Molybdenum recovery from oxygen pressure water leaching residue of Ni–Mo ore

This article investigated molybdenum recovery from oxygen pressure water leaching residue of Ni–Mo ore using alkaline leaching, followed by chemical treatment of leach liquor. Parameters affecting Mo leaching rate, such as sodium hydroxide concentration, reaction time, a liquid-to-solid ratio, and temperature for the preliminary alkaline leaching were experimentally determined. The results showed that more than 88 % of molybdenum was leached under the optimum conditions (2.5 ml·g^?1 NaOH, 80 °C, a liquid to solid ratio 3 ml·g^?1, and reaction time 3 h). After the purification of leach liquor, a CaMoO₄ product of 99.2 % purity could be obtained by CaCl₂ precipitation method. The whole Mo recovery reached about 82.7 %.     

Scanning electron microscopic studies of porous carbon electrodes used in alkaline fuel cells

Multilayer, polytetrafluoroethylene (PTFE)-bonded gas diffusion-type electrodes were prepared by the rolling method. Changing the electrode structure and manufacturing method improved alkaline fuel cell performance. Activated carbon or carbon black was used as the support material, with platinum as a catalyst and nickel screen as the backing material. Double-layer electrodes possessed both active and diffusion layers on the backing layer. However, the single-layer electrodes had only the active layer on the backing layer. The electrodes were prepared by using different PTFE contents and platinum loadings. In this study the surface photographs of the electrodes were taken with a scanning electron microscope. Elemental analyses of the surface elements were performed by energy dispersive X-ray spectroscopy (EDXS). Electrodes having activated carbon on their surfaces were observed to possess a nonuniform and porous structure. These electrodes showed better performance than electrodes having carbon black, which presented a uniform and nonporous structure.     

Utilization of pretreated molasses for serine alkaline protease production with recombinant bacillus species

Recombinant Bacillus amyloliquefaciens, Bacillus cereus, Bacillus subtilis , and Bacillus licheniformis were used for the production of serine alkaline protease (SAP) utilizing chemically and/or physically pretreated molasses. The highest enzyme activity was obtained with r- Bacillus subtilis , with the complex medium involving physically treated molasses having 20 kg m m 3 initial sucrose concentration in small-scale, agitation- and heating rate-controlled bioreactors at t=63 h. Effects of oxygen transfer were investigated in 3.5 dm 3 laboratory bioreactors under two different agitation rates with r- B. subtilis . Increase in the oxygen transfer rate increased the observed activity and caused the cultivation time of maximum activity shift to the earlier stages of the fermentation. At Q/V=0.5 vvm and N=750 min m 1 , SAP activity reached 2250U cm m 3 at t=36 h.     

FED-BATCH FERMENTATION OF BACILLUS CLAUSII FOR EFFICIENT PRODUCTION OF ALKALINE PROTEASE USING DIFFERENT FEEDING STRATEGIES

The effect of different feeding strategies, involving constant rate and linear feeding with negative and positive slopes, on protease production of an indigenous Bacillus clausii was investigated. The results indicated that alkaline protease was produced at high levels soon after glucose was completely consumed. Alkaline protease activity was at a maximum during the constant feeding rate and in the absence of glucose and presence of mineral salts and yeast extract in the feed medium. Maximum protease production in the fed-batch culture using an optimized level of feeding composition was 2430 ± 67 U/mL, which increased by up to 35% when compared to the 1800 ± 14 U/mL produced during batch culture. During batch fermentation, the protease yield and productivity obtained were 90000 U/g and 64285 U/L · h; however, under fed-batch conditions, these were 121500 U/g and 71470 /L · h, respectively. Hence, the suggested strategy has the potential to be applied to industrial production of protease used in detergent products.     

Humic Acid from Livestock Dung: Ecofriendly Corrosion Inhibitor for 3SR Aluminum Alloy in Alkaline Medium

