In this study, chitosan nanoparticles containing palmarosa essential oil (PEO-CNPs) were formed by ionotropic gelation, consisting of two parts: emulsion preparation followed by ionotropic gelation encapsulation with tripolyphosphate ions (TPP) as a crosslinker. The encapsulation method was optimized by varying three parameters, including chitosan concentration, initial oil loading in the emulsion and TPP concentration. The effects of these parameters on the encapsulation efficiency (EE) and loading capacity (LC) were analyzed. EE had an initial increase followed by a decrease in the range of three parameters. However, LC rose with varying initial oil content while it reduced with changing polymer and TPP concentration. The optimum experiment with the highest EE (10.0 g/L of chitosan, 5.0 g/L of TPP and 30.0 g/L PEO) was chosen to analyze the particle size using Dynamic Light Scanning method (DLS). With DLS measurement, the z-average diameter was 235.3 nm, and the particle size distribution was in the range of 100 – 500 nm.

M-OMS-2 materials (M = K+, Cu2+, Co2+) were prepared by an uncomplicated reflux method, and the cryptomelane crystalline structure was confirmed by X-ray diffraction patterns. Element analysis recorded ~56 - ~59 wt.% of Mn in the three synthesized samples and ~2.8 wt.% loadings of dopants over Co-OMS-2 and Cu-OMS-2 materials. A titration method valued the average oxidation states of manganese at 3.60, 3.71 and 3.77 for K-OMS-2, Co-OMS-2 and Cu-OMS-2, respectively. In comparison with K-OMS-2, Co and Cu dopants depicted a significant enhancement catalytic activity in removal of formaldehyde at low (5%) and high (65 %) relative humidity (RH). Cu-OMS-2 showed the highest catalyst performance with ~90 % of formaldehyde conversion at 150 °C, 65% RH, whereas only ~40 % (for Co-OMS-2) and ~26 % (for K-OMS-2) of that were observed. The finding results promised a potential Cu-OMS-2 material for designed low-costly catalyst in formaldehyde removal at a wide range of RH.