The visible spectrum of zirconium dioxide, ZrO2.

The electronic spectrum of a cold molecular beam of zirconium dioxide, ZrO(2), has been investigated using laser induced fluorescence (LIF) in the region from 17,000 cm(-1) to 18,800 cm(-1) and by mass-resolved resonance enhanced multi-photon ionization (REMPI) spectroscopy from 17,000 cm(-1)-21,000 cm(-1). The LIF and REMPI spectra are assigned to progressions in the Ã(1)B(2)(ν(1), ν(2), ν(3)) ← X̃(1)A(1)(0, 0, 0) transitions. Dispersed fluorescence from 13 bands was recorded and analyzed to produce harmonic vibrational parameters for the X̃(1)A(1) state of ω(1) = 898(1) cm(-1), ω(2) = 287(2) cm(-1), and ω(3) = 808(3) cm(-1). The observed transition frequencies of 45 bands in the LIF and REMPI spectra produce origin and harmonic vibrational parameters for the Ã(1)B(2) state of T(e) = 16,307(8) cm(-1), ω(1) = 819(3) cm(-1), ω(2) = 149(3) cm(-1), and ω(3) = 518(4) cm(-1). The spectra were modeled using a normal coordinate analysis and Franck-Condon factor predictions. The structures, harmonic vibrational frequencies, and the potential energies as a function of bending angle for the Ã(1)B(2) and X̃(1)A(1) states are predicted using time-dependent density functional theory, complete active space self-consistent field, and related first-principle calculations. A comparison with isovalent TiO(2) is made.

Nonadiabatic response model of laser-induced ultrafast pi-electron rotations in chiral aromatic molecules.

We theoretically investigated the nonadiabatic couplings between optically induced pi-electron rotations and molecular vibrations in a chiral aromatic molecule irradiated by a nonhelical, linearly polarized laser pulse. The results of wave packet dynamics simulation show that the vibrational amplitudes strongly depend on the initial rotation direction, clockwise or counterclockwise, which is controlled by the polarization direction of the incident pulse. This suggests that attosecond pi-electron rotations can be observed by spectroscopic detection of femtosecond molecular vibrations.

Recovery of isopropyl alcohol from waste solvent of a semiconductor plant.

An important waste solvent generated in the semiconductor manufacturing process was characterized by high isopropyl alcohol (IPA) concentration over 65%, other organic pollutants and strong color. Because of these characteristics, IPA recovery was deemed as a logic choice for tackling this waste solvent. In the present work, an integrated method consisting of air stripping in conjunction with condensation and packed activated carbon fiber (ACF) adsorption for dealing with this waste solvent. The air stripping with proper stripping temperature control was employed to remove IPA from the waste solvent and the IPA vapor in the gas mixture was condensed out in a side condenser. The residual IPA remaining in the gas mixture exiting the side condenser was efficiently removed in a packed ACF column. The air stripping with condensation was able to recover up to 93% of total IPA in the initial waste solvent. The residual IPA in the gas mixture, representing less than 3% of the initial IPA, was efficiently captured in the packed ACF column. Experimental tests were conducted to examine the performances of each unit and to identify the optimum operating conditions. Theoretical modeling of the experimental IPA breakthrough curves was also undertaken using a macroscopic model. The verified breakthrough model significantly facilitates the adsorption column design. The recovered IPA was found to be of high purity and could be considered for reuse.

Chemical and physical treatments of chemical mechanical polishing wastewater from semiconductor fabrication.

Wastewater from chemical mechanical polishing (CMP) process of semiconductor fabrication was treated by physical methods. The CMP wastewater, as obtained from a large semiconductor manufacturer, was characterized by a high oxide particle content, high turbidity (NTU), and a chemical oxygen demand (COD) concentration up to 500 mg/l. Due to these characteristics, treatment of the CMP wastewater by either filtration or by traditional activated sludge method was inadequate. In the present work, physical methods consisting of chemical coagulation and reverse osmosis were employed to tackle the turbidity and COD problems. Experimental tests were conducted to assess the effectiveness of the treatment and to identify the optimum operating conditions. Test results clearly demonstrated the complementary advantages of the two methods. The treatment was capable of realizing over 99% oxide particle removal and lowering the wastewater COD to below 100 mg/l. The overall water quality of the final effluent was excellent and can be considered for reuse. Preliminary treatment of the RO retentate by ozonation was also attempted. The COD removal achieved in the ozonation was over 80% in an hour, rendering the treated RO retentate suitable for direct discharge.

