VOCs (volatile organic compounds) are a major source of air pollutants and are highly toxic to the human body when inhaled over long periods.voc adsorbent VOCs are emitted from various industrial activities, such as automobile exhaust, asphalt applications, biomass combustion, oil refining, and chemicals production, thereby posing a serious threat to human health.voc adsorbent A variety of methods have been developed to remove VOCs from the atmosphere, including physical and chemical adsorption. Adsorption is a physical method of VOC removal that uses Van der Waals and chemical bonding interactions to separate the molecules from each other. The adsorption process is a mature technology that has been extensively utilized due to its advantages such as high removal efficiency, low energy consumption, and cost-effectiveness.
The most common adsorbent for VOCs is activated carbon fiber, which can be easily modified by acid treatment to increase its adsorption capacity.voc adsorbent Activated carbon has a large number of oxygen-containing functional groups, and its polar group distribution promotes the adsorption of polar VOCs.voc adsorbent VOCs such as acetone, benzene, and tetrachloromethane are also adsorbed well by metal oxides like La2O3, CaO, MgO, ZnO, and Al2O3 due to their positive charge, which can be attracted by the negative charges on the surface of the adsorbent.
Other popular adsorbents for VOCs include zeolites and molecular sieves.voc adsorbent Zeolites are microporous crystalline silica-alumina minerals that are widely used in environmental protection due to their adjustable pore structure, hydrophobicity, and ease of surface modification. They can be easily regenerated after multiple cycles of adsorption/desorption without losing their adsorption capability. The adsorption capacity of zeolites for polar and aromatic VOCs is comparable to that of adsorption carbon.
Molecular sieves are molecular-size silica materials with an average diameter of 0.voc adsorbent 25–4 nm. They are available in several forms, including bonded molecular sieves and supported molecular sieve honeycomb ceramics. Compared with the unsupported molecular sieves, the bonded ones have higher adsorption capacities and can be recycled without losing their adsorption capability.
An effective adsorbent for VOCs must have a large specific surface area, good cation-exchange capacity, and a negative surface charge.voc adsorbent The adsorption capacity of supported molecular sieve honeycomb ceramics can be enhanced by increasing the porosity and the nitrogen content of the supporting material. In addition, the use of a heteroatom-containing ion-exchange resin can improve the adsorption selectivity of adsorbents for VOCs.
In this article, we screened 5 kinds of supported adsorption materials for VOCs and determined the saturated adsorption capacity for toluene, ethyl acetate, isopropanol, and acetone on the molecular sieve-supported honeycomb ceramics.voc adsorbent The results indicate that the saturated adsorption capacity increases in the order of ZSM-5-300 > USY > HY > NaY, with ZSM-5-300 showing the highest adsorption capacity for the four adsorbates. This result is attributed to the competitive adsorption between toluene and water vapor on ZSM-5-300. The adsorption capacity of the materials also decreases in the presence of mixed VOCs. This can be attributed to coadsorption and competitive adsorption between different VOCs on the supported molecular sieves.
Tags:co removal adsorbent | molecular sieve adsorbent
