• Analytical Science and Technology
• /
• v.13 no.2
• /
• pp.151-157
• /
• 2000

Effects of acids and pre-reductants in the analysis of arsenic have been studied by hydride generation-atomic absorption spectrometry. The analytical results were strongly dependent on the acid concentrations. All the pre-reductants was very effective to observe the arsenic signal at strong acid concentrations (3 M-5 M). However, at the low acid condition (${\leq}0.1M$), L-cysteine only showed a reasonable effect on the absorption signal. When the sample was treated with the nitric acid, absorption signal was unstable and was also decreased. Although interference effects were observed from metal ions such as $Cr^{6+}$ and $Br^{5+}$ at low acid condition, the generation of hydride could be increased by the strong acid condition.

• Applied Chemistry for Engineering
• /
• v.20 no.5
• /
• pp.557-560
• /
• 2009

In this study, a new wet etching method and the solution for thinning the glass with the thickness below $100{\mu}m$ were investigated. For the preparation of etching solution with low hydrofluoric acid, it was effective to use $NH_4F$ or $NH_4HF_2$ as a main ingredient with the addition of sulfuric acid or nitric acid. Influence of the composition of mixed acid solution and the temperature on the etching rate was investigated. The addition of anionic surfactant provides the function to prevent the adhesion of sludge generated by the etching reaction. A new wet etching pilot device equipped with streaming generation parts was used to test etching of commercial non-alkali glass and soda lime glass. The non-alkali glass with the thickness of 640 ${\mu}m$ and soda lime glass with the thickness of $500{\mu}m$ were etched to $45{\mu}m$ and $100{\mu}m$, respectively, by using the pilot device. After the etching by pilot device, the roughness degree of the glass surface was maintained at $0.01{\sim}0.02{\mu}m$.

• Applied Chemistry for Engineering
• /
• v.7 no.3
• /
• pp.530-535
• /
• 1996

Nitrochlorobenezenes are used as intermediates for dyes, pharmaceuticals and perfumes. By far the most common industrial nitration process employs a mixture of nitric acid and sulfuric acid. Due to water formed in the reaction, the mixed acid nitration requires subsequent separation of spent acid, mainly dilute sulfuric acid. In the stream of ozone, nitrogen dioxide can be used as a nitrating agent for the nitration of chlorobenzene. With 6eq of $NO_2$ and 1.0eq/hr of ozone flow, the mononitration of chlorobenzene ended within 3hr at $0^{\circ}C$ while the dinitration of chlorobenzene did in 12hr. This method can be employed for the nitration of some aromatic compounds to reduce pollutants from the present mixed-acid process.

• Journal of Radiation Protection and Research
• /
• v.20 no.2
• /
• pp.129-136
• /
• 1995

In spite of the prescriptions on the reference X-ray fields given by the International Organization of Strandard(ISO) and American National Standard Institute(ANSI), the measurement of X-ray spectrum is not only time consuming but very difficult, paticularly when significant corrections have to be applied to the measured pulse-height distributions of the observed spectra. This paper describes the calculation method of ISO Narrow Series and ANSI X-ray filtered radiations by theoretical model which is modified framer's theory by target attenuation and backscatter correction. The X-ray spectra, average energies and conversion coefficients are calculated and compared with those obtained using the spectra prescribed by ISO and AMSI to assure good agreement.

• Korean Journal of Food Science and Technology
• /
• v.27 no.3
• /
• pp.303-305
• /
• 1995

The purpose of this study was to investigate aluminum content by atomic absorption spectrophotometry after digestion with mixture of $HNO_3\;and\;HClO_4(2:1,\;v/v)$ on baking powder, wheat flours, noodles and baked foods. The contents of aluminum in baking powder, wheat flour, biscuit and snack, noodle, starch vermicelli, buckwheat vermicelli ranged from 1910 to 1948 mg/100g, 8.5 to 11.0 mg/100g, 15.3 to 19.2 mg/100g and 22.5 to 56.4 mg/100g, 29.7 to 58.5 mg/100g, 63.0 to 80.0 mg/100g, 33.1 to 46.3 mg/100g, 37.8 to 49.9 mg/100g, respectively. Aluminum contents in wheat flour foods were significantly different by added baking powder and different company(p<0.01).

