• Journal of the Korean GEO-environmental Society
• /
• v.23 no.9
• /
• pp.33-40
• /
• 2022

Sedimentation and pH neutralization has been investigated as preteatment of acid contaminate water. The settling and neutralizing process derive more effective degradation efficiency as the pre-treatment process before the removal process of adsorption, volatile, biodegradation, or oxidation. Settling velocity, uniformity coefficient, coefficient of curvature, and grain size index can define in the sedimentation process for characteristics of the soil. The stainless steel sieve has been used to separate each particle size of the dry soil by assembling in order of 4, 10, 20, 40, 80, 100, and 200 mesh sizes. The soil from Gamcheon Port in Busan drops upper side of the sieve and shakes back and forth to separate each different size of the particle. The 1L of Imhoff cone and 200 mL of the mass cylinder were used as settling tanks to calculate settling velocity. Stokes' equation was used to figure out the average density of dry soil with a value from settling velocity. In the results, the average particle density and lowest settling velocity were 1.93 g/cm³ and 0.11 cm/s, respectively. These values can detect the range of settling points of sediment to prevent chemical accidents. In pH neutralization, the initial pH of 2, 3, 4, and 5 of nitric acid and sulfuric acid are used as an acid solution; 0.1, 0.01, and 0.001 M of sodium hydroxide and calcium hydroxide are used as a base solution. The main goal of this experiment is to figure out the volume percentage of the acid solution becomes pH 7. The concentration of 0.001 M of base solution exceeds all the conditions, 0.01 M exceeds partially, and 0.1 M does not exceed 5 v/v% except pH 2. Calcium hydroxide present less volume than sodium hydroxide at pH neutralization both sulfuric and nitric acid.

• Analytical Science and Technology
• /
• v.18 no.2
• /
• pp.112-119
• /
• 2005

This study reports on the efficiency of cleaning enameled magnet wire using a sulfuric acid $H_2SO_4$ and removal of dissolved organic material using hydrogen peroxide $H_2O_2$ and nitric acid $HNO_3$ at $80^{\circ}C$. The method involves the addition of pure $H_2SO_4$ and $H_2O_2$ or $HNO_3$. Layers of enameled organic material were dissolved by 90% $H_2SO_4$ and the solution was maintained as 35% $H_2O_2$ or 60% $HNO_3$. $H_2O_2$ content in aqueous $H_2O_2$ was maintained as 8.8 : 1.0. An initial concentration of $H_2SO_4$ in dissolution conditions was accomplished within 15 min, with a stripping time of about 2 h. The concentrations of $H_2O_2$ and $HNO_3$ in the processing bath were relatively low, but sufficient enough to produce an effective amount of power in the bath for the removal of the enamel material. The cleaning effect of enameled organic material involves the dehydration by $H_2SO_4$ and the oxidation by $H_2O_2$ or $HNO_3$.

• Journal of Microbiology and Biotechnology
• /
• v.22 no.8
• /
• pp.1155-1160
• /
• 2012

Sulfur-utilizing autotrophic denitrification relies on an inorganic carbon source to reduce the nitrate by producing sulfuric acid as an end product and can be used for the treatment of wastewaters containing high levels of nitrates. In this study, sulfur-denitrifying bacteria were used in anoxic batch tests with sulfur as the electron donor and nitrate as the electron acceptor. Various medium components were tested under different conditions. Sulfur denitrification can drop the medium pH by producing acid, thus stopping the process half way. To control this mechanism, a 2:1 ratio of sulfur to oyster shell powder was used. Oyster shell powder addition to a sulfur-denitrifying reactor completely removed the nitrate. Using 50, 100, and 200 g of sulfur particles, reaction rate constants of 5.33, 6.29, and $7.96mg^{1/2}/l^{1/2}{\cdot}h$ were obtained, respectively; and using 200 g of sulfur particles showed the highest nitrate removal rates. For different sulfur particle sizes ranging from small (0.85-2.0 mm), medium (2.0-4.0 mm), and large (4.0-4.75 mm), reaction rate constants of 31.56, 10.88, and $6.23mg^{1/2}/l^{1/2}{\cdot}h$ were calculated. The fastest nitrate removal rate was observed for the smallest particle size. Addition of chemical oxygen demand (COD), methanol as the external carbon source, with the autotrophic denitrification in sufficiently alkaline conditions, created a balance between heterotrophic denitrification (which raises the pH) and sulfur-utilizing autotrophic denitrification, which lowers the pH.

