pd-Au bimetallic catalysts showed synergetic effect in the Cr(VI) degradation reaction, which showed enhancement of reaction rate and catalytic activity of the Pd atoms on the surface of the bimetallic nanoparticles.