Study On The Rare Earth Salts Of Heteropoly Acid To Degrade Dyes

Dye wastewater is one of significient pollution sources for water resources,and also recognized as the most difficult to be degraded among pollutants.Photocatalytic oxidation can degrade most organic pollutants owing to its powerful oxidizability,and could be one of the best ways to degrade dye wastewater.The rare earth salts of heteropoly acids with the special structures and excellent photocatalytic performance are the important and promising photocatalysts.In this paper,the eight new heteropoly complexes with rare earth lanthanide,K₁₃?OH?₂[Ln(PW₁₁O₃₉)₂]·nH₂O?Ln=Nd,Sm,Eu,Gd,Dy,Ho,Er and Yb?were synthesized,and characterized by EA,IR,UV,XRD,CVC and TG-DTA.Aim at the two kinds of the simulated dye wastewater?methyl orange and eosin Y solutions?,we studied the photocatalyst activity of K₁₃?OH?₂[Nd(PW₁₁O₃₉)₂]·nH₂O?NdPW?under irradiated by xenon lamp that simulated the visible light.Several influence factors for dye decolorization rate were also investigated including the pH value of solution,the initial concentration of the dye,catalyst quantity and the illumilation time.The optimum degradation conditions were identified.Furthermore,the reaction kinetics of dye degradation using the photocatalyst of the rare earth heteropoly salts were also explored.Finally,the activity of eight photocatalysts were compared.The main results and conclusions were obtained as follows:?1?The eight molecules of synthesized maintain the basical Keggin structure of H₃PW₁₂O₄₀.However,the Keggin structures of these photocatalysts had a little change due to the addition of rare earth ions,which led to the shoulder peaks in IR spectrum as well as their thermal decomposition were lower than that of H₃PW₁₂O₄₀.?2?The molecules of synthesized eight rare earth complexes of heteropoly contain 18 H₂O.?3?We used these rare earth heteropolyanions as photocatalyst to degrade the dyes for the first time.The optimum degradation condition for NdPW photocatalyst to methyl orange solution was that the initial concentration of dye was 10 mg/L,pH value was 2 and catalyst quantity was 1.0 g/L.For eosin Y solution,there were the initial concentration of 10 mg/L,pH value of 5.0 and catalyst quantity of 1.0 g/L.?4?The photocatalytic degradation reaction of NdPW catalyst for the two solutions of dyes were consistent with the first-order kinetic equation.?5?Although all of these eight catalysts presented photocatalytic activity,there were different.Based on the same condition,the consistent results were obtained for the eight catalysts to degrade the two kinds of simulated dye wastewater,in which EuPW and YbPW had higher photocatalytic activity while GdPW had the lowest activity.