A prolonged evaluation of air contamination level with CO₂ in a college student’s laboratory using nanosized MgO

Abstract

Three nanocrystalline eco-friendly MgO samples, as pure and modified with 1% (wt/wt) F⁻ or K₂O at 600 °C, with high surface area and mesoporous nature were prepared by a simple sonochemical process. The three samples were characterized by XRD, surface area, porosity and TEM techniques. These samples were kept in contact with the atmosphere in the middle of a student’s organic chemistry laboratory and were examined toward capturing the ambient CO₂ molecules through continuous exposure for a period of 8 weeks. The capturing capacity of these samples was shown to be in the following order: MgO > MgO-1%F > MgO-1%K₂O. After 8 weeks, the amount captured by MgO was 346.2 ${\text{mg}}_{{{\text{CO}}_{2} }} \,{\text{g}}^{ - 1}$, while MgO-1%F captured 311.4 ${\text{mg}}_{{{\text{CO}}_{2} }} \,{\text{g}}^{ - 1}$, and finally MgO-1%K₂O had the lowest capturing capacity of 252.9 ${\text{mg}}_{{{\text{CO}}_{2} }} \,{\text{g}}^{ - 1}$. The obtained results showed that our samples are characterized by prolonged activity and reactivity toward the capturing of ambient CO₂ molecules. Another series of experiments were carried out by passing pure CO₂ gas (instead of the atmospheric CO₂) over such samples, inside a glass cubic chamber, for 1 week. The results showed a similar trend in the TG desorption and TPD curves of pure CO₂ as those recorded in ambient atmosphere. Values of the molar enthalpy change (ΔH) for CO₂ desorption, corresponding to the two steps recorded for each sample in all durations, were calculated and were in agreement with those published formerly. Deconvolution of the IR-broad band, between 1800 and 1200 cm⁻¹, revealed the presence of different types of basic sites on the surface of these samples under investigation.