Inorganic solid sorbents

This overall study of acid mists began with the development of a sampling and analytical method for hydrogen chloride ((>,7). Various solid sorbents and filters, both treated and untreated, were evaluated as collection media and for compatibility with ion chromatography. The sorbent of choice was silica gel which had been washed with deionized water to remove inorganic impurities. 

Three general types of solid sorbents are mainly used for trapping VOCs in air inorganic sorbents like silica gels or molecular sieves, carbon-based porous materials and porous organic polymers. 

Therefore, the solid sorbent should ideally have a low affinity to water, a characteristic easily met by the porous organic polymers. In contrast, the carbon-based sorbents and molecular sieves as well as some inorganic sorbents show a comparatively high uptake of water. If such sorbents are used in high-humidity environments special measures have to be employed to remove water during or after sampling. Possible methods are ... 

Nowadays solid sorbents can be bought pre-cleaned and less effort is required before the first use. Nevertheless, all sorbents have to be cleaned thermally or by extraction to remove contaminants that formed during production, shipping or storage. For inorganic and carbon-based sorbents this is most easily accomplished by heating... 

The book is divided into three sections consisting of chapters arranged in a consistent order, though some chapters could be put in the second or third section. On the other hand, a uniform treatment and style cannot be anticipated in the book that represents the efforts of many authors. Despite this, the presented works provide the comprehensive, high standard and modern study on the structure, investigations, preparation of inorganic sorbents, their numerous applications and deal with the adsorption on new and chemically modified inorganic solids. 

Diethyldithiocarbamate, pyrrolidin-1 -yldithioformate, and diphenylthiocarbazone (dithizone), as three mercury chelate forming reagents, were used for the preconcentration of ultratrace amounts of inorganic mercury and methyl mercury in silica Cig minicolumn as the solid sorbent. Sample FI online sorbent extraction was coupled with continuous cold vapor atomic absorption spectrometry (CVAAS) for detection. The results showed the superiority of the carbamate type reagents over the dithizone for the online formation and preconcentration of the corresponding mercury chelate. The detection limit was found to be 16 ng/L of mercury. The structures of these organic chelate modifiers are shown in Scheme 17. 

Similar results are reported by Finocchio et al. [39] that studied the adsorption of D3 on different materials such as activated carbons (ACs), silica, and zeolite. The adsorption and regenerabihty have been investigated by infrared (IR) spectroscopy in the apparatus reported in Fig. 7.1. Pure ACs appeared efficient sorbents for D3, more effective than alkah-impregnated ACs and inorganic solids, such as zeolites and silica gel. The presence of transition metal in ACs enhances the adsorption capacity, although such metals may cause more difficulties in the handling and disposal of spent adsorbents. 

Unlike a Henry s law constant, whose value depends mainly on temperature, the value of a solid-water partition coefficient depends on the type of solid, and may also be affected by factors such as pH and ionic strength. There is considerable uncertainty in predicting Kd values for inorganic chemicals often must be measured in the laboratory. For many organic chemicals, however, a method for approximating values exists, based on the properties of the solid sorbent, particularly its concentration of organic carbon, and the properties of the sorbate. The sorbate properties necessary for predicting values are described below further estimation techniques are presented in Section 3.5. 

V. A Tertykh, L. A. Belyakova, Solid-phase hydrosilylation with participation of modified silica surface", in Adsorption on New and Modified Inorganic Sorbents (Eds A.Dabrowski, V A Tertykh), Elsevier, Amsterdam, 1996, p.l47. 

Characterization of inorganic sorbents by means of adsorption at the liquid - solid interface... 

In terms of this adsorption, properties of various adsorbents, among them the inorganic sorbents can be determined. It must be emphasized that inorganic sorbents such as silica, alumina, titania, complex carbon - mineral sorbents, apatites, e.t.c., are both structurally and energetically heterogeneous. Their total heterogeneity may be described by the kinds of adsorption potential distribution function which is one of the most significant characteristics of the aforementioned solids. 

The simple theoretical description of the adsorption from solutions on solids can be useful for characterizing sorption properties of inorganic sorbents. Such properties as the energetical and structural heterogeneities, surface phase capacity, specific surface area, pore size distribution curves and others are very important with regard to wide application of inorganic adsorbents on laboratory and industrial scales. 

Most competitive sorption studies have been carried out adding the ions contemporaneously. In natural environments, however, it is more likely that the ions will come in contact with a sorbent sequentially (i.e., the solid is exposed to one ion first, with the second ion coming in contact with a solid at a later time). The sorption of trace elements in cationic or anionic form is strongly influenced by the order of addition of organic and inorganic ligands and trace elements on the sorbents. 

---