Mongolian Journal of Chemistry

Influence of co-milling oxide physical properties on the structural changes of natural clinoptilolite zeolites

Narantsogt Natsagdorj — 2023-06-19

Zeolites are a family of open-framework aluminosilicate minerals used in many diverse fields, including building materials, agriculture, water treatment, and catalysis. In this study, natural zeolites were mechano-chemically treated by co-milling with corundum and cristobalite. The idea behind the study was that co-milling with high-hardness oxides would cause natural zeolite to undergo more structural distortion, potentially increasing its reactivity and sorption capabilities. Corundum has a density of 3.95 g/cm³ and a hardness of 9, while cristobalite has a density of 2.27 g/cm³ and a hardness of 6-7, according to the Mohs hardness scale. In a planetary ball mill, the zeolites and 20 wt.% of various oxides were co-ground for 30 min. The grinding media used were hardened steel balls with a weight ratio of 20:1 between the balls and the minerals. Raw minerals and milled products were evaluated using X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. It revealed that co-milling with different hardness oxides had a minor effect on the structural distortion of raw zeolite. Crystallite size reduction and amorphization were observed in high hardness oxides rather than in zeolite particles. After milling, the amorphization of natural zeolite milled alone was 30.4%, while no significant amorphization was observed when co-milled with corundum and cristobalite. Preliminary results of Cr(VI) adsorption tests on raw and milled zeolites indicate that co-milling with high-hardness oxides is not the preferred method to enhance the activity of natural zeolite.

Application of the Fenton-like agent based on magnetic iron and manganese oxide in the degradation process of paracetamol in water

Ha Nguyen Manh — 2023-10-25

A Fenton-like catalyst MnO₂-Fe₃O₄/SiO₂ is synthesized via a two-step approach. The prepared composite has a mesoporous structure and a high surface area of 190 m²/g. The XRD pattern describes a specific peak of Fe₃O₄ magnetite on the baseline of amorphous silica. Furthermore, the FTIR spectra not only show the height assigned to stretching vibrations of Si-O-Si bonds, and Fe–O–Fe connections but also exhibit a small peak that matches the Mn–O bonds. SEM images exhibit a porous network structure of the composites with some holes among 30 – 100 nm clusters. The activity of the catalyst is determined in a paracetamol degradation as a Fenton oxidation. The paracetamol removal efficiency is at 85.6% with the optimal condition as initial pH 3, catalyst dosage of 0.15 g/50mL and H₂O₂ concentration of 1 mL/50 mL. In addition, the catalyst can be reused at least 5 times with a low reduction of the catalytic activity from 85.6% to 80.8%. The experiment results open a direction that has high efficiency in the treatment process of excess paracetamol in pharmacy wastewater.

Treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching

Nyamdelger Shirchinnamjil — 2023-06-19

This research investigates the extraction of copper from copper-containing leaching residue, which includes 33.45% of copper, 14.14% of iron, 23.87% of sulfur and trace amounts of silver and other elements. Roasting the copper-containing residue under air and oxygen flow convert sulfides into sulfate, followed by water and acid leaching to extract copper. The process parameters, including leaching temperature, sulfuric acid concentration, leaching time, solid-to liquid ratio, and agitation speed, were optimized for both water and acid leaching methods. Results showed that the maximum copper dissolution efficiency was 93.12% with water leaching, and 97.16% with acid leaching. Chemical analysis revealed that the water and acid leaching residue contained 48.13% and 31.64% of iron, respectively. This study provides valuable insights into the process optimization for copper extraction from copper-containing leaching residue, which can inform the development of more efficient and sustainable methods for metal recovery.

Chemical profile and biological properties of the essential oil of Rosemary leaves (Rosmarinus officinalis L.)

Pham Thi Quyen — 2023-10-24

Rosemary leaf essential oil (RoEO) is extracted using steam distillation. The aim of study is to determine physicochemical characteristics of essential oil (EO), such as acid/saponification/esterification index, relative/absolute density, freezing point, and fragrance retention. The chemical composition of EOs was analyzed by gas chromatography-mass spectrometry (GC-MS) method and identified 50 volatile compounds, of which α-Pinene (33.76%), 1,8-Cineole (18.47%), and Levoverbenone (6.11%) constituted the highest proportions in EO. The antioxidant capacity (AC) of the EO was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method with a half-maximum inhibitory concentration (IC₅₀) of 425.473 mg/mL. In particular, antibacterial activity (AA) by the paper plate diffusion method for susceptibility testing to essential oil showed that RoEO strongly inhibited the growth of four tested bacterial strains (Staphylococcus aureus, Bacillus cereus, Salmonella typhimurium, and Escherichia coli). Perhaps, it is possible to apply RoEO in the food industry and other fields owing to the good properties of RoEO.

Monte Carlo and DFT calculations on the corrosion inhibition efficiency of some benzimide molecules

Dyari Mustafa Mamand — 2023-06-05

Calculations using density functional theory (DFT) and Monte Carlo methods were performed on 2-methylbenzimidazole, 2-mercaptobenzimidazole, 2-aminobenzimidazole, benzotriazole, and benzimidazole to determine their corrosion inhibition efficiency. The molecular structure was optimized geometrically using DFT calculations at the B3LYP/6– 311 G++(d,p) and b2plypd3/aug-cc-pvdz basis set level in protonated and non-protonated species in gas and water. In this study, HOMO, LUMO, bandgap, ionization energy, electronegativity, hardness, softness, electrophilicity and nucleophilicity, electron transfer, back donation energy and condensed Fukui indices are used to assess a molecule's local reactivity. Theoretical investigations can precisely establish the geometrical dimensions of a molecule and correctly explain the quantum properties of inhibitors. The mechanism of interaction between inhibitors and metal surfaces in a specified molecule is studied using molecular dynamics. The benzimidazole functional groups absorbed energy linearly on metal surfaces, with quantum characteristics determined using density functional theory and an ab initio technique. Importantly, the findings of this conceptual model are consistent with the corrosion inhibition efficiency of earlier experimental investigations.

Hydrothermal treatment of rice straw for carbohydrate production

Enkhtur Munkhbat — 2023-06-05

This study focused on the effect of hydrothermal (HT) treatment at 180 – 210 °C for holding 0 - 15 min on the solubilization of rice straw and the changes of HT residue. The optimum treatment conditions for the highest solubilization and solid reduction of rice straw was 210 °C for holding 0 min. Under this condition, the extraction yield and total organic carbon (TOC) concentration of the HT liquid part were the highest, about 44% and 7850 mg/L, respectively. The dry residue showed that the HT conditions above 200 °C for holding a short time were more efficient, which was confirmed by FT-IR and the changes of surface morphology under microscope. The reactor headspace could be an important factor because HT treatment with a lower headspace (HTp210-0(15)) yielded more soluble carbohydrate under the test conditions. Also, energy input calculated based on the 1 ton removed hemicellulose (extraction yield) in the headspace experiments proved this finding.