• Kyungpook Mathematical Journal
• /
• v.32 no.3_spc
• /
• pp.547-552
• /
• 1992

• Clean Technology
• /
• v.16 no.2
• /
• pp.117-123
• /
• 2010

In this study, we propose two methods able to recover different type of gold from gold-cyanide solutions: biosorption and desorption process for mono-valent gold recovery and biosorption and incineration process for zero-valent gold recovery. The waste bacterial biomass of Corynebacterium glutamicum generated from amino acid fermentation industry was used as a biosorbent. The pH edge experiments indicated that the optimal pH range was pH 2 - 3. From isothermal experiment and its fitting with Langmuir equation, the maximum uptake capacity of Au(I) at pH 2.5 were determined to be 35.15 mg/g. Kinetic tests evidenced that the process is very fast so that biosorption equilibrium was completed within the 60 min. To recover Au(I), the gold ions were able to be successfully eluted from the Au-loaded biosorbent by changing the pH to pH 7 and the desorption efficiency was 91%. This indicates that the combined process of biosorption and desorption would be effective for the recovery of Au(I). In order to recover zero-valent gold, the Au-loaded biosorbents were incinerated. The content of zero-valent gold in the incineration ash was as high as 85%. Therefore, we claim on the basis of the results that two suggested combined processes could be useful to recover gold from cyanide solutions and chosen according to the type of gold to be recovered.

• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.4
• /
• pp.471-479
• /
• 2009

A Nanoscale Zero-Valent Iron(NZVI) was modified to build a reactor system to treat nitrate. Shell layer of the NZVI was modified by slow exposure of the iron surface to air flow, which produced NZVI particles that are resistant to aerial oxidation. A XANES (X-ray Absorption Near-Edge Structure) analysis revealed that the shell consists of magnetite ($Fe_3O_4$) dominantly. The shell-modified NZVI(0.5 g NZVI/ 120 mL) was able to degrade more than 95% of 30 mg/L of nitrate within $30 hr^{-1}$ ( pseudo first-order rate constant($k_{SA}$) normalzed to NZVI surface area ($17.96m^2/g$) : $0.0050L{\cdot}m^{-2}{\cdot}hr^{-1}$). Ammonia occupied about 90% of degradation products of nitrate. Nitrate degradation efficiencies increased with the increase of NZVI dose generally. Initial pH values of the reactor systems at 4, 7, and 10 did not affect nitrate removal rate and final pH values of all experiments were near 12. Nitrate removal experiments by using the shell-modified NZVI immobilized on a cellulose acetate (CA) membrane were also conducted. The nitrate removal efficiency of the CA membrane supported NZVI ($k_{SA}=0.0036L{\cdot}m^{-2}{\cdot}hr^{-1}$) was less than that of the NZVI slurries($k_{SA}=0.0050L{\cdot}m^{-2}{\cdot}hr^{-1}$), which is probably due to less surface area available for reduction and to kinetic retardation by nitrate transport through the CA membrane. The detachment of the NZVI from the CA membrane was minimal and impregnation of up to 1 g of NZVI onto 1 g of the CA membrane was found feasible.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.12
• /
• pp.1262-1267
• /
• 2008

Reductive discolorization studies were conducted. Azo-dyes usually have biological toxicity and it is known that the dyes are hardly removed by biological treatments. One of the simplest way to remove the color is to break the azo-bond and it is possible to break the bond with zero-valent metals. Three types of azo-dyes (Cibacron Briliant Yellow 3G-P (CBY3G-P), Benzopurpurin 4b (B-4B), Chicago sky blue 6b (CSB6B)) were tested. All tested azo-dyes were highly pH dependent and lower pH was preferred. The reaction mechanism was reductive cleavage and amines were expected as products. The dissolved iron ions from zero-valent iron can also remove the color through coagulation and precipitation and a set of experiments were conducted to evaluate the contribution by the dissolved iron. The results indicated that the contribution were also dependent on the type of dyes. This study showed that the reductive cleavage using zero-valent iron could be an alternative for the azo-dye waste water.

• Journal of Environmental Science International
• /
• v.25 no.12
• /
• pp.1717-1726
• /
• 2016

In this study, the reductive decolorization of three acid and basic dyes using modified zero-valent iron (i.e., acid-washed iron (Aw/Fe) and palladium coated iron (Pd/Fe)) at various pH conditions (pH 3~5) was experimentally investigated and the decolorization characteristics were evaluated by analyzing the absorbance spectra and reaction kinetics. In the case of acid dyes such as methyl orange and eriochrome black T, color removal efficiencies increased as initial pH of the dye solution decreased. However, the color removal of methylene blue, a basic dye, was not affected much by the initial pH and more than 70% of color was removed within 10 min. During the decolorization reaction, the absorbance of methyl orange (${\lambda}_{max}=464nm$) and eriochrome black T (${\lambda}_{max}=528nm$) decreased in the visible range but increased in the UV range. The absorbance of methylene blue (${\lambda}_{max}=664nm$) also decreased gradually in the visible range. Pseudo-zero order, pseudo-first order, and pseudo-second order kinetic models were used to analyze the reaction kinetics. The pseudo-second order kinetic model was found to be the best with good correlation. The decolorization reaction rate constants ($k_2$) of methylene blue were relatively higher than those of methyl orange and eriochrome black T. The reaction rate constants of methyl orange and eriochrome black T increased with a decrease in the initial pH.

