Kinetics and mechanism of catalytic oxidation of sodium ethyl mercaptide with microfluidics

Catalytic oxidation desulfurization of gasoline is a key process for the utilization of petroleum hydrocarbons. However, the inherent mechanism still remains unclear and the kinetic investigation is usually performed in processes with limited mass transfer rates. Herein, the kinetics and mechanism of catalytic oxidation of sodium ethyl mercaptide were investigated with microfluidics. On the basis of eliminating mass transfer resistance, the effects of temperature, pressure, residence time, and gas-liquid flow ratio on the oxidation were assessed. According to the results of UV-vis spectra and binding constant, it was confirmed that the catalytic center was in the form of dimer. A heterogeneous reaction kinetic model was proposed as such. The kinetic parameters close to intrinsic kinetics and corresponding kinetic rate expression were obtained.

Interactions of organosulfates with water vapor under sub- and supersaturated conditions

Organosulfates (OSs) are important constituents of secondary organic aerosols, but their hygroscopic properties and cloud condensation nucleation (CCN) activities have not been well understood. In this work we employed three complementary techniques to characterize interactions of several OSs with water vapor under sub- and supersaturated conditions. A vapor sorption analyzer was used to measure mass changes in OS samples with relative humidity (RH, 0 %–90 %); among the 11 organosulfates examined, only sodium methyl sulfate (methyl-OS), sodium ethyl sulfate (ethyl-OS), sodium octyl sulfate (octyl-OS) and potassium hydroxyacetone sulfate were found to deliquesce as RH increased, and their mass growth factors at 90 % RH were determined to be 3.65 ± 0.06, 3.58 ± 0.02, 1.59 ± 0.01 and 2.20 ± 0.03. Hygroscopic growth of methyl-, ethyl- and octyl-OS aerosols was also studied using a humidity tandem differential mobility analyzer (H-TDMA); continuous hygroscopic growth was observed, and their growth factors at 90 % RH were determined to be 1.83 ± 0.03, 1.79 ± 0.02 and 1.21 ± 0.02. We further investigated CCN activities of methyl-, ethyl- and octyl-OS aerosols, and their single hygroscopicity parameters (κccn) were determined to be 0.459 ± 0.021, 0.397 ± 0.010 and 0.206 ± 0.008. For methyl- and ethyl-OS aerosols, κccn values agree reasonably well with those derived from H-TDMA measurements (κgf) with relative differences being < 25 %, whereas κccn was found to be ∼ 2.4 times larger than κgf for octyl-OS, likely due to both the solubility limit and surface tension reduction.

Hydroxypropyl Methylcellulose-Based Edible Coatings Formulated with Antifungal Food Additives to Reduce Alternaria Black Spot and Maintain Postharvest Quality of Cold-Stored ‘Rojo Brillante’ Persimmons

Composite edible coatings based on hydroxypropyl methylcellulose (HPMC), as a polymeric phase, and oleic acid (OA) or beeswax (BW), as a hydrophobic phase, were formulated with different food additives as antifungal ingredients. HPMC–OA coatings containing 2% (w/v) sodium benzoate (SB), 1% ammonium carbonate (AC), 1% potassium carbonate (PC), 1% potassium bicarbonate (PBC), 1% sodium bicarbonate (SBC), 1% potassium silicate (PSi), 0.1% sodium methyl paraben (SMP) or 0.1% sodium ethyl paraben (SEP), and HPMC–BW coatings containing 2% sodium propionate (SP), 2% PBC, 2% SB or 0.1% SEP were evaluated for the control of Alternaria black spot (ABS) on Diospyros kaki Thunb. ’Rojo Brillante’ persimmons artificially inoculated with Alternaria alternata. After 14 days of incubation at 20 °C, HPMC–OA coatings formulated with PBC, PC or SEP were the most effective to reduce ABS incidence (61, 54, and 36% reduction, respectively, concerning uncoated control fruit) and severity (28, 12 and 22% reduction, respectively), while only HPMC–BW coatings formulated with SEP significantly reduced ABS incidence (50% reduction) and severity (36% reduction). HPMC–OA and HPMC–BW coatings containing 2% PBC or 0.1% SEP were selected to evaluate their effect on the weight loss, firmness and respiration rate of healthy ‘Rojo Brillante’ persimmons cold-stored at 1 °C and 90% relative humidity (RH) for 15 and 30 days, followed by 7 days of shelf life at 20 °C. HPMC–BW coatings were more effective in reducing fruit weight and firmness losses than HPMC–OA coatings, while all antifungal coatings significantly reduced fruit respiration. Overall, the HPMC–BW edible coating that contains SEP could be a promising postharvest treatment to control ABS and maintain the quality of cold-stored ‘Rojo Brillante’ persimmons.

