Carbon adsorbents templated carbons

Whitcombe et al. observed a strong decrease of the cholesterol concentration, and hence excellent binding for cholesterol with p(EGDMA-co-CVPC) shell/ pMMA core particles in isohexane. When the carbonate ester was not hydrolyzed and hence no imprinted sites existed in the shell, only 2.7 pmol cholesterol per g particles were bound corresponding to the non-specifically adsorbed templates. Slightly less cholesterol was adsorbed to particles prepared without CVPC at all thus formed with a pure pEGDMA shell (<2 pmol g-1). 

The review by Leboda and coworkers [16] describes the requiranents for carbon adsorbents for HPLC and the methods of their preparation. Preliminary attempts to use general-purpose carbons were basically unsuccessful until the use of porous graphitized carbon prepared using the template-replication method (Hypercarb commercial product [20-22]), resistant to both strongly acidic and basic solutions. 

Graphite and carbon fibers have been used at templates. Thus, nylon 6 has been polymerized on a graphite matrix. Such syntheses of polymers in the presence of a solid template, where the solid acts as a template have been described as polymerization-induced epitaxy (PIE). The monomer and resulting film is adsorbed on the template surface through only van der Waals forces. After polymerization, the polymer is washed from the template. The recovered polymer retains special structural features introduced by the template. 

Type IV isotherms are characterized by the presence of a hysteresis loop (i.e., adsorption and desorption branches are not coincident) due to the capillary condensation on the mesopores. They are characteristic of adsorbents that have a wide proportion of mesopores (i.e., compacted carbon blacks under pressure, nanostructured carbons prepared using mesoporous silica as templates, etc.). 

Recently, there has been an increasing interest in the synthesis of ordered mesoporous carbons, since such materials are very promising as adsorbents, catalyst supports, and electrochemical double-layer capacitors. Ordered mesoporous silicas have been shown as suitable templates to prepare periodic mesoporous carbons with various pore shapes and connectivity. The synthesis procedure involves impregnation of the mesoporous silica with an appropriate carbon precursor, carbonization of carbon source, and subsequent removal of silica using an aqueous solution of HF or NaOH. ... 

In the Pt-doped hexagonal mesophase formed from CPCI (cetyl pyridinium chloride), platinum ions are adsorbed at the surface of the surfactant cylinders. They are reduced radiolytically into a metal layer as a nanotube of around 10 nm diameter and a few hundred nm long (Fig. 3f). Extraction of all these nanostructures is achieved by dissolution of the soft template using alcohol. This possible easy extraction constitutes a marked advantage over the synthesis in hard templates, such as mesoporous silica or carbon nanotubes, the dissolution of which is more hazardous for the metal nanostructures. 

Riccardo and coworkers [50, 51] reported the results of a statistical thermodynamic approach to study linear adsorbates on heterogeneous surfaces based on Eqns (3.33)—(3.35). In the first paper, they dealt with low dimensional systems (e.g., carbon nanotubes, pores of molecular dimensions, comers in steps found on flat surfaces). In the second paper, they presented an improved solution for multilayer adsorption they compared their results with the standard BET formalism and found that monolayer capacities could be up to 1.5 times larger than the one from the BET model. They argued that their model is simple and easy to apply in practice and leads to new values of surface area and adsorption heats. These advantages are a consequence of correctly assessing the configurational entropy of the adsorbed phase. Rzysko et al. [52] presented a theoretical description of adsorption in a templated porous material. Their method of solution uses expansions of size-dependent correlation functions into Fourier series. They tested... 

The nitrogen adsorption isotherm recorded on ZSM-5 zeolite prepared without carbon displays almost rectangular shape being typical for purely microporous materials (Fig. 3). The isotherms on all samples prepared using carbon template (Fig. 3) posses both micro- and mesoporous features. The almost vertical rise of the adsorbed amount of nitrogen up to ptp = 0.05 corresponds to the volume filling of micropores. The isotherms exhibit hysteresis loops at plpo > 0.4, which are indicative for the capillary condensation in mesopores. The distribution of these... 

Porous graphitic carbon is synthesized by a multistep chemical and thermal treatment from organic monomers deposited in the pores of a silica gel particle template and subsequently subjected to polymerization, carbonization, dissolution of the silica template and graphitization [170,172]. The silica gel template allows optimization of the adsorbent particle size, porosity and surface area for liquid chromatography. The selection of monomers and thermal treatment is responsible for the mechanical strength, high purity and absence of significant microporosity. Commercially available materials have particle sizes of 5 or 7 xm, a mean pore diameter of 25 nm and a surface area of 100-120 m /g. 

Carbon foams were also prepared by impregnating poly(amide acid) into poly(urethane) foams used as template, followed by imidization and carbcmization [2]. The foams were tested as adsorbents for atmospheric humidity and also as supfmrts for anatase-type TiOi photocatalysts. In Fig. 47, clmnges in pore morphology with impregnation of poly(imide) and carbonization at 1273 K are shown. 

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