Thermal characterization of methylene blue intercalated montmorillonites by photoacoustic technique

Thermal diffusivity (TD) measurement on commercial K-10 and KSF montmorillonites was carried out by photoacoustic technique. The TD of the montmorillonites after methylene blue adsorption changed with the dye concentration. The repeatedly adsorbed samples showed a lesser TD than the single adsorbed samples. After methylene blue adsorption the acid leached K-10 samples showed well defined changes in TD when compared to the ordered KSF samples.

Optical and Thermal Characterization of Dye Intercalated Montmorillonites and Rare Earth Doped Materials

Nondestructive photothermal methods as well as optical absorption and fluorescence spectroscopy are utilized to characterise three different materials, both thermally and optically. The possibility of using montmorillonite clay minerals, after textile waste-water treatment, is investigated for further applications. The laser induced luminescence studies and thermal characterisation of certain rare earth titanates prepared by self propagating high temperature synthesis method are also presented. Moreover, effort is made to characterise rare earth doped sol gel silica glasses with the help of these nondestructive techniques.

Acidity and catalytic activity of rare earth modified Al/Zr pillared clays

The pillared montmorillonite has been prepared by exchanging Na+ in the interlayer of montmorillonite with Al hydroxy cation followed by calcination. Pillared clays are also prepared after exchanging Na' ions with Ce, La, Sm-ions and then pillarcd with aluminium oxides, The surface characterisation of the prepared catalysts has been done using XRD and surface area measurements. To probe the acidic property of the system, temperature programmed desorption (TPD) of NH, has been done. Toluene alkylation by benzyl chloride has been carried out for the evaluation of catalytic activity. The most active system is found to be mixed Al/Zr pillarcd montrnorillonite.

Liquid phase benzylation of o-xylene over pillared clays

Iron, aluminium and mixed iron aluminium pillared clays have been prepared by partial hydrolysis method and doped with IO% Mo, V and Cr. The samples have been characterised by XRD, FTIR and surface area and pore Volume measurements. The surface acid site distribution has been determined by temperature programmed desorption of ammonia. Vanadia incorporated systems show maximum acidity. Benzylation of o-xylene has been done as probe reaction to test catalytic activity. Benzyl chloride is a superior benzylating agent compared to benzyl alcohol in activity and selectivity. Cent percent selectivity towards monobenzylated product is obtained in all the cases. Fe pillared systems exhibit maximum activity. The catalytic activities of the systems can be correlated with the amount of strong add sites. The effects of various reaction variables on the reaction have been studied. Presence of moisture has a diminishing effect on the reaction rate.

Selective Methyl Tert-Butyl Ether Synthesis over Metal Exchanged Pillared Clays

Iron and mixed iron aluminium pillared montmorillonites prepared by partial hydrolysis method was subjected to room temperature exchange with transition metals of the first series. The materials exhibit good structural as well as thermal stability. Exchanged metals were found to be present inside the porous network, in the environs of the pillars. Mixed pillaring resulted in the intercalation of Al 13 like polymers in which Al is partially substituted by Fe. The acidic structure was followed by temperature programmed desorption of ammonia and cumene cracking test reaction. Weak and medium sites overshadow the strong sites in all systems. However, exchange with metals increases the number of strong sites. The prepared materials are efficient catalysts for gas phase MTBE synthesis. The catalytic activity can be well correlated with the total amount of weak and medium acid sites.

Thermal characterisation of dye-intercalated K-10 montmorillonite ceramics using photoacoustic technique

Thermal diffusivity (TD) measurements were performed on some industrially important dyes – auramine O (AO), malachite green and methylene blue (MB) – adsorbed K-10 montmorillonites using photoacoustic method. The TD value for the dye-adsorbed clay mineral was observed to change with a variation in dye concentration. The contribution of the dye towards TD was also determined. The repeatedly adsorbed samples with MB and AO exhibited a lower TD than the single-adsorbed samples. TD values of sintered MB samples were also obtained experimentally. These sintered samples exhibit a higher TD, although they show a trend similar to that of non-sintered pellets. A variation in dye concentration and sintering temperature can be used for tuning the TD value of the clay mineral to the desired level.

