Mass transfer intensification for carbon quantum dot nanofluid drops under pulsed electric fields

Abstract

Simultaneous use of carbon quantum dot (CQD) nanofluids and pulsed electric fields exhibits amazing mass transfer intensification in liquid–liquid extraction of circulating drops. Here, the chemical system of kerosene–acetic acid–water with mass transfer resistance in the organic phase was used in which organic nanofluid drops contained CQD or modified CQD-Fe. These products with extremely small sizes of 7.2 and 13.4 nm were synthesized and characterized by DLS, Zeta potential, XRD, EDS and SEM techniques. To find optimum conditions, CQD concentrations within (0.0005–0.003) wt%, electric field frequencies within (50–550) Hz and electric field strengths to 16 V/cm were examined. From hydrodynamic point of view, the flow pattern of drops was in circulating mode, and that terminal velocity of drops correctly followed the Grace model. The substantial effect of pulsed electric field on the CQD and CQD-Fe nanofluids, brought about mass transfer enhancements to 263.5 and 291.6%. This can be attributed to the electro-induced motion of global CQDs with pulsed electric fields. For the aim of modelling, the adapted Kumar and Hartland equation with a developed correlation of the enhancement factor versus involved dimensionless variables were satisfactory to reproduce the mass transfer coefficient data.