Treatment of chemical mechanical polishing wastewater by electrocoagulation: system performances and sludge settling characteristics.

Treatment of copper chemical mechanical polishing (CMP) wastewater from a semiconductor plant by electrocoagulation is investigated. The CMP wastewater was characterized by high suspended solids (SS) content, high turbidity (NTU), chemical oxygen demand (COD) concentration up to 500 mgl(-1) and copper concentration up to 100 mgl(-1). In the present study, electrocoagulation was employed to treat the CMP wastewater with an attempt to simultaneously lower its turbidity, copper and COD concentrations. The test results indicated that electrocoagulation with Al/Fe electrode pair was very efficient and able to achieve 99% copper ion and 96.5% turbidity removal in less than 30 min. The COD removal obtained in the treatment was better than 85%, with an effluent COD below 100 mgl(-1). The effluent wastewater was very clear and its quality exceeded the direct discharge standard. In addition, sludge settling velocities after electrocoagulation were measured and the data were employed to verify the empirical sludge settling velocity models. Finally, the sludge settling characteristic data were also utilized to establish the relation between the solids flux (G) and the initial solids concentration.

Industrial wastewater treatment in a new gas-induced ozone reactor.

The present work was to investigate industrial wastewater treatment by ozonation in a new gas-induced reactor in conjunction with chemical coagulation pretreatment. The reactor was specifically designed in a fashion that gas induction was created on the liquid surface by the high-speed action of an impeller turbine inside a draft tube to maximize the ozone gas utilization. A new design feature of the present reactor system was a fixed granular activated carbon (GAC) bed packed in a circular compartment between the reactor wall and the shaft tube. The fixed GAC bed provided additional adsorption and catalytic degradation of organic pollutants. Combination of the fixed GAC bed and ozonation results in enhanced oxidation of organic pollutants. In addition to enhanced pollutant oxidation, ozonation was found to provide in situ GAC regeneration that was considered crucial in the present reaction system. Kinetic investigations were also made using a proposed complex kinetic model to elucidate the possible oxidation reaction mechanisms of the present gas-induced ozonation system. As a complementary measure, chemical coagulation pretreatment was found able to achieve up to 50% COD and 85% ADMI removal. Experimental tests were conducted to identify its optimum operating conditions.

Combined physical, chemical and biological treatments of wastewater containing organics from a semiconductor plant.

Wastewater containing organics from a semiconductor plant was experimentally investigated in this study. The wastewater is characterized by strong color, high chemical oxygen demand (COD), a large amount of refractory volatile organic compounds and low biodegradability. Because of these characteristics, treatment of this wastewater by traditional activated sludge method is essentially impossible. In the present work, combined physical, chemical and biological methods were synergistically utilized to tackle the wastewater. The combined treatment consisted of air stripping, modified Fenton oxidation and sequencing batch reactor (SBR) method. Air stripping was employed to remove the majority of volatile organic components (notably isopropyl alcohol) from the wastewater, while the Fenton treatment decomposed the remaining refractory organics leading to simultaneous reductions of wastewater COD and color. After proper dilution with other low-strength, organics-containing wastewater stream, the wastewater effluent was finally treated by the SBR method. Experimental tests were conducted to determine the effectiveness and the optimum operating conditions of each treatment process. Test results clearly demonstrated the advantages of the combined treatments. The treatment train was found capable of lowering the wastewater COD concentration from as high as 80,000 mg/l to below 100mg/l and completely eliminating the wastewater color. The overall water quality of the final effluent exceeded the direct discharge standard and the effluent can even be considered for reuse.

Treatment of high-strength phenolic wastewater by a new two-step method.

Treatment of high-strength phenolic wastewater by a novel two-step method was investigated in the present study. The two-step treatment method consisted of chemical coagulation of the wastewater by metal chloride followed by further phenol reduction by resin adsorption. The present combined treatment was found to be highly efficient in removing the phenol concentration from the aqueous solution and was proved capable of lowering the initial phenol concentration from over 10,000 mg/l to below direct discharge level (1mg/l). In the experimental tests, appropriate conditions were identified for optimum treatment operation. Theoretical investigations were also performed for batch equilibrium adsorption and column adsorption of phenol by macroreticular resin. The empirical Freundlich isotherm was found to represent well the equilibrium phenol adsorption. The column model with appropriately identified model parameters could accurately predict the breakthrough times.