Dynamic heat of adsorption of water vapour on zeolitic tuff and zeolite 4A by flow microcalorimetry

In this study a practical method for measurement of heat of adsorption of water vapour on adsorbents was developed to evaluate the feasibility of substitution of a zeolitic tuff with zeolite 4A in air drying and heat pumps. The change of heat of adsorption with inlet humidity of the air passing through the calorimeter was investigated. Samples were characterised by X-ray diffraction and thermal gravimetric analysis techniques. Specific heats of the zeolitic tuff and zeolite 4A were measured as 1.01 and 1.42 J/g K, respectively. Adsorption isotherms fitted to the Langmuir model with regression coefficient 0.93 and 0.94 with monolayer capacities, Xm 9.68% and 26.35% H 2O for the zeolitic tuff and zeolite 4A, respectively. The energy storage intensity was measured in the range 48-97 J/g and 464-201 J/g for the tuff and zeolite 4A, respectively. Heat of adsorption of zeolite decreased with surface coverage and it was in the range 1750-2835 and 1104-2640 J/g H 2O for the zeolitic tuff and zeolite 4A, respectively

The Estimation of Peatlands Reserve on Carbon in the Forest and Shrubs That Has Been Drained

Global warming and greenhouse gas emissions (GHGs) became a hot issue in the world today. An increased concentration of carbon in the atmosphere becomes one of the serious problems that can affect life on Earth. Peatlands pointed out as one of the sources of GHG emissions. Drainage of peatlands cause decreased water level so that the decomposition process is faster on a layer above the groundwater table, thus affecting the chemical characteristics of peat. In addition to affecting the ground water level, drainage also leads to a decrease in surface height peat soil (subsidence). Given the magnitude of the role of drainage and land use types in affecting carbon stocks and emissions of CO2 on peat soil, this study is to measure carbon stocks and emissions of CO2 on peat soil in forests and shrubs that have been drained. CO2 emissions increase with the closer spacing of the drainage channel that is at a distance of 50 m to 500 m of drainage channels. Meanwhile, at a distance of 5 m and 10 m of the drainage channel can not be concluded because of the condition of ground water that is stagnant at the time of sampling gas, so be very low CO2 emissions. CO2 emissions on the use of forest land are higher than the shrub land

Water vapour adsorption on DNA

DNA adsorbed very low amount of water at low relative humidities, amount of adsorption increased to 140% at 98% relative humidity at 25°C. Heat of adsorption was 109 kJ mol-1 H2O for the increase of moisture content from 0 to 1.96%. At higher moisture contents the heat released approached heat of condensation of water vapour on free liquid surface, 40 kJ mol-1 H2O

Synthesis of zinc borate by inverse emulsion technique for lubrication

Lubricating oil additives based on boron compounds are promising materials for lubrication due to their tribological advantages such as antiwear efficiency, good film strength, and high temperature resistance. This article deals with the preparation of zinc borate particles that are well dispersed and colloidally stabilized in mineral oil. This method starts with preparing two inverse emulsions (water-in-oil) with sorbitan monostearate (Span 60) as a surfactant, light neutral oil as a continuous phase, and the aqueous solutions of borax decahydrate (Na2B4O7·10H 2O) and zinc nitrate (Zn(NO3)2·6H 2O) as the dispersed phases. The produced particles were zinc borate crystals having both rod-like and spherical morphologies, and the diameters of spherical particles were changing between 20 and 30 nm. FTIR spectra of the obtained particles showed the characteristic peaks of trihedral borate (B(3)-O) and tetrahedral borate (B(4)-O) groups as well as the specific peaks of the sorbitan monostearate. TG showed 30.42% and 22.08% mass loss at 600 °C for the samples prepared by inverse emulsion and precipitation techniques, respectively. The endothermic peak at 50 °C is observed due to the melting of sorbitan monostearate and the heat of melting is evaluated as -3.50 J/g. Tribological studies revealed that sorbitan monostearate not only outperformed as a dispersing agent of inorganic particles, but also it proved to be an anti-wear agent. Zinc borate produced by precipitation decreased the wear scar diameter from 1.402 to 0.639 mm and the friction coefficient from 0.099 to 0.064. The inverse emulsion was effective in decreasing wear scar diameter and the friction coefficient by lowering them to 0.596 and 0.089 mm, respectively.Scientific and Technical Research Council of Turkey (105M358

Effect of temperature and time on zinc borate species formed from zinc oxide and boric acid in aqueous medium

The effect of temperature and time of heating of zinc oxide and boric acid in aqueous medium on product type, dehydration behavior, crystal morphology, and structure was investigated for the production of flame retardant and smoke suppressant zinc borate. Two different products dehydrated at 140 and 350°C were obtained and characterized by thermal gravimetric analysis, X-ray diffraction, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy

Characterization of pure and silver exchanged natural zeolite filled polypropylene composite films

