Sorption instrument

Table 1. Manufacturer of volumetric / carrier gas sorption instruments, gas pycnometers...

We have built a prototype of an interferometric pressure transducer that was designed to be attached to a non-commercial room temperature sorption instrument [3] equipped with a differential membrane sensor (MKS, Baratron 220CD, full range 10 mbar, pressure resolution 0,15 % of full range value). An additional absolute pressure sensor (MKS, Baratron 220 CA) integrated into the set-up provides the average pressure in the manifold and... 

Water sorption-desorption isotherms can be carried out by using thermobalances. Now specific instruments allow to measure water sorption-desorption isotherms at different constant temperatures (e.g., dynamic vapor sorption instrument (DVS), Surface Measurement Systems Ltd., Monarch Beach, US). 

Li, Q. (2010). Investigating the Glassy to Rubbery Transition of Polydextrose and Com Flakes Using Automatic Water Vapor Sorption Instruments, DSC, and Texture Analysis [Thesis]. Urbana, IL University of Illinois at Urbana-Champaign. 

Penner EA (2013) Comparison of the new vapor sorption analyzer to the traditional saturated salt slurry method and the dynamic vapor sorption instrument. M. Sc. dissertation, University of Illinois... 

Yuan X, Carter BP, Schmidt S J (2011) Determining the critical relative humidity at which the glassy to rubbery transition occurs in poly dextrose using an automatic water vapor sorption instrument. 

In practice, activation of a sorbent material much more easily can be accomplished in gravimetric than in volumetric sorption instruments. The main reason for this is that in gravimetry the mass of the sample can be recorded even during the activation process whereas in volumetry / manometry it normally can not. Hence in gravimetry the initial state of a sorbens is fairly well known. Also presorption in a new sorbent sample and remnant sorption after a desorption experiment easily can be checked. 

Automation of gravimetric sorption instruments is not an easy matter and for precision measurements permanent supervision of the adsorption / desorption process by an experienced co-worker is strongly recommended. 

Solids characterization may be performed by Si 9 NMR or XRD. With Si NMR, changes in the crystal dimensions due to sorption have been observed (refs. 1-3). Sorbed phase characterization can be studied by volumetric sorption. Thermodynamically simple molecules (e.g., spherical and small) at low temperatures arc used to study pore volume and sizes. A novel, automated, low pressure sorption instrument (Omicron Tech., Berkeley Heights, NJ, USA) has greatly simplified the analysis of zeolites. The technique has recently been named High Resolution Adsorption (HRADS). 

Sorption mechanisms of Hg(II) by the nonliving biomass of Potamogeton natans was also elucidated using chemical and instrumental analyses including atomic absorption, electron microscopy, and x-ray energy dispersion analyses. The results showed a high maximum adsorption of Hg(II) (180 mg/g), which took place over the entire biomass surface. Nevertheless, there were spots on the surface where apparent multilayer sorption of Hg(II) occurred. The minimum concentration of Hg(II) in solution that can be removed appears to be about 4-5 mg/L.117... 

SORPTION EXPERIMENTS. Sorption experiments were carried out using a Cahn 1000 recording balance, with an accuracy of 0.03 mg. The balance and its accessories are shown in Figure 1. The instrument is equipped with an MKS Baratron pressure transducer (0-100 torr, 0.15% accuracy) with a digital readout for pressure measurements. 

Nitrogen sorption measurements were performed on a Quantachrome Autosorb 6B (Quantachrome Corporation, Boynton Beach, FL, USA). All samples were degassed at 423 K before measurement for at least 12 hours at 1 O 5 Pa. Mercury-porosimetrie has been measured on a Porosimeter 2000 (Carlo Erba Instruments) Scanning electron micrographs were recorded using a Zeiss DSM 962 (Zeiss, Oberkochen, Germany). The samples were deposited on a sample holder with an adhesive carbon foil and sputtered with gold. 

A low temperature nitrogen sorption was carried out on an automated physisorption instrument (ASAP 2000, Micromeritics Instrument Corporation). Before the measurement, the sample was degassed at 350 C for 4-5 h until the vacuum of system was better than 0.67 Pa. The data for micropore were obtained from t-plot, and those for mesopore and distribution of mesopore were calculated by BJH method (using desorption curve). The single point total pore volume at high relative pressure was taken as the total volume. 

Vapour and gas sorption measurements can be performed with static or dynamic methods, either of which can provide information on equilibrium behaviour. Furthermore, the measurements can be performed using gravimetric or volumetric based instrumentation. The most common flow methods are inverse gas chromatography (IGC) [1] for volumetric studies and dynamic gravimetric instrumentation [2]. 

Ultrasonic nebulizers have also been employed in continuous flow systems as interfaces between sample preparation steps in the analytical process and detection by virtue of their suitability for operating in a continuous mode. Thus, preconcentration devices have commonly been coupled to atomic spectrometers in order to increase the sensitivity of some analytical methods. An enhancement factor of 100 (10 due to USNn and 10 due to preconcentration) was obtained in the determination of platinum in water using a column packed with polyurethane foam loaded with thiocyanate to form a platinum-thiocyanate complex [51]. An enhancement factor of 216 (12 with USNn and 18 with preconcentration) was obtained in the determination of low cadmium concentrations in wine by sorption of metallic complexes with pyridylazo reagents on the inner walls of a PTFE knotted reactor [52]. One special example is the sequential determination of As(lll) and As(V) in water by coupling a preconcentration system to an ICP-AES instrument equipped with a USN. For this purpose, two columns packed with two different resins selective for each arsenic species were connected via a 16-port valve in order to concentrate them for their subsequent sequential elution to the spectrometer [53]. 

The pore volumes and the micropore distribution parameters of the carbon samples were analyzed in an automatic volumetric sorption analyzer (model ASAP 2000, Micromeritics Instrument Co. Norcross, GA, USA) using N2 and CO2 adsorption at 77 and 273 K, respectively. Five different experiments were carried out to determine the experimental error with sample CA-3 finding a value around 3%. 

Nitrogen sorption measurements were performed by use of a Sorptomatic 1900 Turbo apparatus by Carlo Erba Instruments. All samples were degassed at 393 K before measurement for at least 24 hours at 10 mbar. The mercury porosimetry measurements were carried out on a Porosimeter 2000 apparatus by Carlo Erba Instruments. A contact angle of 141.3° for Hg was used. The samples were degassed at 393 K before measurement for 24 h. SEM of the porous glass membranes was carried out on a Phillips ESEM XL 30 PEG microscope. 

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