In this study, hemp stem was used to prepare high surface area activated carbon (AC) by KOH activation. The structure, characterization, thermal and structure analysis on reaction mechanisms of AC were investigated via N2 adsorptionâdesorption isotherm, Fourier transform infrared (FTIR) spectroscopy and thermogravimetric-mass (TG-MS) spectrometry. Results show that when the impregnation ratio is 4.5:1 (KOH/char), the activation temperature is 800 °C, and the activation time is 1.5 h, AC has the highest specific surface area of 2388 m2·gâ1 and exhibits narrow pore size distributions with maxima in the micropore areas. The reaction mechanism of AC from hemp stems by KOH activation is as follows: In the first carbonization stage, it is primarily because of the substitution, scission, and oxidization reactions of methylene. Then in the second activation stage, it is mainly related to polycyclic reactions, reactions between carbon and KOH, and reactions between intermediate potassium oxide species and carbon. Keywords: Hemp stem, Activated carbon, Characterization, Reaction mechanis

Nitrogen functional groups were introduced by urea and melamine onto the surface of two bamboo processing residues derived activated carbons (ACs) and Cr(VI) adsorption was investigated by changing various parameters. The results suggested that the incorporation of nitrogen species caused a visible increase in the adsorption capacity. The ACs with melamine and urea modification showed that the maximum removal of Cr(VI) from the solution having an initial Cr(VI) concentration of 100 mg L⁻¹ was obtained at pH 2.0 as 89% and 85%, respectively. The adsorption capacity of Cr(VI) for unmodified AC was 78%. Langmuir adsorption model was applied to experimental equilibrium data of Cr(VI) adsorption and the adsorption kinetic followed pseudo-second-order model for these two ACs. Besides, the intraparticle diffusion kinetic model suggested the Cr(VI) adsorption could be divided into two phases: the diffusion controlled by external surface followed by an intra-particle diffusion.

At present, the technology used for the extraction and purification of Camellia oleifera saponins generally has the problems of high cost and low purity, and the quantitative detection of Camellia oleifera saponins also has the problems of low sensitivity and easy interference from impurities. To solve these problems, this paper aimed to use liquid chromatography for the quantitative detection of Camellia oleifera saponins, and to adjust and optimize the related conditions. In our study, the average recovery of Camellia oleifera saponins obtained was 100.42%. The RSD of precision test was 0.41%. The RSD of the repeatability test was 0.22%. The detection limit of the liquid chromatography was 0.06 mg/L, and the quantification limit was 0.2 mg/L. In order to improve the yield and purity, the Camellia oleifera saponins were extracted from Camellia oleifera Abel. seed meal by methanol extraction. Then, the extracted Camellia oleifera saponins were extracted with an ammonium sulfate/propanol aqueous two-phase system. We optimized the purification process of formaldehyde extraction and aqueous two-phase extraction. Under the optimal purification process, the purity of Camellia oleifera saponins extracted by methanol was 36.15%, and the yield was 25.24%. The purity of Camellia oleifera saponins obtained by aqueous two-phase extraction was 83.72%. Thus, this study can provide a reference standard for rapid and efficient detection and analysis of Camellia oleifera saponins for industrial extraction and purification.

In order to develop a new type of antioxidants with high efficiency, a series of β-ionone thiazolylhydrazone derivatives were designed and synthesized from β-ionone, and their structures were characterized by ¹H-NMR, ¹³C-NMR, FT-IR, and HR-MS. The antioxidant test in vitro indicated that most of the target compounds had high biological activity. Among them, compound 1k exhibited very strong DPPH (1,1-diphenyl-2-picrylhydrazyl radical)-scavenging activity with a half-maximal effective concentration (IC₅₀) of 86.525 μM. Furthermore, in the ABTS (2,2-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt)-scavenging experiment, compound 1m exhibited excellent activity with an IC₅₀ of 65.408 μM. Their biological activities were significantly better than those of the positive control Trolox. These two compounds, which have good free-radical-scavenging activity in vitro, were used as representative compounds in the anti-browning experiment of fresh-cut potatoes. The results showed that 1k and 1m had the same anti-browning ability as kojic acid, and they were effective browning inhibitors. In addition, it is well known that microbial infection is one of the reasons for food oxidation. Therefore, we investigated the antifungal activity of 25 target compounds against eight plant fungi at a concentration of 125 mg/L. The results indicated that these compounds all have some antifungal activity and may become new potential fungicides. Notably, compound 1u showed the best inhibitory effect against Poria vaporaria, with an inhibition rate as high as 77.71%; it is expected to become the dominant structure for the development of new antifungal agents.

Phenol Adsorption on Nitrogen-enriched Activated Carbon Prepared from Bamboo Residues