Dispersion And Photocatalytic Behavior Of Organic Modified TiO₂ Powders In Medium

Titanium dioxide?TiO₂?is a kind of metal oxide with excellent properties.As white pigment,submicron scale TiO₂ has been widely used in the field of pigment coatings,plastics,papermaking and other industrial fields.Nano TiO₂ has a good application prospect in the field of photocatalysis.The organic modification on the surface of TiO₂ has a positive significance in the research of the surface hydrophobicity,the influence of the dispersion and photocatalytic properties.In this paper,the particle dispersion of sodium stearate and oleic acid modified micron TiO₂ in water and kerosene was tested.The dispersion mechanism of modified TiO₂ in water medium was discussed.The photocatalytic degradation of methyl orange by citric acid and tartaric acid modified micron and nanoscale TiO₂ was tested and characterized.The optimum conditions and properties of micron TiO₂ modified by sodium stearate and sodium oleate were studied under the premise of both surface hydrophobicity and dispersibility in aqueous medium.The optimum conditions for the modification of sodium stearate are as follows:the dosage of the modifier is 2%,the solid content is 20%,the modification time is 15min,the suspension is pH=11,the modified temperature is 70?,and the optimum conditions for the sodium oleate are2%,40%,15min,pH=7 and 80?.The modified sodium stearate and sodium oleate have strong hydrophobicity and good dispersibility under the optimized conditions.The wetting contact angles of the TiO₂ are 120 and 129,and the dispersion stability index is 93%and 97%.The dispersion mechanism of modified TiO₂ in water medium is discussed by calculating the Fan Dehua action energy,electrostatic action energy,hydrophobicity energy and the combined effect of them.It is considered that the modified TiO₂ exist repulsive interaction between particles in a long distance,especially energy barrier results in good dispersion.The optimum conditions,dispersing property and photocatalytic activity of micron TiO₂ modified by citric acid and tartaric acid were studied.The micron grade TiO₂ modified by citric acid and tartaric acid has good dispersibility,and the dispersion stability index is 79%and 85%,respectively.The efficiency of photocatalytic degradation of methyl orange under the irradiation of 1000W mercury lamp is significantly higher than that of unmodified TiO₂,and the degradation rate of light 90min is close to 100%.The photocatalytic degradation of methyl orange by citric acid modified nano TiO₂ is higher than that of unmodified and tartaric acid modified nano TiO₂,and the degradation rate of light 60min is nearly 100%.