Barsha Dash

Influence of Synthesis Temperature on the Growth and Surface Morphology of Co3O4 Nanocubes for Supercapacitor Applications

A facile hydrothermal route to control the crystal growth on the synthesis of Co3O4 nanostructures with cube-like morphologies has been reported and tested its suitability for supercapacitor applications. The chemical composition and morphologies of the as-prepared Co3O4 nanoparticles were extensively characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Varying the temperature caused considerable changes in the morphology, the electrochemical performance increased with rising temperature, and the redox reactions become more reversible. The results showed that the Co3O4 synthesized at a higher temperature (180 °C) demonstrated a high specific capacitance of 833 F/g. This is attributed to the optimal temperature and the controlled growth of nanocubes.

Role of hydrazine and hydrogen peroxide in aluminium hydroxide precipitation from sodium aluminate solution

Aluminium hydroxide precipitation from synthetic sodium aluminate solution was studied in the presence of hydrazine or hydrogen peroxide. The addition of low concentration of hydrazine is found to be effective, while higher amount of hydrogen peroxide is required to generate similar effect. XRD data confirm the product phase to be gibbsitic by nature. The scanning electron micrographs (SEM) show that agglomerated products form in the presence of hydrazine while fine discrete particles are produced with hydrogen peroxide. The probable mechanism of precipitation in the presence of hydrazine and hydrogen peroxide is also discussed.

Adsorption of Pb(II) Ions from Aqueous Solutions Using a Low Grade Iron Ore as an Effective Adsorbent

The use of banded hematite quartzite (BHQ), a low-grade iron ore, as an adsorbent for the removal of lead(II) ions from aqueous solutions was studied. X-Ray diffraction (XRD) studies of BHQ ore showed the presence of hematite and quartz as the major mineral phases, while FT-IR studies showed the presence of Si-OH and Fe-OH sites capable of exhibiting strong adsorption properties. SEM/EDS studies indicated that the particles of the materials were relatively fine and contained Fe, Si and O, together with trace amounts of Al. Batch adsorption studies demonstrated that BHQ exhibits a significant capacity towards the adsorption of Pb(II) ions from aqueous solution. The parameters of the adsorption process investigated in this study included the effect of agitation time, initial Pb(II) ion concentration, adsorbent dosage, pH and temperature. The adsorption of Pb(II) ions onto BHQ increased as the pH of the aqueous medium increased from 1.8 to 6.5. Maximum removal of Pb(II) ions (99.8%) from aqueous solutions with an initial Pb(II) ion content of 10 mg/ℓ occurred at pH 5.0. The sorptions data for Pb(II) ions were correlated using the Langmuir and Freundlich isotherms, thereby allowing an analysis of the equilibrium data obtained at room temperature. The Langmuir isotherm indicated monolayer formation on the adsorbent surface.

Synthesis and characterization of fibrous nickel hydroxide obtained from spent nickel catalyst

The recovery of nickel from spent nickel catalyst for the preparation of nickel hydroxide was studied. Nickel was extracted from the spent catalyst by acid leaching with 1 mol/L sulfuric acid at 90 C. Purified nickel solution was used in the preparation of nickel hydroxide. Three different methods, namely urea hydrolysis, conventional, and hydrothermal methods, of precipitation using NaOH were employed to get various nickel hydroxides samples named as Ni(OH) 2-U, Ni(OH)2-C, and Ni(OH)2-H, respectively. Hydrothermal treatment induced better crystallinity in the Ni(OH)2 compared with conventional method. Both Ni(OH)2-C and Ni(OH) 2-H samples have mixed phases of β-Ni(OH)2 and α*-Ni(OH)2·0.75H2O phases, whereas Ni(OH)2-U has only α*-Ni(OH) 2·0.75H2O. TEM image of Ni(OH)2-U sample shows rod-like Ni(OH)2 structures. Among all, Ni(OH)2-U shows the best electrochemical activity.

Extraction of copper by leaching of electrostatic precipitator dust and two step removal of arsenic from the leach liquor

The paper deals with the extraction of copper from the deposited material of the liner of the electrostatic precipitator (ESP) of the copper smelter plant. These precipitates of ESP liner (ESP dust) generally contain mixed phases of copper and arsenic. An attempt is made to extract copper from ESP dust, subsequently removing arsenic from the leach liquor. The ESP dust containing paramelaconite (6CuO·Cu2O), α-domeykite (Cu3As), metadomeykite (Cu3As), enargite (Cu3AsS4) and (Cu,Fe) SO4·H2O is not a naturally occurring geological mineral; thus comparatively high acid concentration and temperature are required to break the matrix of this mixed material so as to liberate the content. The leaching efficiency of copper was 97% at 97 °C. The acid concentration of 1.5M and pulp density of 20% was found to be optimum. The removal of arsenic as ferric arsenate was carried out in two stages: increasing the pH and precipitation of arsenic by adjusting pH of the solution and by adding ferrous sulfate and hydrogen peroxide. The optimum removal of arsenic was 95% when pH was raised to 2.35 followed by precipitation. The key progression of the process is the recovery of copper from ESP dust as well as removal of arsenic from the leach liquor.