• Environmental Engineering Research
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• v.20 no.2
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• pp.199-204
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• 2015

In this study, a novel phosphorus removal filter made of brass scrubber with higher porosity of over 96% was fabricated and evaluated. The brass scrubber was surface-modified to form copper hydroxide on the surface of the brass, which could be a phosphate removal filter for advanced wastewater treatment because the phosphates could be removed by the ion exchange with hydroxyl ions of copper hydroxide. The evaluation of phosphate removal was performed under the conditions of the batch type in wastewater and continuous type through filters. Filter recycling was also evaluated with retreatment of the surface modification process. The phosphate was rapidly removed within a very shorter contact time by the surface-modified brass scrubber filter, and the phosphate mass of 1.57 mg was removed per gram of the filter. The possibility of this surface-modified brass scrubber filter for phosphorus removal was shown without undesirable sludge production of existing chemical phosphorus removal techniques, and we feel that it would be very meaningful as a new wastewater treatment.

• Journal of the Korean Chemical Society
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• v.20 no.1
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• pp.48-55
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• 1976

The rate constants of the derivatives of N-(2,4-dinitrophenyl)-benzimidoyl chloride were determined at various pH and a rate equation which can be applied over wide pH range was obtained. The reaction mechanism of hydrolysis of N-(2,4-dinitrophenyl)-benzimidoyl chloride which has not been studied carefully earlier in acidic and basic solution can be fullly explained by the rate equation obtained. The rate equation reveals that, beow pH 7.00, the hydrolysis of benzimidoyl chloride proceeds through $S_N2$ reaction to form a carbonium ion intermediate.Above pH 8.5, however, the hydrolysis proceeds through the $S_N2$ type reaction which depends on hydroxide ion and imidoyl chloride concentration. At pH 7.0∼8.5, two reactions occur competitively.

• Journal of the Korean Chemical Society
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• v.20 no.3
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• pp.221-228
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• 1976

The kinetics of hydrolysis of hydrazonyl bromides $(p-H,\;p-CH_3,\;p-OCH_3,\;p-Br,\;p-Cl\;&\;p-NO_2)$ have been investigated by UV spectrometry in $60{\%}$ dioxane-water at $25^{\circ}C$ and a rate equation which can be applied over wide pH range was obtained. Below pH2, the rate of hydrolysis of a series of hydrazonyl bromide is accelerated by electrondonating group (${\rho}$ = -0. 94) whereas at the pH values greater than 4, the ${\rho}$-value is 0.54. The rate equation, solvent-, substituent-and bromide ion-effect on the rate of hydrolysis are rationalized in terms of $S_N1$ and $S_N2$ mechanism: below pH 2, the hydrolysis proceed through $S_N2$, however, above pH 4, the hydrolysis is started by the attack of hydroxide ion and in the range pH 2{\sim}$4, these two reactions occur competitively.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.919-924
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• 1992

The kinetics of the hydrolysis of N-benzylidenebenzenesulfonamide derivatives have been investigated by ultraviolet spectrophotometry in $H_2O$ at $25^{\circ}C$. A rate equation which can be applied over a wide pH range was obtained. The substituent effect on the hydrolysis of N-benzylidenebenzenesulfonamide derivatives were studied and rate of hydrolysis is known to be accelerated by electron withdrowing group. Final product of the hydrolysis was benzenesulfonamide and benzaldehyde. Base on the rate equation, substituent effect, general base effect and final products, hydrolysis of N-benzylidenebenzenesulfonamide derivatives seemed to be initiated by the hydronium ion at the pH 0.2${\sim}$2.5 and proceeded by the neutral $H_2O$ molecule at pH 3.0${\sim}$8.0 but proceeded by the hydroxide ion at above pH 8.5.

• Journal of the Korean Chemical Society
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• v.18 no.2
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• pp.110-116
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• 1974

Reduction of chromate ion at the Pt-electrode was investigated in neutral unbuffered solutions, in buffered solutions of pH between 8 and 10, and in strongly alkaline medium. In buffered solutions of pH between 8 and 10, the number of electrons transfered in the reduction of chromate ion increased progressively with increasing pH. When chromate ion was reduced in 0.2 N sodium hydroxide medium the following mechanism was suggested: $CrO_4^=+H_2O+2e{\rightarrow}CrO_3^=+2OH^-,\;CrO_3^=3H_2O+e{\rightarrow}Cr(OH)_3+3OH^-$ When tetramethylammonium hydroxide (pH=13.5) was used as the supporting electrolyte, a second wave indicated strong adsorption. In unbuffered solutions of 0.1 N potassium chloride the linear sweep voltammogram consists of three or four distinct waves depending on the initial voltage and the voltage sweep rates, but the first wave was difficult to explain as a diffusion controlled wave.

