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- 학과정보 : 환경공학과 환경공학전공 (검색결과 5,904 건)
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선택성 복합탄소전극을 이용한 축전식 탈염에서 경도물질의 선택적 제거율 향상
Capacitive deionization technology based on the principle of electrical double layer is one of desalination technologies which remove ions in water. Capacitive deionization(CDI) is an electrochemically controlled process for removing ionic salts from aqueous solutions by alternatively adsorbing and desorbing excess ions in the electrical double layer region at an electrode-solution interface when a pair of electrodes are electrically charged by some external power supply. When the electrodes are charged, all counter ions in aqueous solutions are adsorbed on electrode surface nonselectively. Because removing all ions including non-targeting ions consume much energy, it is needed to remove specific target ions selectively to minimize consuming energy in the desalination process. In this study, we fabricated selective composite carbon electrodes using hardness-selective ion-exchangeable materials and performed desalination experiments by means of the CDI cells with selective composite carbon electrodes to selectively remove hardness materials. CMP28 resin was introduced as hardness selective material which has excellent hardness ion selectivity. Adsorption equilibrium experiment was performed to evaluate permselectivity of hardness ions, i.e., Ca2+ and Mg2+, for the CMP28 resin. The CMP28 resin showed much higher selectivity of Ca2+ and Mg2+ than Na+ and had more higher selectivity of Ca2+ than Mg2+. The adsorption equilibrium of the CMP28 resin represents that the selectivity increases with the following order: Na+ ≪ Mg2+ < Ca2+ due to the number of charge, hydrated radius, ionic concentration and etc. Thus, we fabricated selective composite carbon electrodes by coating the CMP28 resin powder on the original carbon electrodes and made up a selective capacitive deionization(SCDI) cell using the selective composite carbon electrode only in cathode. To investigate the improvement of hardness-selective removal in the SCDI cell, we performed the desalination experiments in two solutions (SC solution : Na+ + Ca2+, SM solution : Na+ + Mg2+). In the SC and SM solutions, selective removal of hardness materials was increased by using the selective composite carbon electrode in the SCDI cell up to 10% and 7% higher than the original CDI