Luminomagnetic bifunctionality of Mn(2+)-bonded graphene oxide/reduced graphene oxide two dimensional nanosheets.

Herein, we report the luminomagnetic bifunctional properties of two-dimensional (2D) Mn(2+) bonded graphene oxide (GO)/reduced graphene oxide (RGO) nanosheets synthesized using a facile route of oxidation followed by a solvothermal reduction method. Photoluminescence (PL) studies (excited by different wavelengths) revealed that the resonant energy transfer between Mn(2+) and sp(3)/sp(2) clusters of GO/RGO is responsible for the enhancement of emissions. Moreover, pH-sensitive PL behaviors have also been investigated in detail. The ferromagnetic behavior is believed to arise due to defects in Mn(2+) bonded GO composites. Thus, present reduction method provides a direct route to tune and enhance the optical properties of GO and RGO nanosheets bonded with Mn(2+) ions, which creates an opportunity for various technological applications.

Manganese recovery from secondary resources: a green process for carbothermal reduction and leaching of manganese bearing hazardous waste.

During the hydrometallurgical extraction of zinc by electrowinning process, a hazardous solid waste called anode mud is generated. It contains large quantity of manganese oxides (55-80%) and lead dioxide (6-16%). Due to the presence of a large quantity of lead, the anode mud waste is considered hazardous and has to be disposed of in secure landfills, which is costly, wastes available manganese and valuable land resources. For recovery of manganese content of anode mud, a process comprising of carbothermal treatment using low density oil (LDO) followed by sulphuric acid leaching is developed.

Removal of Zn (II) from aqueous solution by using hybrid precursor of silicon and carbon.

Hybrid precursor (HP) of silicon and carbon was synthesized from rice hulls by a novel low temperature method, using sol-gel route. The potential of hybrid precursor to remove Zn (II) ions from aqueous solutions was investigated under different experimental conditions. Hybrid precursor removes Zn (II) ions with efficiency higher than 95% at low concentration. The data revealed that initial uptake was rapid and equilibrium was established in 30min. Pseudo first order, Pseudo second order and Intraparticle diffusion kinetic models were applied to the kinetic data and it was found that adsorption process followed pseudo second order with activation energy of 1.093kJmol(-1). Zn (II) removal was quantitatively evaluated using Langmuir and Freundlich isotherm model and monolayer sorption capacity show the value 28.76mg/g indicating the affinity of HP for Zn (II) ions. The negative value of Gibbs free energy obtained in this study with hybrid precursor confirms the feasibility and spontaneous nature of adsorption process.

Sequestration of carbon dioxide (CO2) using red mud.

Red mud, an aluminium industry hazardous waste, has been reported to be an inexpensive and effective adsorbent. In the present work applicability of red mud for the sequestration of green house gases with reference to carbon dioxide has been studied. Red mud sample was separated into three different size fractions (RM I, RM II, RM III) of varying densities (1.5-2.2 g cm(-3)). Carbonation of each fraction of red mud was carried out separately at room temperature using a stainless steel reaction chamber at a fixed pressure of 3.5 bar. Effects of reaction time (0.5-12 h) and liquid to solid ratio (0.2-0.6) were studied for carbonation of red mud. Different instrumental techniques such as X-ray diffraction, FTIR and scanning electron microscope (SEM) were used to ascertain the different mineral phases before and after carbonation of each fraction of red mud. Characterization studies revealed the presence of boehmite, cancrinite, chantalite, hematite, gibbsite, anatase, rutile and quartz. Calcium bearing mineral phases (cancrinite and chantalite) were found responsible for carbonation of red mud. Maximum carbonation was observed for the fraction RM II having higher concentration of cancrinite. The carbonation capacity is evaluated to be 5.3 g of CO(2)/100 g of RM II.

Synthesis and characterization of nano-sized zirconia powder synthesized by single emulsion-assisted direct precipitation.

For the first time, single reverse microemulsion-assisted direct precipitation route has been successfully used to synthesize tetragonal zirconia nanoparticles in narrow size range. The synthesized powder was characterized using FT-IR, XRD and HRTEM techniques. The zirconia nanoparticles obtained were spherical in shape and has narrow particle size distribution in the range of 13-31nm and crystallite size in the range of 13-23nm.

Removal of lead from aqueous solution by hybrid precursor prepared by rice hull.

Use of low-cost hybrid precursor, prepared from rice hull has been studied as a sorbent for the removal of Pb(2+) from aqueous solutions. Effect of contact time, initial concentration, pH and temperature has been studied. The effect of temperature (30, 40, 50 and 60 degrees C) on adsorption phenomena has been studied and data have been analyzed using Langmuir isotherm. The change in enthalpy (Delta H) (-14.6179 kJ/mol), free energy (Delta G) and entropy (DeltaS) has also been evaluated. The negative values of Delta G and Delta H indicate the adsorption of lead ions on the surface of hybrid precursor to be spontaneous and exothermic under the experimental condition.

Coal fly ash utilization: low temperature sintering of wall tiles.

We present here a study of the sintering of fly ash and its mixture with low alkali pyrophyllite in the presence of sodium hexa meta phosphate (SHMP), a complex activator of sintering, for the purpose of wall tile manufacturing. The sintering of fly ash with SHMP in the temperature range 925-1050 degrees C produces tiles with low impact strength; however, the incremental addition of low alkali pyrophyllite improves impact strength. The impact strength of composites with >or=40% (w/w) pyrophyllite in the fly ash-pyrophyllite mix satisfies the acceptable limit (19.6 J/m) set by the Indian Standards Institute for wall tiles. Increasing the pyrophyllite content results in an increase in the apparent density of tiles, while shrinkage and water absorption decrease. The strength of fly ash tiles is attributed to the formation of a silicophosphate phase; in pyrophyllite rich tiles, it is attributed to the formation of a tridymite-structured T-AlPO(4) phase. Scanning electron micrographs show that the reinforcing rod shaped T-AlPO(4) crystals become more prominent as the pyrophyllite content increases in the sintered tiles.

Detoxification of aqueous zinc using fluorapatite--bearing lean grade rock phosphate.

Detoxification of aqueous zinc was studied using the adsorption technique by application of fluorapatite bearing low grade phosphate as a sorbent. The effects of particle size of adsorbent, contact time, initial concentration of zinc and temperature on the adsorption process were studied. Initial rate of adsorption of zinc increases with time up to 30 min and thereafter it reaches equilibrium. Percent adsorption is adversely affected by increase in initial concentration of zinc and increase in particle size of sorbent. Adsorption processes follow first order kinetics and are found to be exothermic.