Phase vapor–liquid equilibrium for the solutions of diethyl selenide and diethylzinc

Using a semi-empirical Wilson’s model, the vapor-liquid equilibrium in the “diethylzinc - diethyl selenide” system is described: the activity coefficients of the solution components, the separation coefficient, the excess functions of the solution (HE, GE, TSE) are calculated, and isothermal P-X diagrams are obtained. The parameters of the Wilson’s model were calculated on the basis of our data on measuring the temperature dependence for saturated vapor pressure of high-purity samples of diethylzinc, diethyl selenide and their equimolecular solution using iterations from the mathematical software package Mathsad 14. Peculiarities of intermolecular interaction in the “diethylzinc – diethyl selenide” system and the presence of a negative deviation from Raoul's law have been found. The studied system is homogeneous in the whole concentration range. The concentration dependence of the enthalpy of mixing is alternating for the researched temperature range (280-340 K).

Synthesis of a Fe/Ca-based phosphate material and its application for adsorption of uranium ions from aqueous solution

Uranium (U) ion contamination in aquatic systems has received considerable attention worldwide. In this paper, an adsorption material was synthesized with Fe/Ca-based phosphate (CFB-PM) by a sol-gel method. The effect of pH, reaction time and initial concentration of U ions on its capacity of removing U ions from aqueous solution was investigated by static batch experiments. Comparative studies of U ion removal by CFB-PM with four sorbents, namely: nano zero-valent iron (nZVI), hydroxyapatite (HAP), hydroxyapatite-loaded nano zero-valent iron (HAP@nZVI) and high basicity steel slag loaded hydroxyapatite (HBSS@HAP), were performed. Results showed that U ion adsorption capacity of CFB-PM was better than that of nZVI, HAP, HAP@nZVI and HBSS@HAP. The adsorption capacity showed a decreasing order as: CFB-PM (643.34 mg/g) > HAP (549.86 mg/g) > HBSS@HAP (321.82 mg/g) > HAP@nZVI (153.62 mg/g) > nZVI (102.65 mg/g). SEM-EDS examination suggested that the adsorbed U ions were mainly in the form of spheres, sheets or petals on the surfaces of CFB-PM. XRD detection revealed several U-bearing mineral phases (i.e. Ca(UO2)2(PO4)2·3H2O, HPUO6·4H2O and (UO2)3PO4·4H2O). The U ion adsorption behaviors were further explored by FTIR spectroscopy. The uranium ion adsorption process of CFB-PM could be well described by quasi-second-order adsorption kinetics model and the Langmuir adsorption isotherm model. The separation coefficient (RL) was close to zero, indicating that U ion adsorption was dominated by single-layer chemisorption. The findings reported in this study have implications for applying the synthesized material for remediation of U ion-contaminated groundwater.

Effects of micropore structure of activated carbons on the CH4/N2 adsorption separation and the enrichment of coal-bed methane

In the process of enriching CH4 from coal-bed methane, the separation of CH4/N2 is very difficult to accomplish by an adsorption process due to the similar physico-chemical properties of the two molecules. A series of coconut-shell-based granular activated carbons (GACs) with different pore structures were prepared, which were characterized by different methods. The influence of the pore structure on the separation properties was investigated in detail. The results show that one of the carbons prepared (GAC-3) has high CH4 equilibrium adsorption capacity (3.28 mol·kg–1) at 298 K and equilibrium separation coefficient (3.95). The CH4/N2 separation on the GACs is controlled by adsorption equilibrium as compared with the dynamic effect. Taking the specific surface area, for example, the common characterization index of the pore structure is not enough to judge the separation performance of the GACs. However, the microstructure of carbon materials plays a decisive role for CH4/N2 separation. According to the pore-structure analysis, the effective pore size for the CH4/N2 separation is from 0.4 to 0.9 nm, with the optimum effect occurring in the range of 0.6–0.7 nm, followed by the range of 0.7~0.9 nm. Also, a four-bed vacuum pressure swing adsorption process was adopted to evaluate the performance of GACs for the separation of CH4 from nitrogen.

