Earticle

Large-scale civil engineering works discharge a large amount of soil suspension contaminated with natural heavy metals. Most of the heavy metal ions due to industrial activities and minings are accumulated in the soils and the sediments of lakes and inner bays through the rivers. It is necessary to remove heavy metals from the soils and the sediments, because some of these heavy metals, such as arsenic and cadmium, have significant biological effects even in small amounts. This study proposes a new volume reduction method of the contaminated soils and sediments by superconducting magnetic separation. Our process can remove the specific minute minerals selectively, which adsorbs heavy metals depending on pH. As a fundamental study, the adsorption behaviors of arsenic and cadmium on minute minerals as a function of pH were investigated, and the adsorption mechanism was discussed based on the crystal structure and pH dependence of surface potential in each minute minerals.

해사 중 유용광물의 부유선별을 위한 기초연구로서 중광물과 경광물에 대한 제타전위와 부유특성을 조사하였다. 제타전위 측정 결과, 중광물인 모나자이트와 티탄철석의 등전위점은 각각 pH 6.1과 6.4이었다. 그리고 경광물인 석영과 백운모의 등전위점은 각각 pH 2.8과 1.4에 존재하였다. Hallimond tube에 의한 단일광물 부선실험 결과, pH 7.5 이하인 부선조건에서 음이온 포수제인 도데실황산나트륨(SDS)에 의한 모나자이트의 부유율은 87%로 다른 포수제와 비교하여 상대적으로 높았다. 그러나 모나자이트의 부유율과 주요 경광물인 석영과의 부유율의 차는 pH 3.5에서 가장 크게 나타났다.

The objective of this study is to investigate electrokinetic properties and floatability of valuable minerals in sea sand. The results of measuring the zeta potentials of main heavy minerals were that the isoelectric point(IEP) of monazite and ilmenite is pH 6.1 and pH 6.4 respectively. The IEP of quartz and muscovite, main gangue minerals was pH 2.8 and pH 1.4 each. As a result of single mineral flotation using Hallimond tube, flotability of monazite with sodium dodecyl sulfate(SDS), anionic collector, was relatively high as 87% at less than pH 7.5 in the solution, compared to other collectors. However, the flotation difference between quartz, a main gangue mineral and monazite, a main ore mineral was shown highest at pH 3.5.

Fractional precipitation is a simple, efficient method for purifying paclitaxel extracted from plant cell cultures. However, fractional precipitation process has been inherently problematic due to the lengthy precipitation time that is required. An improved fractional precipitation process could significantly reduce the precipitation time by increasing the surface area available for precipitation. Silica-alumina was used to increase the surface area, and the optimal surface area per working volume (i.e. volume of reaction solution) (S/V) for achieving the highest purity and yield of paclitaxel possible was found to be 1007.6 mm-1. In this study, we evaluated the effects of the zeta potential of silica-alumina on the behavior (purity, yield, fractional precipitation time, precipitate shape and size) of fractional precipitation for improving the purification efficiency of paclitaxel. As the zeta potential of surface area-increasing materials were increased, the yield of paclitaxel was increased and the precipitation time and precipitate size were decreased. Furthermore, we also found that the purity of paclitaxel was constant regardless of the zeta potential of silica-alumina.

국내의 하수슬러지 발생량은 1996년 129만톤/년에서 2007년에 274만톤/년으로 점차 증가하고 있다 [1,2]. 유기물 함량이 높은 하수슬러지는 부패 및 위생적인 측면에서 환경 적인 위해성이 높아 폐기물관리법에서 “하수슬러지의 직 매립을 금지하는 규정 (시행：2003년 7월 1일)”을 도입 [3] 하여 하수슬러지의 감량화 및 재이용을 유도하고 있다. 하수처리 공정에서 발생되는 하수슬러지는 1차 침전지 에서 농축된 활성슬러지와 소화공정을 거친 혐기성 슬러지 로서 구분된다. 하수슬러지는 농축, 소화 및 탈수공정을 거 쳐 처리되고 있으며, 탈수공정은 하수의 성상 및 슬러지의 생물학적인 구조에 개량조건이 달라지므로 경제적인 운전 이 쉽지 않다. 하수슬러지의 탈수효율은 원수 및 처리공정 의 운전방법에 따라 플럭 크기 및 형태 [4], F/M비 [5], 체외 고분자물질량 [6] 등에 따라 영향을 받는다고 알려져 있다. Bruus 등 (1993) [7]은 미생물 농도, 침강속도, 슬러지 부피 지수 (sludge volume index)과 같은 거시적인 요소보다 활 성슬러지의 비표면적이 탈수효율과 직접적인 상관관계가 있다고 보고한 바 있다. Sorensen과 Wakeman (1996) [8]은 하수슬러지는 혐기성 보관시간에 따라 플럭 구조가 느슨해 지고 사상성 미생물이 증가되어 슬러지 플럭의 밀도가 낮 아져 침강성이 나빠지고 여과비저항이 증가한다고 하였다. 본 연구는 하수슬러지의 조성, 양이온 함량, 제타전위 및 pH의 변화에 따른 슬러지 탈수성을 비교하여 연관성을 제 시하고자 한다.

