Pradip K. Gogoi

Kinetics of dehydroxylation of kaolin in presence of oil field effluent treatment plant sludge

Abstract Oil field effluent treatment plant (ETP) sludge contains high amounts of hydrocarbon and its disposal by land filling is a problem. Various methods to utilize the sludge and circumvent the disposal problem have been suggested. The high calorific value of the sludge may be used in calcination of clay and manufacture of ceramic materials. This communication reports the kinetics of dehydroxylation of a kaolin clay in presence of ETP sludge. Nonisothermal methods are applied to obtain the thermal curves. Nine solid-state mechanisms are applied for analysing the data obtained in the temperature range of 450–750 °C. Random nucleation is the major process of decomposition in both the clay and clay–sludge mixture at the lower temperature range (450–600 °C). At higher temperatures (600–750 °C), the thermal decomposition of the sludge follows a three-dimensional diffusion process and occurs at the phase boundary with spherical symmetry. The thermal decomposition of the clay–sludge mixture, in the temperature range of 600–750 °C, occurs at the phase boundary with cylindrical symmetry. The kinetic parameters follow the kinetic compensation effect.

Cementitious properties of metakaolin-normal Portland cement mixture in the presence of petroleum effluent treatment plant sludge

Abstract The physicochemical characteristics of cocalcined kaolin and petroleum effluent treatment plant (ETP) sludge and its effect on the technological and hydration characteristics of cement have been presented. Conductivity measurements indicate that both the sludge ash (SA) and cocalcined kaolin–sludge mixtures in aqueous medium are reactive in nature. The rate of hydration was investigated by determining the combined water (CW) and Ca(OH) 2 content in the hydration products. The hydration products were characterized by FTIR spectrophotometric method and XRD analysis technique. The rates of hydration of cement containing cocalcined kaolin–sludge mixtures are comparatively higher than the others. Blended cements with improved technological properties may be prepared by replacing 20% cement with cocalcined kaolin–sludge mixtures containing up to 30% sludge.

Hydration behaviour of lime–co-calcined kaolin–petroleum effluent treatment plant sludge

Abstract Petroleum effluent treatment plant (ETP) sludge contains hydrocarbons and its ash is pozzolanic in character. The hydrocarbon may be utilized in the calcination of clay. The present communication reports on the hydration behaviour of lime–metakaolin mixtures produced in the presence of the sludge. The hydration products were characterized by using FTIR, TG, DTA and XRD methods. Use of sludge in metakaolin preparation increases the initial hydration rate and enhances the production of C–S–H or C–A–S–H gel.

Palladium-Schiff-base-silica framework as a robust and recyclable catalyst for Suzuki–Miyaura cross-coupling in aqueous media

A silica supported palladium catalyst, Pd@imine–SiO2 was prepared by immobilizing Pd(OAc)2 onto silica gel through coordination of imine, generated via Schiff-base condensation between 3-aminopropyltriethoxysilane (APTES) functionalized silica gel and salicylaldehyde. The prepared catalyst was characterized by FT-IR, BET surface area measurements, XRD, SEM-EDX, EDS-mapping and ICP-AES analysis. The imine-based catalyst exhibited excellent activity in the Suzuki–Miyaura cross-coupling reactions of aryl bromides with arylboronic acids in iPrOH/H2O (1 : 1) at room temperature. The reaction proceeds under mild reaction conditions and the catalyst is recyclable, thus offering an environmentally benign alternative to the existing protocols.

Thermal decompostion studies on nickel(II) bis(oxalato)nickelate(II) pentahydrate

The paper describes the synthesis and thermal decomposition of nickel(II)bis(oxalato)nickelate(II)pentahydrate, Ni[Ni(C2O4)2].5H2O. The complex was characterized by elemental analysis, infrared, electronic, e.s.r., magnetic moment measurement and X-ray powder diffraction studies. The thermal decompostion of the complex led to NiO in air at about 338° and in nitrogen at about 720°. The activation energies (E*) for the dehydration and decompostion reactions in air and nitrogen were evaluated. Tentative reaction mechanisms have been suggested for the termal decompostion of the complex in air and nitrogen.ZusammenfassungEs wird die Synthese und thermische Zersetzung von Nickel(II) -bis(oxalato)- nickelat(II) - pentahydrat beschrieben: Ni[Ni(C2O4)2].5H2O. Dieser Komplex wurde mittels Elementaranalyse, IR-Spektroskopie, ESR-Spektroskopie, der Messung des magnetischen Momentes sowie mittels Pulverdiffraktionsuntersuchungen charakterisiert. Im Ergebnis der thermischen Zersetzung entsteht NiO, in Luft bei etwa 338°, in Stickstoffatmosphäre bei ca. 720°. Die Aktivierungsenergien (E*) der Dehydratations- und Zersetzungsreaktionen in Luft und in Stickstoff wurden ermittelt. Für die thermische Zersetzung des Komplexes in Luft bzw. in Stickstoff wurde ein Reaktionsmechanismus entwickelt.

