The structure and magnetic properties of composite powders prepared by ball milling a mixture of Fe2O3 ‧ (0.4-1.0)Fe were investigated. Hysteresis loops and differential scanning calorimetry (DSC) curves are used to characterize the materials and to examine the effect of the solid state reaction induced by ball milling. The results showed that a solid state reaction in Fe2O3 ‧ (0.4-1.0)Fe clearly proceeds after only 1 h of ball milling. The system is characterized by a positive reaction heat of +2.23 kcal/mole. The diffraction lines related to Fe2O3 and Fe disappeared after 1 h of ball milling and, instead, diffraction lines of the intermediate phase of Fe3O4 plus FeO formed. The magnetization and coercivity of the Fe2O3 ‧ 0.8Fe powders were changed by the solid state reaction process of Fe2O3 by Fe during ball milling. The coercivity of the Fe2O3 ‧ 0.8Fe powders increased with increasing milling time and reached a maximum value of 340 Oe after 5 h of ball milling. This indicates the grain size of Fe3O4 was clearly reduced during ball milling. The magnetic properties of the annealed powders depend on the amount of magnetic Fe and Fe3O4 phases.

Various kinds of friction materials were manufactured by adding 10%, 20%, and 30% of reduced iron, respectively, which has been obtained during the reduction process of blast furnace sludge extracted from the blast furnace, and its iron oxide, instead of existing barium sulfate(BaSO4) among the components of automobile brake friction materials. Fundamental physical property test and friction performance test, etc., using a brake dynamometer were carried out against these friction materials. Furthermore, when the expensive filling material, BaSO4 was substituted by reduced iron and added to the friction material, the added content of reduced iron for an excellent friction characteristic considering the heat emission temperature, wear, etc., was 10%. In the fundamental physical property test, as the added content of blast furnace sludge or reduced iron increased, and as the content increased, the shear strength and bonding strength of friction materials decreased, but both of them indicated sufficient strengths to be applied to a friction material. Even in the frictional performance test using a brake dynamometer, as the added content of blast furnace sludge or reduced iron increased, the friction coefficient reacted insensibly to brake deceleration, and its stability was improved.

In this study, we compared the MZVI (Microscale Zero-Valent Iron) and NZVI (Nanoscale Zero-Valent Iron) for reactivity and mobility in a column to reduce nitrate, which is a major pollutant in Korea, and investigated the effect of operational parameters on the NZVI filled column. For the comparison of MZVI and NZVI, samples were collected for 990 minutes using fractionator in the similar operation conditions (MZVI 10g, NZVI 2g). The nitrate reduction efficiency of NZVI was about 5 times higher than that of MZVI, which was about 7.45% and 38.75% when using MZVI and NZVI, respectively. In the mobility experiment, the MZVI descended due to gravity while NZVI moved up with water flow due to its small size. Furthermore, the optimum condition of NZVI filled column was determined by changing the flow rate and pH. The amount of Fe ions was increased as the pH of the nitrate solution was lowered, and the nitrate removal rate was similar due to the higher yield of hydroxyl groups. The removal rate of nitrate nitrogen was stable while flow rate was increased from 0.5 mL/min to 2.0 mL/min (empty bed contact time: 2.26 min to 0.57 min). NZVI has a high reduction rate of nitrate, but it also has a high mobility, so both of reactivity and mobility need to be considered when NZVI is applied for drinking water treatment.

