Yi-Ming Kuo

Removal of COD from laundry wastewater by electrocoagulation/electroflotation.

The removal efficiency of COD in the treatment of simulated laundry wastewater using electrocoagulation/electroflotation technology is described. The experimental results showed that the removal efficiency was better, reaching to about 62%, when applying ultrasound to the electrocoagulation cell. The solution pH approached neutrality in all experimental runs. The optimal removal efficiency of COD was obtained by using the applied voltage of 5V when considering the energy efficiency and the acceptable removal efficiency simultaneously. The Cl(-) concentration of less than 2500ppm had a positive effect on the removal efficiency. The performance of the monopolar connection of electrodes was better than that of the bipolar connection in this work. In addition, the removal efficiency of using Al electrodes was higher in comparison with using Fe electrodes in the study. The highest COD removal amount per joule was found to be 999mgdm(-3)kWh(-1) while using two Al electrodes, although the removal efficiency increased with the number of Al plates.

Paired removal of color and COD from textile dyeing wastewater by simultaneous anodic and indirect cathodic oxidation

The anodic and indirect cathodic removals of color and COD from real dyeing wastewater were investigated simultaneously using a stacked Pt/Ti screen anode and a graphite packed-bed cathode in a divided flow-by electrochemical reactor. The anodically generated hypochlorite and cathodically generated hydrogen peroxide were the main species used to remove color and COD in the wastewater. Various experimental operating factors that can affect the removal efficiency were investigated, including the applied current density, the amount of NaCl added, the solution pH in alkaline ranges and the temperature. The color and COD removal efficiencies in the anodic chamber were much higher than those in the cathodic chamber. The overall (anodic plus cathodic) removal efficiencies increased with the applied current density, the amount of NaCl added and the temperature. In contrast, increasing the solution pH decreased the overall removal efficiency. The anodic and cathodic current efficiencies at 20 mA/cm(2) were 63.50% and 19.57%, respectively. In this work the total treatment cost for removing 1g COD was US

Associations of polybrominated diphenyl ethers (PBDEs) in breast milk and dietary habits and demographic factors in Taiwan.

0.643 when an air cylinder was used.

Vitrification for reclaiming spent alkaline batteries

The aim of this study was to examine levels of PBDEs in breast milk associated with seafood consumptions of Taiwanese mothers. Our participants were selected from healthy women recruited between December 2000 and November 2001 from a medical center in central Taiwan. The congeners of PBDEs in 20 milk samples were analyzed by a gas chromatograph with a high resolution mass detector. The mean level of BDE47 in breast milk from mothers with pre-pregnant BMI <22.0kg/m2 had a significantly higher magnitude compared to those with pre-pregnant BMI > or = 22.0kg/m2 (1.59 vs. 0.995ng/g lipid, p=0.041). We did not find significant correlations between PBDEs exposure levels and womens age, parity, blood pressure, annual household income, and education level. Women who ate more fish and meat did not show significantly higher PBDE levels than those who ate less, but a significant difference in PBDE levels was demonstrated between the higher (2.15ng/g lipid) and lower (3.98ng/g lipid) shellfish consuming subjects (p=0.002) after an adjustment for the confounders. The ratios of PCB153/BDE47, PCB153/BDE153, and PCB153/PBDEs were significantly correlated with frequent consumption of fish and shellfish. The PCB153/BDE153 ratio was not associated with the other dietary habits (i.e. meat). The ratios of PCB153/PBDEs may therefore be a new indicator for exposure as a result of seafood consumption.

An alternative approach to recovering valuable metals from zinc phosphating sludge.

The object of this study is to stabilize spent alkaline batteries and to recover useful metals. A blend of dolomite, limestone, and cullet was added to act as a reductant and a glass matrix former in vitrification. Specimens were vitrified using an electrical heating furnace at 1400 degrees C and the output products included slag, ingot, flue gas, and fly ash. The major constituents of the slag were Ca, Mn, and Si, and the results of the toxicity leaching characteristics met the standards in Taiwan. The ingot was a good material for use in production of stainless steel, due to being mainly composed of Fe and Mn. For the fly ash, the high level of Zn makes it economical to recover. The distribution of metals indicated that most of Co, Cr, Cu, Fe, Mn, and Ni moved to the ingot, while Al, Ca, Mg, and Si stayed in the slag; Hg vaporized as gas phase into the flue gas; and Cd, Pb, and Zn were predominately in the fly ash. Recovery efficiency for Fe and Zn was >90% and the results show that vitrification is a promising technology for reclaiming spent alkaline batteries.

Chemical and physical properties of plasma slags containing various amorphous volume fractions

This study used a vitrification process (with good potential for commercialization) to recover valuable metals from Zn phosphating sludge. The involved vitrification process achieves two major goals: it transformed hazardous Zn phosphating sludge into inert slag and it concentrated Fe (83.5%) and Zn (92.8%) into ingot and fine particulate-phase material, respectively. The Fe content in the ingot was 278,000 mg/kg, making the ingot a potential raw material for iron making. The fine particulate-phase material (collected from flue gas) contained abundant Zn (544,000 mg/kg) in the form of ZnO. The content (67.7%) of ZnO was high, so it can be directly sold to refineries. The recovered coarse particulate-phase material, with insufficient amount of ZnO, can be recycled as a feeding material for Zn re-concentration. Therefore, the vitrification process can not only treat hazardous materials but also effectively recover valuable metals.

