Continuous Degradation of Formaldehyde by Using NaClO2-SA/CMC-Na Composite Microcapsules

Sodium chlorite (NaClO₂) is a new type of air disinfectant, which can oxidize formaldehyde into carbon dioxide (CO₂) on account of releasing chlorine dioxide (ClO₂) gas under acidic condition. Unfortunately, NaClO₂ is prone to moisture absorption and decomposition when exposed to air. In this paper, NaClO₂ was microencapsulated based on emulsion crosslinking method for improving its stability and controlled release properties. Due to their high biocompatibility, sodium alginate (SA) and sodium carboxymethyl cellulose (CMC-Na) were selected as the wall material to prepare NaClO₂-SA/CMC-Na composite microcapsules. The results showed that mean particle size of NaClO₂-SA/CMC-Na composite microcapsules was about 225 nm, and their encapsulation ratio was up to 73.18%. In addition, the thermal stability and environmental tolerance of NaClO₂ are improved greatly through microencapsulating. It was proved by formaldehyde degradation testing that the efficiency of formaldehyde degradation using resulted samples can continue to increase after seven days in pH 6.5 environment, indicating their good controlled-release performance. Moreover, degradation efficiency on 30 µg/mL formaldehyde solution using the resulted microcapsules is up to 97.08%. Meanwhile, after 20 repetition degradation, NaClO₂-SA/CMC-Na composite microcapsules can still continuously degrade formaldehyde gas. Therefore, NaClO₂-SA/CMC-Na composite microcapsules reveal good stability and prolonged action on formaldehyde degradation.