Trimethylchlorosilane modified activated carbon for the adsorption of VOCs at high humidity

Water vapor is inevitable in practical volatile organic compounds (VOCs) exhaust emission, leading to the deterioration of activated carbon adsorption performance. A hydrophobic modification method of activated carbon (AC) using tetraethyl orthosilicate (TEOS) and trimethylchlorosilane (TMCS) was developed to improve the selectivity of VOCs. A series of characterization and toluene dynamic adsorption experiments at the relative humidity (RH) between 0% and 90% were conducted to find the optimal condition of TMCS and evaluate the modification method. The results showed that TEOS constructed -Si-O-Si- structure and introduced Si-OH to react with TMCS. 30%(w/w) TMCS impregnation for 24 h was an appropriate condition, which improved the water contact angle from 111.6 degrees to 143.6 degrees. When the RH increased from 0% to 60% and 90%, the saturated adsorption capacity of Bare-AC decreased by 45% and 64%, respectively. However, for the TMCS modified activated carbon, the decreases could reduce to only 6% and 9%. At high humidity, the improvement in hydrophobicity compensated the damage of microstructure and provided 52% better toluene adsorption capacity at RH 60%, and 91% better at RH 90%.

Automated summary

The hydrophobic modification of activated carbon using TEOS and TMCS can enhance the selectivity of VOCs and improve adsorption performance at high humidity, resulting in better toluene adsorption capacity and increased water contact angle.