Purpose: The interaction of methylene blue (MB) with Na-saturated clay from Maghnia deposit in aqueous suspension was investigated using visible absorption spectroscopy. Methods: The effect of the optical properties of dyes in aqueous solutions and adsorbed onto Na-saturated clay was assessed in terms of the absorption bands maxima and the removal rate as a function of pH. Results: The adsorption of MB dye onto Na-saturated clay surface leads to the methacromatic effect in the absorption spectrum of the dye. Formation of MB dimers and higher agglomerates depended sensitively on the potential of the layer charge density. MB agglomerates occurred predominantly in the Na-saturated clay with high charge density, even with low charge density. The redistribution of MB molecules over the surface of Na-saturated clay of lower charge density (high acidic medium) leads to a reduction of the dye aggregation, accompanied by a bathochromic shift of the band maximum of MB dye to the longer wavelengths. Conclusion: The methachromatic effect was analyzed by the R=A(MB+)/A(MB+)n parameter, which decreases with the charge density, owing to the increase in the pH solution. To explain the relationship between the layer charge density and the adsorption, so- colled model 2-pKa of surface complexation (SCM) was developed.

Chemically activated carbons were prepared from maize cobs, using phosphoric acid of variable concentration. The texturalparameters of the activated carbons were determined from the nitrogen adsorption isotherms measured at 77K. The chemistryof the carbon surface was determined by measuring the surface pH, the pHPZC and the concentration of the carbon - oxygengroups of the acid type on the carbon surface. Kinetics of Cr(VI) sorption/reduction was investigated at 303K. Two processeswere investigated in terms of kinetics and equilibrium namely; Cr(VI) removal and chromium sorption were studied at variousinitial pH (1-7). Removal of Cr(VI) shows a maximum at pH 2.5. At pH<2.5, sorption decreases because of the protoncompetition with evolved Cr(III) for ion exchange sites. The decrease of sorption at pH>2.5 is due to proton insufficiencyand to the decrease of the extent of Cr(VI) reduction. The chemistry of the surface of activated carbon is an important factorin determining its adsorption capacity from aqueous solutions particularly when the sorption process involves ion exchange.

The adsorption and reduction of Cr (VI) to Cr (III) by surface modified activated carbon (AC) in an aqueous solution was studied. The effects of surface modifications on the properties of the carbons were investigated by the analysis of specific surface area, carbon surface pH, acid/base surface values and functional groups. In order to understand the Cr(VI) adsorption and reduction ratio from Cr(VI) to Cr(III), the Cr adsorption capacity of AC was also measured and discussed by using inductively coupled plasma and UV spectrophotometer. The modifications bring about substantial variation in the chemical properties whereas the physical properties such as specific surface area, pore volume and pore size distribution nearly were not changed. Total Cr adsorption efficiency of as-received activated carbon (R-AC) and nitric acid treated activated carbon (N1-AC and N2-AC) were recorded on 98.2, 99.7 and 100%. Cr(III) reduction efficiency of R-AC increased largely from 0.4% to 28.3% compared to N1-AC and N2-AC.

Oxidized activated carbons were prepared by reacting steam-activated carbon developed from pecan shells with nitric acid of varying strength (15, 30, 45 and 60%). The textural properties and the chemistry of the surface of the non-oxidized and of the oxidized carbons were determined from nitrogen adsorption and base neutralization capacities. The uptake of Pb(II) and Cd(II) from aqueous solution by these carbons was determined by kinetic and equilibrium experiments as well as by the column method. Treatment with nitric acid brought about drastic decrease in surface area and remarkable increase in the pore size of the carbon with these changes depending on the strength of nitric acid. Nitric acid increased the surface acidity by developing new surface oxygen functional groups of acidic nature. HNO3-oxidized carbons exhibited high adsorption capacities for Pb(II) and Cd(II). The adsorption of these ions increased with the decrease of the surface pH of the carbon and with the increase of the solution pH from 2.5 to 6 and 7. The amount adsorbed from lead and cadmium was also related to the amount of surface acidity, the pH of the point of zero charge and on some metal ion parameters. Cadmium and lead uptake by the investigated carbons followed pseudo-second order model and the equilibrium sorption data fitted Langmuir adsorption model.