In this study, we found that dewatering properties were related with physico-chemical properties such as sludge concentration, pH, and zeta potential with sewage sludge. Ionic contents in digested sludge were in the order of Ca2+ (14.2 mg/g) ＞ Mg2+ (1.9 mg/g) ＞ Na+ (1.4 mg/g) ＞ K+ (1.0 mg/g). Divalent ion more than monovalent have influenced on physico-chemical and dewatering properties. Floc size distribution in activated (AS) and digested sludge (DS) increased on lower pH range to be near isoelectric point and than specific resistance to filtration (SRF) decreased. A linear increase in SRF (5.25 × 1013～2.86 × 1014 m/kg in AS and 6.89 × 1014～ 1.09 × 1015 m/kg in DS) was observed throughout low concentration range of 1230～9960 mg/L in AS and 2700～5400 mg/L in DS.

The red tide organisms occurring at seashores in Korea damage the marine fish-raising industry every summer. Several methods to prevent the occurrence of red tide organisms, therefore, have been tried; one of them is to filter out red tide organisms using a membrane filled with porous ceramic bodies, allowing only fresh seawater to pass into a fish farm. When this method is used for long period of time, however, the problem of marine bio-fouling can develop on the surfaces of the porous ceramic body, deteriorating the filtering function of the porous bodies. In this paper, the influences of the zeta potential, water absorption and surface roughness of porous ceramics on marine bio-fouling have been inspected. In order to control the above three factors, three kinds of ceramic powders, alumina, titania and zirconia, were coated on the porous bodies. As a result, the water absorption and the surface roughness of the porous ceramics were found to be equally important factors in preventing bio-fouling, while the zeta potential of the specimens did not show a prominent effect. In detail, the water absorption of specimens was an effective factor in the early stages of bio-fouling for about one month; on the other hand, the surface roughness of the specimen was a main factor that could be used to control the amount of bio-fouling after one month. Among the three ceramic powders used as coatings, alumina, by imparting lower water absorption and higher surface roughness to the specimens, proved to be the optimum one to prevent marine bio-fouling.

This study investigates the distribution stability of binary nanofluids where binary mixtures such as $NH_3/H_2O$ and $H_2O/LiBr$ solution are used as a base fluid. When a little amount of certain nanosized particles is added into a basefluid, the thermal conductivity of that mixture increases greatly. Such mixtures are named 'nanofluids' where nano-particles should be distributed stably and uniformly so the distribution stability of nanoparticles in nanofluids is one of the most important factors for nanofluid application. Therefore, binary nanofluids in which binary mixtures are applied as the basefluids are considered as working fluids. The kind and the concentration of nanoparticles, and the concentration of ammonia are considered as the key parameters. The objectives of this paper are to visualize the dispersed status of particles in binary nanofluids and to find the effect of key parameters on the distribution stability in the ammonia absorption system.

