The Study Of Adsorption And Photocatalysis For TiO₂in Different PH And High-salinity Solution

The advantage of pollutant degradation by photocatalysis includes low energyconsumption, high activity of catalysis and no secondary pollution; as the typicalphotocatalyst, TiO₂has stable property and extensive source. Thus, the research of TiO₂photocatalysis has beening extensively developed, and focus on solar cell, doping, modifyingsurface and so on. But returning to the TiO₂photocatalysis, much effect and mechanism in thecourse are not still clear, especially in extreme condition. If the effect and mechanism can beexplained, the influence of photocatalysis can be perfected and the study also will beimproved. Therefore, in different pH and high-salinity solution, the adsorption andphotocatalysis for TiO₂were studied carefully by various ways.Under the condition of ultrasonic dispersion and agitating of simulating reality, theagglomerate and sedimentation course of TiO₂nanoparticle was studied. The result showedthat the agglomerate of suspension always caused sedimentation in which the small diameterparticle remarkable assembled. The sedimentation included stable, high speed and low speedstages. The stability of suspension in acidic situation was stabler than that in alkaline,espcially when the pH was1. Under the diffrent concentration of salts, the ability of assembleTiO₂particle in suspension by KCl, NaCl, MgCl₂, CaCl₂, NaNO₃and Na₂SO₄were various.The agglomerate image from microscope responded to the experiment result.The adsorption of methylthionine chloride onto TiO₂nanoparticle in different pH and saltsconcentration solutions, the result of conductivity, FTIR and Uv-vis were used to analyse themechanism. The result displaied that the adsorption is physical and remarkably influence byhigh salts concentration, the adsorption rate decreased with salts concentration increase andfinally dropped to5%. Increasing temperature could shorten the time of reachingadsorption equilibrium, high salts concentration could raise the rate within small range （themaximum growth rate was10%）. Ionic association is the important rule for expaining theresult.Degussa P-25was used to removaled the methylthionine chloride in different pH and highconcentration solutions of NaCl and Na₂SO₄. Total organic carbon （TOC） change showedmethylthionine chloride could be removaled by photochemical degradation. Under high pH condition, the degradation rate reached92%. The inhibition of Cl-to photocatalysis was lowerthan SO₄^2-. The total influence of NaCl, Na₂SO₄and pH for photocatalysis were the additionof3three elements in which “the optimal inhibition” existed. The result of high efficiencyliquid chromatography （HPLC） showed that the adsorption of anion onto TiO₂raised with ionconcentration increase, thus further expained the mechanism about ion adsorption influencefor the photocatalysis.Degussa P-25was also used to removaled the methylthionine chloride in highconcentration solutions of NaCl, MgCl₂and CaCl₂. Total organic carbon （TOC） changeshowed methylthionine chloride Na⁺、Mg²⁺、Ca²⁺could hindered photocatalysis, the inhibitionof Mg²⁺and Ca²⁺was various （1%-3%）in different concentration range，The total influenceof NaCl, MgCl₂and CaCl₂for photocatalysis were the addition of3three elements in which“the optimal inhibition” also existed. The result of inductively coupled plasma-atomicemission spectrometry （ICP-AES） showed the inhibition was related to ion adsorption inwhich the different hindering effect between Mg²⁺and Ca²⁺was proved. In addtion, theanalysis of ICP-AES revealed that the inhibition was not only determined by adsorption of ion,but also other factor.