PRESSURE INFLUENCE TO EXTRACTION SYSTEM HELICHRYSUM ITALICUM – SUPERCRITICAL CARBON DIOXIDE

Supercritical fluid extraction (SFE) is an efficient extraction technique for the separation of various organic compounds from herbs, or more generally, from plant materials. As cultivate plant (plant from plantation) Helichrysum italicum from municipality Novi Grad was used in this research. The influence of pressure on total extract yield at flow rate 53.5 dm3 /h (calculated at normal state), for extraction time 3 h was investigated. Extraction was performed by supercritical carbon dioxide at different pressures (80, 150, 250 and 350 bar) and constant temperature of 40°C. The extraction yield increase from 0.35 to 5.71% (g/100g drug) by pressure increasing of supercritical extraction by carbon dioxide (isothermal process, t = 40°C). Essential oil content in obtained CO2 extracts was from 6.70 to 31.12%. The highest content of essential oil was in CO2 extract obtained by extraction of drug at p = 80 bar and t = 40°C (31.12%). Qualitative and quantitative determination of CO2 extracts obtained at pressure of 80 and 350 bar as well as of essential oils obtained from extracts, were performed using GC - MS method. The main component were tritriacontane (27.13%) and nonacosane (13.28%). The dominant component in essential oils obtained from extracts was γ – curcumene (28.27 and 27.42%, respectively)

A FUNCTION PROPERTY OF POLYTROPHIC PROCESS WITH ASPECT OF TANGENT CONSTRUCTION

In this paper, starting from general tangent equation in arbitrary point of specified curve, using principles of differential geometry and given mathematical transformation tangent equation of polytrophic function in p – v diagram was obtained. This form is convenient for solving numerous practical and theoretical problems in engineering thermodynamic by means of graphical method. It was shown that tangent can be constructed easily, using polytrophic equation only, but it is not example with other functions appearing in thermodynamics. Later, in this paper, we have given some methods, which refer to more exact construction of polytrophic and graphical analyze of polytrophic process

Influence of pressure and time on extraction process using supercritical CO2

The supercritical fluid extraction (SFE) by carbon dioxide (CO2) of Salvia officinalis L. was investigated. SFE by CO2 was performed at different pressure (80, 100, 150, 200 and 300 bar) and constant temperature of 40ºC (all other extraction conditions, such are flow rate, particle diameter of Salvia officinalis, extraction time were kept constant. The GC-MS method was used for determination of qualitative and quantitative composition of obtained extracts and essential oils

PRESSURE INFLUENCE TO EXTRACTION SYSTEM HELICHRYSUM ITALICUM – SUPERCRITICAL CARBON DIOXIDE

Supercritical fluid extraction (SFE) is an efficient extraction technique for the separation of various organic compounds from herbs, or more generally, from plant materials. As cultivate plant (plant from plantation) Helichrysum italicum from municipality Novi Grad was used in this research. The influence of pressure on total extract yield at flow rate 53.5 dm3 /h (calculated at normal state), for extraction time 3 h was investigated. Extraction was performed by supercritical carbon dioxide at different pressures (80, 150, 250 and 350 bar) and constant temperature of 40°C. The extraction yield increase from 0.35 to 5.71% (g/100g drug) by pressure increasing of supercritical extraction by carbon dioxide (isothermal process, t = 40°C). Essential oil content in obtained CO2 extracts was from 6.70 to 31.12%. The highest content of essential oil was in CO2 extract obtained by extraction of drug at p = 80 bar and t = 40°C (31.12%). Qualitative and quantitative determination of CO2 extracts obtained at pressure of 80 and 350 bar as well as of essential oils obtained from extracts, were performed using GC - MS method. The main component were tritriacontane (27.13%) and nonacosane (13.28%). The dominant component in essential oils obtained from extracts was γ – curcumene (28.27 and 27.42%, respectively)

