Development of environmental cleanup system with spontaneous running droplet

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K14523
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Green/Environmental chemistry
• Research Institution: Shizuoka Institute of Science and Technology
• Principal Investigator: NANZAI Ben 静岡理工科大学, 理工学部, 准教授 (20563349)
• Research Collaborator: KASAI Keigo ; SHIGEMOTO Aya
• Project Period (FY): 2017-04-01 – 2019-03-31
• Keywords: アクティブマター / 汚染除去材料 / 非線形現象

Outline of Final Research Achievements

We observed that nitrobenzene droplet including BTB (bromothymol blue) ran spontaneously on glass substrate in cationic surfactant aqueous solution under basic condition. Dewetting effect and Marangoni convection due to interfacial gradient around droplet were considered as the droplet motion mechanisms. The process of nitrobenzene distribution to the aqueous phase is supposed to affect the variation of interfacial tension around the droplet; however, the effect of solvent distribution on spontaneous running droplet motion is still unclear. We considered the effect of nitrobenzene distribution on the spontaneous droplet motion. The running velocity decreased with increasing ethanol concentration in the aqueous solution. BTB concentration in aqueous solution also decreased with ethanol concentration although that of nitrobenzene was almost constant. The motility of droplet was affected by the distribution of solute rather than that of solvent.

Free Research Field

環境化学

Academic Significance and Societal Importance of the Research Achievements

水中に低濃度で存在することから回収や分解が困難な界面活性剤を，基板上に静電吸着させることで濃縮させ，これを油滴が自発走行しながら回収していくことで，さらに効率的に濃縮できる。界面活性剤と天然有機物が混ざった複合廃液を生物処理すれば，易分解性の有機物が優先的に分解され難分解性である界面活性剤は残存することから，選択的に濃縮する手法が必要である。このシステムは溶質濃度の非平衡を利用するため，外力を全く必要としない省エネシステムであり，溶質の回収後は油滴ごと水相から分離するだけで良いため，非常に安価で簡便な手法である。