Structural tuning of Montmorillonite clays by pillaring: Designing of shape selective solid acid catalysts and PANI - Montmorillonite nanocomposites

Green chemistry boots eco-friendly,natural clays as catalysts in the chemical as well as in the pharmaceutical industry.Industry demands thermal stability,mechanical strength etc for the catalyst and there the modification methods becomes important.Pillaring tunes clays as efficient catalytic templates for shape selective organic synthesis.Here pillared clays are used as promising alternatives for the environmentally hazardous homogeneous catalysts in some industrially important Friedel-Crafts alkylation reactions of arenes with lower alchohols and higher olefins.The layer structure is enhanced upon pillaring and allows the nanocomposite formation with polyaniline to develop today’s nanoscale diameter devices.Present work gives an entry of pillared clays to the world of conducting composite nanofibers.

Organic Reactions Catalysed by Modified Clays

Department of Applied Chemistry, Cochin University of Science and Technology

A Study of the Physical and Engineering Behaviour of Cochin Marine Clays

With the increase in population, housing and construction of various facilities have been a problem with urbanization. Having exhausted all the trouble free hand, man is nowon the lookout for techniques to improve areas which were originally considered uninhabitable. Thus this study is based on the nature and engineering behavior of soft clays covering long stretches of coastal line and methods to improve their geotechnical properties .The main aim of the present investigation is to study in detail the physical and engineering behavior of the marine clays of Cochin. While it is well known that the marine clays have been posing numerous problems to foundation engineers all along, the relevant literature reveals that no systematic and comprehensive study has been attempted to date. The: knowledge gained through the study is suitably used to improve these properties with appropriate additives.

A Study Of The Strength And Compressibility Characteristics Of Cochin Marine Clays

With the advent of urbanisation and consequent search for more and more habitable land, it was imperative that the large tracts of marine clays, considered inhabitable earlier, had to be reclaimed and developed. These marine clays, wellknown for its high compressibility and poor shear strength, posed numerous problems to the builders and Cochin was no exception. It is only less than a decade since active research work was initiated on marine clays in general and Cochin marine clays in particular. Eventhough some systematic studies are available on compressibility characteristics, attempts to study the shear strength aspects and development of techniques to improve it have been very limited. This work is an investigation on the consolidation and shear strength characteristics of Cochin marine clays including methods to improve the same

Optical and thermal characterization of dye intercalated montmorillonites and rare earth doped materials

The advent of high optical quality transparent nano—structured glasses, the so-called transparent glass ceramics or vitroceramics disclosed the possibility of producing nano-sized photonic devices based on rare-earth doped up—converters. Transparent glass ceramics have been investigated as hosts for lanthanide ions envisioning the production of materials that are easy to shape and with high performance for photonic applications. Rare earth doped glasses have been extensively studied due to their potential applications in optical devices such as solid state lasers and optical fibers. Various photothermal and optical techniques have been successfully applied for the thermal and optical characterization of these rare earth doped materials. In the present thesis, the effective thermal parameters like thermal diffusivity and thermal effusivity of complex materials for various applications have been investigated using photothermal methods along with their optical characterization utilising the common optical absorption as well as fluorescence spectroscopic techniques. These sensitive optical procedures are also essential for exploiting these materials for further photonic applications.

A study on the parameters affecting the compressibility characteristics of Cochin marine clays

There are numerous parameters affecting the compressibility characteristics of soft clays. A few of them such as load increment ratio, type of drainage and thickness of sample were taken up for detailed investigation. However, the main thrust in the present investigations was to develop an insight into the benefits of preloading technique, envolve procedures and establish design charts for preparation of a precompression programme which will substantially reduce the consolidation settlements of the extremely soft deposits of Cochin marine clays.

Thermal characterisation of dye-intercalated K-10 montmorillonite ceramics using photoacoustic technique

Thermal diffusivity (TD) measurements were performed on some industrially important dyes – auramine O (AO), malachite green and methylene blue (MB) – adsorbed K-10 montmorillonites using photoacoustic method. The TD value for the dye-adsorbed clay mineral was observed to change with a variation in dye concentration. The contribution of the dye towards TD was also determined. The repeatedly adsorbed samples with MB and AO exhibited a lower TD than the single-adsorbed samples. TD values of sintered MB samples were also obtained experimentally. These sintered samples exhibit a higher TD, although they show a trend similar to that of non-sintered pellets. A variation in dye concentration and sintering temperature can be used for tuning the TD value of the clay mineral to the desired level