Optimization of oscillated gas-liquid separator for simultaneous heavy metals determination in water sample

A technique has been developed to detect and determine multi heavy metals simultaneously in a water sample. Hydride generating technique was implemented to convert the analyte which present in the water sample (liquid phase) into another form with an improved separation coefficient, called “derivative”. This process occurred without changing the original chemical structure. Derivatives were separated from the liquid phase by applying custom made gas-liquid separator (GLS), operated with oscillation. Separated species then transferred into a die-electric barrier discharge (DBD) plasma atomizer where a fragmentation of the analyte into free atoms is occurred. The generated atoms were detected by emission spectroscopy. The presented technique was applied for detection of individual and multi heavy metals simultaneously in water sample and proved useful in terms of reducing the effect of the hydrogen generated, through the process, on suppressing the atoms signal in the DBD atomizer.

Equilibrium and thermodynamic investigation of biosorption of nickel from water by activated carbon made from palm kernel chaff

Novel biosorbents were derived from a waste product of palm kernel oil extraction known as palm kernel chaff (PKC). One portion of the PKC was carbonized in a furnace and then activated chemically, while the other half was activated without carbonization. Both were designated as CPKC and UPKC, respectively. The two biosorbents so produced were then used to conduct batch equilibrium and kinetic sorption studies at 30 °C, 35 °C and 40 °C and pH 3.0 and 9.0 for an agitation period of 5, 10, 20, 40, 60, 90, and 120 min. The Koble-Corrigan, Dubinin-Radushkevich, and the Freundlich isotherms fitted the experimental data very well with R2 values of 0.97 to 1.0, 0.95 to 1.0, and 0.96 to 1.0, respectively. The linear type II Langmuir isotherm performed much better (0.96 ≤ R2 ≤ 1.0) than the nonlinear isotherm. The maximum sorption capacity was obtained as 120.6 mg/g using CPKC at pH 9.0 and 35 °C. The Langmuir separation coefficient values (0.022 ≤ RL ≤ 0.926) show that the sorption of nickel to PKC is favorable. The most favorable sorption condition was found for CPKC at pH 9 and temperature of 40 °C. The values of sorption energy (8.21 ≤ E ≤ 14.27) and the isosteric heat of sorption (−133.09 ≤ ∆Hx ≤ −17.92) indicate that the mode of sorption is mostly ion exchange. Thermodynamic parameters also show that the process is exothermic and entropy-driven. The pseudo-second-order kinetic model shows the best correlation compared to the other kinetic models. The coefficient of correlation for the pseudo-second-order model was mostly within the range of 0.999–1.000 for 90% of all kinetic studies carried out.

Estimating the Economic Value of Soundscapes in Nature-Based Tourism Destinations: A Separation Attempt of a Pairwise Comparison Method

Recent soundscape research is notable owing to the increasing demand for “multisensory” tourism experiences. However, the traditional economic value assessment of tourism destinations mostly takes each type of landscape as a whole for measurement, and it has been challenging to separate the soundscape from the whole landscape. Therefore, research on the economic value of soundscapes is still lacking. This study chose the characteristic soundscape of the Qiantang River tide as the research object, and tried to apply the pairwise comparison method to calculate the separation coefficient of the soundscape from the overall landscape. The results showed that the separation coefficient of the soundscape was 0.138 and the economic value of the Qiantang River tide soundscape was between CNY 315.145 million (USD 48.7 million) and CNY 333.841 million CNY (USD 51.6 million). Finally, we discuss the effectiveness of the separation methods, the differences in willingness to pay between the interviewees, and the sustainable use of the natural soundscape resources in tourism destinations.