In the present study, untreated and silver exchanged natural zeolite-polypropylene (PP) composites were prepared and characterized by means of different techniques (TGA, DSC, mechanical tests, density measurements, optical microscopy and colorometer). The effects of zeolite loading and silver concentration on the composite properties were investigated. The thermal characterization studies showed that the addition of the zeolite increased the crystallinity of the composites acting as a nucleating agent in PP crystallization and retarded the degradation of PP. At low silver concentrations, the zeolite behaved as a decelerating agent in PP degradation, however at higher silver concentrations, the composites degraded at a faster rate than pure PP. The experimental densities of the composites were found to be lower than the theoretical densities. When the tensile tested samples are considered, the densities were even lower indicating porous structure of the films. From the optical micrographs of the tensile tested films, it was clearly seen that the stretching along the machine direction caused hole formation around the particles. The optimum conditions obtained in this study for the PP-silver zeolite composite film production are in the range of 2-4 wt% zeolite treated with 4.36 mg Ag+/g zeolite. At higher zeolite loadings, the film becomes brittle and at higher Ag+ concentrations, the film produced was discolored.TÜBİTAK (MISAG 129) and Government Planning Institute Grant (120290 K

Water vapour sorption and humidity - a survey on measuring methods and standards

Under environmental conditions water exists in all three classical states of matter: solid, liquid and gas. The water molecule is non-linear and therefore polar. In comparison with other liq-uids water has anomalous features; about 63 exceptional properties are recorded. This article starts with reviewing properties of water, typical occurrences and definitions such as relative and absolute humidity and moisture content. Water is present everywhere in nature and engineering; it may be helpful or harmful. The survey concerns both: atmospheric hygrometry and usual measuring methods of the mois-ture content of solids and liquids as well as water sorption. The determination of the atmos-pheric humidity is among the more difficult problems in metrology. In contrast, humidity de-termination of materials is simple; however the definition of the dry state is difficult. Because water is bound at and in solids and liquids in many different ways it turns out that the humidi-ty content of materials is difficult to define and to measure accurately. We provide a survey on the measuring methods, describe the most important ones and discuss advantages and ac-curacy. In the search for extraterrestrial water special remote measuring methods have been developed analysing the spectrum of electromagnetic radiation either of natural sources or produced by a probe and reflected. Spacious deposits have been detected photographically. In situ investigations are made using conventional methods. With regard to the problems of measurements, standardisation of measuring methods and procedures is required. There exist many institutions, which are engaged in investigating the use of water and standardising measuring methods. In tabular form, we give a survey on existing standards

Zinc stearate production by precipitation and fusion processes

In this study, the production of ZnSt2 using sodium stearate and zinc sulfate in a precipitation process, and stearic acid and zinc oxide in a fusion process, was investigated with regard to product purity. In the fusion process, an increase in mixing rate decreased the induction time occurring at the beginning of the reaction. While the melting point of the zinc stearate prepared by the precipitation process was found to be about 122°C by optical microscopy, it was slightly lower than 122°C for zinc stearate produced by the fusion process. Differential scanning calorimetry (DSC) indicated onset of melting at 120°C and 118°C for samples prepared by precipitation and fusion processes, respectively. Characteristic peaks of ZnSt2 were present in XRD patterns of the products obtained by both processes. From SEM micrographs, it was seen that zinc stearate obtained by both processes had lamellar structure.TÜBİTAK: MISAG-185; İzmir Institute of Technology Research Fund: 2001MÜHYL-0

A study of chemical and physical changes during biaxially oriented polypropylene film production

Polypropylene films obtained during the biaxial orientation process were characterized by energy dispersive X-ray analysis (EDX), scanning electron microscopy. X-ray diffraction, differential scanning calorimetry, infrared spectroscopy. Inorganic particles with Al, Si, Na, Mg, Ti, K,O elements were present in biaxially oriented films. Polypropylene had molecules with both isotactic configuration and it was crystallized only in isotactic α phase. The films drawn in one and two directions had unit cells with b axis parallel to surface of the films. The antioxidants present in the films were consumed during processing, preventing polypropylene oxidation in air at high processing temperatures. One surface of the films contained less polypropylene and had functional groups rich in oxygen such as C=O and COO

The effect of fiber surface treatments on the tensile and water sorption properties of polypropylene-luffa fiber composites

The effects of coupling agents on the mechanical, morphological, and water sorption properties of luffa fiber (LF)/polypropylene(PP) composites were studied. In order to enhance the interfacial interactions between the PP matrix and the luffa fiber, three different types of coupling agents, (3-aminopropyl)-triethoxysilane (AS), 3-(trimethoxysilyl)-1-propanethiol (MS), and maleic anhydride grafted polypropylene (MAPP) were used. The PP composites containing 2-15 wt% of LF were prepared in a torque rheometer. The tensile properties of the untreated and treated composites were determined as a function of filler loading. Tensile strength and Young's modulus increased with employment of the coupling agents accompanied by a decrease in water absorption with treatment due to the better adhesion between the fiber and the matrix. The maximum improvement in the mechanical properties was obtained for the MS treated LF composites. The interfacial interactions improved the filler compatibility, mechanical properties, and water resistance of composites. The improvement in the interfacial interaction was also confirmed by the Pukanszky model. Good agreement was obtained between experimental data and the model prediction. Morphological studies demonstrated that better adhesion between the fiber and the matrix was achieved especially for the MS and AS treated LF composites. Atomic force microscope (AFM) studies also showed that the surface roughness of LFs decreased with the employment of silane-coupling agents