H. Paul Wang

Fate of bromine in pyrolysis of printed circuit board wastes.

Behavior of Br in pyrolysis of the printed circuit board waste with valuable copper and oil recycling has been studied in the present work. Experimentally, pyrolysis of the printed circuit board waste generated approximately 40.6% of oils, 24.9% of noncondensible gases and 34.5% of solid residues that enriched in copper (90-95%). The cuts of the oils produced from pyrolysis of the printed circuit board waste into weighted boiling fraction were primarily light naphtha and heavy gas oil. Approximately 72.3% of total Br in the printed circuit board waste were found in product gas mainly as HBr and bromobenzene. However, by extended X-ray absorption fine structural (EXAFS) spectroscopy, Cu-O and Cu-(O)-Cu species with bond distance of 1.87 and 2.95 A, respectively, were observed in the solid residues. Essentially, no Cu-Br species was found.

Synthesis of zeolite ZSM-48 from rice husk ash

Abstract Zeolite ZSM-48 with a very high crystallinity (99% + ) can be synthesized from a reaction mixture containing a silica source from rice husk gasification ash. The difference in the cracking behavior of n -hexane for zeolites ZSM-5 and ZSM-48 may be attributed to the unique two-dimensional channel structure for the ZSM-48. The ammonia desorption data also indicate that the influence of the channel system of ZSM-48 could play an important role in the molecular traffic control.

Pyrolysis kinetics of refuse-derived fuel

Refuse-derived fuel (RDF) was mechanically separated from municipal solid waste (MSW) in a 300 TPD (tons per day) waste pretreatment plant. Pyrolysis of the RDF produced approximately 28% of oils, and 30% of noncondensible hydrocarbon gases and 42% of solid residues at 773 K. Thermal gravimetric analysis (TGA) techniques were used in quantitative prediction of the RDF pyrolysis rate. The global pyrolysis reaction rate was calculated from key component fractions (paper, LDPE, HDPE, PS, and PVC) of RDF using the weighed sum method. Good agreement was found in pyrolysis kinetics between RDF itself and the weighed sum method of the plastic components in RDF. Pyrolysis of RDF in the fixed-bed reactor also had a similar result. This approach allows one to easily account for RDF composition variations, thus rendering the model more generally valid.

Point defects in sputtered NiO films

The dominant point defects in p-type NiO films were determined by analyzing the coordination number (CN) change with various annealing temperatures and the composition profile of double-layer films deposited individually in oxygen and in argon atmospheres. The results show that the nonstoichiometry of sputtered NiO film is determined by the number of nickel atoms rather than by the number of oxygen atoms. It is concluded that nickel vacancies are the dominant point defects that result in the electrical conductivity of NiO films.

Shape selectivity of trace by-products for supercritical water oxidation of 2-chlorophenol effected by CuO/ZSM-48

Abstract Shape selectivity of trace by-products in supercritical water oxidation (SCWO) of 2-chlorophenol (2CP) catalyzed by CuO/ZSM-48 has been investigated. Experimentally, destruction efficiency of 2CP in the SCWO process is effectively enhanced by CuO/zeolite catalysts. In the two-dimensional (2D) channels of ZSM-48, formation of undesired by-products such as polycyclic aromatic hydrocarbons (PAHs) and higher chlorinated phenols (via the Cl-reinsertion) is extremely suppressed in the SCWO of 2CP compared to those observed for zeolites ZSM-5 and Y with three-dimensional (3D) channel structure and larger pore sizes, respectively. The main oxidation active species on CuO/ZSM-48 surfaces were CuO and Cu 2 O determined by X-ray photoelectron spectroscopy (XPS). Ratios of the surface species CuO/Cu 2 O are between 13.4 and 14.1 in the SCWO process. However, the existence of the Cu–O and Cu–Cu species with a Cu–O/Cu–Cu ratio of 3.5 in the copper catalyst is also observed by extended X-ray absorption fine structure (EXAFS) spectroscopy. Furthermore, since the absence of Cu–Cl species in the XPS and EXAFS spectra, one would suggest that copper in the channels of ZSM-48 is unlikely involved in the abstraction of Cl species from 2CP in the SCWO process.

