Ex-situ

Studies of the liquid-solid interface can be divided into those that are perfonned ex situ and those perfomied in situ. In an ex situ experiment, a surface is first reacted in solution, and then removed from the solution and transferred into a UFIV spectrometer for measurement. There has recently been, however, much work aimed at interrogating the liquid-solid interface in situ, i.e. while chemistry is occurring rather than after the fact. 

As a furtlier example for tire meaning of ex situ investigations of emersed electrodes witli surface analytical teclmiques, results obtained for tire double layer on poly crystalline silver in alkaline solutions are presented in figure C2.10.3. This system is of scientific interest, since tliin silver oxide overlayers (tliickness up to about 5 nm) are fonned for sufficiently anodic potentials, which implies tliat tire adsorjDtion of anions, cations and water can be studied on tire clean metal as well as on an oxide covered surface [55, 56]. For tire latter situation, a changed... 

Figure C2.10.3. Ex situ investigation of the electrochemical double layer on Ag after hydrophobic emersion from 1 M NaClO + 0.1 M NaOH. (a) Peak deconvolution of the XPS 01s signals after emersion at +0.2 V A surface...

The presented examples clearly demonstrate tliat a combination of several different teclmiques is urgently recommended for a complete characterization of tire chemical composition and tire atomic stmcture of electrode surfaces and a reliable interiDretation of tire related results. Stmcture sensitive metliods should be combined witli spectroscopic and electrochemical teclmiques. Besides in situ techniques such as SXS, XAS and STM or AFM, ex situ vacuum teclmiques have proven tlieir significance for tlie investigation of tlie electrode/electrolyte interface. 

Yamada T, Ogaki K, Okubo S and itaya K 1996 Continuous variation of iodine adiattices on Ag(111) eiectrodes In situ STM and ex situ LEED studies 1996 Surf. Sc/. 369 321-35... 

Wohimann B, Park Z, Kruft M, Stuhimann C and Wandeit K 1998 An in situ and ex situ study of chioride adsorption on Cu(111) eiectrodes in diiute FICi soiutions 1998 Colloids Surfaces A 134 15-19... 

They may be favored over in situ treatment where they will reduce cleanup times, their operation and capabiHties are considered more reHable or better understood, or they can achieve lower cleanup levels. Both in situ and ex situ treatment for soil and ground water rely on a combination of unit processes, which often include biological degradation of organics. 

Ex situ bioremediation may use various biological wastewater treatment processes, soil piles, or land appHcation. With in situ bioremediation, the basic process is the same microbes, soil, and water working together as a bioreactor. Where the in situ techniques differ are in how contaminants and microbes are brought in contact and how oxygen, nutrients, and other chemical supplements ate distributed in the soil—water—air matrix. Typical in situ bioremediation techniques include natural or intrinsic attenuation, air sparging, and bioventing. 

Other Techniques. Other methods, more conventional in type, are employed for ex-situ treatment. These include solvent extraction and thermal desorption, which are detailed under the "Physical/Chemical Treatment" and "Thermal Treatment" sections, respectively. 

Ex situ or off-site, regeneration of noble metal catalysts is not commonly practiced by commercial petroleum refiners because it requires either an extended period with the process shut down or requires that a spare load of cosdy catalyst, which would only be used for a fraction of the time, be purchased and kept available. 

Ex situ or off-site, regeneration of base metal catalysts is a service offered by several vendors worldwide, including Catalyst Recovery, Inc., of Lafayette, Louisiana, and Medicine Hat, Alberta, Canada Catalyst Recovery, Europe of Rodange, Luxembourg Nippon CRI of Miyako, Japan Englehard (formerly Edtrol) of Salt Lake City, Utah Eurecat, U.S., of Pasadena, Texas and Eurecat, SA of La Voulte, Erance (22—28). 

Unfortunately, only thin films of about 20 nanometers in thickness could be obtained with Gel4 An ex situ analysis was difficult, because of experimental limitations, but XPS clearly showed that elemental Ge was also obtained, besides... 

Pandya et al. have used extended X-ray ascription fine structure (EXAFS) to study both cathodically deposited -Ni(OH)2 and chemically prepared / -Ni(OH)2 [44], Measurements were done at both 77 and 297 K. The results for / -Ni(OH)2 are in agreement with the neutron diffraction data [22]. In the case of -Ni(OH)2 they found a contraction in the first Ni-Ni bond distance in the basal plane. The value was 3.13A for / -Ni(OH)2 and 3.08A for a-Ni(OH)2. The fact that a similar significant contraction of 0.05A was seen at both 77 and 297K when using two reference compounds (NiO and / -Ni(OH)2) led them to conclude that the contraction was a real effect and not an artifact due to structural disorder. They speculate that the contraction may be due to hydrogen bonding of OH groups in the brucite planes with intercalated water molecules. These ex-situ results on a - Ni(OH)2 were compared with in-situ results in I mol L"1 KOH. In the ex-situ experiments the a - Ni(OH)2 was prepared electrochemi-cally, washed with water and dried in vac-... 

The availability of high-intensity, tunable X-rays produced by synchrotron radiation has resulted in the development of new techniques to study both bulk and surface materials properties. XAS methods have been applied both in situ and ex situ to determine electronic and structural characteristics of electrodes and electrode materials [58, 59], XAS combined with electron-yield techniques can be used to distinguish between surface and bulk properties, In the latter procedure X-rays are used to produce high energy Auger electrons [60] which, because of their limited escape depth ( 150-200 A), can provide information regarding near surface composition. 

Li DIOX, LiMe or Lilm or LiAsF6 FTIR (ex situ) Li2CO, R0C02Li, ROLi, Li02CH (LiMe and LiAsF6 only), reaction products from Lilm NS, S = O, CF bonds Li vAsFv from LiAsF6 [169]... 

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