The ability of cow dung ash without any pretreatment to remove color from textile dyes N Blue RGB, Green B and EOSIN YWS from aqueous solution has been investigated in this work. Cow dung ash, an ecofriendly and low cost adsorbent was prepared by burning cow dung cakes in the muffle furnace at 500℃. The adsorption was achieved under different pH and adsorbate concentration. The data was fitted to simple polynomial and the isotherms similar to Langmuir and Freundlich isotherms.

고분자 분리막에 비하여 열적, 기계적, 화학적 안정성이 우수한 친수성 NaY 제올라이트 분리막을 이용한 투과 증발 막분리 공정을 적용하여 이소프로필 알코올(iso-propyl alcohol, IPA)/물 혼합물에서 선택적으로 물을 분리하고자 하였다. 공급되는 IPA의 몰분율 변화 및 투과 증발 실험 온도의 변화가 투과플럭스와 물 선택도에 미치는 영향을 고찰하였다. IPA의 몰분율이 증가함에 따라 물 투과플럭스와 선택도는 감소함을 관찰할 수 있었다. 실험 온도의 증가에 따라 물 투과플럭스는 증가하였으나 선택도는 감소하였다 친수성 NaY 제올라이트 투과증발 실험 결과 1.9×10 2∼3.5×10 3 g/m 2 ⋅hr의 물 투과플럭스와 7.0×10 2∼2.0×10 4의 선택도를 나타내었다.

A carbonaceous sorbent was prepared from rice husk via sulphuric acid treatment. After preparation and washing, the wet carbon with moisture content 85% was used in its wet status in this study due to its higher reactivity towards Cr(VI) than the dry carbon. The interaction of Cr(VI) and the carbon was studied and two processes were investigated in terms of kinetics and equilibrium namely Cr(VI) removal and chromium sorption. Cr(VI) removal and chromium sorption were studied at various initial pH (1.6-7), for initial Cr(VI) concentration (100 mg/l). At equilibrium, maximum Cr(VI) removal occurred at low initial pH (1.6-2) where, Cr(III) was the only available chromium species in solution. Cr(VI) removal, at such low pH, was related to the reduction to Cr(III). Maximum chromium sorption (60.5 mg/g) occurred at initial pH 2.8 and a rise in the final pH was recorded for all initial pH studied. For the kinetic experiments, approximate equilibrium was reached in 60-100 hr. Cr(VI) removal data, at initial pH 1.6-2.4, fit well pseudo first order model but did not fit pseudo second order model. At initial pH 2.6-7, Cr(VI) removal data did not fit, anymore, pseudo first order model, but fit well pseudo second order model instead. The change in the order of Cr(VI) removal process takes place in the pH range 2.4-2.6 under the experimental conditions. Other two models were tested for the kinetics of chromium sorption with the data fitting well pseudo second order model in the whole range of pH. An increase in cation exchange capacity, sorbent acidity and base neutralization capacity was recorded for the carbon sorbent after the interaction with acidified Cr(VI) indicating the oxidation processes on the carbon surface accompanying Cr(VI) reduction.

[ α ]-알루미나 튜브 지지체의 내부에 1Si : 1Na : 4Na : 6H2O의 비율로 제조한 합성 용액을 사용하여 수열합성법으로 NaA 제올라이트 분리막을 제조하였다. 합성된 제올라이트 분리막을 이용하여 iso-propyl alcohol (IPA)/물 혼합물의 조성비와 조업 온도 변화에 따른 선택도와 투과도의 변화를 알아보기 위한 투과증발 실험을 수행하였다. 총투과도는 공급 측 IPA의 농도가 증가함에 따라 감소하였고, 온도가 상승함에 따라 증가하는 경향을 보였다. 총투과도는 60℃에서 공급물의 IPA농도가 0.6 몰분율일 때 4.0×103g/m2;hr로 가장 높은 값을 보였다. 선택도는 IPA의 몰비가 0.8까지 증가하는 경향을 보였고 0.9 이상에서 감소하는 경향을 나타내었다 선택도는 60℃, 0.8 몰분율에서 1.8×107의 값으로 최고치를 나타내었다. NaA 제올라이트 분리막을 이용한 투과증발은 기존의 증류공정과 비교 시 훨씬 우수한 선택적 물 분리 성능을 나타내었다.