• Journal of the Mineralogical Society of Korea
• /
• v.27 no.3
• /
• pp.115-124
• /
• 2014

In order to leach Au and Ag from gold-silver bearing sulfide concentrate, the sulfide concentrate was ground in a ball mill for a dry pre-treatment and a wet pre-treatment process. Mineralogical studies and thiourea leaching experiments were carried out with the pre-treated sulfide concentrate. The results of the pre-treatment with the concentrate samples showed the mean particle size and iso-electrical potential was smaller in the dry pre-treatment sample than in the concentrate sample, and the contents was lower in the wet pre-treatment sample than in the dry pre-treatment sample. In XRD analysis, amorphous properties were only shown in the wet pretreatment sample. The results of the concentrate sample leaching experiments showed that the best Au, Ag leaching parameters were when the addition of thiourea was at a 1.0 g concentration, ferric sulfate was 1.0 M, sulfuric acid was 2.0 M and the leaching temperature was at $60^{\circ}C$. The Au, Ag leaching rate was always much greater and faster with the wet pre-treatment samples than with the dry pre-treatment samples. Accordingly, it is expected that more Au, Ag can be leached in an eco-friendly methodology using wet pre-treatment. The pre-treatment could be improved with an optimized grinding additive reagent and through researching grinding time in future non-cyanide processes.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.15 no.1
• /
• pp.47-53
• /
• 2012

As one of the methods for recycling the FRP from the waste ships, separation of roving layer from the mat has some merits in a sense of the eco-friendly and economical recycling process. Similar characteristics, however, between the roving and the mat even with different ratio of the resin and the glass and the thickness of the roving, much thinner than the mat, make the mechanically automatic differentiation difficult. In this study spectrochemical differentiation between the two layers has been made using boiling concentrated sulfuric acid, methanol and isopropanol solution saturated with KOH, or hydrogen fluoride (HF) solution. Furthermore efficiently coloring water-soluble dye following the HF treatment makes the roving layer more distinguishable photophysically. The layer differentiation and the automatic layer distraction move up the date of simple and automatic separation process for the waste FRP.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.12 no.1
• /
• pp.55-59
• /
• 2009

As one of the methods for recycling the FRP from the small and medium waste ships, separation of roving layer from the mat has some merits in a sense of the recycling energy and the environmental effects. Similar characteristics, however, between the roving and the mat even with different ratio of the resin and the glass and the thickness of the roving, much thinner than the mat, make the mechanically automatic differentiation difficult. In this study spectrochemical differentiation between the two layers has been made using (1) boiling concentrated sulfuric acid which can dissolve the resin in the FRP layer, (2) methanol and isopropanol solution saturated with KOH which can dissolve the glass, or (3) hydrogen fluoride(HF) solution which can reacts with $SiO_2$ fragments of the glass. Furthermore coloring water-soluble dye following the HF treatment makes the roving layer more distinguishable photo-physically.

• Journal of the Korean Magnetics Society
• /
• v.22 no.1
• /
• pp.11-14
• /
• 2012

The composites of expanded graphite oxide and magnetic nanoparticle (Ni and Co) were synthesized by using simple chemical method. From the raw material natural graphite, the expanded graphite was fabricated using sulfuric acid and $1^{st}$ heat treatment at $600^{\circ}C$ for 1 hour. The expanded graphite was changed to expanded graphite oxide by 2nd heat treatment at $1050^{\circ}C$ for 15 sec and chemical oxidation. The expanded graphite oxide/1-methyl-2-pyrrolidone solution reacts with the magnetic nanoparticle to form a magnetic graphite oxide composite. These graphite-based materials were characterized by x-ray diffractometer, Raman spectroscopy, transmission electron microscope, and vibration sample magnetometer. We expect that these results of this paper were become basis research of graphite oxide composite.

