Hydrometallurgical Treatment of Waste Printed Circuit Boards: Bromine Leaching

This paper demonstrates the recovery of valuable metals from shredded Waste Printed Circuit Boards (WPCBs) by bromine leaching. Effects of sodium bromide concentration, bromine concentration, leaching time and inorganic acids were investigated. The most critical factors are sodium concentration and bromine concentration. It was found that more than 95% of copper, silver, lead, gold and nickel could be dissolved simultaneously under the optimal conditions: 50 g/L solid/liquid ratio, 1.17 M NaBr, 0.77 M Br2, 2 M HCl, 400 RPM agitation speed and 23.5 °C for 10 hours. The study shows that the dissolution of gold from waste printed circuit boards in a Br2-NaBr system is controlled by film diffusion and chemical reaction.

Fabrication and characterization of brominated matrimid® 5218 membranes for CO2/CH4 separation: application of response surface methodology (RSM)

In the present study, special effort was focused on increasing permeability of matrimid membranes. For this objective, a bromination reaction was carried out. The reaction of bromine with polymer was investigated using Fourier transform infrared (FTIR) spectroscopy analysis. A combination of pristine and brominated matrimid was used to prepare modified membranes due to the fact that brominated matrimid membranes were too delicate. Employing a gas separation membrane unit, the permeability of pristine and modified membranes for pure gases (CO2 and CH4) was studied. Modified membranes were much more permeable and less selective than pristine membranes. In fact, the increase in permeability of modified membranes can be attributed to the rise in the fractional free volume of modified membranes. Thermal properties of modified and unmodified membranes were also studied by thermal gravimetric and differential scanning calorimetry analysis. As a result, thermal resistance of modified membranes decreased in a limited temperature range. Modified membranes indicated smaller values of tensile strength than pristine membranes which were assessed using tensile strength analysis. The parameters which can affect the pure gases permeation through membranes such as, bromine concentration in modified membranes and operating pressure were considered as variables and the experimental design was carried out.

Removal of Gas-Phase Elemental Mercury by Bromine-Impregnated Activated Carbon

Br-impregnated activated carbon for gas-phase elemental mercury adsorption experiments were carried out at a fixed-bed system to get the suitable mass fraction of KBr impregnation solution. Hg removal efficiency of 1% wt KBr-ACs was 69.0%, while that of 10% wt KBr-ACs was 57.9%. Both of them were higher than that of the raw activated carbon, 42.2%. The removal efficiency of Hg0 was not proportional to bromine concentration. Under 80-180°C, Hg removal efficiency of 1% wt KBr-ACs were 68.3%-71.8%, and at 140°C it reached the highest due to the increasing chemical adsorption ability of the functional groups which was on the surfaces of activated carbons by impregnating. At 160°C, Hg removal efficiency was lower than that at 140°C due to desorption making physical adsorption decrease, so that the total adsorption decreased.

ELEMENTAL BALANCE IN SOY SAUCE

We have measured the elemental concentrations of soy sauce and its actual raw materials which are used in a certain soy sauce factory. In the present measurement, we measured de-fatted soybean, wheat and salt as raw materials and soy sauce and soy sauce waste as final products. Five kinds of elements, such as Mn, Fe, Cu. Zn and Br, were detected. We obtained elemental concentrations of them except for Mn in each materials. The measured elemental concentration in soy sauce agreed well each other with the calculated one within the experimental errors using the measured concentration in the raw mateials and their weight in actual producing process. Contrary to our expectation, it was found that wheat contributes to soy sauce bromine concentration dominantly in the present case.

TRACE ELEMENT ANALYSIS IN SOY SAUCE II

Trace elements in four kinds of soybean and three kinds of salt have been measured by means of in-air PIXE. In soybeans, which were made in Japan, America, Canada and China, six kinds of trace elements were detected, such as Mn, Fe, Ni, Cu, Zn and Br. The concentration of these elements varied depending on the place they were made. American soybean showed characteristic feature compared with other soybeans. As to the bromine concentration, American soybean contains ten times as much as Japanese one. In salts Br and Sr were detected.

The Wet Etching of CdZnTe Substrates for OMVPE Growth

ABSTRACTThe etching of CdZnTe substrates by bromine-methanol solutions was studied by chemi-mechanical polishing. Over a bromine concentration of 0.5 to 3.5 volume percent, the etch rates varied linearly with bromine concentration, were independent of substrate orientation, and, within experimental uncertainties, were identical to those for the etching of CdTe. The etched samples were used as substrates for the organometallic vapor phase epitaxy (OMVPE) growth of CdTe in an impinging jet reactor. The bromine concentration used in etching did not affect the growth rate or the morphology of the deposited CdTe films, but a higher defect density was found for the film grown on a substrate with the orange-peel structure.