A process development for gasification of rice husk

Abstract Rice husk has been recognized as a potential source of energy. Thus, the main objective of this work was to develop a rice husk gasification process. Diffuse reflectance infrared spectra reveal that partial oxidation of rice husk at reaction temperatures below 1000 K would also allow recover valuable of amorphous silica materials. In the laboratory-scale fixed-bed and bench-scale downdraft experimental approaches, gasification of rice husk was accompanied by a substantial production of syngas at 760–900 K. It appears that in order to generate 10 kW electric power, approximately 28 kg/h of rice husk must be gasified. The rice husk gasification process, in terms of heat requirements, can be self-sustaining.

Oxidation of printed circuit board wastes in supercritical water

Abstract A feasibility study for oxidation of printed circuit board wastes with NaOH in supercritical water has been investigated. Experimentally, Br species in the printed circuit board resin was abstracted by sodium cations and the destruction efficiency of the waste was enhanced in the supercritical water oxidation (SCWO) process. By X-ray diffraction (XRD) spectroscopy, Cu2O, CuO, and Cu(OH)2 were found in the SWCO solid residue of the printed circuit board wastes. The extended X-ray absorption fine structural (EXAFS) spectra indicated that the bond distance of Cu–O in the residue was 1.87 A with a coordination number of 2.61. Since the Cu–Br species was not observed by XRD and EXAFS spectroscopies, one may eliminate the possibility that the copper was involved in the abstraction of bromine species from the resin matrix in the SCWO process.

Recycling of harbor sediment as lightweight aggregate

Sediment sampled from Taichung Harbor was mixed with local reservoir sediment at different weight ratios to prepare lightweight aggregate at 1050, 1100, and 1150 degrees C. A pressure of 3000 or 5000 psi was used to shape the powder mixtures into pellets before the heating processes. The results indicate that the leaching levels of trace metals from the lightweight aggregate samples are considerably reduced to levels less than Taiwan Environmental Protection Administration regulatory limits. Increasing final process temperature tends to reduce the bulk density and crushing intensity of lightweight aggregate with a concomitant increase in water sorption capability. Lightweight aggregate with the lowest bulk density, 0.49 g cm(-3) for the 5000 psi sample, was obtained with the heating process to 1150 degrees C. Based on the X-ray absorption near edge structure results, FeSO(4) decomposition with a concomitant release of SO(x) (x = 2,3) is suggested to play an important role for the bloating process in present study.

Photocatalytic generation of hydrogen on Zr-MCM-41

Abstract Zr-MCM-41 was prepared via incorporation of Zr into the amorphous wall of MCM-41 in the hydrothermal synthesis process. Experimentally, photocatalytic generation of hydrogen on Zr-MCM-41 was investigated in a total reflectance system. In the presence of Zr-MCM-41, hydrogen yield ( 22.4 μmol H2/h) in the photocatalytic decomposition of H2O was highly enhanced by at least 2.5 times over that of the conventional photocatalyst ZrO2. The enhancement may be due to the high dispersion of ZrO2 and the justified band gap between the conduction band and valance band of ZrO2 in the wall of MCM-41. This work demonstrates how photodecomposition of H2O was affected by high dispersion of photoactive species (ZrO2) in the amorphous wall of MCM-41.

Oxidation of 2,4-dichlorophenol in supercritical water

Disappearance kkinetics of 2,4-dichlorophenol (DCP) oxidation in supercritical water was investigated. The experimental data reveal that the reaction is 0.97 order for DCP and 1.16 order for oxygen. The activation energy and the Arrhenius pre-exponential constant are 13.6 kcal/mol and 72.9 M−1.13 s−1, respectively. Several condensation by-products, such as trichlorophenols and dibenzo-p-dioxin, from supercritical water oxidation (SCWO) of DCP at 673 K were determined. We also found experimentally that the presence of sodium or iron cations in oxidation of DCP in supercritical water suppressed the formation rate of condensation by-products and enhanced the reaction conversion.