Modification of Zeolites Y and ZSM-5 adsorption of nanoparticles of transition metals from back-micellar solutions for separation of gas mixtures

On the basis of granular synthetic zeolites NaY, HY, and ZSM-5, adsorbents containing nanoparticles of silver, cobalt, molybdenum, and tungsten were obtained. The samples have a lower surface polarity in comparison with the initial zeolites, which is reflected in the selectivity of a number of samples with respect to argon. This is due to the fact that the argon molecule interacts with zeolites only through nonspecific forces. Modification was performed by interacting with reverse-micellar solutions of nanoparticles. The actual sizes of metal particles and their distribution over the surface of the modified samples of zeolites have been determined by the method of transmission electron microscopy. The samples’ equilibrium adsorption capacities for oxygen and argon (25°С and atmospheric pressure) and the separation coefficient of the argon–oxygen mixture as the ratio of Henry’s coefficients have been determined. It has been demonstrated that samples of the NaY zeolite modified with silver nanoparticles have the separation coefficient value of the argon–oxygen gas mixture equal to 1.6.

Study on the 4-ethyl-2(α-methyl benzyl) phenol Extraction-Separation Between Rubidium and Potassium

More than 92% of rubidium resources on the earth exist in salt lake brine and underground brine. Rubidium in brine coexists with a large amount of potassium with very similar physical and chemical properties, making the extraction technology of rubidium extremely difficult, and a large amount of rubidium resources in brine have not been rationally utilized. Therefore, the development of a new type of high-selectivity rubidium-potassium separation extractant is of great significance to the establishment of efficient separation and extraction technology of rubidium. By modifying the structure of 4-tert-butyl-2-(α-methylbenzyl)phenol, the traditional rubidium extractant, the steric hindrance effect of tert-butyl is reduced and the reaction efficiency of rubidium and extractant is improved. A new extractant 4-ethyl-2-(α-methylbenzyl)phenol was obtained. The thesis carried out the research on the extraction and separation performance of potassium rubidium 4-ethyl-2-(α-methylbenzyl)phenol. The results show that the new extraction agent 4-ethyl-2-(α-methylbenzyl)phenol and potassium rubidium brine are extracted and separated with a ratio of 10:1. The minimum separation coefficient of rubidium potassium can reach 15 or more, showing excellent separation performance ; When the organic phase is composed of 0.8mol/L extractant and D60 solvent oil, the alkalinity of the aqueous phase is 0.5mol/L sodium hydroxide, and the extraction time is 3 minutes, the single-stage extraction rate of rubidium can reach more than 76.0%, rubidium potassium The separation coefficient can reach more than 26. After repeated use, the extraction rate of rubidium can be maintained above 73% and the separation coefficient of rubidium potassium can reach 23, without a significant drop. It provides a new way and idea for the extraction and separation technology of rubidium in high potassium brine.

Equilibrium and Thermodynamic Investigation of Biosorption of Nickel from Water by Activated Carbon Made from Palm Kernel Chaff

Novel biosorbents were derived from a waste product of palm kernel oil extraction known a palm kernel chaff (PKC). One portion of the PKC was carbonized in a furnace and then activated chemically while the other half was activated without carbonization. Both were designated as CPKC and UPKC respectively. The two biosorbents so produced were then used to conduct batch equilibrium sorption studies at 30 ºC, 35 ºC and 40 ºC and pH 3.0 and 9.0. The Koble-Corrigan, Dubinin-Radushkevich and the Freundlich isotherms fitted the experimental data very well with R2 values of 0.97 to 1.0, 0.95 to 1.0 and 0.96 to 1.0 respectively. The linear type II Langmuir isotherm performed much better (0.96 ≤ R2 ≤ 1.0) than the nonlinear isotherm. The maximum sorption capacity was obtained as 120.6 mg/g using CPKC at pH 9.0 and 35ºC. The values of Langmuir separation coefficient (0.022 ≤ RL≤0.926) show that the sorption of nickel to PKC is favourable. The most favourable sorption condition was found for CPKC at pH 9 and temperature of 40 ºC. The values of sorption energy (8.21 ≤ E ≤ 14.27) and the isosteric heat of sorption (-133.09≤∆Hx≤-17.92) indicate that the mode of sorption is mostly ion exchange. Thermodynamic parameters also show that the process is exothermic and entropy-driven.