Orange mesocarp was obtained after removal of the epicarp and the endocarp from oranges. It was dried, pulverized and digested with 2% w/v sodium hydroxide at 80°C for 3 h. Alphaand micro-crystalline celluloses were extracted from the pulp using 17.5% w/v and 2.5 N hydrochloric acid, respectively. The physicochemical and powder properties of the extracted material were evaluated. Results obtained showed that the yield of a-cellulose from the orange mesocarp was 62.5% and that of microcrystalline cellulose 25.3%. The total watersoluble substances were 0.0018 g/g, ash 0.00035 g/g and the true density 1.760 g cm À1 , while the pH and hydration capacity are 6.61 and 2.916, respectively. Elemental analysis of the cellulose ash shows the absence of Pb and Mn and the preponderance of K, Na and Fe. The water sorption profile of the microcrystalline cellulose was also studied.

Biodiesel is the mono-alkyl esters of long chain fatty acids derived from renewable lipid feedstock, such as vegetable oils and animal fats, for use in compression ignition (diesel) engines. The conversion of component triglycerides in oils to simple alkyl esters with short chain alcohols like methanol and ethanol amongst others is achieved mainly by transesterification. The transesterification reaction, a reversible process proceeds appreciably by the addition of catalysts, which can be acidic, basic or organic in nature, usually in molar excess of alcohol. The economy of the process depends on the type and quantity of catalyst used among other factors. The catalyst can be homogeneous or heterogeneous depending on whether it is in the same or different phase with the reactants; oils and alcohols. This paper attempts to give an insight into some of the various types of catalysts that have been used to effect the transesterification of vegetable, waste and animal oils in biodiesel production.

We present a study on the pseudocapacitive properties of birnessite-type MnO 2 grafted on highly graphitized onion-like carbon (OLC/MnO 2 ). In a three-electrode setup, we evaluated two different substrates, namely a platinum disc and nickel foam. The OLC/MnO 2 nanohybrid gave large specific capacitance (C sp ) of 295 and 323 F g -1 (at 1 A g -1 ) for the Pt disc and Ni foam, respectively. In addition, the Ni foam substrate exhibited much higher rate capability (power density) than the Pt disc. A symmetrical two-electrode device, fabricated with the Ni foam, showed a large C sp of 254 F g -1 , specific energy density of 5.6 Wh kg -1 , and a high power density of 74.8 kW kg -1 . These values are the highest for onion-based electrodes so far. The device showed excellent capacity retention when subjected to voltage-holding (floating) experiments for 50 h. In addition, the device showed low equivalent distributed resistance (EDR ≈ 3 Ω cm 2 ) with very short time constant (τ = 40 ms). This high rate handling ability of the OLC/MnO 2 nanohybrid, compared to literature reports, promises new opportunities for the development of aqueous-based pseudocapacitors.

No abstract

Activated carbon produced from fluted pumpkin (Telfairia occidentalis) seed shell was utilized for the removal of lead (II) ion from simulated wastewater. Adsorption tests were carried out in series of batch adsorption experiments. Several kinetic models (Bhattacharya-Venkobacher, Elovich, pseudo first and second order, intra-particle and film diffusion) were tasted for conformity to the experimental data obtained. The Langmuir and Freundlich adsorption models were also used to test the data. The amount of lead (II) ion adsorbed at equilibrium from a 200 mg/L solute concentration was 14.286 mg/g. The experimental data conform very well to the pseudo-second order equation where equilibrium adsorption capacities increased with increasing initial lead (II) concentration. The rate of the adsorption process was controlled by the film (boundary layer) diffusion as the film diffusion co-efficient values obtained from data analysis were of the order of 10 6 cm 2 /s. From the plots, the linear regression coefficient (R 2 ) of the Langmuir model was higher than that of the Freundlich: the adsorption isotherm obeyed the Langmuir model better than the Freundlich model.