Effect Of Acid Leaching Research Articles

Combined Diffusion, Adsorption, and Reaction Studies of n-Hexane Hydroisomerization over Pt/H–Mordenite in an Oscillating Microbalance

Uptake experiments under full catalytic conditions have been performed using a tapered element oscillating microbalance. The effect of acid leaching on the diffusivity and reaction of n-hexane in Pt/H–mordenite has been established from these experiments. For acid-leached Pt/H–mordenite the hydroisomerization activity is four times higher than for untreated Pt/H–mordenite. Acid leaching gives rise to an acceleration of the uptake of n-hexane under reaction conditions. Analysis of the data implies the faster uptake to be predominantly accounted for by a shorter intracrystalline diffusion path length, as diffusivities are in the same range for both catalysts. The shorter path length results from the mesoporous structure of H-mordenite generated by acid leaching. From the diffusivities, from the path lengths, and by using the Thiele model, it is inferred that the intrinsic rate constant of acid-leached Pt/H–mordenite is twice that of the untreated Pt/H–mordenite. The facilitated transport of reactants and products doubles the effectiveness factor, thus also contributing to the overall activity enhancement for n-hexane hydroisomerization after acid leaching.

Effect of organic acids on ferric iron removal from iron-stained kaolinite

The effect of various organic acids viz. acetic, formic, citric, ascorbic, succinic, tartaric and oxalic acids, on the iron removal and the resulting brightness improvement of an iron-stained kaolinitic clay from Kalliyur, Thiruvananthapuram, South India, has been investigated. Oxalic acid was found to give the best results both at room temperature as well as at high temperatures because of its high acid strength, good complexing capacity and reducing power. The reaction parameters such as time, temperature and reagent concentration were optimised. The optimum conditions required for achieving brightness ≥80% were: temperature — 100°C, oxalic acid concentration — 0.1 M and reaction time — 90 min. The leaching tests at room temperature for 30 days improved the brightness from 66.3 to 83.5% ISO. The corresponding iron oxide removal was of the order of ∼80%. The addition of ferrous ions and protons improved the reaction kinetics. The leaching tests carried out on previously beneficiated samples using magnetic separation showed only a slight improvement in brightness indicating that brightness depended more on the surface coated iron oxides rather than on the discrete particles. The effect of acid leaching on the physical properties of the clay such as brightness, plasticity, viscosity, specific surface area and pore volume were compared. The slight increase in the specific surface area and the pore volume are suggestive of removal of the cementing non-crystalline alumina, silica and iron oxides from the clay surface and also due to the resulting delamination to a limited extent. No marked change was observed in the viscous as well as the plastic properties due to the deferration treatments.

Effect of acid leaching on rheological behavior of silicon nitride aqueous suspension

Effect of acid leaching on rheological behavior of silicon nitride aqueous suspension

Effects of acid leaching on the shear strength of Namurian shale : Anderson, W F; Cripps, J C Proc 26th Annual Conference of the Engineering Group of the Geological Soceity, The Engineering Geology of Weak Rock, Leeds, 9–13 September 1990P159–168. Publ Rotterdam: A A Balkema, 1993 (Engineering Geology Special Publication No. 8)

Effects of acid leaching on the shear strength of Namurian shale : Anderson, W F; Cripps, J C Proc 26th Annual Conference of the Engineering Group of the Geological Soceity, The Engineering Geology of Weak Rock, Leeds, 9–13 September 1990P159–168. Publ Rotterdam: A A Balkema, 1993 (Engineering Geology Special Publication No. 8)

Microcalorimetric and Gas Chromatographic Studies of Microbial Activity in Water Leached, Acid Leached and Restored Soils

The effect of acid leaching on the microbial activity in soil, was studied by simultaneous measurements of heat production using microcalorimetry and of carbon dioxide evolution employing gas chromatography. As the activity decreased after acid leaching, attempts were made to restore the soil, i.e. increase the microbial activity to a normal level again. This was performed by increasing the pH of the soil and by different additions to the soil. As judged by calorimetry, significant, but not complete, restoration was obtained. The results from the C02-measurements indicate complete restoration. The differences in results could partly be explained by the fact that some of the CO2 evolved from soil may have nonbiological origin.

The effect of acid leaching and heating on flux inclusions in flux-grown lanthanum lead manganite catalyst

The formula of flux-grown lanthanum lead maganite catalyst, La .7Pb .3MnO 3, was determined by flame spectrometry. Sequential acid leaching studies of the crushed crystals have shown that minute flux inclusions significantly alter the apparent surface composition. These inclusions were readily removed by acid etching thereby exposing La .7Pb .3MnO 3. Heating the crystals at 1200°C caused Pb inclusions to migrate from the bulk to the surface.

K-Ar ages of seamounts along the Japan Trench and the effect of acid leaching on the K-Ar age of a dredged submarine rock

The ages of, submarine rocks dredged from seamounts along the Japan Trench were determined by K-Ar method. In order to obtain more reliable age, the effect of acid leaching on an altered submarine rock was examined. Some samples treated by acid solution gave K-Ar ages up to 20% older than the original untreated sample. This result suggests a possibility that, if suitable acid teratment conditions are found, they would result in more reliable ages for submarine rocks. Some submarine rocks dredged from seamounts along the Japan Trench on the oceanic side gave K-Ar ages of about 70-80 m.y, whereas a sample dredged from a seamount on the Japanese Islands side gave a substantially younger age. Considering the present result as well as previous data, the last volcanic activity along the Japan Trench seems to have occurred about 70-80 m.y ago or older.