<table class="NormalTable"><tbody><tr><td width="550"><span class="fontstyle0">This study intends to investigate the relationship between disclosure, asymmetry<br />information and cost of capital. The samples of this study cover about 40 manufacturer companies listed at the Jakarta Stock Exchange in 2004 that selected using purposive random sampling. The analysis method used to test is simple regression, Kolmogorov-Smirnov and P-Plot. The study result were as follows, first hypothesis show there is no relationship between disclosure and asymmetry information. Second hypothesis result show that there is a positive relationship between asymmetry information and cost of capital. Third hypothesis, there is a relationship between disclosure and cost of capital.</span></td></tr></tbody></table>
Humic acid modifying magnetite particles (Mag-HA) were developed for recovery of gold from chloride solution (HAuCl4). The Mag-HA particles were prepared by co-precipitation procedure with Fe(III) and Fe(II) chloride salts, sodium hydroxide, and humic acid. FTIR characterization for Mag-HA after modification indicated the presence of the specific absorption for functional groups of humic acid and Fe-O bonds, though with lower intensity. The Mag-HA particles exhibited a typical superparamagnetic characteristic with a saturation magnetization of 66.99 emu/g. The Mag-HA particles were applied for AuCl4- adsorption and results showed that the optimum adsorption of [AuCl4]- onto Mag-HA was found at pH 3. The adsorption kinetics can be described by a pseudo-second order equation and the adsorption isotherm of the Mag-HA particles agreed well with Langmuir adsorption equation. The maximum adsorbed amount of [AuCl4]- was 0.62 mmol/g and the XRD analysis confirms that the adsorption of Au(III) by Mag-HA was accompanied by the formation of elemental gold.
Gallic acid-modified magnetites were synthesized by one and two-step reactions via the newly developed sonochemical co-precipitation method. The two-step reaction included the formation of magnetite powder and mixing the magnetite powder with gallic acid solution, while the one-step reaction did not go through the formation magnetite powder. The obtained gallic acid-modified magnetites were characterized by the Fourier Transform Infrared (FTIR) spectroscopy, the X-Ray Diffraction (XRD) and the Scanning Electron Microscopy (SEM). More over, the magnetic properties were studied by using a Vibrating Sample Magnetometer (VSM). The characterization results showed that there were differences in crystalinity, surface morphology and magnetic properties of products that were formed by one and two-step reactions.
Sonochemical technology is a technology that involves ultrasonic waves in chemical reactions. In this study, humic acid isolated from peat soil has been successfully modified with magnetite (HA-Fe3O4) using sonochemical technology. Characterization of the physical and chemical properties of HA-Fe3O4 was carried out using FTIR, XRD, SEM and VSM. HA-Fe3O4 was used for recovery of gold from simulated gold waste (HAuCl4). FTIR characterization showed that the interaction between HA and Fe3O4 was through hydrogen bonds. The crystal size of HA-Fe3O4 using the Debye-Scherrer equation based on the XRD diffractogram was 12.4 nm. The saturation magnetization value of HA-Fe3O4 obtained was 52.80 emu/g. Adsorption studies at various pH showed that HA-Fe3O4 has been successful in recovering of gold from simulated gold waste. The % recovery of gold was 99%. Gold recovery occurs through the adsorption process followed by reduction of Au (III) to Au(0).
The rapid development of the batik industry can pollute water resources and become an increasingly severe problem. This research studies the adsorption-desorption of naphthol blue-black (one of the dyes in batik liquid waste) by magnetite modified humic acid (HA-Fe 304 ). The adsorption isotherm was studied using the Langmuir and Freundlich isotherm models. Meanwhile, desorption agents used in this study were distilled water and hydrochloric acid. The results show that the adsorption isotherm followed the Langmuir adsorption model with a maximum adsorption capacity of 2.41 mmol / g. Desorption studies show that the desorption efficiency of naphthol blue-black on HA-Fe 304 is 0.058 % and 5.86 % in the desorption agent of distilled water and HC1 (1M)
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