최근 선박용 연료유에 대한 황 함유량 규제를 준수하기 위해 저유황유의 수요가 증가하고 있다. 그러나 저유황유를 공급하는 시기, 지역, 회사 별로 그 품질이 상이함에 따라 선내 연료유 저장탱크에서는 과도한 슬러지가 발생하는 등 혼합 안정성에 대한 문제가 제기되고 있다. 따라서 본 연구는 초음파의 캐비테이션 현상을 이용하여 저유황유의 품질 향상을 하고자 하였다. 선내 저장 탱크에서 이종의 연료유가 혼합되는 상황을 모사하기 위해 두 가지 종류의 저유황유(황 함유량 0.5 % 이하 MGO, MDO)를 혼합하여 시료유로 사용하였다. 원료유와 50 wt.% 씩 혼합한 시료유를 120분 동안 초음파 처리하였으며, 40분 주기로 채취된 샘플은 GC/MS 분석을 수행하여 초음파 조사 시간에 따른 시료유의 조성 변화를 분석하였다. 연구결과, 초음파의 캐비테이션 효과로 인하여 화학결합이 깨지면서 MGO 내 존재하는 고분자량 화합물의 감소와 저분자량의 화합물 증가가 관찰되었다. MDO와 혼합유의 경우, 초음파 조사 후 저분자 화합물에 대한 상대 존재 비의 부분적 증가가 관찰되었지만 시간과 상대 존재비 사이의 상관관계는 관찰되지 않았다.

Membrane distillation (MD) is a novel separation process that have drawn attention as an affordable alternative to conventional desalination processes. However, membrane fouling and pore wetting are issues to be addressed prior to widespread application of MD. In this study, the influence of ultrasonic irradiation on fouling and wetting of MD membranes was investigated for better understanding of the MD process. Experiments were carried out using a direct contact membrane distillation apparatus Colloidal silica was used as a model foulants in a synthetic seawater (35,000 mg/L NaCl solution). A vibrator was directed attached to membrane module to generate ultrasonic waves from 25 kHz (the highest energy) to 75 kHz (the lowest energy). Flux and TDS for the distillate water were continuously monitored. Results suggested that ultrasonic irradiation is effective to retard flux decline due to fouling only in the early stage of the MD operation. Moreover, wetting occurred by a long-term application of ultrasonic rradiation at 75 kHz. These results suggest that the conditions for ultrasonic irradiation should be carefully optimized to maximize fouling control and minimize pore wetting.

폐식용유를 원료로 한 바이오 디젤의 제조 과정에 초음파 에너지를 조사하여 폐식용유의 전이에스테르 화반응 특성을 조사하였다. 초음파 조사는 두 가지 효과가 있는데 촉매의 대체역할과 공동현상이다. 실험의 매개 변수는 메탄올의 몰비, 반응온도, 촉매량이며 이를 변수로 최적공정조건을 구명한 결과 최적의 공정조건은 몰비가 1:7, 온도가 55 ℃, 촉매량은 1 wt％로 나타났다. 또한 초음파 에너지를 조사하는 실험의 매개변수는 초음파에너지 조사시간과 초음파에너지의 세기로서 이를 변수로 하여 초음파에너지조사가 바이오디젤 성능에 미치는 영향을 비교 하였다. 그 결과 최적의 초음파에너지 조사시간은 30분, 초음파에너지의 세기는 500 W로 나타났다. 또한 초음파에너지의 촉매 대체 가능성을 알아보기 위해 최적공정조건에서 촉매를 넣지 않고 초음파에너지를 30분간 조사하였을 때는 초음파에너지를 조사하지 않은 일반공정보다 바이오디젤의 성능은 BD(BioDiesel)수율이 2.4 %, FAME (Fatty Acid Methyl Ester)함량이 1.3 % 증가한 것으로 나타나, 초음파에너지가 촉매를 대체 할 수 있다는 것을 알 수 있었다.

Sediments of Little Scioto (LS) River in Ohio was contaminated by poor disposal of creosote from Baker Wood Creosoting Facility. Among the primary compounds of creosote, Polycyclic Aromatic Hydrocarbons (PAHs) are the most common ingredient. PAHs are known for toxic, carcinogenic and mutagenic compounds. There are many difficulties to remove the PAHs in nature environment because their characteristics are having a less water-solubility, volatile and low mobility properties as increasing the molecular weight. The generation of hydroxyl radicals (ㆍOH) and hydrogen peroxide (H2O2) forms as well as high temperature (5000 K) and pressure (1000 atm) by a physico-chemical effects of ultrasound during a cavitation collapse can promote the degradation and desorption of PAHs in sediment And it can also produces shock wave and microjets which are able to change the size and surface of particle in solid-liquid system as one of physical effects. Therefore, we explored to understand the role of particle size, the effect of elimination for PAHs concentration by ultrasound and optimize the conditions for ultrasonic treatment. The condition of various size of particles ( > 150㎛, < 150㎛) and solid-liquid ratio (12.5g/L, 25g/L) for the treatment was considered and ultrasonic power (430 W/L) with liquid – hexane extraction and microwave extraction method were applied after ultrasound treatment.

PAHs are major pollutants that are widely distributed in soil and groundwater environment, so that may be regarded as carcinogens. We investigated the degradation kinetics of PAH in aqueous solution when low pressure UV energy and ultrasonic irradiation were applied. Phenanthrene and pyrene were used as model compounds. The degrees of degradation of these compounds with time were analyzed with a GC/MSD (SIM-mode). UV photolysis experiments showed that phenanthrene was reduced by 90～67% at initial concentrations of 1 ppm to 8ppm whilst it decreased to 50% at 10 ppm. Under the same conditions pyrene was degraded up to about 75% at lower initial concentrations but the reduction efficiency dropped to a level of 34 to 29% at the higher concentrations above 8 ppm. The reaction orders for phenanthrene and pyrene were found to be zero-th and ca. -0.4th order, respectively, thus implying that the reported assumption of pseudo 1st order reaction for some PAHs would be no longer valid. PAH degradation was roughly proportional to the intensity of UV (number of lamps), exhibiting maximum 92.5% of the degradation efficiency. The solution pH was lowered to 4.4 from 6.4 during the experiments partially because the carbons decomposed by the energy reacted with oxygen radicals to produce carbon dioxides. Ultrasonic irradiation on phenanthrene solutions gave relatively poor results which matched to 50 to 70% of degradation efficiency even at 2 ppm of initial concentration. Phenanthrene was found to be degraded more efficiently than pyrene for the two energy sources. Ultrasound also followed the same reaction kinetics as UV energy on PAH degradation.