Production of metallic iron nanoparticles in a baffled stirred tank reactor: Optimization via computational fluid dynamics simulation--颗粒学报PARTICUOLOGY

Vilardi, G., & Verdone, N. (2020). Production of metallic iron nanoparticles in a baffled stirred tank reactor: Optimization via computational fluid dynamics simulation. Particuology, 52, 83-96. https://doi.org/10.1016/j.partic.2019.12.005

Production of metallic iron nanoparticles in a baffled stirred tank reactor: Optimization via computational fluid dynamics simulation

Giorgio Vilardi ^*, Nicola Verdone

Sapienza University of Rome, Department of Chemical Engineering Materials Environment, Via Eudossiana 18, 00184, Rome, Italy

10.1016/j.partic.2019.12.005

Volume 52, October 2020, Pages 83-96

Received 11 May 2019, Revised 9 July 2019, Accepted 6 December 2019, Available online 23 January 2020, Version of Record 24 June 2020.

E-mail: giorgio.vilardi@uniroma1.it

Highlights

• nZVI particles were synthesized with both radial and mixed flow impellers.

• The synthesis was successfully described as pseudo-nth-order kinetic.

• A unimodal particle size distribution was achieved via process optimization.

• The optimized production was characterized by a mean particle size of 40 nm.

• The calculated mixing Damkohler number indicated a mixed control process.

Abstract

The aim of this work is to optimize iron nanoparticle production in stirred tank reactors equipped with two classical impellers: Rushton and four-pitched blade turbines, which are largely used in batch industrial synthesis and efficient scale-up. The main operative parameters of nanoparticle synthesis are the precursor initial concentration, reducing agent/precursor molar ratio, impeller–tank clearance, and impeller rotational velocity. These parameters were varied during the synthesis to find the optimal operating values based on the Fe(0) (%) production, zeta potential, particle size distribution, and powder X-ray diffraction pattern obtained. We found that the optimal operating conditions for nanoparticle production were an impeller velocity of 1500 rpm, initial iron precursor concentration of 20 mM, molar ratio of reducing agent to iron precursor of 3 mol/mol, and impeller clearance of 0.25 and 0.4 times the vessel diameter for Rushton and four-pitched blade impellers, respectively. Setting these conditions achieved a total conversion of 0.94–0.98 and yielded a product with a unimodal size distribution and average diameters in the range 30–50 nm. The computational fluid dynamics results agreed with the expectations, and the obtained mixing Damkohler numbers show that the process is mixed controlled.

Graphical abstract

Keywords

Nano zero-valent iron; Computational fluid dynamics; Turbulence; MicromixingLength scale

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