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

Abstract

• Hydrophobic coating formed on activated carbon by hydrolysis of TEOS and impregnation of TMCS. • The best condition of TMCS impregnation was investigated. • Morphology and hydrophobicity of activated carbon changed after modification using TMCS. • TMCS modified activated carbon maintains great VOCs adsorption capacity under humid condition. 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° to 143.6°. 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%.