Molecular dynamics study on the coalescence and break-up behaviors of ionic droplets under DC electric field

Abstract

Electric coalescence is an effective way to achieve high performance of separating small dispersed water droplets from oils. We investigated the coalescence and break-up behaviors of double conducting droplets dissolved 0.4394 M NaCl in the presence of electric field using molecular dynamic simulations. Our results provide that the critical electric field (Ec) and the corresponding conical angle for coalescence are 0.52 V/nm and 42°. Two conducting droplets are driven to approach, contact, and eventually coalescence by the electric field when the applied electric field is weaker than Ec. Nevertheless, in the presence of the electric field stronger than Ec, the partial break-up that small daughter droplets break away from their mother droplet occurs due to the exchange and neutralization of positive and negative charged ions in the connecting liquid bridge. As the electric field increases further to 0.80 V/nm or stay above, the strong electric field leads to the entire break-up process, accompanied with ion jetting before droplets contacting.