Interactions of organosulfates with water vapor under sub- and supersaturated conditions

Organosulfates (OS) are important constituents of secondary organic aerosols, but their hygroscopic properties and cloud condensation nucleation (CCN) activities have not been well understood. In this work we employed three complementary techniques to characterize interactions of several OS with water vapor under sub- and supersaturated conditions. A vapor sorption analyzer was used to measure mass changes of OS samples with RH (0–90 %); among the 11 organosulfates examined, only sodium methyl sulfate (methyl-OS), sodium ethyl sulfate (ethyl-OS), sodium octyl sulfate (octyl-OS) and potassium hydroxyacetone sulfate were found to deliquesce as RH increased, and their mass growth factors at 90 % RH were determined to be 3.652 ± 0.064, 3.575 ± 0.024, 1.591 ± 0.004 and 2.202 ± 0.031. Hygroscopic growth of methyl-, ethyl- and octyl-OS aerosols was also studied using a humidity tandem differential mobility analyzer (H-TDMA); continuous hygroscopic growth was observed, and their growth factors at 90 % RH were determined to be 1.83 ± 0.03, 1.79 ± 0.02 and 1.21 ± 0.02. We further investigated CCN activities of methyl-, ethyl- and octyl-OS aerosols, and their single hygroscopicity parameters (κccn) were determined to be 0.459 ± 0.021, 0.397 ± 0.010 and 0.206 ± 0.008. For methyl- and ethyl-OS aerosols, κccn values agree reasonably well with those derived from H-TDMA measurements (κgf), whereas κccn was found to be significantly larger than κgf for octyl-OS, likely due to both solubility limit and surface tension reduction.

Investigating the Electrochemical Interaction of a Thiol Collector with Chalcopyrite and Galena in the Presence of a Mixed Microbial Community

High microbial cell counts have been recorded in sewage waters employed as process water in mineral beneficiation plants across the world. The presence of these microbes can negatively impact flotation performance through mineral passivation, although some microbes improve flotation performance as investigated in various bio-flotation studies. The current study aims to understand the electrochemical behaviour of minerals in the presence of a sodium ethyl xanthate (SEX) collector and microbes originating from a sulphide ore processing plant in South Africa. The electrochemical response was correlated to observe flotation performance. Mixed potential measurements were conducted in parallel to microflotation tests, to assess the hydrophilicity or hydrophobicity induced on sulphide minerals adapted to microbe-laden synthetic plant water. Sulphide minerals’ mixed potentials and interactions of SEX with sulphide minerals were dramatically reduced in the presence of the mixed microbial community (MMC). The observations were correlated with poor flotation efficacy noted in microflotation tests. These fundamental results shed light on how the adsorption of thiol collectors on sulphide minerals is adversely affected by microbes, prompting a discussion on flotation process monitoring when mineral beneficiation is conducted using microbe-laden water.