Thermal decomposition of manganese(II) bis(oxalato)manganate(II) tetrahydrate

A mixed metal oxalate, manganese(II)bis(oxalato)nickelate(II)tetrahydrate, has been synthesized and characterized by elemental analysis, IR spectral and X-ray powder diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to Mn2O3, MnO2 and NiO at ca.1000°C, via. the formation of several intermediates. DSC study in nitrogen upto 500°C showed the endothermic decomposition. The tentative mechanism for the thermal decomposition in air is proposed.

Physicochemical and cementitious properties of sludge from oil field effluent treatment plant

Abstract Sludge generated in the effluent treatment plants (ETPs) of oil fields contain calcite, clay and other inorganic materials as well as hydrocarbon oil. The amount of the latter is often more than the permissible level for safe disposal by landfilling. The thermoanalytical characteristics of the sludge generated in the ETP of Lakwa oil field, Assam, India were investigated by using TG, DTG, DTA, XRD, FTIR techniques and chemical methods. The lime reactivities of the sludge ash and the physical properties of blended cement containing the ash were evaluated. Decomposition of calcite starts from above 550°C and it is succeeded by several solid state reactions involving CaO and aluminosilicates forming new phases. Gehlenite (Ca 2 Al 2 SiO 7 ) has been identified as one of the products and it forms above 750°C. Sludge ash prepared at 750°C consumes considerable amount of lime but it is not suitable for preparation of blended cement.

Thermal decomposition kinetics of zinc(II) bis(oxalato)zincate(II) tetrahydrate

Abstract Zinc(II) bis(oxalato)zincate(II) tetrahydrate, Zn[Zn(C 2 O 4 ) 2 ]·4H 2 O, was prepared and characterized by elemental analysis and reflectance and IR spectral studies. From thermal decomposition studies (DTA, TGA, DTG and DSC) in air and nitrogen, the kinetic parameters, e.g. activation energies and entropies of activation, were evaluated by Freeman and Carroll, Flynn and Wall and modified Freeman and Carroll methods. The kinetic parameters evaluated from the TG data differed considerably from those evaluated from DSC, which showed a dependence of the decomposition temperature on the heating rate. The X-ray powder diffraction and IR spectral data were used to identify the final product. A tentative mechanism for the thermal decomposition of the complex in air has been proposed.

Rice husk derived nanosilica supported Cu(II) complex: an efficient heterogeneous catalyst for oxidation of alcohols using TBHP

We have developed a heterogenized catalyst of Cu(II) complex immobilized onto nanosilica obtained from rice husk (RH), through coordination of imine, generated via Schiff-base condensation between 3-aminopropyltriethoxysilane (APTES) functionalized nanosilica and acetamide. The synthesized catalysts were characterized by FT-IR, XRD, BET surface area measurements, ESR, SEM-EDX and ICP-AES. The synthesized catalyst showed excellent activity towards controlled oxidation of different primary and secondary alcohols in the presence of tert-butyl hydrogen peroxide (TBHP). Furthermore, the catalysts could be recovered by simple filtrations and can be reused upto many consecutive cycles without loss in activity.

X-ray (Radial Distribution Function, RDF) and FT-IR analysis of high sulphur Tirap (India) coal

AbstractA preliminary study has been performed on high sulphur coals from Tirap colliery of Assam, India, using X-ray (RDF) technique and FT-IR spectroscopy. XRD pattern of the coal shows that it is amorphous in nature. Function of radial distribution analysis (FRDA) indicates that coal is lignite in type and there is no evidence of graphite like structures. The first maximum in the FRDA at R=0·133 nm relates to the C–C aliphatic bond (type C–CH=CH–C), and the second maximum at R=0·25 nm relates to the distance between carbon atoms of aliphatic chains that are located across one carbon atom. The curve intensity profiles obtained from FRDA show quite regular molecular packets for this coal. FT-IR study shows the presence of aliphatic –CH, –CH2 and –CH3 groups, aliphatic C–O–C stretching associated with –OH and –NH stretching vibrations and HCC rocking (single and condensed rings).