Many important properties in colloidal systems are usually determined by surface charge ($\zeta$-potential) of the contacted solid surface. In this study, $\zeta$-potential of glass $\mu$-channel was evaluated from the electro-osmotic velocity distribution. The electro-osmotic velocity inside a glass $\mu$-channel was measured using a micro-PIV velocity field measurement technique. This evaluation method is more simple and easy to approach, compared with the traditional streaming potential technique. The $\zeta$-potential in the glass $\mu$-channel was measured for two different mole NaCl solutions. The effect of an anion surfactant, sodium dodecyl sulphate (SDS), on the electro-osmotic velocity and $\zeta$-potential in the glass surface was also studied. In the range of $0\∼6$mM, the surfactant SDS was added to NaCl solution in four different mole concentrations. As a result, the addition of SDS increases $\zeta$-potential in the surface of the glass $\mu$-channel. The measured $\zeta$-potential was found to vary from-260 to-70mV. When negatively charged particles were used, the flow direction was opposite compared with that of neutral particles. The $\zeta$-potential has a positive sign for the negative particles.

Most experimental studies available in the literature on filtration are based on observed average zeta potential of particles (usually 10 measurements). However, analyses of data using the average zeta potential alone can lead to misleading and erroneous conclusions about the attachment behavior because of the variation of particle zeta potentials and the heterogeneous distribution of the collector surface charge. To study characteristics of zeta potential, zeta potential distributions (ZPDs) of silica particles under 9 different chemical conditions were investigated. Contrary to many researchers’ assumptions, most of the ZPDs of silica particles were broad. The solids concentration removal was better near the isoelectric point (IEP) as many researchers have noticed, thus proper destabilization of particles is very important to achieve better particle removal in particle separation processes. While, the mean zeta potential of silica particles at a given coagulant dose was a function of particle concentration; the amount of needed coagulant for particle destabilization was proportional to the total surface charge area of particles in the suspension.

Viscosity and zeta-potential of 11.0 wt. % aqueous bentonite suspension containing various electrolytes and hydrogen-ion concentration were measured by using a Couette type automatic rotational viscometer and Zeta Meter, respectively. The effects of pH and elcctrolytes on the rheological properties of the suspension were investigated. A system, which has a large zeta-potcntial, has a small intrinsic relaxation time ${\beta}$ and a small intrinsic shear modulus $1/{\alpha}$ in the Ree-Eyring generalized viscosity equation, i.e., such a system has a small viscosity value, since ${\eta}={\beta}/{\alpha}$. In general, a stable suspension system has large zeta-potential. The stability condition of clay-water suspension can be estimated by viscometric method since stable suspension generally has small viscosity. The correlation between the stability, viscosity and zeta-potential has been explained by the Ree-Eyring theory of viscous flow.

본 연구에서는 전기삼투 배수와 제타포텐셜과 상관성을 규명하고자 하였다. 실험으로 직경 10cm, 길이 16cm의 원형 압밀시료에 일정 전압경사법으로 1V/cm의 직류접압을 가하여 0, 500, 3000 ppm의 납농도와 0, 230, 2300, 23000 ppm의 염분농도에서 각각 12일 과 14일 동안 전지삼투 배수량을 측정하였고, 같은 농도에서 kaolinite 현탁액의 제타포텐셜을 pH2부터 14범위에서 측정하였다. 실험결과 제타포텐셜은 전해질 농도와 pH 변화에 의존적이고, 전기삼투 투수계수와 비례관계가 있음을 확인할 수 있었다. 제타포텐셜에 따른 전기삼투 배수량과 비교한 결과, 전해질 농도가 낮을수록 제타포텐셜은 음의 값은 크고, 전기삼투 배수량도 더 증가하였다.

Many important properties in colloidal systems are usually determined by surface charge $({\zeta}-potential)$ of the contacted solid surface. In this study, ${\zeta}-potential$ of glass ${\mu}-channel$ was evaluated from the electro-osmotic velocity distribution. The electro-osmotic velocity inside a glass f-channel was measured using a micro-PIV velocity field measurement technique. This evaluation method is more simple and easy to approach, compared with the traditional streaming potential technique. The ${\zeta}-potential$ in the glass ${\mu}-channel$ was measured fur two different mole NaCl solutions. The effect of an anion surfactant, sodium dodecyl sulphate (SDS), on the electro-osmotic velocity and f-potential in the glass surface was also studied. In the range of $0{\sim}6mM$, the surfactant SDS was added to NaCl solution in few different mole concentrations. As a result, the addition of SDS increases ${\zeta}-potential$ in the surface of the glass ${\mu}-channel$. The measured $\zeta-potential$ was found to vary from -260 to -70mV. When negatively charged particles were used, the flow direction was opposite compared with that of neutral particles. The ${\zeta}-potential$ has a positive sign for the negative particles.

