TiO₂Powder And Ultrasonic Degradation Of Organic Dyes

Organic dye has become a major water pollutant, which traditional degradation methods areinsufficient to deal with because of the high-toxic and persistent high-molecular compound of agreat quantity contained in it. As a new material, Nano-TiO₂has been widely used in dyedegradation. And with a better penetrating power than ultraviolet source, ultrasonic can effectivelyresolve the degradation limitation of cloudy liquid.This experiment is based on hydrolysis to prepare titanium dioxide through the followingsteps. Firstly, put the beaker with45mL distilled water into a ice-water bath; add5mLTiCl4solution into the beaker dropwise and stir the mixture which is reserved as Mixture A. Secondly,dissolve26.4g solid ammonium sulfate into solution with a concentration of2mol/L and filter thesolution; add5mL hydrochloric acid into45mL of the filtrate which is reserved as Mixture B.Thirdly, blend Mixture A and Mixture B thoroughly in ice-water bath under15℃;30minutes later,transfer the new mixture into a constant-temperature water bath of90℃; add ammonia waterdropwise into the mixture until white precipitate is generated, and at the same time keep the pH at7; after keeping the mixture under the constant temperature for an hour, take the mixture out of theconstant-temperature water-bath and cool it down. Next, deal with the precipitate by lavation andsuction filtration repeatedly until there is no chloridion in it, then wash it with absolute ethylalcohol; after drying the precipitate, calcine it with a constant temperature of500℃for2hours.Finally, grind the cooled solid titanium dioxide into powder.This experiment respectively probes into four materials—OrangeΙΙ，xylenol orange，malachite green，crystal violet from aspects of the amount of catalyst, the initial concentration ofthe degradation liquor, degradation time and temperature etc.; and measures the COD of thedegradation product.It is concluded from the results of this experiment that dye can be best degraded in ultrasonicwave with TiO₂as the catalyst under these conditions--OrangeΙΙ: the temperature is at20℃；theinitial concentration is40mg/L; the pH is1; the addition of the catalyst is2.0g/L; the degradationtime is60min; the degradation rate is at its maximum; xylenol orange：the temperature is at20℃；the initial concentration is20mg/L; the pH is1; the addition of the catalyst is1.0g/L; thedegradation time is40min; the degradation rate is at its maximum; malachite green: thetemperature is at20℃, the initial concentration is20mg/L; the pH is4; the addition of the catalystis1.0g/L; the degradation time is100min; the degradation rate is at its maximum; and crystalviolet: the temperature is at15℃, the initial concentration is10mg/L; the pH is7; the addition ofthe catalyst is1.0g/L; the degradation time is120min; the degradation rate is at its maximum.After5hours of the catalytic degradation mechanism, COD of the OrangeΙΙ solutionelimination ratio is60.3%; that of xylenol orange is55.3%；malachite green is39.5%; and that ofcrystal violet solution is65.6%.