• Journal of the Korean Society of Clothing and Textiles
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• v.12 no.1 s.26
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• pp.27-35
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• 1988

In order to investigate a practical application of the fibrous adsorbent to heavy metal ions, acrylic fibers were treated with the hydroxylamine solution that was producted by hydroxylamine hydrochloride and potasium hydroxide in a condition of strong alkaline and $70^{\circ}C$. The adsorption mechanism of copper(2) ion on the fibrous adsorbent, that is hydroxylaminated acrylic fibers, was studied. The adsorption of copper(2) ion was explained in terms of the activated adsorption that are formed the complex with the ligand, such as C=N, N-H, NHOH, on the surface of the adsorbent. The activation energy was evaluated to be 3.8 Kcal/mol. and the times of adsorption equilibrium was approximately 10 minutes. The uptake of copper(2) ion was found to be effected with the increase of temperatures and the pH dependence.

• Journal of the Korean Society of Safety
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• v.8 no.2
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• pp.44-50
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• 1993

The objective of this study was to investigate the extraction of chromium(Vl) ion in waste water through the liquid surfactant membrane with open-type Perforated Reciprocating-Plate Column. Extraction experiments were conducted to measure the effect of flow characteristics of continuous and dispersed phase and stroke velocity, sodium hydroxide concentraction in internal aqueous phase, sulfuric acid concentraction in outer phase, and residence time distribution and measured extraction velocity. The result of experiments showed that extraction velocity of chromium ion was maximum when stroke velocity was 180 1/min and dispersion phase velocity was 30m11min, continuous phase velocity was 20m1/min. Extraction velocity of chromium ion increased with increasing difference of hydrogen ion concentraction of dispersion and continuous phase and column stage decreased.

• Journal of Powder Materials
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• v.21 no.2
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• pp.131-136
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• 2014

Cathode materials and their precursors are prepared with transition metal solutions recycled from the the waste lithium-ion batteries containing NCM (nickel-cobalt-manganese) cathodes by a $H_2$ and C-reduction process. The recycled transition metal sulfate solutions are used in a co-precipitation process in a CSTR reactor to obtain the transition metal hydroxide. The NCM cathode materials (Ni:Mn:Co=5:3:2) are prepared from the transition metal hydroxide by calcining with lithium carbonate. X-ray diffraction and scanning electron microscopy analyses show that the cathode material has a layered structure and particle size of about 10 ${\mu}m$. The cathode materials also exhibited a capacity of about 160 mAh/g with a retention rate of 93~96% after 100 cycles.

• Advances in environmental research
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• v.5 no.2
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• pp.141-151
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• 2016

Large amounts of aluminum hydroxide ($Al(OH)_3$) exist in water purification sludge (WPS) because of the added aluminum coagulant in water treatment process. Notably, $Al(OH)_3$ is an amphoteric compound, can be dissolved in its basic condition using sodium hydroxide to form aluminate ions ($Al(OH)_4{^-}$). However, in a process in which pH is increasing, the humid acid can be dissolved easily from WPS and will inhibit the recovery and reuse of the dissolved aluminate ions. This study attempts to fix this problem by a novel approach to separate $Al(OH)_4{^-}$ ions using nanofiltration (NF) technology. Sludge impurity in a alkaline solution is retained by the NF membrane, such that the process recovers $Al(OH)_4{^-}$ ions, and significantly decreases the organic matter or heavy metal impurities in the permeate solution. The $Al(OH)_4{^-}$ ion is an alkaline substance. Experimental results confirm that a recovered coagulant of $Al(OH)_4{^-}$ ion can effectively remove kaolin particles from slightly acidic synthetic raw water.

• Journal of the Korean Applied Science and Technology
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• v.12 no.2
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• pp.107-113
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• 1995

Benzoyl styrene derivatives were synthesized by Claisen-Schmidt condensation. It was measured that nucleophilic addition of thiourea for benzoyl styrene made use of ultraviolet spectrophotometery at a wide pH $1.0{\sim}13.0$ range in 5% $dioxane-H_2O$ at $40^{\circ}C$. On the basis of general base catalysis, substitutent effect, and confirmation of addtion reaction product, the nucleophilic addtion kinetics of thiourea for benzoylstyrene derivatives were measured by pH change. It maybe concluded that a part was unrelated to pH and another part was in proportion to concentration of hydroxide ion : Above pH 10.0. It was in propotion to concentration of hydroxide ion, a part having no concern with pH was added to the neutral thiourea molecule. From the results of measurement the reaction rate and there findings, nucleophilic addition of thiourea to benzoylstyrene derivative was proposed a fitting mechanism.