• 생태와환경
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• 제35권3호통권99호
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• pp.213-219
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• 2002

녹조 제어를 위하여 수중의 인 제거에 관여하는 CellCaSi의 여러 가지 조건별 인 제거효과를 조사하였다. CellCaSi의 입도에 따른 인 제거효과는 직경 1, 2 그리고 4mm 이하의 3가지 중 1mm 이하의 작은 입자를 사용했을 때 가장 우수하였다. CellCaSi의 인 제거효과는 처리량의 증가에 비례하였다. 수중의 pH 5, 7, 9에서 초기 인 농도 0.20mg/l는 각각 0.09, 0.08및 0.08mg/l로 감소되어 상이한 pH조건에 따른 CellCaSi의 인 제거효과는 큰 차이를 보이지 않았다. CellCaSi에서 용출되는 양이온은 Ca이며, Al과 Fe양이온은 검출되지 않았다. 초기에 급격히 용출된 Ca양이온은 수중의 인과 반응하는 것으로 확인되었다. 초기 인 농도 0.10, 1.0mg/1는 CellCaSi와 Ca, Fe 화합물을 첨가한 처리구에서 8일 후 각각 0.03,0.47mg/l를 기록하며 가장 많이 감소하였다. 이에 따라 인 제거효과는 CellCaSi와 Ca, Fe 화합물을 동시에 처리하였을 때 가장 좋은 것으로 조사되었다. CellCaSi의 처리에 따라 pH가 약간 증가하였고, 전기전도도도 증가되지만 상수원수 기준 허용치 (500${\mu}$S/cm) 이내였다.

• 멤브레인
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• 제27권1호
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• pp.77-83
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• 2017

무기실리카 입자로 구성된 고탁도 원수를 처리하는 침지식 정밀여과 운전에서 휴민산과 2가 양이온의 존재유무에 따라 시간에 따른 파울링 저항을 관찰하였다. 공기폭기로 인한 무기실리카 입자의 파울링 감소효과는 휴민산과 칼슘이 혼합으로 존재 시 감소하였다. 파울링층의 전자현미경 관찰결과 칼슘의 존재 시 휴민산의 무기실리카 입자 표면흡착이 관찰되었다. 이는 멤브레인 표면에 조밀한 파울링층을 형성시켜 공기폭기 효과를 감소시킨 것으로 판단된다. 용액의 조성에 따른 고탁도 원수의 탁도 제거율에는 큰 변화가 없었으나 공기폭기량에 따라 칼슘과 무기실리카 입자의 혼합 존재 시 유기물질의 제거율은 80% 이상으로 증가하였다. 이는 공기폭기 하에 무기실리카 입자 표면에 흡착된 일부 휴민산들이 멤브레인 표면으로부터 함께 역수송 되어 유기물질 제거율을 증가시킨 것으로 사료된다.

• 환경생물
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• 제25권3호
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• pp.228-238
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• 2007

Calcium plays an important role for the organisms' physiology, reproduction, and growth. Calcium amount and transfer efficiency along trophic levels were compared at two different geological areas, Limestone area (LS) and Granitic Gneiss area (GG) in 1992 and 1993. Biomass and calcium amount of plants, herbivores and carnivores were seasonally measured. The removal sweeping net method was used to collect the quantitative insect samples. Calcium content (mgCa $g^{-1}$ DM) and pH of soil were 4.85 and 7.3 at LS and 0.21 and 7.3 at GG. The calcium transfer efficiencies (%) at LS and CG were 0.2 and 4.2 from soil to plants, 0.002 and 0.02 from plants to herbivores, and 73 and 47 from herbivores to carnivores, respectively. As a whole, the high calcium content of the LS soil reduced the utilization of calcium by plants. The higher trophical levels were, the higher ecological efficiency of the biological levels was. The calcium transfer amount was higher at LS, but its efficiency was rather higher at GG.

• 대한치과보철학회지
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• 제34권3호
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• pp.593-610
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• 1996

