Sustained and controlled release of natural volatile organic compounds from hydrophilic-lipophilic balance-optimized phytoncide emulsion-zeolite composites for indoor application

초록

Existing approaches for applying essential oils to indoor environments remain limited by their temporary effects and insufficient control over release behavior. This study develops a sustained natural volatile organic compounds (NVOC) release system using a hydrophilic-lipophilic balance (HLB)-optimized phytoncide emulsion-zeolite composite. Phytoncide oil and hydrosol were emulsified with nonionic surfactants (Tween 80 and Span 80) across various HLB values and loaded into zeolite. High-HLB emulsions (HLB 14) showed enhanced stability, generating small and uniform droplets (similar to 170 nm, polydispersity index similar to 0.13). It was confirmed that NVOC was adsorbed into zeolite pores without significant morphological or structural deterioration of the zeolite. The optimized composite achieved a loading capacity of up to 47%, surpassing previously reported zeolite-based carriers through finer droplets and more uniform adsorption. Short- and long-term release behavior followed the Weibull model (R & sup2; >= 0.99), with release exponents consistent with Fickian diffusion-influenced transport. The optimized emulsion-zeolite composite markedly improved release persistence, reducing the cumulative release after 14 days by approximately 55% compared with pure phytoncide oil. Quantitative analysis of VOC emissions emitted from the composite revealed that twenty-five NVOC species were detected-mainly cymene, limonene, and valencene. To provide a regulation-relevant context for indoor use, the measured VOC concentrations were evaluated against health-based indoor guideline values, confirming that hazardous VOCs and major terpenes remained below the most stringent guideline under the test conditions. Overall, the composite shows potential as a bio-based controlled-release material for moderating NVOC emission intensity and extending release persistence under indoor-use conditions.

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