A FUNCTION PROPERTY OF POLYTROPHIC PROCESS WITH ASPECT OF TANGENT CONSTRUCTION

In this paper, starting from general tangent equation in arbitrary point of specified curve, using principles of differential geometry and given mathematical transformation tangent equation of polytrophic function in p – v diagram was obtained. This form is convenient for solving numerous practical and theoretical problems in engineering thermodynamic by means of graphical method. It was shown that tangent can be constructed easily, using polytrophic equation only, but it is not example with other functions appearing in thermodynamics. Later, in this paper, we have given some methods, which refer to more exact construction of polytrophic and graphical analyze of polytrophic process

Katalitički uticaj sumporne kiseline u procesu taloženja prevlaka hroma

This paper analyzes the catalytic effect of sulphuric acid on current efficiency, the coating thickness and the rate of deposition of electrochemical chromium coatings. According to the properties of chrome, there are three types of chrome coatings: decorative, hard and porous. The quantitative composition of baths and working conditions are the factors which determine which type of a coating will be obtained. The cathodes are made of copper electrolitical plates (99.99%), which are submitted to mechanical smoothing and chemical preparation. Electrochemical chromium coatings were deposited galvanostaticaly from bath I (250 g/dm3 CrO3 + 2.0 g/dm3 H2SO4), are then deposited on the cathodes prepared in this way, also from bath II (250 g/dm3 CrO3 + 2.5 g/dm3 H2SO4), and from bath III (250 g/dm3 CrO3 + 3.0 g/dm3 H2SO4), at current densities of 10 A/dm2, 15 A/dm2 and 30 A/dm2. Deposition was performed for 5, 10 and 15 minutes intervals in all three baths and for all three current densities. The difference in samples mass before and after electrochemical deposition was measured on the analytical scale. Cathodic current efficiency, the coating thickness and deposition rate increase with the increase of acid concentration, current density and deposition time. The average deposition rates are approximately the same for baths II and III, for the same deposition time, at the same current densities. This shows that the increase of the concentration of sulphuric acid above 2.5 g/dm3 is not justifiable. The ratio of these parametres, according to the quantity of the sulphuric acid used is the best for bath II, which makes deposition of electrochemical chrome coatings from this bath most profitable, from the aspect of current efficiency, deposition rate, coatings quality and chemicals consumption of bath.Ispitivan je katalitički uticaj sumporne kiseline na iskorišćenje struje, debljinu i brzinu taloženja prevlaka hroma dobijenih elektrohemijskim putem. Zahvaljujući osobinama hroma razlikuju se tri vrste prevlaka: dekorativne, tvrde i porozne. Kvantitativni sastav kupatila i radni uslovi su faktori koji određuju koji tip prevlaka će biti dobijen. Katode su bile od tehničkog bakra nepoznatog sastava, koje su mehanički glačane pa zatim hemijski pripremljene. Za elektrohemijsko taloženje prevlaka hroma, koje su taložene galvanostatski, ispitivana su tri elektrolita čiji se kvantitativni sastav razlikuje u koncentraciji sumporne kiseline, dok je koncentracija CrO3 bila ista u sva tri kupatila i to: kupatilo I (250 g/dm3 CrO3 + 2.0 g/dm3 H2SO4), zatim kupatilo II (250 g/dm3 CrO3 + 2.5 g/dm3 H2SO4), i na kraju kupatilo III (250 g/dm3 CrO3 + 3.0 g/dm3 H2SO4), pri gustinama struje 10 A/dm2, 15 A/dm2 i 30 A/dm2. Katodno iskorišćenje struje, debljina prevlaka i brzina taloženja se povećava sa povećanjem koncentracije sumporne kiseline, gustine struje taloženja i vremena taloženja. Srednje brzine taloženja prevlaka hroma su približno iste za kupatila II i III, pri istim vremenima taloženja i pri istim gustinama struje. S tim u vezi, povećanje koncentracije sumporne kiseline iznad 2,5 g/dm3 nije opravdano. Odnos ovih parametara, prema koncentraciji sumporne kiseline, je najbolji za kupatiko II, koje daje optimalne prevlake hroma dobijene elektrohemijskim putem, u pogledu iskorišćenja struje, brzine taloženja, kvalitata prevlake i hemijskog sastava kupatila