cell, respectively. To investigate the change of hardness-selective removal performance with various applied current densities to the SCDI cell, we carried out desalination experiments by applying various current densities (5, 7.5, 10, 12.5, 15 A/m2) in the SCM solution containing three ions (Na+ + Ca2+ + Mg2+). When the lowest current density (5 A/m2) is applied to the SCDI cell, most of ions were removed and the selective removal of hardness materials were increased because of the longest residence time for reaching the equilibrium state between the selective layer on the carbon electrode and the solution. It is concluded that we successfully developed the SCDI technology using the proprietary composite selective carbon electrode to increase selective removal of hardness materials. 축전식 탈염 기술은 전기이중층의 원리를 바탕으로 물속에 존재하는 이온들을 제거하는 탈염 기술이다. 축전식 탈염장치는 두 다공성 탄소전극 사이로 이온들을 함유한 용액이 통과하는 동안 전극에 전위를 인가하면 전위차로 인해 전극 표면에 전기이중층이 형성되는 원리를 통해 반대전하를 갖는 이온들을 흡착하여 용액으로부터 이온들이 분리된다. 하지만 이때 반대전하를 갖는 모든 이온들을 비선택적으로 흡착하게 되는데 이 과정에서 제거하지 않아도 되는 이온들을 제거함으로써 불필요한 에너지가 소모된다. 따라서 축전식 탈염 공정에는 선택적으로 이온들을 분리하여 제거할 수 있는 부가적인 기술 개발이 요구된다. 선택적으로 제거해야하는 이온의 대상으로 경도물질이 있다. 수중에서 경도물질은 급수관거 내 스케일 형성 및 부식이 발생하고 체내로 섭취 시 위장관 질환을 유발하는 등 악영향을 미친다. 이러한 경도물질을 제거하기 위해 본 연구에서는 축전식 탈염 기술에 이온 선택성 전극 기술을 도입하려고 한다. 경도물질(Ca2+, Mg2+)의 선택적 제거율을 향상시킬 수 있는 선택성 복합탄소전극을 제작하기 위해 경도물질에 대한 선택성이 우수한 CMP28 수지를 선정하였고 흡착평형 실험을 진행하였다. Na+과 Ca2+ 이온을 혼합한 용액과 Na+과 Mg2+ 이온을 혼합한 용액에서 CMP28 수지는 Na+ 이온에 비해 Ca2+과 Mg2+ 이온에 더 높은 선택성을 보여주었다. Na+, Ca2+과 Mg2+ 이온을 혼합한 용액에서는 Na+ < Mg2+ < Ca2+ 이온 순으로 CMP28 수지가 높은 선택성을 나타내었다. 여기서 Ca2+과 Mg2+ 이온은 수화반경에 의해 선택도가 결정되며 수화반경이 더 작은 Ca2+ 이온이 CMP28 수지에 대해 높은 선택성을 가지고 있었다. Ca2+과 Mg2+ 이온에 대한 선택성을 확인한 CMP28 수지를 탄소전극 위에 코팅함으로써 선택성 복합탄소전극(Selective Capacitive Deionization, SCDI)을 제조하였고 탄소전극을 양극으로 하여 SCDI 셀을 제작하였다. 또한 탈염 성능을 확인하기 위해 두 탄소전극으로 조립한 셀과 비교분석하였다. SCDI 셀로 운전을 진행하였을 때 CDI 셀보다 Na+과 Ca2+ 이온을 혼합한 용액에서 Ca2+ 이온의 선택적 제거율이 10% 이상 증가하였고 Na+과 Mg2+ 이온을 혼합한 용액에서 Mg2+ 이온의 선택적 제거율이 7% 이상 증가하였다. 따라서 본 연구에서 개발한 SCDI 셀을 이용하여 Ca2+과 Mg2+ 이온에 대한 선택적 제거율이 향상되었다고 판단할 수 있다. 셀에 다양한 전류밀도를 공급함으로써 선택적 제거율에 대한 변화를 관찰하기 위해 Na+, Ca2+과 Mg2+ 이온을 혼합한 용액에서 SCDI 셀을 이용하여 다양한 전류밀도(5, 7.5, 10, 12.5, 15 A/m2)로 탈염 운전을 진행하였다. 가장 낮은 전류밀도인 5 A/m2을 셀에 공급하여 운전하였을 때 가장 많은 이온들을 제거할 수 있었고 경도물질에 대한 선택성이 가장 높게 나타났다. 전류밀도는 흡착속도를 의미하는 것으로 흡착속도가 감소할수록 선택성 층과 용액사이에서 평형이 이뤄지는 시간이 길어지기 때문에 경도물질에 대한 선택성 제거율이 증가하게 되었다. 따라서 본 연구에서는 CMP28 수지를 코팅하여 제작한 선택성 복합탄소전극으로 셀을 구성한 SCDI 기술을 개발함으로써 경도물질에 대한 선택적 제거율을 증가시켜 주었다.
