Fluorine (F) recovery from wet process phosphoric acid (WPA) is essential for sustainable resource utilization and environmental protection. This work systematically investigates the F recovery mechanism by air stripping from three simulated systems: H3PO4- H2SiF6-H2O, H3PO4- HF-H2O, H3PO4- H2SiF6-HF-Al3+-H2O, and from two industrial systems: WPA and WPA-Al3+ under different stripping temperatures (60–110 ℃) and stripping times (0–120 min). The influence on the existence form of F, the content of Al3+ cations and the addition of active silica on the F removal rate in the phosphoric acid solution is studied by analyzing the changes in the contents of F, P and Si. The results indicate that the F in the form of H2SiF6 is more easily released from the phosphoric acid solution than that in the form of HF. While, the release of F is inhibited in the presence of the Al3+ in the solution due to the formation of Al-F complexes that are characterized by 19F NMR, 31Si NMR and FTIR techniques. Interestingly, the addition of active silica can promote the conversion of HF to H2SiF6 in the solution and significantly improve the release rate of F. The researching results can provide an important guidance for industrial practice of WPA.

PURPOSES : The current research aims to evaluate the impact of coating materials and temperature on the percentage of bead loss in pavement markings. METHODS : Five mixtures with varying numbers of coating layers (C0, C1, C2, C3, and C4) were prepared to assess the effect of coating layers on bead loss. The effect of stripping was simulated using a modified Hamburg Wheel Tracking test. Furthermore, the influence of temperature and coating material on bead loss was examined using control mixture (without coating), YR, and SY coating mixtures. The percentage bead loss was evaluated by a developed image analysis program. RESULTS : The results demonstrated a substantial reduction in bead loss as the number of coating layers increased, with the C4 mixture showing an impressive 4.3% bead loss after 500 HWT braking cycles compared to 27.4% for the C0 mixture. Higher testing temperatures resulted in increased bead loss, with the control mixture exhibiting the highest percentage loss at 7,500 HWT rolling cycles. Conversely, the YR and SY coating mixtures displayed superior resistance to bead loss. Statistical analysis confirmed the significance of coating layers in reducing bead loss, further supporting the effectiveness of coatings in preserving bead adhesion during HWT cycles. CONCLUSIONS : The findings highlight the potential of coating materials as a key protective measure for enhancing the longevity and performance of pavement markings.

PURPOSES : The aim of this study is to evaluate the stripping resistance of a bead coating via the Hamburg wheel tracking test and image analysis. METHODS : First, the stripping resistance of the bead coating was evaluated via the Hamburg wheel tracking test. A pneumatic wheel with a load of 175±2 N was used to simulate repeated skid cycles. Several bead coating mixtures with different numbers of coating layers, i.e., zero, one, two, three, and four layers, i.e., zero, one, two, three, and four layers,were conducted. Finally, an image analysis program was developed to analyze surface images captured from the Hamburg wheel tracking test. RESULTS : The results show that the samples with more coating layers exhibit higher stripping resistance. After 500 stripping cycles, the percentage of bead loss is 4% to 28%. At 80% bead loss, the mixture with one coating layer presents more skid cycles than the control sample without a coating layer. CONCLUSIONS : Incorporating a coating layer can improve the stripping resistance of glass beads under repeated skid cycles. Additionally, an image analysis program is established in this study to determine the percentage of bead loss caused by the stripping test.

We study galaxies undergoing ram pressure stripping in the Virgo cluster to examine whether we can identify any discernible trend in their star formation activity. We first use 48 galaxies undergoing different stages of stripping based on Hi morphology, Hi deficiency, and relative extent to the stellar disk, from the VIVA survey. We then employ a new scheme for galaxy classification which combines Hi mass fractions and locations in projected phase space, resulting in a new sample of 365 galaxies. We utilize a variety of star formation tracers, which include g - r, WISE [3.4]-[12] colors, and starburstiness that are defined by stellar mass and star formation rates to compare the star formation activity of galaxies at different stripping stages. We find no clear evidence for enhancement in the integrated star formation activity of galaxies undergoing early to active stripping. We are instead able to capture the overall quenching of star formation activity with increasing degree of ram pressure stripping, in agreement with previous studies. Our results suggest that if there is any ram pressure stripping induced enhancement, it is at best locally modest, and galaxies undergoing enhancement make up a small fraction of the total sample. Our results also indicate that it is possible to trace galaxies at different stages of stripping with the combination of Hi gas content and location in projected phase space, which can be extended to other galaxy clusters that lack high-resolution Hi imaging.

We propose a novel stripping solution containing acids (HCl and HNO3), an oxidant [(NH4)2S2O8], and complexing agents (NaCl and citric acid) to remove surface passivation layers from 14K gold alloys fabricated using an investment casting process. The optimized solution employing only HCl acid is determined by varying molar fractions of HCl and HNO3 on 14K yellow gold samples. Stripping properties are also identified for red and white gold alloy samples under the optimized stripping conditions. The removal of passivation layers, weight loss, and microstructure evolution are characterized using Raman spectroscopy, a precision scale, and optical microscopy. The proposed stripping solution effectively removes passivation layers more rapidly than conventional cyanide stripping. Weight loss increases linearly for up to 5 min for all 14K gold alloys. Red gold exhibits the greatest weight loss, followed by yellow gold and white gold. The results of microstructural analysis reveal that the conformal stripping occurs according to time. These results imply that the proposed oxidative chloride stripping might replace conventional cyanide stripping.

