Organo-mineral composites

Polyisocyanates can initiate tripolymerization reactions in the presence of a catalyst, leading to the formation of strong triisocyanurate cycles [67]. Alkalis, acetates, alcoholates of alkali metals, tertiary amines, and many other substances are efficient catalysts of diisocyanate trimerization [50, 55, 57]. However, many of these catalysts proved to be of low effciency for trimerization of industrial polyisocyanates containing large quantities of impurities. Consequently, two catalysts—an alkaline medium formed by sodium waterglass and a tertiary amine [2,4,6-tri(dimethylaminomethyl)phenol]—were used for the polyisocyanate trimerization process. 

Crown-complexes and their open-chain analogs, of which MGF-9 may considered one, are known to act as catalysts carrying ions in two-phase processes and to be efficient catalysts of isotyanate addition polymerization [103, 106]. 

A variety of reactive fragments (isocyanate, hydroxyl and ester groups, unsaturated bonds, aromatic rings) are known to facilitate and support parallel and serial competing reactions in the system tmder investigation polyisocyanate-waterglass-MGF-9-UP 606/2. The impurities in the commercial products on which OMC development is based further complicate studies of this system. Consequently, investigations of OMC formation were performed on model systems. 

The simplest representative of aromatic isocyanates, phenylisocya-nate (PHI), served as the polyisocyanate (PIC) model. The choice of phenylisocyanate as the model PIC is connected with the absence from its absorption spectrum of the 1440-1420 cm band that could impede spectral interpretation with triisocyanurates in the end products. 

The kinetics of NCO group consumption at 295 K was investigated by IR spectroscopy in the following model systems  

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While important for the quantitative characterization of adsorption processes, adsorption studies provide only a phenomenological description of the process and do not generally reveal much in the way of a detailed molecular picture of the resulting organo-mineral composite. 

Three specific areas can be identified to serve as foci for expanding the research on this material (i) The nature of the organic components interactions need to be ascertained. Do the lipids (whose chemistry is dominated by aliphatic components) and humic (whose chemistry is dominated by aromatic, carboxyl, and carbohydrate components) actually exist as distinct domains in organo-mineral complexes (ii) What is the effect of the mineral surface on adsorbed macromolecule conformation How does conformation impact the adsorption of additional NOM components (iii) Finally, a better understanding of the interfacial chemistry of these organo-mineral composites needs to be developed in order to understand the fate of many organic contaminants introduced into natural systems. 

Various compositions of natural zeolites modified for the remediation of soils contaminated by heavy metals and radionuclides are discussed. Modified zeolites are selective adsorbents in respect to bivalent cations including Sr, Cd, Cu, Pb, Zn. Incorporation of modified zeolites into soils reduces the content of lead and other heavy metals by a factor of 4-5 and prevents or diminishes the transport processes from soil into ground water and plant biomass. Using of organo-mineral composites, containing 1-5 % selective sorbent "Zeolite P", is efficient to get ecologically cleaned harvests of com, bean and vegetable cultures under low contamination. 

Let us consider the influence of catalytic activity of ethylene glycol homologues on the rate of organo-mineral composite formation. Polyoxyethylene glycols (POEG) were taken in equal mole content with the MGF-9 content in actual OMC, where the waterglass/poly-isocyanate/MGF-9 ratio is 9 9 2. 

All the results of the organo-mineral composition investigations correlated well with puhhshed data, giving sufficiently conclusive evidence of complex proceeding hy crown type processes. 

Chemical studies of the cured organo-mineral composition end products by IR spectroscopy showed that the ratio of triisocyanurates, disuhstituted ureas, amines, sodium carbamates, carbonates, phtha-lates, and methacrylates, as well as the composition of the silicic acid... 

The influence of the waterglass silica modulus on physical and mechanical properties of organo-mineral composites is explained mainly by change in the composition of the products of reaction of... 

The result of MGF-9 pseudo-crown complexation with waterglass sodium cations is a desolvated active hydroxyl ion whose initiating ability is considerably higher in the organo-mineral compositions investigated. Participation of phthalic, methacrylic, and carbamic adds, and sdicon-oxygen anions forms loose ion pairs with sodium cations whose activity in the cydotrimerization process is more than twofold higher [50, 94, 103]. 

It thus may be concluded that introduction of sodium waterglass with various silica moduh into organo-mineral compositions leads to multiple influences on the composite formation process. First, change of the medium alkalinity dters the ratios of disubstituted ureas,... 

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