Materials for environmental applications
Nanomaterials have been applied for variety of applications. Nanomaterials for environmental applications require a design or modification for particular functions such as for water or air treatment. The advantages of nanomaterials for environmental applications are high reactivity and target specific due to their nanosized scale and large surface area. In the past, nanomaterials that contain porous structure were commonly used as an adsorbent for pollution treatment. Adsorption is a process that the adsorbate migrates and penetrates onto the surface of adsorbent. The removal of some pollutants is based on adsorption mechanism by physical adsorption (Van der Waals forces or ion-induced dipole forces) or chemical adsorption (chemical bonding). For example, the physical adsorption of positive charge pollutant can be achieved by negatively charged adsorbent. The chemical adsorption occurs when the functional groups of pollutant reacts with the functional groups of adsorbent. Apart from pollutant adsorption, porous nanomaterials have been applied as a gas sensor by incorporating electrical circuit with the porous layer that is modified for specific gas target. During gas adsorption, the resistivity of the circuit will be changed and then provides the signal related to the amount of gas adsorbed.
Nowadays, the concept of “Green Chemistry”, which focuses on the reduction or minimization of environmental impacts, becomes more popular. This causes a big change in pollution treatment technology. By adsorption concept, the adsorbed pollutants are just removed from water or air and then accumulated in the porous materials. However, the pollutants are still in the adsorbent, not completely destroyed. Additionally, the contaminated adsorbent needs to be treated with further appropriate methods. As a result, “Green Chemistry and Pollution Treatment” such as ozonation and photocatalytic oxidation-reduction are recommended because these methods are more highly effective and sustainable than adsorption. Pollutants can be destroyed and no further treatment is required.
Research and development
Our research team has studied and developed a mesoporous molecular sieve from abundant rice husk waste, called “RH-MCM-41”. Silica is extracted from rice husk and used as a precursor for RH-MCM-41 synthesis. CTAB is used as organic template during self-assembly process, resulting in hexagonal array of cylindrical pores and thin walls, likes honeycomb structure. Its pore diameter is approximately 3 nm, classified as mesopore and its BET surface area is more than 800 m2/g.
This material has been utilized for BTEX (Benzene, Toluene, Ethylbenzene and Xylene) adsorption and applied as a BTEX gas sensor. Recently, nano-hybrid or nano-composite between RH-MCM-41 and other element such as titanium dioxide, silver, zirconium, nitrogen, carbon nanotube is synthesized to enhance the removal efficiency of some indoor air pollutants such as VOCs, fungal, bacteria.