Thermal characterization of methylene blue intercalated montmorillonites by photoacoustic technique

Thermal diffusivity (TD) measurement on commercial K-10 and KSF montmorillonites was carried out by photoacoustic technique. The TD of the montmorillonites after methylene blue adsorption changed with the dye concentration. The repeatedly adsorbed samples showed a lesser TD than the single adsorbed samples. After methylene blue adsorption the acid leached K-10 samples showed well defined changes in TD when compared to the ordered KSF samples

A study on mitigating the effect of sulphates in lime stabilised Cochin marine clays

Soft clays known for their high compressibility, low stiffness and low shear strength are always associated with large settlement. In place soil treatment using calcium-based stabilizers like lime and cement is a feasible solution to readdress strength deficiencies and problematic shrink/swell behaviour of unstable subgrade soils. Out of these, lime has been proved unambiguously as the most effective and economical stabilising agent for marine clays. Lime stabilisation creates long-term chemical changes in unstable clay soils to create strong, but flexible, permanent structural layers in foundations and other pavement systems. Even though calcium-based stabilizers can improve engineering properties of soft clays, problems can arise when they are used in soils rich in sulphates. It is possible for marine clays to be enriched with sulphates, either by nature or due to the discharge of nearby industrial wastes containing sulphates. The presence of sulphates is reported to adversely affect the cation exchange and pozzolanic reactions of cement and lime treated soil systems. The anions of sulphates may combine with the available calcium and alumina, and form insoluble ettringite in the soil system. Literature on sulphate attack in lime treated marine clays reports that formation of ettringite in lime-sodium sulphate-clay system is capable of adversely affecting the engineering behavior of marine clays. Only very few studies have been conducted on soft marine clays found along the coastal belt of Kerala and that too, is limited to Cochin marine clays. The studies conducted also have the limitation that the strength behaviour of lime stabilised clay was investigated only for one year. Practically no data pertaining to long term adverse effects likely to be brought about by sulphates on the strength and compressibility characteristics of Cochin marine clays is available. The overriding goal of this investigation was thus to examine the effectiveness of lime stabilisation in Cochin marine clays under varying sulphate contents. The study aims to reveal the changes brought about by varying sulphate contents on both physical and engineering properties of these clays stabilised by lime and the results for various curing periods up to two years is presented in this thesis. Quite often the load causing an unacceptable settlement may be less than the load required to cause shear failure and therefore attempt has been made in this research to highlight sulphate induced changes in both the compressibility and strength characteristics of lime treated Cochin marine clays. The study also aimed at comparing the available IS methods for sulphate quantification and has attempted to determine the threshold level of sulphate likely make these clays vulnerable by lime stabilisation. Clays used in this study were obtained from two different sites in Kochi and contained sulphate in two different concentrations viz., 0.5% and 0.1%. Two different lime percentages were tried out, 3% and 6%. Sulphate content was varied from 1% to 4% by addition of reagent grade sodium sulphate. The long term influence of naturally present sulphate is also investigated. X-ray diffraction studies and SEM studies have been undertaken to understand how the soil-lime reactions are affected in the presence of sodium sulphate. Natural sulphate content of 0.1% did not seem to have influenced normal soil lime reactions but 0.5% sulphate could induce significant changes adversely in both compressibility and strength behaviour of lime treated clays after long duration. Compressibility is seen to increase drastically with increasing sulphate content suggesting formation of ettringite on curing for longer periods. Increase in compression index and decrease in bond strength with curing period underlined the adverse effects induced in lime treated marine clays by the presence of sulphates. Presence of sulphate in concentrations ranging from 0.5 % to 4% is capable of adversely affecting the strength of lime treated marine clays. Considerable decrease is observed with increasing concentrations of sulphate. Ettringite formation due to domination of sodium ions in the system was confirmed in mineralogical studies made. Barium chloride and barium hydroxide is capable of bringing about beneficial changes both in compressibility and strength characteristics of lime treated Cochin marine clays in the presence of varying concentrations of sulphate and is strongly influenced by curing time. Clay containing sodium sulphate has increased strength values when either of barium compounds was used with lime ascompared with specimens treated with lime only. Barium hydroxide is observed to remarkably increase the strength as compared to barium chloride,when used in conjunction with lime to counteract the effect of sulphate.