# Effect of Monoethylene Glycol on the Nucleation and Growth of Calcium Carbonate from Supersaturated Solutions in Microchannels of Varying Wettability

## TL;DR

This study explores how monoethylene glycol affects calcium carbonate crystal formation in microchannels, revealing how it can control crystal growth and nucleation.

## Contribution

The first investigation of MEG's effect on CaCO3 nucleation and growth in microchannels with varying wettability.

## Key findings

- 10% MEG decreased the time to first crystal observation and favored secondary nucleation.
- 30% MEG completely inhibited nucleation and crystal growth of calcium carbonate.
- Raman spectroscopy showed aragonite formation, with higher MEG favoring amorphous calcium carbonate at low supersaturation.

## Abstract

The control of calcium carbonate formation is of high
importance
for a wide range of applications in the pharmaceutical industry and
membrane processes as well as in the oil and gas industry. Herein,
for the first time, the effect of monoethylene glycol (MEG) on the
formation of calcium carbonate (CaCO3) crystals from supersaturated
solutions flowing through microchannels (volume 0.36 mL) of varying
wettability was investigated. The use of microdevices enabled the
observation of the scaling phenomenon in the early stages. Solutions
supersaturated with respect to calcite, containing MEG (10, 20, and
30% v/v), were injected into the microchannel under a constant total
flow rate and under laminar flow conditions (Re = 0.052). The growth
of calcium carbonate crystals was monitored by video recording. The
effect of the wettability on crystal formation was tested using glass
and silane-coated microchips. The microchannel walls were wet and
neutral-wet by the supersaturated solutions with a low MEG concentration.
In the presence of a high MEG concentration in the supersaturated
solutions, the walls of both types of microchips were neutral-wet.
The results showed that the addition of MEG at a concentration of
10% v/v in the supersaturated solutions decreased the time of observation
of the first crystal, favored secondary nucleation, and in general
decreased the crystal growth rates. Raman spectroscopy identified
the formation of aragonite in most cases, while as SR values increased,
the formation of aragonite aggregates was favored. Further increases
of the MEG concentration in the supersaturated solutions to 20% v/v,
at low supersaturation ratio (SR) values, favored the formation of
amorphous calcium carbonate (ACC) while at higher SR values aragonite
crystals and aragonite aggregates formed. Further increases in the
MEG concentration in the supersaturated solutions up to 30% v/v completely
inhibited the nucleation and crystal growth of calcium carbonate.