• Korean Journal of Environmental Agriculture
• /
• v.24 no.3
• /
• pp.203-209
• /
• 2005

Objective of this research was to assess the effectiveness of the different sources of the zero-valent irons (ZVIs) on the reduction of the toxic Cr(VI) to the nonhazardous Cr(III) in an aqueous solution. The physical and chemical properties of the six ZVIs were determined. Particle size and specific surface area of the ZVIs were in the ranges of $85.55{\sim}196.46{\mu}m\;and\;0.055{\sim}0.091m^2/g$, respectively. Most of the ZVIs contained Fe greater than 98% except for J (93%) and PU (88%). Reduction efficiencies of the ZVI for Cr(VI) reduction were varied with kinds of ZVIs. The J and PU ZVIs reduced 100% and 98% of Cr(VI) in the aqueous solution, respectively, within 3 hrs of reaction. However, PA, F, Sand J1 reduced 74, 65, 29 and 11% of Cr(VI), respectively, after 48 hrs. The pH of the reacting solution was rapidly increased from 3 to $4.34{\sim}9.04$ within 3 hrs. The oxidation-reduction potential (Eh) of the reacting solution was dropped from 600 to 319 mV within 3 hrs following addition of ZVIs to the Cr(VI) contaminated water. The capability of ZVIs for Cr(VI) reduction was the orders of PU > J > PA > F > S > J1, which coincided with the capacities to increase the pH and decrease the redox potentials. Results suggested that the reduction of Cr(VI) to Cr(III) was derived from the oxidation of the ZVI in the aqueous solution.

• Journal of Soil and Groundwater Environment
• /
• v.18 no.4
• /
• pp.50-57
• /
• 2013

For the last couple of decades, the Fenton (-like) systems have been extensively studied for oxidation of organic contaminants in water. Recently, zero-valent iron (ZVI) has received attention as a Fenton catalyst as well as a reducing agent capable of producing reactive oxidants from oxygen. In this study, the ZVI-based Fenton reaction was assessed for the oxidative degradation of phenol using $ZVI/O_2$, $ZVI/H_2O_2$, ZVI/Oxalate/$O_2$ and hv/ZVI/Oxalate/$O_2$ systems. Reaction parameters such as pH and reagent dose (e.g., ZVI, $H_2O_2$, and oxalate) were examined. In the presence of oxalate (ZVI/Oxalate/$O_2$ and hv/ZVI/Oxalate/$O_2$ systems), the degradation of phenol was greatly enhanced at neutral pH values. It was found that ZVI accelerates the Fenton reaction by reducing Fe(III) into Fe(II). The conversion of Fe(III) into Fe(II) by ZVI was more stimulated at acidic pH than at near-neutral pH values.

• Korean Journal of Mathematics
• /
• v.19 no.1
• /
• pp.1-16
• /
• 2011

In this paper, using differential operator, we have introduce new class of p-valent uniformly convex functions in the unit disc U = {z : |z| < 1} and obtain the coefficient bounds, extreme bounds and radius of starlikeness for the functions belonging to this generalized class. Furthermore, partial sums $f_k(z)$ of functions $f(z)$ in the class $S^*({\lambda},{\alpha},{\beta})$ are considered. The various results obtained in this paper are sharp.

• Kyungpook Mathematical Journal
• /
• v.47 no.3
• /
• pp.393-401
• /
• 2007

In the present paper we introduce the subclass $S^{\lambda}_{a,c}(p,A,B)$ of analytic functions and then we investigate some interesting properties of functions belonging to this subclass. Our results generalize many results known in the literature and especially generalize some of the results obtained by Ling and Liu [5].

• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.4
• /
• pp.431-438
• /
• 2009

The purpose of this study was to evaluate the performances of zero-valent iron (ZVI) combined SBR (Z-SBR) process in decolorization and organic removal of synthetic dye wastewater. The batch test for optimizing the operation parameters of ZVI column showed that the appropriate EBCT was around 11 min and the pH of the dye wastewater was below 7.0. During the step increase of influent color unit from 300 to 1,000cu, about 53 to 79% decolorization efficiency could be achieved in control SBR (C-SBR, without ZVI column), which resulted from destroying azo bond of synthetic dye in anaerobic condition. For the same influent color loading, Z-SBR showed always higher decolorization efficiency than C-SBR with an aid of ZVI reducing power. The TCOD concentration in Z-SBR effluent was 20-30mg/L lower than C-SBR effluent although the TCOD before and after ZVI column was nearly same. It means that breakdown of azo bond by ZVI reducing power could increase biodegradability of synthetic dye wastewater.