Synthesis of TiO2 nanoparticles in a spinning disc reactor

Abstract

Reactive precipitation of TiO 2 in a spinning disc reactor (SDR) has been performed. Physical parameters such as rotational speed, disc surface texture, and operating parameters such as flowrate, ratio of water to precursor and location of feed introduction points have been studied in terms of their effects on TiO 2 particle size, particle size distribution (PSD) and particle yield. Smaller particles of less than 1 nm mean diameter with narrower PSDs are generally formed at higher yields at higher disc speeds, higher flowrates and on grooved disc surfaces, all of which provide the best hydrodynamic conditions for intense micromixing and near ideal plug flow regime in the fluid film travelling across the disc surface. Similar observations are made for particle characteristics at higher water/TTIP ratios which are attributed to the increased rate of the hydrolysis reaction favouring nucleation over growth. The introduction of the TTIP feed stream into the water stream away from the centre of the disc is also conducive to the generation of smaller and more uniformly sized particles due to the greater energy dissipation for improved micromixing at these locations. Comparisons with reactive-precipitation of TiO 2 in a conventional stirred tank reactor (STR) also demonstrate that the SDR performs better in terms of much improved particle characteristics and higher TiO 2 yields per unit processing time. This is attributed to more uniform and intense mixing conditions in the smaller volume, continuous SDR than in the STR.

Flow field and homogenization time assessment in continuously-fed stirred tanks

“…Detailed knowledge of homogeneity within stirred vessel is of crucial importance for vessel operation, such as in precipitation reactors (David et al, 2003;Mohammadi et al, 2014). In large scale bioreactors, nutrients and oxygen unevenly distribution may lead to different microbial behavior in different zones of the reactor, with increasingly dramatic problem at larger scales (Keshtar et al, 2003;Heins et al 2014).…”

Process control in intensified continuous solids handling

“…The spinning disc reactor (SDR) provides fast mixing, mass and heat transfer rates, which can be usefully exploited in, for example, nanoparticle precipitation [44][45][46], polymerization processes [47,48] and organometallic processes in the pharmaceutical industry [49], among others. The process involves a rotating disc with controllable speed and temperature.…”

“…Additionally, the reagent concentrations (ratio of reagents) have a strong effect on the operating windows and dynamics, as they determine whether the system is residence time controlled (kinetically limited) or mixing intensity controlled (mixing limited). Therefore, maximizing yield and optimizing product quality require balancing between rotational speed and flow rates [46]. Particle accumulation can disturb the process measurements, but it may also disturb the particle growth mechanisms on the disc.…”

“…Ghiasy et al [18,19] have used sensors and actuators available on the market and linear control strategies for SDR in their experiments, but they also expressed mathematical relations between the disc rotational speed and the micromixing time constant (affecting the rate of precipitation), as well as the disc speed and the residence time in their experimental conditions. Additionally, the effects of several operating parameters on product size distribution and yield in a crystallization process have been systematically studied [46]. These studies generate a framework for a model-based process control.…”

A review on the classification, characterisation, synthesis of nanoparticles and their application

“…precursor and water is pumped in. The spinning causes the atoms or molecules to fuse together and is precipitated, collected and dried [11]. The various operating parameters such as the liquid flow rate, disc rotation speed, liquid/precursor ratio, location of feed, disc surface, etc.…”