EFFECT OF SOLVENT EXTRACTION SYSTEM ON THE ANTIOXIDANT ACTIVITIES OF ALGAE

Objective: The present study aimed to determine the antioxidant activities of five algae including Oedogonium globossum, Pithophora oedogonia, Rhizoclonium hieroglyphicum, Scytonema ocellatum and Spirogyra communis and the effect of different solvent (benzene, chloroform, acetone and methanol) used for the extraction of active components from algae. Methods: The five algae were extracted with four different solvents e. g benzene, chloroform, acetone and methanol. The Folin-Ciocalteu procedure was used to estimate the amount of total phenolic content in different extracts of algae. Total flavonoid content was estimated by aluminium chloride colorimetric method. The DPPH radical scavenging assay was used to find out the antioxidant activities of algae under investigation. Results: The total phenolic content varied from 9.80±0.29 to 44.44±2.26 mg/g, 7.26±0.08 to 21.30±0.17 mg/g, 9.82±0.12 to 50.14±0.99 mg/g and 11.51±0.17 to 54.02±0.58 mg/g dry material in the benzene, chloroform, acetone and methanol extracts of the algae respectively. The flavonoid content was found to be the highest in the acetone extract of Scytonema ocellatum (593.81±2.69 mg/g) and flavonol content was found to be the highest in the chloroform extract of Scytonema ocellatum (448.22 ± 4.36 mg/g) whereas least amount of flavonoid present in the benzene extract of Oedogonium globossum 8.91±0.37 and least amount of flavonol was present in the chloroform extract of Spirogyra communis (13.54±1.07 mg/g). The highest DPPH radical scavenging was observed in the methanol extract of Scytonema ocellatum with IC50 = 0.24±0.003 mg dry material. The reducing power of the extracts of the algae was also evaluated as mg AAE (ascorbic acid equivalent)/g dry material. Chloroform extract of Rhizoclonium hieroglyphicum showed the highest reducing power 185.56±2.00 mg AAE/g dry materials. Conclusion: Thus it could be suggested that these algae can be utilized as natural antioxidant

Polypropylene-clay composite prepared from Indian bentonite

In the present work, a set of experimental polypropylene (PP) clay composites containing pristine bentonite clay of Indian origin has been prepared and then characterized. The polymer clay composites are processed by solution mixing of polypropylene with bentonite clay using a solvent xylene and high speed electric stirrer at a temperature around 130 degrees C and then by compression molding at 170 degrees C. The mechanical properties of PP-clay composites like tensile strength, hardness and impact resistance have been investigated. Microstructural studies were carried out using scanning electron microscope and transmission electron microscope and the thermal properties were studied using differential scanning calorimeter. Mechanical properties of the prepared composites showed highest reinforcing and toughening effects of the clay filler at a loading of only 5 mass % in PP matrix. Tensile strength was observed to be highest in case of 5 mass % of clay loading and it was more than 14% of that of the neat PP, while toughness increased by more than 80%. Bentonite clay-PP composite (5 mass %) also showed 60% increase in impact energy value. However, no significant change was observed in case of hardness and tensile modulus. Higher percentages of bentonite clay did not further improve the properties with respect to pristine polypropylene. The study of the microstructure of the prepared polymer layered silicate clay composites showed a mixed morphology with multiple stacks of clay layers and tactoids of different thicknesses

Evolution of molecular structure and conformation of n-alkylammonium intercalated iron rich bentonites

Clay-surfactant hybrids were prepared from three montmorillonites of different cation exchange capacity (CEC) and iron-content using n-alkylammonium surfactants with varying alkyl chain length from C(10) to C(16). Structure of clay-surfactant hybrids were evaluated using basal spacing from XRD, organic loading from Thermogravimetric Analysis (TGA) and conformational analysis from FUR. It was found that the structure of the clay-organic hybrid depends mostly on CEC and marginally on iron-content. The systematic study of structural evolution and comparable swelling nature of clay-surfactant hybrids of the low-CEC, high iron-variety indicates its potential industrial application like high-CEC montmorillonite. (C) 2011 Elsevier B.V. All rights reserved

Thermogravimetric study of n-alkylammonium-intercalated montmorillonites of different cation exchange capacity