• Journal of the Korean Society for Heat Treatment
• /
• v.36 no.3
• /
• pp.153-160
• /
• 2023

The use of biogas is an industrially necessary means to achieve resource circulation. However, since biogas obtained from waste frequently causes corrosion in pipes, it is important to elucidate corrosion mechanisms of the pipes used for biogas transportation. Recently, corrosion failure occurred in a pipe which supplied for the biogas at the speed of 12.5 m/s. Pinholes and pits were found in a straight line along the seamline of the pipe. By using corrosion-damaged samples, residual thickness, microstructure, and composition of oxide film and inclusion were examined to analyze the cause of the failure. It was revealed that the thickness reduction of biogas pipe was ~0.11 mm per year. A thin sulfuric acid film was formed on the surface of the interior of a pipe due to moisture and hydrogen sulfide contained in a biogas. Near the seamline, microstructure was heterogeneous and manganese sulfide (MnS) was found. Pits were generated by micro-galvanic corrosion between the manganese sulfide and the matrix in the interior of the pipe along the seamline. In addition, microcracks formed along the grain boundaries beneath the pits revealed that hydrogen-induced cracking (HIC) also contributed to accelerating the pitting corrosion.

• Composites Research
• /
• v.13 no.4
• /
• pp.42-53
• /
• 2000

A study has been made to establish an optimum condition in the surface treatment and curing method that is important for the fabrication of Al 7075/CFRP laminates. PAA(Phosphoric Acid Anodizing) provided a good adhesive strength and FPL(Sulfuric / Sodium Dichromate Acid Etching) had a similar adhesive strength with PAA. On the other hand, the poor adhesive strength was shown on vapor degrease and CAA(Chromic Acid Anodizing). By using the atomic force microscope(AFM), it was found that the PAA oxide surface obviously had a greater degree of microroughness as compared to vapor degrease, CAA and FPL treated surfaces. These results support the concept of a mechanical interlocking of the adhesive with-in the oxide pores as the predominant adhesion mechanism. In curing methods, the adhesive strength of co-curing method was higher than that of secondary curing method. With respect to stability of specimen shape, the secondary curing method was better than co-curing method. DMA(Dynamic Mechanical Analysis) test revealed $T_g$ in curing times over 60 min is nearly same, so it is estimated they will have similar degree of curing and joint durability in using FM300M adhesive film.

• Resources Recycling
• /
• v.19 no.6
• /
• pp.51-60
• /
• 2010

A study on the recovery of cobalt and lithium from Lithium Ion Battery(LIB) scraps has been carried out by a physical treatment - leaching - solvent extraction process. The cathode scraps of LIB in production were used as a material of this experiment. The best condition for recovering cobalt from the anode scraps was acquired in each process. The cathode scraps are dissolved in 2M sulfuric acid solution with hydrogen peroxide at $95^{\circ}C$, 700 rpm. The cobalt is concentrated from the leaching solution by means of a solvent extraction circuit with bis(2-ethylhexyl) phosphoric acid(D2EHPA) and PC88A in kerosene, and then cobalt and lithium are recovered as cobalt hydroxide and lithium carbonate by precipitation technology. The purity of cobalt oxide powder was over 99.98% and the average particle size after milling was about 10 lim. The over all recoveries are over 95% for cobalt and lithium. The pilot test of mechanical separation was carried out for the recovery of cobalt from the scraps. The $Co_3O_4$ powder was made by the heat treatment of $Co(OH)_2$ and the average particle size was about 10 ${\mu}m$ after grinding. The recovery was over 99% for cobalt and lithium each other and the purity of cobalt oxide was over 99.98%.