Humic acids (HAs) extracted from cow, goat, and poultry dung were studied. Extraction was performed by treating the source materials with acid hydrolysis using hydrochloric acid (HCl) before alkaline extraction with sodium hydroxide (NaOH). Yields of 3.33, 2.67, and 1.28% dry weight were obtained from cow, goat, and poultry dung respectively. The extracted humic acids were characterized using Fourier transform-infrared (FT-IR) and ultraviolet-visible (UV-vis) spectroscopy techniques. The results obtained were in good agreement with commercial HA (Sigma-Aldrich). The humic acid extracted from cow dung was used to evaluate its corrosion inhibition potential for alkaline-induced corrosion of 3SR aluminum alloy using weight loss and electrochemical (potentiodynamic polarization) techniques at 30°–60°C. Results obtained show that the humic acid functions as an excellent corrosion inhibitor for aluminum alloy in 0.1 M NaOH solution. Corrosion inhibition efficiency increased with increase in humic acid concentration but decreased with rise in temperature. Results from potentiodynamic polarization measurements show that the HA behaved mostly as a mixed-type inhibitor. Adsorption of the humic acid was found to obey the Langmuir adsorption isotherm at all concentrations and temperatures studied. The mechanism of physical adsorption has been proposed based on the trend of inhibition efficiency with temperature. The proposed mechanism was also corroborated by kinetic and thermodynamic parameters obtained.     

Generation of Oxygen-Containing Radicals in the Aqueous Media of Mechanical Pulping

Mechanical treatments of veratrylglycerol-β-syringaldehyde ether (M) were conducted with a ceramic ball mill or a vibration ball mill in the presence of water and n-paraffin alcohols which were used as ·OH scavengers. Addition of 1% each of the alcohols to the milling process of Compound (M) greatly decreased the yields of the products, e.g. veratryl alcohol 2, vanillin 3, syringaldehyde 4, 3,5-dimethoxy-p-benzoquinone 5, 3,5-dimethoxy-p-hydroquinone 6 and others. Another addition of n-paraffin alcohols to aqueous media during the millings also significantly reduced the concentration of H₂O₂. When phthalic hydrazide (P) was treated in the mills in the aqueous media, triacetoxyphthalazine (1A), 3-acetoxyphthalic acid (2A) and other products were separated from the acetates of the reaction mixtures. Results mentioned above disclosed the generation of ·O₂H, ·OH, and ·H in the aqueous media during the mechanical treatments.     

The Influence of Alkaline Surface Fibre Treatment on the Impact Properties of Sugar Palm Fibre-Reinforced Epoxy Composites

The aim of this study is to determine the impact properties of sugar palm fibre-reinforced epoxy polymer composite after introduce the alkaline treatment to the fibre. The fibre was treated by alkaline solution with 0.25 M and 0.5 M NaOH solution for 1 hour, 4 hours, and 8 hours soaking time. Hand lay up process was used to prepare the composite specimens with 10% volume fraction. The dimensions of the specimen used to carry out the test were adapted from ASTM D256 for Izod Impact testing. The higher impact strength of treated sugar palm fibre reinforced epoxy composite took place at 0.5 M NaOH solution with 8 hours soaking time, i.e., 60 J/m with improving by 12.85% from untreated composite.     

Economical and Ecological Biotreatment/Half Bleaching of Cotton-Containing Knit Fabrics on Industrial Scale

ABSTRACT

Bio-scouring/half bleaching of cotton-containing knit fabrics was carried out on an industrial scale. A comparison between the traditional hot-alkaline scouring/half bleaching and the enzymatic scouring/half bleaching from product quality, economic as well as environment perspectives were made. The results detailed in this case study indicate that (1) the loss in fabric weight as well as the improvement in degree of whiteness are governed by the treatment method (i.e., hot-alkaline scouring/half bleaching > bio-scouring/half bleaching; (2) bio-scouring/half bleaching technique gives rise to better bleaching fabric softness, higher strength retention along with greater depth of shades; (3) the extent of improvement in fabric wettability follows the descending order: hot-alkaline scouring/half bleaching = bio-scouring/half bleaching > > untreated; and (4) the saving in materials and energy costs, the improvement in fabric properties as well as the reduction in pollutants concentrations (i.e., better wastewater quality are determined by the pretreatment technique and follow the descending order: bio-scouring/half bleaching > alkaline-scouring/half bleaching.     

Synthesis and electrochemical properties of two types of highly ordered mesoporous MnO2

Mesoporous MnO₂ with uniform nanorod morphology and mesoporous β-MnO₂ were prepared using SBA-15 and KIT-6 as the templates, respectively. XRD, nitrogen adsorption analysis, SEM, TEM and EDX techniques were used for the structural characterization. The electrochemical properties of the MnO₂ samples were studied using alkaline Zn/MnO₂ batteries in a 9 M KOH electrolyte solution. Compared to the commercial electrolytic manganese dioxide (EMD), the discharge capacity of the mesoporous MnO₂ nanorods increased by 74.98%, 119.74% and 146.19% at constant currents of 50, 250 and 500 mA g⁻¹, respectively, while the discharge capacity of the mesoporous β-MnO₂ increased by 63.58%, 95.14% and 100.23%.