Three n-alkylammonium salts of varying alkyl chain length were ion exchanged with montmorillonites (MMT) of different cation exchange capacity (CEC). The intercalated MMTs were characterized by thermogravimetry (TG), XRD, FTIR to acquire an insight into the intergallery structural arrangement of the organic alkylammonium cations (AAC). The increment in the intergallery spacing from XRD pattern was correlated with chain length and interlayer arrangement of AAC. Multiple organic mass-loss stages in thermogravimetric analysis indicate two types of anchorage of AAC in intercalated clay. CEC of MMT was found to influence the intergallery confinement and excess adsorption of AAC

Pyrophyllite - a potential material for application in tri-axial porcelain systems

Pyrophyllite is largely an overlooked raw material available in huge quantities in nature. This is mainly due to the fact that other comparable aluminosilicate raw materials like china clay are available in much purer form. However, fast depleting reserves of standard raw materials necessitated renewed attention on so far sparingly used raw materials like pyrophyllite. Investigative work on pyrophyllite is also insignificant in comparison to other ceramic raw materials. Available information are scattered and it is felt that a comprehensive review is needed for effective dissemination of the information already generated and available in the public domain. In the present article salient points on the material including structure, chemistry of heating and possibility of future applications particularly in triaxial ceramic system is discussed. In a case study one Indian pyrophyllite was incorporated (15%) in a triaxial body composition replacing both china clay and quartz. The changes in fired properties was tried to correlate with phase development and microstructure

Pressureless reaction sintering of yttrium aluminium garnet (YAG) from powder precursor in the hydroxyhydrogel form

Pressureless reaction sintering of YAG was carried out by using a precursor powder in the hydroxyhydrogel form synthesized by flash polycondensation technique. Reactive silica additive was used to modify Al-O-Y network where Si(4+) was incorporated in the solvated form. The sintering experiments were carried out with the processed powder up to 1650 degrees C under ambient ambience. Densification indicated effective sintering with well-formed microstructure. Phase identification by XRD indicated only YAG in the sintered specimen. (C) 2011 Elsevier Ltd and Techna Group Sri. All rights reserved

Studies on the suitability of iron-rich Indian bentonites for synthesis of organoclays by intercalation

In the present study intercalation behaviour of two bentonites from Indian origin were compared with a high-purity commercial montmorillonite. Experimental bentonites of Indian origin showed low cation exchange capacity (CEC) due to limited Mg(2+). substitution. Infra-red spectral study revealed the presence of Fe(3+) in octahedral positions. Organic loading of intercalated clays increased with CEC

Simultaneous intercalation of two quaternary phosphonium salts into montmorillonite

Intercalation of montmorillonites with a mixture of intercalates has not been studied extensively. The objective of the present investigation was to study the effects of phosphonium-based intercalate mixtures on the properties (organic loading and basal spacing) of montmorillonite. These phosphonium-intercalated montmorillonites are promising candidates as high-temperature stable nanofillers for application in clay polymer nanocomposites. Two salts with different cationic heads and chain lengths were mixed in varying molar ratios and the mixtures were intercalated into the interlayer space of montinorillonite. Two sets were chosen based on the chain length and the cationic head-group structure of the two intercalated salts (referred to hereafter as set 1 and set 2). The resultant intercalated montmorillonite was characterized by thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The organic loading of the intercalated montmorillonite increased with the proportion of longer carbon-chain intercalate in the mixture. The intensity of the characteristic XRD peak of each intercalate varied with the mole fraction percent of that intercalate in the solution mixture. No marked synergistic effect of the intercalate mixture on the basal spacing and organic loading properties of the intercalated montmorillonite was observed the proportional influence of individual components was found to be more prominent

Thermal degradation of alkyl triphenyl phosphonium intercalated montmorillonites

The decomposition mechanism of intercalated montmorillonites at a particular temperature region and the activation energy involved in it are the two important aspects which determines the thermal stability of intercalated montmorillonites. In this study, montmorillonite was intercalated with alkyl (methyl, ethyl, propyl, and dodecyl) triphenyl phosphonium intercalates. Differential thermogravimetric analysis of each intercalated montmorillonites showed different peaks with associated organic loss at different temperature zone. Intercalated montmorillonites were subjected to isothermal kinetic analysis corresponding to selected temperature zone obtained from DTG peaks. Activation energies of organic decomposition process at selected temperature zones were determined. Mass spectral analysis and FTIR were done to understand the decomposition mechanisms and to relate them with the estimated activation energies