본 연구는 에스텔화 막반응공정에 의한 2,2,2-trifluoroethyl metacrylate (TFEMA)의 생산을 위한 선행연구로, 가교된 poly(vinyl alcohol)막을 이용하여 TFEA (2,2,2-trifluoroethanol)/water과 MA (methacrylic acid)/water 혼합용액을 대상으로 투과증발특성을 연구하였다. 산 저항성을 가진 가교된 PVA막은 PVA와 EGDE를 같이 녹인 수용액을 Teflon plate 위에 캐스팅한 후 140℃에서 열 가교시킴으로써 제조하였다. 제조된 막의 특성을 알아보기 위해 FT-IR과 팽윤도 측정을 실시하였다. TFEA/water 혼합용액에 대한 투과증발실험은 가교제인 EGDE농도와 운전온도를 변화시켜가면서 실시하였으며, MA/water 혼합용액에 대한 투과증발실험은 최적화된 PVA막을 가지고 실시하였다. 투과증발실험결과로부터 제조된 막은 TFEA와 MA의 에스테르화 반응온도인 80℃ 이상에서 96%의 TFEA 및 MA 수용액에 대해 각각 100, 900 이상의 매우 높은 물에 대한 선택도와 0.1, 0.3;kg/m2h의 투과도를 얻을 수 있었다.

비대칭 폴리비닐리덴플루오라이드(PVDF) 막을 상전환법으로 제조하였다. 도포용액은 PVDF를 용매인 N-ethyl-2-pyrrolidone (NMP)와 비용매인 1,4-dioxane, diethyleneglycol dimethyl ether (DGDE), acetone, (equation omitted)-butyrolactone(GBL)의 혼합용매에 녹여서 제조한다. 여러 첨가제가 도포용액 특성, 투과특성과 막 구조에 미치는 영향을 조사하였다. 응고제인 물과 1,4-dioxane, DGDE, acetone과의 상용성이 NMP보다 낮아서 기공크기가 작아진다. 첨가제의 양을 조절하여 기공크기를 변화시켰다. 혼합용매(수계 및 비수계)가 막의 투과성능에 미치는 영향을 살펴보았다. 용액점도뿐만 아니라 표면장력도 용매 투과특성에 영향을 끼침을 알 수 있었다.

The preparation of CaSO4 nanoparticle by vesicles formed spontaneously in cationic OTAC and anionic ADS mixed surfactant solution whose ratio is 0.3/0.7 is investigated. Added electrolytes for preparing nanoparticles reduce vesicle size about 200-300 nm comparing with that of pure vesicle whose size is 700-800 nm by DLS. The core of vesicles has 200 nm size and acts as nanoreactors which same size of monodisperse CaSO4 nanopaticles are formed. Although CaSO4 particles are formed at the outer of vesicles, they are very large and amorphous. The formed particles are identified with XRD analysis after separation due to coinciding with CaSO4 particles.

Adsorption isotherms of p-nitrophenol from its aqueous solutions on two samples of activated carbon fibres and two samples of granulated activated carbons have been determined in the concentration range 40~800 mg/L (ppm). The surface of these carbons was modified by oxidation with nitric acid and oxygen gas, and by degassing the carbon surface under vacuum at temperatures of 400℃, 650℃ and 950℃. The oxidation of carbon enhances the amount of carbon-oxygen surface groups, while degassing decreases the amount of these surface groups. The adsorption of p-nitrophenol does not depend upon the surface area alone but appears to be influenced by the presence of oxygen groups on the carbon surface. The adsorption decreases on oxidation while the degassing of the carbon surface enhances the adsorption. The decrease in adsorption depends upon the strength of the oxidative treatment being much larger in case of the oxidation with nitric acid, while the decrease in adsorption on degassing depends upon the temperature of degassing. The results show that while the presence of acidic surface groups which are evolved as CO2 on degassing suppress the adsorption of p-nitrophenol, the presence of non acidic surface groups which are evolved as CO on degassing tend to enhance the adsorption. Suitable mechanisms compatible with the results have been presented.