Journal of Flow Chemistry ( IF 2.0 ) Pub Date : 2021-10-20 , DOI: 10.1007/s41981-021-00208-8 Hilman Syaeful Alam 1, 2 , Priyono Sutikno 1 , Tubagus Ahmad Fauzi Soelaiman 1 , Anto Tri Sugiarto 2
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Research on bulk nanobubbles with various applications has been widely reported in the literature. However, the majority of studies are still limited to small scales with non-continuous generation processes, thus, the results may be difficult to apply on large-scale applications. In this work, a nanobubble generator was developed based on hydrodynamic cavitation using a two-chamber swirling flow nozzle that efficiently produced nanobubbles and had the potential to be applied to continuous flow systems and processes. The bulk nanobubble characteristics were evaluated according to the hydrodynamic diameter, zeta potential, and dissolved oxygen (DO) concentration based on the influence of the gas flow rate ratio (Ql/Qg), generation time, gas type, pH value, and NaCl concentration on the generated nanobubbles. The results show that oxygen and air nanobubbles smaller than 200 nm were successfully generated in pure water. The oxygen and air nanobubbles were negatively charged in pure water. The effects of pH and salt addition were similar to those during nanobubble generation using ultrasonic cavitation. In alkaline medium, nanobubbles were smaller and more stable than in acidic medium. The addition of salt to the nanobubble suspension reduced the repulsive electrostatic forces between the nanobubbles by increasing their size and decreasing their negative zeta potential. The resulting oxygen and air nanobubbles in pure water were verified to be stable for up to 10 and 5 months, respectively, without any significant changes in size or zeta potential. These results corresponded to predictions by the ionic repulsion model based on microbubble shrinkage.
Graphical abstract
中文翻译：
大体积纳米气泡：使用两室旋流喷嘴产生并在水中长期稳定
对具有各种应用的大块纳米气泡的研究已在文献中得到广泛报道。然而，大多数研究仍局限于具有非连续生成过程的小规模，因此，结果可能难以应用于大规模应用。在这项工作中，纳米气泡发生器是基于流体动力空化开发的，使用两室旋流喷嘴，可有效产生纳米气泡，并有可能应用于连续流动系统和工艺。基于气体流速比（Q l /Q g)、生成时间、气体类型、pH 值和生成的纳米气泡的 NaCl 浓度。结果表明，在纯水中成功生成了小于200 nm的氧气和空气纳米气泡。氧气和空气纳米气泡在纯水中带负电。pH 值和盐添加的影响与使用超声波空化产生纳米气泡期间的影响相似。在碱性介质中，纳米气泡比在酸性介质中更小且更稳定。向纳米气泡悬浮液中添加盐通过增加纳米气泡的尺寸和降低它们的负 zeta 电位来降低纳米气泡之间的排斥静电力。经证实，纯水中产生的氧气和空气纳米气泡分别可稳定长达 10 个月和 5 个月，尺寸或 zeta 电位没有任何显着变化。
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