Katalitičko delovanje sumporne kiseline na morfologiju elektrohemijski dobijenog bakarnog praha

The subject of the research is influence of sulfuric acid on morphology of electrochemically obtained copper powder during galvanostatic electrolysis mode. In this paper electrodeposition of copper powder from sulphate electrolyte was carried out. Electrolytes with three different concentrations of Cu2+ (7 g/dm3, 18 g/dm3 and 33 g/dm3) were used, each in combination with three different concentrations of H2SO4 (100 g/dm3, 150 g/dm3 and 200 g/dm3), so that copper powder was deposited from nine electrolytes. Copper wire with surface area of 1cm2 was used as cathode, and copper anode in the form of metal sheet was pressed against the wall of electrochemical cell that had volume of 500 cm³. Experiments were carried out at room temperature, and electrolyte stirring was performed using a magnetic stirrer. Copper powder was deposited galvanostatically at current densities of j = 1500 A/m2, j=2000 A/m2 and j=2500 A/m2. Produced copper powder was removed from cathode every three minutes. All the characteristics of powder depend on the size and shape (morphology) of particles and they are mutually correlated. Research of morphology and size of particle was carried out using scanning electron microscopy (SEM). Increase of H2SO4 concentration causes increase in branching of copper powder. It was concluded that the size of copper powder grains reduces with the increase in concentration of H2SO4.Predmet istraživanja je uticaj sumporne kiseline na morfologiju elektrohemijski dobijenog bakarnog praha pri galvanostatskom režimu elektrolize. U ovom radu je vršeno elektrohemijsko taloženje bakarnog praha iz sulfatnih elektrolita. Korišćeni su elektroliti sa tri koncentracije Cu2+ (7 g/dm3, 18 g/dm3 i 33 g/dm3) i svaka u kombinaciji sa tri koncentracije H2SO4 (100 g/dm3, 150 g/dm3 i 200 g/dm3), tako da je bakarni prah taložen iz devet elektrolita. Kao katoda je korišćena bakarna žica površine 1cm2, a bakarna anoda u obliku lima je bila priljubljena uz zid elektrohemijske ćelije, zapremine 500 cm³. Eksperimenti su izvođeni na sobnoj temperaturi, a mešanje elektrolita vršeno je pomoću magnetne mešalice. Bakarni prah taložen je galvanostatski pri gustinama struje od: j=1500 A/m2, j=2000 A/m2 i j=2500 A/m2. Proizvedeni bakarni prah je uklanjan sa katode svaka tri minuta. Sve osobine praha zavise od oblika i dimenzija čestica (morfologije) i međusobno su povezane. Ispitivanje morfologije i veličine čestica vršeno je pomoću skenirajuće elektronske mikroskopije (SEM). Sa povećanjem koncentracije H2SO4, povećava se i razgranatost bakarnog praha. Utvrđeno je da se veličina čestica smanjuje sa povećanjem koncentracije H2SO4

Effect of the Surface on the Electron Quantum Size Levels and Electron g-Factor in Spherical Semiconductor Nanocrystals

The structure of the electron quantum size levels in spherical nanocrystals is studied in the framework of an eight--band effective mass model at zero and weak magnetic fields. The effect of the nanocrystal surface is modeled through the boundary condition imposed on the envelope wave function at the surface. We show that the spin--orbit splitting of the valence band leads to the surface--induced spin--orbit splitting of the excited conduction band states and to the additional surface--induced magnetic moment for electrons in bare nanocrystals. This additional magnetic moment manifests itself in a nonzero surface contribution to the linear Zeeman splitting of all quantum size energy levels including the ground 1S electron state. The fitting of the size dependence of the ground state electron g factor in CdSe nanocrystals has allowed us to determine the appropriate surface parameter of the boundary conditions. The structure of the excited electron states is considered in the limits of weak and strong magnetic fields.Comment: 11 pages, 4 figures, submitted to Phys. Rev.