M1 Master Nuclear Energy 29th June 2015 Modelling and simulation of a microfluidic solvent extraction process using a CFD software M1 Master Nuclear Energy 29th June 2015 Student: Vera De la Cruz Gerardo Supervisors: Siméon Cavadias, Clarisse Mariet and Gérard Cote Referee: Eric Royer

Presentation display Global Objective Procedure Extraction Process and Microfluidics Difficulties and constraints CFD Software Flow Patterns tried Previous works Results Assumptions-Modelling Conclusions

General Objective Simulation of a solvent extraction process in a Y-Y shaped microfluidic device, using the COMSOL Multiphysics software.

Industry Laboratories Extraction Process Figure 1: Solvent extraction procedure with an additional Stripping step in the end. Source: Solvent Extraction Cours notes, Pr. D. Pareau, Ecole Centrale Paris fall 2014.

Why a microchip? Microfluidics  Small amounts of fluids ( 10 −18 − 10 −09 litres)  Dimensions of tens to hundreds of micrometers. Work with small volume Better performance with lower power Precise mixing/dosage Ease of disposing of device and fluids Can be integrated with other devices – lab on a chip Minimize dead space, void volume and sample carryover Reduce cost of reagents and power consumption High surface to volume ratio / Low Reynolds number

Features CFD software Dynamic interface Worldwide well-known software in the science field Constant improvement Specific websites and blogs Dynamic interface

Previous Research Works Research Cooperation Project HDR Clarisse Mariet M1 Student Sean Robertson

Geometry and assumptions used Constant all along the microchannel 𝜌 𝑎,𝑜 → 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝜇 𝑎,𝑜 →𝐷𝑦𝑛𝑎𝑚𝑖𝑐 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦 𝜎→ 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑡𝑒𝑛𝑠𝑖𝑜𝑛 Defined for each one of the phases 𝐷 𝑈𝑟𝑎𝑛𝑖𝑢𝑚 → 𝐷 𝐶𝑜𝑚𝑝𝑙𝑒𝑥 → Uranium diffusion coefficient Complex diffusion coefficient

Complex Formation Reaction 𝑈 𝑂 2 𝐶𝑙 𝑛 2−𝑛 + 𝑛−2 𝑅 4 𝑁 + , 𝐶𝑙 − → 𝑅 4 𝑁 + 𝑛−2 𝑈 𝑂 2 𝐶𝑙 𝑛 2−𝑛 + 𝑛−2 𝐶𝑙 − for 𝑛≥3 Simplification 𝜕𝐶 𝜕𝑡 = 𝑘 1 𝐴−0.1709𝐶 A  Uranium concentration C  Complex concentration 𝑘 1  Mass transfer global coefficient Relation 𝑹 𝑼𝒓𝒂𝒏𝒊𝒖𝒎 =− 𝒌 𝟏 𝑨−𝟎.𝟏𝟕𝟎𝟗𝑪 𝑹 𝑪𝒐𝒎𝒑𝒍𝒆𝒙 = 𝒌 𝟏 𝑨−𝟎.𝟏𝟕𝟎𝟗𝑪 Uranium reaction rate Complex reaction rate

Physics Application modes Fluid Flow Laminar Two-Phase Flow Level Set Chemical Species Transport Transport of Diluted Species Laminar Two-Phase Flow Level Set  Laminar flow Moving interface Immiscibility. Transport of diluted Species  Diluted species diffusion phenomena Complexation reaction

Study steps Steady state

The solutions obtained from the software are based on three pillars HOW THE SOFTWARE WORKS? 1° Model Equations 2° Treatment of the Interface 3° Boundary conditions setting The solutions obtained from the software are based on three pillars

Table 1. Numerical stabilization parameters to be considered First difficulties No convergence Physical settings Numerical stabilization parameters Table 1. Numerical stabilization parameters to be considered Symbol Definition Parameter 𝛾 Reinitialization parameter 𝜖 𝑙𝑠 Parameter controlling interface thickness Memory and time Mesh optimization

Mesh Optimization Conditions to take into account Immiscibility between the organic and the aqueous phases Strong kinetics present in the interface region Conditions to take into account Sequence type: Physics-controlled mesh Element size: Extremely coarse Sequence type: Physics-controlled mesh Element size: Fine User-controlled mesh

Simulation models – flow patterns Two basic flow patterns can be defined for all fluid systems COUNTER CURRENT FLOW CO-CURRENT FLOW Internal Surface and Fluids properties Initial fluid Flow rates Dispersed Flow Continuous Co-current Flow Continuous Counter-current Flow

1) Co-current flow with moving interface, Laminar flow In a first trial the objective was to observe how the interface changed its appearance and to obtain the required time for its stabilization.

1) Co-current flow with moving interface, Laminar flow + chemical species transport Stationary study after the flow stabilization and a time dependent study in parallel with the laminar flow study.

Interface instability 2) Counter current flow Interface instability

2) Wettability and contact-angle This surface characteristic is defined by the surface wettability, characterized by the contact angle. Figure 2: Contact angle, graphic definition.

3) Co-current droplet formation Phase initialization  Droplet Formation  Kinetics reaction in the interface

3) Co-current droplet formation The variations of the Uranium and the Complex concentrations can be observed in next figures.

Conclusions The software utilized in the simulations executed in this report is a very useful tool that allows the users and researchers to obtain faster and cheaper results as compared to traditional experiments. The several scientific fields in which microfluidics are used allow the radiochemists to take advantage of the innovations and the constant research carried out with regards to this kind of technology. In previous works the phases interface had been considered fixed and the formation of droplets had not been studied. The results obtained for this last case in this report permit analyzing the essential characteristics of the extraction process in a microdevice for this flow pattern and are suitable to be modified for different parameters values. One of the next objectives in order to improve the yields of the microdevices is to calculate and verify the relation between the inlet uranium concentration and the length necessary to extract it. Although the surface hydrophobicity has been one of the topics more studied during the last years because of its relevance concerning the microfluidics the software available to date is not able to consider this aspect.

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