The process of fabricating the solar absorbing spinel-structured CuCr2O4 black oxide pigment doped with different metals (Mn, Ni, Co, Al, Zn, and Sn) was discovered to improve the solar selective property. Manganese stands out as an ideal dopant to copper chromite (CuCr2O4) for highly solar absorptive pigments compared to the other metal dopings. XRD analysis confirmed that various molar ratios of CuCr(2–x)Mn x O4 spinel black oxides were successfully fabricated. Mn-doped black oxide has the highest absorptivity (the lowest band gap value of 1.35 eV) among various metal doped black oxides produced by the hydrothermal synthesis. Manganese is the only dopant that suppresses reflectance peaks exhibited by the copper chromium oxide at 1 and 1.5 μm in the light spectrum, raising the solar absorptivity of the pigment. Different manganese doping compositions are introduced to CuCr(2–x)Mn x O4 where x = 0.1, 0.25, 0.5, 1, 1.5, 1.75, and 1.9. The high selective solar absorptivity appears after 100% (x = 1) manganese doping with solar absorbance 0.9874 and a figure of merit (FOM) value of 0.9284.

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In this study, we have prepared a composite adsorbent with highly dispersed Mn and Ag nanocatalyst on the surface of activated carbon (AC) by applying the Radio-Frequency (RF) thermal plasma technique for the efficient removal of VOCs. The ACs before and after metal impregnation with RF plasma treatment were characterized by SEM, TEM, EDS, and nitrogen adsorption analysis. Adsorption behaviors of toluene, acetaldehyde, and formaldehyde on ACs before and after modification were also investigated in fixed-bed systems. The experimental adsorption results for VOCs on parent ACs and metal impregnated ACs (Mn-AC and Mn/Ag-AC) were well explained by modified continuous sigmoidal (MCS) model.

In this study, we prepared chitosan beads cross-linked with epichlorohydrin (CB-ECH) to improve the removal of nitrate in groundwater. It was confirmed that CB-ECH exhibited higher thermal stability and well-developed nano-pores compared to the pure chitosan beads (CB) by the thermogravimetric analyzer, nitrogen gas adsorption and desorption isotherm, and field emission scanning microscopy analysis. The CB-ECH showed a higher nitrate adsorption amount than the pure CB. Nitrate adsorption behaviors of CB-ECH were further investigated using adsorption isotherm, adsorption kinetics, adsorption energy distribution, and Gibbs free energy distribution models. The adsorption equilibrium and kinetics of nitrate ion on CB-ECH were well explained by the Sips isotherm and homogeneous surface diffusion model, respectively. It was also found from the AED analysis that the CB-ECH represent the heterogeneous adsorption behaviors for nitrate.