Evaluation of HKUST-1 as Volatile Organic Compound Adsorbents for Respiratory Filters

Abstract

Cyclohexane is a representative of volatile organic compounds (VOCs). VOCs can cause serious health problems in case of continuous exposure; therefore, it is essential to develop efficient personal protective equipment. Historically, activated carbons are used as VOC adsorbents. However, the emergence of promising novel adsorbents, such as metal–organic frameworks, has pushed the research to study their behavior under the same conditions. In this work, the use of the well-known HKUST-1 MOF of different particle sizes (20 μm, 300–600 μm, and 1–1.18 mm) for the adsorption of low-grade (5000 ppm) cyclohexane combined with different water concentrations (dry, 27 and 80% RH) in a fixed bed is proposed. The results were compared under the same conditions for a typically used activated carbon, PICACTIF TA 60. HKUST-1 has higher affinity to cyclohexane than PICACTIF for the whole pressure range studied, especially at low partial pressures. It begins to adsorb much earlier (0.0025 kPa) than the activated carbon (0.01 kPa). However, a different adsorption behavior is evidenced for both materials in the presence of water vapor since HKUST-1 is very hydrophilic in the zone near to the copper open metal sites, whereas PICACTIF is hydrophobic. After three consecutive cycles, good stability results were obtained for the MOF, comparable to activated carbon, even in the presence of water. As the main finding, although the unstability of HKUST-1 is well established under high humid conditions, the kinetic of degradation has not been established so far. Here, it is shown that the time usage of HKUST-1 as the adsorbent for respiratory mask (single pass) is not affected by the degradation of the structure, which may occur on a longer time scale. Finally, shaping by tableting provides good results since it is possible to increase the MOF density by around 69% with minor loss of adsorption capacity. The best fraction is 300–600 μm, reaching cyclohexane breakthrough times around 85 min/cm3 at 80% RH, comparable with PICACTIF-activated carbon and promising for practical applications.

Modeling of Water Vapor Adsorption and Desorption in an Industrial Medical Air Dryer

“…The characteristics of the reduced column and the operating conditions are listed in Table . Although the particle diameter to column diameter ratio (δ = D c / d pe ) is relatively low, which may lead to preferential flow paths and nonuniform flow, it is worth noting that this column diameter is not uncommon in the literature and has been used in previous studies. , In addition, we are aware of the potential for preferential flow paths in our study and have attempted to address this issue by careful packing of the adsorbent bed and a relatively low flow rate. A recent study by Petrazzuoli et al showed that preferential pathways through the wall can occur when the value of δ (column-to-sphere diameter ratio) is less than 1.78, whereas in our study, the value of δ is between 2 and 2.7.…”

Fabrication of Cellulose Filters Incorporating Metal–Organic Frameworks for Efficient Nicotine Adsorption from Cigarette Smoke

“…Metal–organic frameworks (MOFs) possess unique properties that include high specific surface area, flexible structures, open metal sites, and high thermal stability, which explain their prospective use in gas storage and separation, adsorption, and many other fields. , Benefiting from a large specific surface area, high porosity, low density, structural variability, and chemical stability, MOFs are widely regarded as very promising adsorbents . However, in practical applications, MOFs exhibit some technical limitations such as particle agglomeration and difficulty in recycling .…”

“…29,30 Benefiting from a large specific surface area, high porosity, low density, structural variability, and chemical stability, MOFs are widely regarded as very promising adsorbents. 31 However, in practical applications, MOFs exhibit some technical limitations such as particle agglomeration and difficulty in recycling. 32 On the other hand, biopolymers such as cellulose fiber have good processability, softness, heat and weather resistance, 33 and chemical stability, 34 in addition to various surface functional groups to anchor metal ions or participate in intermolecular interactions with guest molecules.…”

New Porous Carbon Material Derived from Carbon Microspheres Assembled in Hollow Carbon Spheres and Its Application to Toluene Adsorption

“…At the same time, the air pollution evaluation index of SO 2 was replaced by VOCs in the 14th Five-Year Plan (2021–2025) for National Economic and Social Development and Vision 2035 of the People’s Republic of China. Therefore, a lot of VOCs control technologies such as thermal oxidization, catalytic oxidization, , absorption, − condensation, , and adsorption , were developed. Currently, the adsorption technology is reported as the most promising VOCs control technology due to its low operation cost, convenient operation, and high removal efficiency. , …”