Comparative Effectiveness of Flotation Technique at Varying Conditions for Beneficiation of Itakpe and Agbaja Iron Ores

Itakpe and Agbaja iron ores are part of prominent iron deposits in Nigeria, yet studies on their beneficiation via froth flotation are relatively limited. Thus, this research investigated comparatively the flotation behaviour of both ores at varied pulp pH, particle size, and collector type. The ores were also examined using Energy Dispersive X-ray Fluorescence Spectroscopy, Petrological, and fractional sieve size analyses. Fifty (50) kg sample each of the ores was sourced for the research. Then, size fractions (63, 75, and 125 mm) of each ore were prepared and subjected to froth flotation using different collectors; Potassium Amyl Xanthate (PAX), Sodium Ethyl Xanthate (SEX), and Oleic Acid, at varying pulp pH ranging from 9-11. From the results obtained Itakpe iron ore assayed 36.18% Fe2O3 and contains predominantly haematite, sillimanite, and quartz while Agbaja iron ore contains chiefly, quartz and haematite, and assayed 40.6% Fe2O3 alongside 1.505% P2O5. The liberation sizes of both ores lie favouraby in the range -125+75 µm. Beneficiation studies carried out revealed that significant enrichment of both ores was actualized. Thus, it was established that Itakpe iron ore is best processed using PAX at pH 11 and particle size of 125 µm yielding concentrates assaying 67.66% Fe2O3 at a recovery of ~90% while for Agbaja iron ore, PAX at pH 9 and particle size of 63 µm is considered best to yield enriched concentrates assaying 65.5% Fe2O3 at 52.5%.recovery.

Investigation of the catalуtic activitу of K2CO3 in the carboxуlation reaction of phenol with sodium ethуl carbonate

The catalуtic activitу of К2СО3 in the carboxуlation reaction of phenol with sodium ethуl carbonate has been investigated. The aim of the research was to develop a new efficient method for producing salicylic acid which is widely used in pharmaceuticals and other type preparations, also used in agriculture as an effective plant growth promoter. The most widespread synthesis method of salicylic acid is the Kolbe-Schmitt of phenol carboxylation, but it has a number of serious disadvantages. One of the alternative methods is the use of alkali metal salts of mono ethers of the carbonic acids as carboxylating agents in the carboxylation of phenol. In order to improve the method of production of salicylic acid, the catalytic activity of the К2СО3 catalyst at the carboxylation of phenol with sodium ethyl carbonate was studied for the first time. The effect of the process parameters (temperature, pressure, reaction time, ratio of catalyst to carboxylating agent) on the yield of the target product was studied. It was found optimal conditions: T=160°C, PCO2=10 atm, τ=7(4+3) h, [К2СО3]:[SEC]=0.07:1 at which the yield of the target product was 80%. The yields of the target product at phenol carboxylation with sodium ethyl carbonate in the presence and without K2CO3 were determined. It was found that К2СО3 shows the catalytic activity during carboxylation reaction.

Multidimensional Analysis of Copper Ore Flotation in Terms of Applied Hydrophobizing Agents

Flotation is a method of enrichment used to distribute particles, which differ in their surface properties. Hydrophobic solids intrinsically create contact at the solid-liquid-gas interface. However, not all minerals, including copper minerals, can be characterized by this crucial ability. In that case it is necessary to use the collector reagents which guarantees a high efficiency of the enrichment process. The main aim of the paper was to examine the impact of selected collector types and dosages on the results of Polish sandstone copper ore flotation and to find optimal parameter values for products that meet quality and quantity requirements. The laboratory tests were carried out with an application of two types of collectors (Hostaflot, sodium ethyl xanthate aqueous solution) in dosages 100 and 150 g/Mg. Data analysis was based on the use of the taxonomy methods in order to select optimal conditions of collector dosage and type. Based on the indexes, it was found that the best enrichment effects were obtained with a sodium ethyl xanthate aqueous solution 150 g/Mg.

Carboxylation of phenol and its derivatives with sodium ethyl carbonate

A comparison activity of phenol and its derivatives in carboxylation reaction with sodium ethyl carbonate was carried out (the ratio between substrate and sodium ethyl carbonate was 2:1, T=185°С, Pco