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순환여과시스템에서 오존을 이용한 암모니아성 질소의 탈질화 연구
Recently, the amount of fish caught has decreased gradually owing to ocean pollution and overfishing. Because of these problems, fish farming using enclosing calm waters with nets in bays or lakes has increased greatly. However, fish farming causes a pollution problem in open water due to the residual diets and the excrement from fish. Therefore a closed recirculating culture system incorporating water purifying technique has recently been introduced to remove ammonium nitrogen excreted by fish and to prevent diseases. In this work, the denitrification of ammonium nitrogen and the growth rate of fish using a closed recirculating culture system incorporating the processes of biofilm filtration and ozonation were systematically investigated and the finally results were obtained. 1. After 90 days, Monthly mean body weight and length of fish gained in Ozonation tank and Control tank were 35.83g and 15.36cm, 28.81g and 14.25cm, respectively. The survival rate of fish was 83% in both culture tank. There was no significant differences among the mean body weight of fishes(P>0.05). Therefore ozonation for a closed recirculating culture system had no bad effects on the growth of fish. 2. During the experiment period, pH was 7.8∼8.8 and DO was above 5mg/ℓ. SS was below 5∼8mg/ℓ after biofilm was formed in the biofilm filtration reactor. In addition, it can be known that the culturing water was improved greatly from the investigation of T-N, T-P and TIN by biofilm and ozonation. 3. As the result of a variation of circulation ratio, Denitrification of ammonium nitrogen was increased in proportion to the circulation ratio. But Nitrification of microorganism was opposite to the circulation ratio. 4. With increasing injected ozone concentration in ozonation tank under a 21cycle(6.7ℓ/min), denitrification of ammonium nitrogen was increased linearly in proportion to the increasing of injected ozone concentration. 5. This experiment demonstrated that ozonation for a closed recirculating system was effective for disinfection of virus and algae. But residual oxidants in the culturing water affected the growth and survival rate of fish. Therefore if the culturing water is treated by ozonation, the either equipment which alarms residual oxidant concentration or the exchange of activated carbon is needed.
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박은수 朝鮮大學校 産業大學院 1999 국내석사
The results of treating hot spring wastewater by contact oxidation method using HBC-Briquette complicated media are as follows. 1. Complicated media was dipped into water and it was contacted two way like cycling and only aeration. The amount of eluted ion was more in being cycled than being aerated. Watersoluable cation ion like Ca^(2+) was shown high with this order, Ca^(2+)>Na^(+)>K^(+)>Si^(4+)>Mg^(2+)>Al^(3+), The concentration of these ion could have a positive effect for the removal of organic matter because they are higher than concentration of these ions, required in biological treatment. 2. The removal rate of organic matter is higher in HRT 2.5hr than 5hr and 7hr's (SS 87.5%, BOD 88.8%, COD_(Cr), 84.5%). And effluent concentration was determined as SS 2.95mg/ℓ, BOD 4.55mg/ℓ and COD_(Cr), 6.93mg/ℓ. 3. T-N removal rate was 53.1% as the highest in HRT 2.5hr and effluent concentration was determined as T-N 2.3mg/ℓ, NH_(3)-N 1.05mg/ℓ, NO_(3)-N 0.15mg/ℓ, NO_(3)-N 0.6mg/ℓ and Organic-N 0.56mg/ℓ. The longer its HRT was applied, the higher the removal rate of Organic-N was obtained. 4. T-P removal rate was achieved higher as 48.5% in HRT 5hr than 45.7% (7.5hr) and 42.9%(2.5hr). Its effluent concentration was 0.18mg/ℓ. 5. HRT 2.5hr and DO concentration 6-7 mg/ℓ were applied to the pilot scale reactor. The removal rates of organic matter in pilot were shown as SS 89.19%, BOD 89.95%, COD_(Cr) 85.34%. These results are 7-17 limes higher in each parameters than the established facilities's using HBC ring. Effluent concentration of SS was 2.55mg/ℓ, and it had BOD 4.08mg/ℓ, COD_(Cr) 6.55mg/ℓ, T-N 1.95mg/ℓ and T-P 0.19mg/ℓ. 6. Wastewater sample has BOD 37.5~42.4mg/ℓ, COD_(Cr) 36.4~42.4mg/ℓ, SS 22.6-25.3mg/ℓ, TS 256.4-275.5mg/ℓ, T-N 4.53~6.09mg/ℓ and T-P 0.43-0.56mg/ℓ. These values of each parameters means this wastewater can be included into sewage wastewater having low concentration and a few ion like F (6.05~1.21mg/ℓ), Cl turned out to be contained as hot spring was te-water. From the results above, we can surely say, contact oxidation method using HBC-Briquette media is useful for the hot spring zone having low organic matter concentration, and it must be possible to obtain high removal rate even in winter because of wastewater characteristics.
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