硅藻土基纳米TiO2降解甲醛的实验研究

对比研究了硅藻土和硅藻土基纳米二氧化钛光催化剂对甲醛的吸附降解特点.通过改变反应器内甲醛的初始浓度、反应温度、光照强度和相对湿度,研究了涂覆量为62.5 g·m^-2的硅藻土基纳米TiO₂光催化剂对甲醛气体的降解效果.研究结果表明,硅藻土只对甲醛有一定的吸附作用,而硅藻土基纳米TiO₂对甲醛具有持续的吸附和降解作用.反应器内甲醛初始浓度越高,降解时间越长;初始浓度为6.0×10^-3 mg·L^-1的甲醛气体,经过150 h降解率才能达到99%以上,而初始浓度为2.0×10^-3 mg·L^-1和4.0×10^-3 mg·L^-1的甲醛气体分别在14 h和32 h内就可以达到相同的降解率.反应温度越高,硅藻土基纳米TiO₂降解甲醛所需要时间越短;15 ℃时将初始浓度为2.0×10^-3 mg·L^-1的甲醛完全降解需要50 h,而45 ℃时仅需12 h.光照是硅藻土基纳米TiO₂降解甲醛的直接动力,光照强度为0时,甲醛几乎不能被降解,只被硅藻土基纳米TiO₂光催化剂吸附;在8100 lx的照度下,浓度为2.0×10^-3 mg·L^-1的甲醛在14 h内能被完全降解.环境相对湿度越大,该催化剂对甲醛的降解越彻底;相对湿度50%时, 硅藻土基纳米TiO₂光催化剂14 h内能将2.0×10^-3 mg·L^-1的甲醛降解到3.72×10^-5 mg·L^-1,在相对湿度80%时,甲醛能被降解到1.0×10^-5 mg·L^-1.

Experimental study on the formaldehyde degradation by nano-TiO2 immobilized on diatomite

The characteristics of the diatomite powder and the nano-TiO2 immobilized on diatomite for formaldehyde adsorption were compared.The formaldehyde degradation of the nano-TiO2 immobilized on diatomite by the dosage of 62.5 g·m-2 was studied under the condition of varying original formaldehyde concentration,reaction temperature,light intensity and relative atmosphere humidity in the reactor.The results showed that the diatomite powder can only adsorb formaldehyde but the nano-TiO2 immobilized on diatomite can adsorb and degrade formaldehyde continuously.The degradation time was long for high formaldehyde original concentration.The degradation time of formaldehyde with original concentration of 6.0×10-3 mg·L-1 were 150 h,whereas only 14 h and 32 h for the original concentration of 2.0×10-3 mg·L-1 and 4.0×10-3 mg·L-1 respectively when the degradation ratio above 99%.The higher reaction temperature was,the shorter time of degrading formaldehyde.50 h was needed for the complete photocatalyst oxidation of formaldehyde with original concentration 2.0×10-3 mg·L-1 under reaction temperature 15 ℃,but only 12 h under 45 ℃.Light was the key driving power of the nano-TiO2 immobilized on diatomite degrading formaldehyde.The degradation time of formaldehyde of 2.0×10-3 mg·L-1 was 14 h when the light intensity was 8100 lx,but formaldehyde could hardly be degraded when the light intensity was 0 lm·m-2.The rate of formaldehyde degradation by the photocatalyst was also enhanced by the relative humidity in the reactor.The formaldehyde degradation time from 2.0×10-3 mg·L-1 to 3.72×10-5 mg·L-1 was 14 h under the relative humidity of 50%,but to 1.0×10-5 mg·L-1 under the relative humidity of 80%.