고도산화공정(Advanced Oxidation Process, AOP) 중 하나인 펜톤 산화법은 과산화수소(H2O2)와 2가철 이온(Fe2+)이 반응하여 OH 라디칼을 생성함으로써 OH 라디칼의 강한 산화력으로 유기물을 분해하는 방법이다. 펜톤 산화는 다양한 유기물과의 높은 반응성을 지닌다는 점과 생물학적으로 분해가 어려운 물질을 산화･분해시켜 생물학적 처리가 가능하도록 한다는 등의 장점을 지니고 있다. 그러나 펜톤 산화는 유기물과의 반응 후 펜톤 슬러지를 부산물로 다량 생성하기 때문에 발생된 슬러지를 처리하는 공정이 추가적으로 요구된다. 또한, 펜톤 슬러지는 원수에 따라 다량의 난분해성 물질과 철염 등을 함유하고 있기 때문에 처리하는 방법이 까다롭다. 펜톤 슬러지는 주로 매립으로 처리하였으나 매립지 크기의 한계 및 수명 단축, 비싼 처리비용 등의 문제가 뒤따르기 때문에 이에 대한 대책이 필요한 실정이다. 이러한 펜톤 슬러지를 처리하고자 다양한 연구가 진행되고 있다. 그 중 펜톤 슬러지를 촉매, 응집제 등으로 재이용하는 연구가 각광받고 있다. 한 연구는 펜톤 슬러지를 산에 용해하여 그대로 펜톤 산화 공정에 사용하는 방법과 산에 용해하여 환원을 거친 후 펜톤 산화 공정에 사용하는 방법을 비교하였다. 재생 횟수를 고려했을 때 환원을 거친 펜톤 슬러지가 효율적인 촉매 역할을 한다고 나타났다. 또한, 대부분의 펜톤 슬러지 환원은 철편을 사용한 것으로 나타났다. 그러나 철편을 사용할 경우, 기존 펜톤 슬러지가 가지고 있는 총 철의 농도에 영향을 미칠 뿐만 아니라 회수하는 것 또한 어려움이 있다. 본 연구는 환원제를 사용하여 펜톤 슬러지 내 철 이온을 전환함으로서 펜톤 산화용 철 촉매로 재이용하고자 하는 기초연구이다. 본 연구에서는 다양한 황 계통의 환원제를 사용하여 펜톤 슬러지 내 철 이온 형태를 Fe3+에서 Fe2+로 전환하고 각각의 환원제 별로 철 이온 전환 정도를 비교하여 최적의 환원제를 찾고자 하였다. 본 연구에서 사용한 환원제는 Sodium sulfite (Na2SO3), Potassium sulfite (K2SO3), Sodium bisulfite (NaHSO3)로 총 3가지이다. 본 연구는 ‘D’ 산업용수센터에서 발생하는 RO 농축폐수를 펜톤 산화로 처리한 후 부산물로 생성되는 펜톤 슬러지를 대상으로 실시하였다. 펜톤 슬러지는 황산을 사용하여 용해액 상태로 전환하여 실험에 사용하였다. 슬러지 용해액 1 L를 기준으로 각각의 환원제를 0.5 g씩 투입 후, 2 시간까지의 철 이온 농도 변화를 살펴보았다.

In this study, the reductive dechlorination of triclosan using zero-valent iron (ZVI, Fe0) and modified zero-valent iron (i.e., acid-washed iron (Aw/Fe) and palladium-coated iron (Pd/Fe)) was experimentally investigated, and the reduction characteristics were evaluated by analyzing the reaction kinetics. Triclosan could be reductively decomposed using zero-valent iron. The degradation rates of triclosan were about 50% and 67% when Fe0 and Aw/Fe were used as reductants, respectively, after 8 h of reaction. For the Pd/Fe system, the degradation rate was about 57% after 1 h of reaction. Thus, Pd/Fe exhibited remarkable performance in the reductive degradation of triclosan. Several dechlorinated intermediates were predicted by GC-MS spectrum, and 2-phenoxyphenol was detected as the by-product of the decomposition reaction of triclosan, indicating that reductive dechlorination occurred continuously. As the reaction proceeded, the pH of the solution increased steadily; the pH increase for the Pd/Fe system was smaller than that for the Fe0 and Aw/Fe system. Further, zero-order, first-order, and second-order kinetic models were used to analyze the reaction kinetics. The first-order kinetic model was found to be the best with good correlation for the Fe0 and Aw/Fe system. However, for the Pd/Fe system, the experimental data were evaluated to be well fitted to the second-order kinetic model. The reaction rate constants (k) were in the order of Pd/Fe > Aw/Fe > Fe0, with the rate constant of Pd/Fe being much higher than that of the other two reductants.