硅胶表面TEOS疏水化改性及吸附VOCs特性

Hydrophobic modification of TEOS on silica gel surface and its adsorption characteristics of VOCs

以正硅酸乙酯(TEOS)为疏水改性剂,通过硅胶表面的羟基接枝反应,得到具备一定疏水性的改性硅胶;利用BET、FT-IR、XRD和TG-DTG等手段对改性硅胶的结构及稳定性进行了表征;在此基础上考察了改性硅胶对各类有机废气的吸附性能.结果表明,TEOS成功接枝在了硅胶表面,改性硅胶不仅具备一定的疏水性,而且机械强度增加到原来的66.85%,稳定性也都得到了提高;550℃空气下焙烧后的改性硅胶仍具有疏水性且吸附容量是焙烧之前的2倍;在高湿度高浓度的废气治理中,TEOS改性硅胶表现出更高的吸附能力和优良的热再生性能.高浓度下改性硅胶的吸附容量是低浓度下的10倍且不受水汽的影响;改性硅胶循环10次的吸附/脱附几乎不变,且在一定条件下,15~30min就达到90%的脱附率.

Volatile organic compounds(VOCs)have become one of the main atmospheric pollutants.Most of VOCs contain a large amount of water vapor,and the relative humidity(RH)is>60%.Therefore,it is crucial to developing hydrophobic adsorbents.In this contribution,tetraethyl orthosilicate(TEOS)was used as a hydrophobic agent to modify the surface of hydrophilic silica gel and prepare the hydrophobic silica gel through hydroxyl grafting reaction.The structure and stability of the adsorbent after grafting reaction was characterized by BET,FT-IR,XRD and TG-DTG.The performances of adsorption on various VOCs were investigated.The results shown that TEOS was successfully grafted on the surface of silica gel and hydrophobic silica gel was prepared.In addition,the mechanical strength has been increased to 66.85%,and stability of silica gel have been improved,the adsorbent after calcination in air at 550℃is still hydrophobic and its adsorption capacity is twice than before.Last but the most important,higher adsorption capacity of VOCs as well as excellent thermal regeneration of this hydrophobic silica gel could be received under the conditions of high humidity and high concentration VOCs.The adsorption capacity of the hydrophobic silica gel at high concentration was 10 times than that at the low concentration and not affected by water vapor;the adsorption/desorption of the silica gel for 10 cycles was almost unchanged and the desorption rate of 90%was reached in 15-30min under certain conditions.