The objective of this paper was to evaluate the shear bond strength of luting glass ionomer cement with defferent calcium based solution treatment on dentin surface. 120 extracted human teeth were classified into 12 group based on presence of smear layer on dentin surface and type of treatment solution. Smear layer remove on dentin surface was done using 6% citric acid for 60 seconds. Five different dentin surface treatment solutions(calcium acetate, calcium carbonate, clacium chlorided, calcium hydroxide, and calcium phosphate) were evaluated in this study. After surface modification, metal ring(inner diameter : 3mm, depth : 1mm) was placed to expose the same dentin surface area and inner space was filled with luting glass ionomer cement according to the recommended procedure for stadard clinical procedure. The shear bond strength of glass ionomer cement was determined after 24 hours. SEM was used for the evaluation of the surface morphologic changes and EDAX analysis was done for determination of the change of the calcium contents of treated dentin. Follwing conclusion can be drawn : 1. In the group of the dentin surface with smear layer, the calcium carbonate solution was the most effective for the increase of the clacium content and the shear bond strength of glass ionomer cement to dentin surfaces. 2. In the group of the calcium carbonate treated dentin with msear layer, the shear bond strength was increased twice compared to the control group and cohesive failure mode was observed. 3. The shear bond strength of cement was increased significantly be the removal of smear layer using 6% citric aicd. However, additional calcium solution treatments were not effective for further bond strength increase. 4. The shear bond strength of cement was significantly improved by both of the removal of smear layer and the calcium solution treatment, and the former was more effective for bond strength improvement. 5. The smear layer removed/calcium solution treated groups showed dentinal tubule obstruction and crystal attachment in SEM evaluation. However, the shear bond strengths of these groups were not increased compared to the smear layer removed/no dentin treatment group.

• Environmental Engineering Research
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• 제15권3호
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• pp.149-156
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• 2010

The objective of this study was to investigate microbial removal using layered double hydroxides (LDHs) and iron (hydr)oxides (IHs) immobilized onto granular media. Column experiments were performed using calcium alginate beads (CA beads), LDHs entrapped in CA beads (LDH beads), quartz sand (QS), iron hydroxide-coated sand (IHCS) and hematite-coated sand (HCS). Microbial breakthrough curves were obtained by monitoring the effluent, with the percentage of microbial removal and collector efficiency then quantified from these curves. The results showed that the LDH beads were ineffective for the removal of the negatively-charged microbes (27.7% at 1 mM solution), even though the positively-charged LDHs were contained on the beads. The above could be related to the immobilization method, where LDH powders were immobilized inside CA beads with nano-sized pores (about 10 nm); therefore, micro-sized microbes (E. coli = 1.21 ${\mu}m$) could not diffuse through the pores to come into contact with the LDHs in the beads, but adhere only to the exterior surface of the beads via polymeric interaction. IHCS was the most effective in the microbial removal (86.0% at 1 mM solution), which could be attributed to the iron hydroxide coated onto the exterior surface of QS had a positive surface charge and, therefore, effectively attracted the negatively-charged microbes via electrostatic interactions. Meanwhile, HCS was far less effective (35.6% at 1 mM solution) than IHCS because the hematite coated onto the external surface of QS is a crystallized iron oxide with a negative surface charge. This study has helped to improve our knowledge on the potential application of functional granular media for microbial removal.

• 대한환경공학회지
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• 제32권5호
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• pp.437-442
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• 2010

본 연구에서는 반도체 폐수에 함유된 불소 처리 시 유동상 반응기 (FBR)을 이용하여 불소 제거 효율을 극대화 시키는 조건에서 발생하는 슬러지의 함수율을 최소화 시키고 $CaF_2$의 순도를 높이고자 하였다. 이를 위해 최적 pH 및 $Ca^{2+}$ 주입몰 비 ($[Ca^{2+}]/[F^-]$)가 도출되었다. 연구 결과 pH 및 $Ca^{2+}$ 주입 몰비가 증가함에 따라 불소 제거효율은 증가하였으며, 최적조건에서 79.8%의 불소제거효율이 관찰되었다. 불소 제거 효율이 최적인 조건에서 인 제거 효율은 약 9.3% 로서 불소 제거시 $Ca^{2+}$과 ${PO_4}^{3-}$-P의 부 반응이 거의 발생하지 않아 높은 순도의 $CaF_2$이 침전 슬러지로 발생하는 것으로 나타났다. 또한 이때 슬러지 함수율은 약 19.3%로 매우 낮은 것으로 나타나 불소 제거, 슬러지 순도 및 함수율 측면에서 FBR은 매우 효과적인 불소 제거 공정인 것으로 나타났다.

• 한국세라믹학회지
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• 제24권4호
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• pp.343-348
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• 1987

The effects of salts such as aluminum sulfate as inorganic salt(2-4%), and sodium salts of citrate, tartrate, succinate, potassium tartrate and gelatin as organic salts(0.1%) on the formation of ${\alpha}$-calcium sulfate hemihydrate from by-product gypsum of phosphoric acid process under hydrothermal condition at 123$^{\circ}C$ and 133$^{\circ}C$ were investigated. Aluminum sulfate solution exhibited the catalystic effected on the crystallization of ${\alpha}$-calcium sulfate hemihydrate of which was assumed in the prismatic form, and organic salts solution exhibited little effect on the catalystic action to the crystallization, than inorganic salts. In the acidic solution with sulfuric acid(pH=2), needle like crystal of calcium sulfate hemihydrate was obtained. Hydrothermal process with aluminum sulfate solution also showed certain amounts of impurity removal such as phosphorus penataoxide from calcium sulfate hemihydrate.