Purpose: This study was conducted in order to examine the usefulness of osteoconductive bone substitutes with zeta potential control (geneX?? ds; Biocomposites, England) by comparing the complications and radiographic evaluation with or without geneX?? ds augmentation for internal fixation with proximal femur nail antirotation (PFNA) for treatment of osteoporotic unstable intertrochanteric fractures. Materials and Methods: A retrospective study of 101 patients who underwent fixation with PFNA in osteoporotic unstable intertrochanteric fractures was conducted from December 2015 to August 2020. The radiographic evaluation and complication rates were compared between patients with geneX?? ds (Group A: 41 cases) and those without geneX?? ds (Group B: 60 cases). Results: In radiological valuation, the degree of blade sliding from the time immediately after surgery to one year after surgery was 1.4±1.2 mm and 5.8±2.7 mm in Group A and Group B, respectively (P<0.001). During the same time frame, a significant difference of 2.3±2.2。and 7.4±3.1。, respectively (P<0.001), in varus collapse, was observed for Group A and Group B. Conclusion: Among patients fixed with PFNA for treatment of unstable intertrochanteric fractures, less blade sliding and varus collapse was observed for those with geneX?? ds augmentation compared to those without it. In addition, there was no increase in the incidence of complications. The authors believe it can be regarded as a safe and effective additive for intramedullary fixation for treatment of unstable intertrochanteric fractures.

Iron hydroxides are good adsorbents for uncomplexed metals, some metal-ligand complexes and many metal oxyanions. However, their adsorption properties of these precipitations are not fully exploited in wastewater treatment operations because of difficulties associated with their separation from the aqueous phase. This study describes experiments in which iron hydroxides were coated onto the surface of ordinary adsorbents(Sea sand) that are very resistant to acids, The coated adsorbents were used in adsorption of oxyanionic metals. The process was successful in removing some anions such as $SeO_3(-II)$ over a wide range of metal concentrations and sorption of oxyanionic metals increased with decreasing pH. Formation of two surface complexes for oxyanionic metals adsorption on iron hydroxides comprise (1) complexation of the free anion by a positively charged surface site, and (2) protonation of the adsorbed anion (or alternatively adsorption of a protonated form from solution) The coated adsorbents are inexpensive to prepare and could serve as the basis of a useful oxyanionic metal removal.

The steric stability by adsorption of surfactant to the labric and interfacial electrical condition such as the ${\zeta}-potential$ and the interaction energy between substrate and particle of fabric treated with hydrophilic and hydrophobic chemical was examined as a fundamental environment of detergency of particulate soil. The hydrophilic and hydro-phobic finish for PET fabric were treated with polyester, silicone and fluorine organic compound of resin respectively. The adsorption of anionic and nonionic surfactant to fabric were measured by abbott method and HPLC analysis. And the ${\zeta}-potential$ of particles and fabric were measured by microelectrophoresis and streaming potential method, respectively. The potential energy of interaction between u·Fe201 particle and fiber were calculated by using the heteroco-agulation theory for a sphere-plate model. The adsorption of anionic and nonionic surfactant to polyester fabric was largely influenced by concentration of surfactant and ionic strength as compared to concentration of finishing agent and adsorption time of surfactant regardless of chemicals. And the adsorption of surfactant to fabric treated with hydrophobic chemicals was higher than fabric treated with hydrophilic chemicals. With the increase of concentration of finishing agent, the ${\zeta}-potential$ of fiber treated with hydrophilic and hydrophobic chemical were converted from negative to positive regardless of chemicals. And the potential energy of interaction between ${\alpha}-Fe_2O_3$ particle and fiber were adhesion force in fabric treated with hydrophobic chemical and repulsion force in fabric treated with hydrophilic chemical.

The sapphire wafer for blue light emitting device was manufactured by the implementation of the chemical and mechanical polishing process. The surface polishing of crystalline sapphire wafer was characterized by zeta potential measurement. The reduction process with the alkali slurry provides the surface chemical reaction with sapphire atoms. The poly-urethane pad also provides the frictional force to take out the chemically-reacted surface layers. The surface roughness was measured by the atomic force microscope and the crystalline quality was characterized by the double crystal X -ray diffraction analysis.