Volatile Organic Compound Sensing with WO₃-Based Gas Sensors: Surface Chemistry Basics

In this work, we present a cost-effective and affordable inorganic silicon material known as nano-SiO2. The purpose of this work is to enhance the performance of toluene separation by utilizing modified-SiO2/polydimethylsiloxane (PDMS) nanocomposite membranes. To achieve this, we successfully grafted hexadecyltrimethoxysilane (HDTMS) onto the surface of nano-SiO2 and systematically investigated the impact of SiO2 concentration on the separation efficiency. Various techniques such as scanning electron microscopy (SEM) and water contact angle (WCA) and Fourier transform infrared (FT-IR) spectrum analyses were employed to analyze the surface morphology, hydrophobic properties, and functional groups of modified polyvinylidene fluoride (PVDF) hollow fiber membranes. In brief, 400 ppm of each volatile organic compound (toluene) was injected into the module as a feed for 10 min at 25 degrees C under a pressure of 1 bar at room temperature. Gases in the retentate were analyzed by GC/FID in purge and trap analyzers at 250 degrees C. The VOCs were sampled using an Automated Purge & Trap Sampler. After comparing the chromatographic data to the reference compounds, the adsorption capacity was calculated to identify residual VOCs collected after separation by the nanocomposite membrane as present in the feed. Among the tested modules, 0.2HPM (hollow fiber membranes coated with 20 wt% PDMS and 0.2 wt% hexadecyl-modified SiO2) exhibited the highest toluene removal efficiency of 95.7 % under conditions of 400 mL/min flow rate and 1 bar pressure. The findings of this study provide valuable insight into the hydrophobic modification of nano-SiO2 and its potential application as a membrane-based separation technique.