An alternative approach for reusing slags from a plasma vitrification process.

In this study, municipal solid waste incinerator fly ash was vitrified using a plasma torch. The fly ash contained rich Ca, causing a high basicity of 2.43. Pure quartz was used as an additive to adjust the basicity. BET surface area analysis, X-ray diffraction analysis, and a scanning electron microscope were used to examine the physical properties of slags. The chemical stability and the acid resistance of slags were evaluated using the toxicity characteristics leaching procedure and tests of acid bathing. The results indicate that the plasma torch effectively vitrified the fly ash. Anthropogenic metals with low boiling points, such as Cd, Pb, and Zn, were predominately vaporized into flue gas. Most of the metals with high boiling points, such as Cr, Cu, and Mn, remained in the slag. After the vitrification, hazardous metals were noticeably immobilized in all slags. However, the slags with higher amorphous volume fractions were more effective in metal immobilization and in resisting acid corrosion. This indicates that SiO(2) enhanced the formation of the glassy amorphous phase and improved the resistance of acid corrosion and the immobilization of hazardous metals.

Encapsulation Behaviors of Metals in Slags Containing Various Amorphous Volume Fractions

Vitrification is widely applied to transform hazardous materials into inert slags. Raising the value of the recycled slag is an important issue from an economic point of view. In this study, an alternative approach for mixing a plasma slag with unsaturated polyester resin for making the dough-like molding composites is proposed. Physical properties, including ultimate tensile strength, Rockwell hardness, and the elongation at break, were measured to evaluate the characteristics of the composites. A scanning electron microscope and an X-ray diffractometer were used to examine the micro characteristics of the specimens. The chemical stability of the composites was estimated using the toxicity characteristic leaching procedure and a hot water bathing process. In an optimal slag loading (mass ratio of slag to unsaturated polyester resin) ranged from 0.1 to 0.2, the slag powder improved the physical properties of the composites. With an increased slag loading, excess slag powder weakened the structure of the resin, reducing the ultimate tensile strength and Rockwell hardness. The acid and water bathing tests indicated that the resin is decomposed in a hot environment. However, the slag was not destructed nor were the hazardous metals leached out. The results show that the molding method is an effective technology to recycle the slag.

Effect of NaOH on the vitrification process of waste Ni–Cr sludge

Abstract In this study, a melting process with addition of SiO2was applied to treat incinerator fly ash. To describe the encapsulation behaviors of metals quantitatively, the amorphous volume fraction (AVF) of slags was initially determined. Vitrification appeared to reduce the mobility of Cr, Cu, Mn, and Ni instead of significantly immobilizing Cd, Pb, and Zn. It was verified that SiO2enhanced the formation of an amorphous glassy structure. With the increase of SiO2, the crystalline phases would gradually diminish and transform into a higher silica-connected species. During the formation of slag matrix, Al, Ca, and Mg could modify the glass network, and consequently the encapsulation behaviors of these species would noticeably affect the chemical stability of slags. Significant immobilization of crust metals could be achieved only when a more compact and interconnected amorphous glass network was formed. Hence, it indicated that a higher AVF silica-based slag had a better potential to resist acid attack. In conclusion, for environmental protection, it is important to investigate the correlation between the encapsulation behaviors of metals and the crystalline characteristics of slag structure.

Effect of Al2O3 mole fraction and cooling method on vitrification of an artificial hazardous material. Part 1: variation of crystalline phases and slag structures.

This study investigated the effect of NaOH on the vitrification of electroplating sludge. Ni, the major metal in the electroplating sludge, is the target for recovery in the vitrification. Sludge and encapsulation materials (dolomite, limestone, and cullet) were mixed and various amounts of NaOH were added to serve as a glass modifier and a flux. A vitrification process at 1450 °C separated the molten specimens into slag and ingot. The composition, crystalline characteristics, and leaching characteristics of samples were measured. The results indicate that the recovery of Ni is optimal with a 10% NaOH mass ratio; the recoveries of Fe, Cr, Zn, Cu, and Mn all exhibited similar trends. The results of the toxicity characteristic leaching procedure (TCLP) show that leaching characteristics of the slag meet the requirements of regulation in Taiwan. In addition, a semi-quantitative X-ray diffraction analysis revealed that the main crystalline phase of slag changed from Ca(3)(Si(3)O(9)) to Na(4)Ca(4)(Si(6)O(18)) with a NaOH mass ratio of over 15%, because the Ca(2+) ions were replaced with Na(+) ions during the vitrification process. Na(4)Ca(4)(Si(6)O(18)), a complex mineral which hinders the mobility of metals, accounts for the decrease of metal recovery.