LAUSR

Following a tradition of 40 years, since 1979, these two special issues focus on separation science and technology (SS&T) for energy applications. They contain papers that have been presented at the 20 Symposium on Separation Science and Technology for Energy Applications, in Gatlinburg, Tennessee, on October 21–24, 2018. The SS&T Symposium occurs every two years, and attracts international participation. More information about the 2018 Symposium can be found at sst2018.ornl.gov. A wide range of research topics are covered in these special issues, which together contain 25 papers. While these special issues represent a variety of energy research topics, there is a strong focus on nuclear energy applications. The first issue is titled “Separations for Nuclear Energy Applications” and includes 13 papers (#1–13), which deal with current problems in nuclear energy. The first three of the nuclear-energy related papers (#1–3) are focused on the dissolution of used nuclear fuel for recycling purposes. The fourth paper (#4) is on the filtration of particles from tank supernate solution. The next four papers (#5–8) describe the performance of various materials in adsorption and ion exchange processes developed for the separation of various ions from solutions including cesium, uranium, and thorium. The remaining five papers (#9–13) deal with various nuclear energy problems as listed below: (i) selective capture and analysis of purgeable mercury species in high activity tank waste, (ii) effect of cesium and strontium separation on occupied area reduction in a current nuclear energy system, (iii) simulant testing of a co-decontamination flowsheet for a product with a controlled uranium-to-plutonium ratio, (iv) real-time monitoring of the chemistry of hydroxylamine nitrate and iron as surrogates for nuclear materials processing, and (v) microfluidics-based separation of actinium225 from radium-225 for medical applications. The second issue is titled “Separations for Energy Applications” and includes 12 papers (#14–25), which deal with current energy problems. The first paper (#14) is focused on liquid-liquid extraction fundamentals, specifically on volume fraction, axial dispersion, and droplet size distribution in two-phase Taylor-Couette contactors. The following four papers in the second issue (#15–18) are focused on CO2 capture from flue gas generated by fossil-energy power plants. Two papers (#19–20) are then focused on the separation of rare earth elements, followed by two papers (#21–22) on materials for membrane separations. The last three papers (#23–25) deal with water and wastewater treatment by capacitive deionization and adsorption. Observations from statistics on the number of papers and citations over the past 19 special issues show that SS&T Symposia issues have a history of good citation rate, with some highly rated papers. This special issue continues the tradition of adding high-quality papers to the literature of separations for energy applications including new separations processes (e.g., intensified processes by electric and magnetic fields), novel and emerging materials (e.g., new membranes and adsorbents), and current energyrelated problems (e.g., separation of rare-earth elements, CO2 capture, wastewater treatment). It is our hope that, like the previous issues, the 20 SS&T special issues will be well received by the community. We thank all the authors, who contributed to these special issues, as well as the reviewers who volunteered their time for the review process. We also thank Drs. David DePaoli, Ken Nash, and Jack Watson, current and past Chairs of the Symposia on Separation Science and Technology for Energy Applications, and Dr. Ranil Wickramasinghe, Editor of Separation Science and Technology, for making these special issues possible and for continuing this special relationship with the journal that was started with the first SS&T Symposium in 1979. We particularly thank Ms. Amber Friday-Brown for her valuable help to both the editors and authors of the special issues in every step of the manuscript submission, review, and acceptance process.