• Analytical Science and Technology
• /
• v.10 no.1
• /
• pp.35-42
• /
• 1997

The sample pretreatment technique using a high pressure acid digestion bomb for the analysis of ceramic capacitor materials, such as barium titanate and PZT, was studied. When the concentrations of hydrochloric acid were varied with the addition of nitric acid or distilled water, quantitative measurements for those samples were carried out using inductively coupled plasma atomic emission spectrometry. From this experiment the results indicate that most of elements, such as Ba, Mn, Zn, Si, etc., aren't affected by the concentration of hydrochloric acid but Nb and Zr are very susceptable to it. It however turns out that the digestion time relatively gave little effects on the analytical result. In case of Nb the ratio of hydrochloric acid to water should be greater than 3:1(v / v) for the best analytical result. For the Pb determination use of diluted hydrochloric acid compared to the mixture of nitric acid and hydrochloric acid showed a better analytical result.

• Proceedings of the Korean Institute of Resources Recycling Conference
• /
• 2006.05a
• /
• pp.47-55
• /
• 2006

Recovery of acids from the waste etching solution of containing nitric, hydrofluoric and acetic acid discharged from silicon wafer manufacturing process has been attempted by using solvent extraction method. With EHA (2-Ethylhexlalcohol) for acetic acid and TBP(Tri-butly Phosphate) for nitic and hydrofluoric acid as extraction agent was carried on experiment to obtain the process design data in separation procedure. From the McCabe-Thiele diagram analysis, we obtained the optimum conditions of phase ratio(O/A) and stages to separate the each acid sequently from the mixture acids. The recovery yield was obtained 90% above for acetic acid from the acid mixtures, 90% above for nitric acid from acetic acid extraction raffinate and then 67% above for hydrofluoric acid from final extraction raffinate.

• Resources Recycling
• /
• v.1 no.1
• /
• pp.23-28
• /
• 1992

The process for recovery of acids and valuable metals such as nickel and chromium from the stainless-steel pickling acids has been developed vased on the use of solvent extraction technique. Until now, several processes for the treatment of waste acids were already developed in such countries as Japan, Swden and Canada. Those methods are, however, forcussed on the recovery of acids from them discarding the metals included in them as the hydroxides sludge. In the present work, the recovery of nickel and chromium in addition to nitric acid and hydrofluoric acid has been aimed so as to recycle them to the stainless-steel pickling lines and also to minimize the amount of sludge generated during the treatment of waste acids. The establishment of the process to recover the acids has been carried out based on the solvent extraction with TBP. The iron was eliminated from the waste solutions by precipitating in the form of hydroxide through the adjustment of pH with calcined limestone and the selective extration of chromium and nickel from the resultant solutions has been conducted by using D2EHPA as extractant.

• Resources Recycling
• /
• v.20 no.2
• /
• pp.45-53
• /
• 2011

We devised a procedure for the recovery of silicon and tempered glass from waste photovoltaic (PV) modules using optimized conditions. The tempered glass was recovered without any damage using organic solvents. The surface material is removed by applying an acid solution on the surface of the PV cell. Through our proposed method, we offer a much more efficient approach for recycling solar cells with a surfactant than the conventional method. This process, we obtained pure silicon with a yield of 90% by chemical treatment with the surfactant at room temperature for 18 min. The silicon yield was characterized using an inductively coupled plasma-atomic emission spectrometer.

• Resources Recycling
• /
• v.17 no.2
• /
• pp.36-45
• /
• 2008

Pickling of oxidized 304 stainless steel has been investigated using rotating disk electrode in waste acid solutions generated from the etching process of silicon wafer in order to recycle them. The waste acid solution contained acetic, nitric, hydrofluoric acids, and silicon of $19.6g/L^{-1}$. Electrochemical behavior during the pickling was distinctively different between the original and silicon-removed acid solutions. Open circuit potential was continuously changed in the original solution, while it was discontinuously changed and fluctuated in the silicon-removed solution. Fast and abrupt removal of surface oxide layer with severe pitting was observed in the silicon-removed solution. It was found that solution temperature had the most influential effect on glossiness. Surface glossiness after pickling was decreased with solution temperature. At the same condition, the glossiness was higher in the original solution than in the silicon-removed solution.