• 자원리싸이클링
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• 제16권4호
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• pp.27-32
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• 2007

불소함유 폐수의 처리 후의 재사용 방안과 관련하여 칼슘을 침전제로 한 침전법에 의한 불소제거양상에 관해 조사하였다. 초기 불소농도를 10 mM로 고정한 상태에서 pH 4의 조건에서 칼슘 첨가에 따른 불소의 제거는 반응개시 수 분 이내에 신속히 진행되었으며 반응속도론적으로 2차 반응을 따르는 것으로 파악되었다. 또한 첨가된 칼슘의 양이 증가할수록 반응속도상수가 커지는 것으로 관찰되었다. pH 4에서의 불소제거율을 최대제거율로 설정한 상태에서 pH 2 및 pH 3의 조건에서 칼슘을 당량비 이상으로 첨가하여 불소의 제거율을 관찰한 결과, 칼슘의 첨가량이 당량비의 10 배로 첨가되었을 때 pH 2에 대해서는 불소제거율이 약 70%,그리고 pH 3에서는 약 96%의 불소가 제거되는 것으로 나타났다. 온도의 증가시 칼슘 첨가에 따른 불소의 제거율은 상승하여 침전반응은 흡열반응의 특성을 나타내었다. 불소폐수에 $SiF_6{^{2-}}$가 공존할 경우 불소의 제거율은 감소하였으며 침전반응에 의해 형성된 침전물의 등전점은 pH 5 부근인 것으로 파악되었다.

• Journal of Nutrition and Health
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• 제31권3호
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• pp.279-288
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• 1998

This study explored the effect of calcium levels and/or ovariectomy on bone metabolism using female Sprague-Dawley weanling rats as a model . Rats received a low (0.1%) calcium diet for 8 weeks. The rats were then divided into three subgroups that were fed 0.1% ,0.5% and 1.5% calcium diets for 8 weeks after operation. The results of this experiment indicate that body weight gin was higher in ovariectomy groups than in sham groups regardless of calcium level and food intake. Serum Ca and P concentrations were of normal level regardless of calcium level and ovariectomy. Estrogen concentration was low in the ovariectomized group. Serum alkaline phophatase activity and urinary hydroxyproline have been used as markers of bone formation and resorption. These values were increased in ovariectomized groups. The weight, length and breaking force of femur were not significantly different between the groups. Ash, Ca, P and total lipid contents in femur and lumbar were decreased in the groups fed low calcium . Mg content was decreased in the ovariectomy and total protein content was not affected by calcium level and ovariectomy. The effect groups of ovarectomy on calcium contents of bone was more prominent in lumbar than in femur. In conclusion, though low calcium intakes during growth period may retard the attainment of peak bone mass, calcium supplementation after this period increased bone growth and mineral contents, but not significant effect in three calcium levels. Furthermore, calcium intake was shown to have a greater influence on the mineral contents of femur than of lumbar, and removal of endogenous estrogen production by ovariectomy was shown to be more deleterious on the ash and calcium contents of the lumbar than of femur.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제23권5호
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• pp.396-405
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• 2001

Osseointegrated implants are used for the fixation of dental prosthesis with good long-term clinical results. In an attempt to improve the quantity and quality of the bone-implant interface, numerous implant modification have been used. Implants surface modifications have been used such as titanium-plasma sprayed, hydroxyapatite-coating, sandblasted, sandblasted and acid-etched, acid-etched. Rough surface implants have greater implant surface area and enhance the bone-implant interface and improve stabilization. The purpose of present study was to evaluate light microscopic and scanning microscopic examinations and removal torque value of newly developed calcium phosphate blast and acid-etched implant in the femur of rabbits. Titanium plasma sprayed(TPS) implant served as controls. After 12 weeks of healing of the femurs of 12 rabitts, the implant-containing segments of femur were removed on bloc and bone block including sections. Histologic examination and histomorphometric and removal torque values comparision were made for two implants. Obtained results are follows: 1. Newly developed calcium phosphate blasted and acid-etched implants were in close contact with bone under light microscopic examinations. 2. New implants showed mean bone-to implant contact 59.8%, whereas TPS implants showed mean bone-to implant contact 54.5% (statistically no difference p<0.05). 3. New implants showed mean bone density 56.7%, whereas TPS implants showed mean bone density 49.2% (statistically difference p<0.05). 4. New implants demonstrated mean removal torque values 40.5Ncm, whereas the mean removal torque values of TPS implants ranged 39.3Ncm. No statistical differences(p<0.05) were observed between two groups of implants nor was there any difference between the two implants at the clinical level.