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Regeneration of Sn4+ from Sn2+ solution during electrowinning process using anion exchange membrane
정문철,유경근,Richard Diaz Alorro 한국자원공학회 2019 Geosystem engineering Vol.22 No.1
Electrowinning process to regenerate Sn4+ from Sn2+ in HCl solution using an electrowinning cell with anion exchange membrane was proposed to suggest a novel recycling process to recover Sn. During the tests, the effects of initial Sn2+ concentration on the regeneration of Sn4+ were investigated under the following condition; 7,000 mg/L, 10,000 mg/L, and 13,000 mg/L of Sn2+, 1 M HCl, 250 A/m2 of current density, graphite anode, titanium cathode, room temperature, and 2 h. Electro-deposited Sn on the cathode showed dendritic structure regardless of the Sn2+ concentration and no change of Sn concentration was observed in the anolyte. Leaching tests were performed using the anolyte, obtained from the electrowinning tests, to examine the amount of regenerated Sn4+ concentration during electrowinning process. Based on the results of Sn leaching tests, it was found that 84.44%, 81.03%, and 79.43% of Sn4+ were regenerated from 7,000 mg/L, 10,000 mg/L, 13,000 mg/L initial concentration of Sn2+ solution, respectively. Consequently, it was found that the regeneration of Sn4+ can occur during the electrowinning process at the same time with Sn recovery and Sn4+ can be reused as an oxidant to leach Sn successfully.
바스트나사이트, 모나자이트, 제노타임의 부유선별 연구동향
정문철,유경근 한국자원공학회 2020 한국자원공학회지 Vol.57 No.6
A literature review was conducted to summarize the types of minerals containing rare earth elements, their chemical composition, surface characteristics, adsorption mechanism with various collectors, reagent scheme, and their effects on the flotation process using currently available studies on rare earth mineral flotations. Minerals that are commercially exploited to recover rare earth elements include bastnaesite, monazite, and xenotime. Using hydroxamate, carboxylate, and phosphate collectors, the surface of minerals became hydrophobic, and high floatability was readily achieved. It was concluded that adsorption occurs chemically by interacting with the functional group of collectors and the trivalent rare earth cation on the mineral surface. The use of a depressant was necessary to achieve better selectivity, as it commonly occurs with various types of gangue minerals. It is expected that this study will provide fundamental information to design effective flotation processes for both currently available and newly found deposits. 이 글에서는 대표적 희토류 광물인 바스트나사이트, 모나자이트, 제노타임의 부유선별 연구에 대한 문헌 정보를 통해, 희토류 광물의 화학적 조성 및 기원, 표면 특성, 흡착 메커니즘, 부유선별 시약의 종류 및 효과 등에 대한 정보를 정리하였다. 자연발생적으로 친수성 표면을 갖는 희토류 광물은 하이드로자믹산, 지방산 및 인산 계열의 포수제를 통해 높은 부유도를 얻을 수 있다. 포수제와광물 표면의 흡착 메커니즘은 희토류 광물 표면에 존재하는 희토류 3가 양이온과 포수제의 작용기의 화학적 결합으로 설명된다. 또한, 부유선별의 주요 목적인 선택적인 광물의 회수를 위해서는 억제제의 사용이 필수적이며, 희토류 광물의 부유선별에 사용되는 다양한 억제제 및 활성제에 대한 사례를 정리하였다. 본 연구에서 제공한 정보는 현재 생산 중이거나 새롭게 발견되는 희토류 광상에대한 효율적인 부유선별 공정 설계를 위한 기본적인 참고자료가 될 것으로 기대된다.
Differential Expression of TGF-β Isoforms in Human Kerationocytes by Narrow Band UVB
정문철,신민영,홍경국,정기헌,김낙인 대한피부과학회 2008 Annals of Dermatology Vol.20 No.3
Background: Transforming growth factor-β (TGF-β), a multifunctional growth factor, has three isoforms: TGF-β1, TGF-β2, and TGF-β3. Different isoforms of TGF-β are associated with different proliferation and differentiation states of the epidermis. Narrow band ultraviolet B (NBUVB) emits a concentrated UVB source of 311 nm. NBUVB 1,000 mJ/cm2 induces apoptosis in approximately 50% of keratinocytes. Objective: The purpose of this study was to evaluate whether irradiation with NBUVB would alter the expression and production of TGF-β1, 2, and 3. Methods: We measured TGF-β1, 2, and 3 mRNA and TGF-β1 and 2 protein levels at 800, 1,000, and 1,200 mJ/cm2 for 24 hours and 48 hours. Results: TGF-β1 mRNA levels were increased at both 24 hr and 48 hr, TGF-β2 mRNA levels were decreased at both 24 hr and 48 hr, and TGF-β3 mRNA levels were increased at 24 hr and similar to control at 48 hr. TGF-β1 protein levels were increased at 48 hr but decreased at 24 hr. TGF-β2 protein levels were decreased at both 24 hr and 48 hr. Conclusion: The results suggest a possible role for TGF-β1 after NBUVB irradiation and opposing roles for TGF-β1 and TGF-β2 isoforms in NBUVB irradiation. (Ann Dermatol (Seoul) 20(3) 113∼119, 2008) Background: Transforming growth factor-β (TGF-β), a multifunctional growth factor, has three isoforms: TGF-β1, TGF-β2, and TGF-β3. Different isoforms of TGF-β are associated with different proliferation and differentiation states of the epidermis. Narrow band ultraviolet B (NBUVB) emits a concentrated UVB source of 311 nm. NBUVB 1,000 mJ/cm2 induces apoptosis in approximately 50% of keratinocytes. Objective: The purpose of this study was to evaluate whether irradiation with NBUVB would alter the expression and production of TGF-β1, 2, and 3. Methods: We measured TGF-β1, 2, and 3 mRNA and TGF-β1 and 2 protein levels at 800, 1,000, and 1,200 mJ/cm2 for 24 hours and 48 hours. Results: TGF-β1 mRNA levels were increased at both 24 hr and 48 hr, TGF-β2 mRNA levels were decreased at both 24 hr and 48 hr, and TGF-β3 mRNA levels were increased at 24 hr and similar to control at 48 hr. TGF-β1 protein levels were increased at 48 hr but decreased at 24 hr. TGF-β2 protein levels were decreased at both 24 hr and 48 hr. Conclusion: The results suggest a possible role for TGF-β1 after NBUVB irradiation and opposing roles for TGF-β1 and TGF-β2 isoforms in NBUVB irradiation. (Ann Dermatol (Seoul) 20(3) 113∼119, 2008)