PURPOSES : The use of hydrated lime or other liquid anti-stripping agents (ASA) is the most common method of improving the moisture susceptibility of asphalt mixes. ASAs are also known to have an anti-aging effect, according to several researchers. Therefore, the use of ASAs is expected to enhance the stability of asphalt pavements. The purpose of this study is to investigate the anti-aging effect of ASAs that are found in the domestic market. METHODS : In this study, an asphalt binder and a mixture mixed with typical domestic solid and liquid ASAs were prepared and aged to evaluate the physicochemical changes. A liquid additive developed by a Korean oil refinery was used as the liquid ASA, and hydrated lime was utilized as the solid ASA. The aging process of the asphalt was determined in the laboratroy based on previous studies to simulate the aging process inh te field. RESULTS : The result of the laboratory experiment indicates that both the solid and liquid ASAs have an anti-aging effect. Moreover, the liquid additive performed relatively better than the hydrated lime. CONCLUSIONS : If ASAs have an anti-aging effect in addition to the anti-stripping function, it is expected to improve the stability of the asphalt pavement significantly. However, few studies have been carried out on the anti-aging effect of ASAs found in the domestic market. In this study, we conducted a fundamental study on the anti-aging effect to help in the selection and use of ASAs in the domestic asphalt-paving industry.

When there is a significant stripping in asphalt pavement, it is common practice to use a hydrated lime (HL) as an anti-stripping additive (ASA). However, since many asphalt plants do not have facilities for weighing and casting HL, they prefer to use of a liquid-type ASA (LA). Therefore, various brands of LAs which show proper anti-stripping function are currently developed, imported, and marketed in Korea. In addition to the anti-stripping effect, the HL has been known to give a significant age-retarding effect on paved asphalt in the field. Therefore, there was a question about whether or not the LA provides the same anti-aging effect as The HL. This study investigated anti-aging effect of the asphalt mixes which were prepared using both ASAs and short-term aged and long-term aged in the laboratory. The absolute viscosity was measured as an aging index from the binder recovered from the mixes after short-term aging (STA) and long-term aging (LTA) processes. The results showed that there was a significant higher aging found from the LA-added mix than the normal mix without any ASA. On the other hands, the mix with HL showed significantly lower ageing level than the LA-added mix and normal mix. The retardation of age-hardening by using HL was more effectively observed when the STA condition was stronger.

압력-분배 탈기방식으로 막접촉기를 구성하여 바이오가스 정제를 하였다. 폴리프로필렌(PP) 중공사막 모듈과 물리흡수제를 이용하여 막접촉기 성능 평가를 수행하였다. 실험은 흡수 압력, 가스의 유량, 흡수 온도 및 흡수제의 농도등 다양한 조건에서 수행하였다. 특히 CO2 흡수능이 높은 상용 흡수제인 프로필렌카보네이트(PC)와 물의 혼합흡수제를 사용하여 회수성능이 향상되었다. 탈기 방법이 개선된 압력-분배 탈기방식의 막접촉기는 50% CO2/50% CH4의 바이오가스 모사가스로부터 바이오메탄을 98% CH4 순도와 91%의 회수율로 정제하였다. 따라서 압력-분배 막접촉기를 통해 바이오가스로부터 수송용 바이오메탄의 생산이 가능함을 확인하였다.

Carbon dioxide recovery by vacuum stripping at low temperatures (below 100°C) could be a promising technology to substitute the desorption process in conventional aqueous amine absorption process. We prepared composite membranes by coating hydrophobic silicalite-filled PDMS layers on porous PE supports and used as new membrane strippers for CO2 recovery to prevent typical pore wetting problem of hydrophobic PTFE porous membranes. CO2 fluxes were measured under various operation conditions, such as different vacuum pressures, stripping temperatures, CO2 loadings, types of amine solutions and operation time. The composite membranes showed excellent long-term stability in vacuum stripping process when compared with porous PTFE membranes.

아스팔트 혼합물이 운반·대기 중에 단기노화(short-term aging: STA)되는 것은 잘 알려진 사실이며 노화정도는 혼합물의 온도가 높음에 따라 그리고 시간이 길어짐에 따라 지수 함수적으로 증가되는 것으로 알려져 있다. 또한 같은 온도와 시간에 같은 바인더, 골재 및 입도를 사용한 같은 혼합물이라도 사용되는 첨가제의 종류에 따라 노화도에 차이가 난다. 그리고 혼합물의 종류에 따라서도 노화도에 차이가 큰 것으로 알려져 있다. 따라서 본 연구에서는 박리방지제(anti-stripping agent: ASA)의 종류와 혼합물의 종류에 따른 노화도의 차이를 비교분석 하였다. ASA로는 박리방지효과가 우수한 분말의 소석회와 액상 ASA를 비교하였다. 혼합물은 밀입도 아스팔트 (dense-graded asphalt: DGA) 표층용 혼합물과 쇄석 매스틱 아스팔트 (stone mastic asphalt: SMA) 혼합물을 비교하였다. 노화도는 아스팔트 노화의 척도로는 가장 많이 쓰이는 절대점도(absolute viscosity: AV)를 이용하였다. STA 온도와 시간에 따른 AV의 차이를 STA 처리된 혼합물로부터 추출·회수하여 60℃에서 측정하였다. 시험결과 같은 온도와 시간으로 STA 처리된 혼합물에서 소석회가 사용된 혼합물의 노화도가 월등히 낮았으며, 혼합물의 종류로는 SMA 혼합물의 노화도가 DGA 혼합물보다 낮게 나타났다. 이는 소석회가 박리방지효과 뿐만 아니라 노화억제 효과가 크기 때문이며, SMA는 바인더 함량이 높아 골재를 피복한 아스팔트 필름의 두께가 두꺼워 노화도가 적게 나타난 것으로 판단되었다.