Effect Of Hydroxide Concentration Research Articles

Effect of Hydroxide Concentration and Adding Ascorbic Acid on Morphology Shape of Zinc Oxide Nanostructure Prepared by Simple Chemical Precipitation Method

A chemical precipitation method was used to prepare zinc oxide (ZnO) nanostructure in the present of zinc nitrate and ammonium hydroxide as zinc precursor and hydroxide precursor respectively. The effect of the hydroxide concentration and the effect of adding ascorbic acid as modifier into the mixture solution on the morphology property of zinc oxide was studied. The morphology and the structural of ZnO nanostructures were investigated by field-emission scanning electron microscope (FE-SEM) and X-ray diffractometer (XRD) techniques, respectively. The results showed that the basicity solution and adding stabilizer are important parameters on the morphology and structural properties of ZnO nanostructure. At a low hydroxide concentration, ZnO exhibited flower-like structure with short petal. With a further increase to higher concentration, ZnO crystal have more crystal directional growth. When the ascorbic acid was added, the morphology changed to particle-like structure. ZnO nanostructure with different shape might be used for specific applications such as gas sensor etc.

Spectral Induced Polarization Signatures of Hydroxide Adsorption and Mineral Precipitation in Porous Media

The spectral induced polarization (SIP) technique is a promising approach for delineating subsurface physical and chemical property changes in a minimally invasive manner. To facilitate the understanding of position and chemical properties of reaction fronts that involve mineral precipitation in porous media, we investigated spatiotemporal variations in complex conductivity during evolution of urea hydrolysis and calcite precipitation reaction fronts within a silica gel column. The real and imaginary parts of complex conductivity were shown to be sensitive to changes in both solution chemistry and calcium carbonate precipitation. Distinct changes in imaginary conductivity coincided with increased hydroxide ion concentration during urea hydrolysis. In a separate experiment focused on the effect of hydroxide concentration on interfacial polarization of silica gel and well-sorted sand, we found a significant dependence of the polarization response on pH changes of the solution. We propose a conceptual model describing hydroxide ion adsorption behavior in silica gel and its control on interfacial polarizability. Our results demonstrate the utility of SIP for noninvasive monitoring of reaction fronts, and indicate its potential for quantifying geochemical processes that control the polarization responses of porous media at larger spatial scales in the natural environment.

THE OXIDATION OF MANGANATE BY PERIODATE

The reaction between periodate and manganate ions in alkaline solution has been examined, and at 35 °C the rate is given by the equation, time being measured in minutes,[Formula: see text]It is proposed that the main reaction mechanism is[Formula: see text][Formula: see text]Hence k1 = 107 (g-molecule/l.)−1 min−1 at 35 °C, and it was found that the activation energy is about 13.9 kcal/g-molecule. Data of Carrington and Symonds (2), combined with the value for k1, make k2 = 2.8 × 106 (g-molecule/l.)−1 min−1. Added permanganate ions slow up the reaction; this is ascribed to the reverse of reaction (i) competing with reaction (ii). This gives a value for k3 of 2 × 107 (g-molecule/l.)−1 min−1; this is so large a rate constant as to make it probable that the hypomanganate ions are hydrolyzed. The effect of hydroxide concentration on the rate is ascribed to partial hydrolysis of manganate ions. The observed results would require the ionization constant of HMnO4− to be 7 × 10−11.