Calcium carbonate polymorph control using droplet-based microfluidics

Abstract

Calcium carbonate (CaCO 3 ) is one of the most abundant minerals and of high importance in many areas of science including global CO 2 exchange, industrial water treatment energy storage, and the formation of shells and skeletons. Industrially, calcium carbonate is also used in the production of cement, glasses, paints, plastics, rubbers, ceramics, and steel, as well as being a key material in oil refining and iron ore purification. CaCO 3 displays a complex polymorphic behaviour which, despite numerous experiments, remains poorly characterised. In this paper, we report the use of a segmented-flow microfluidic reactor for the controlled precipitation of calcium carbonate and compare the resulting crystal properties with those obtained using both continuous flow microfluidic reactors and conventional bulk methods. Through combination of equal volumes of equimolar aqueous solutions of calcium chloride and sodium carbonate on the picoliter scale, it was possible to achieve excellent definition of both crystal size and size distribution. Furthermore, highly reproducible control over crystal polymorph could be realised, such that pure calcite, pure vaterite, or a mixture of calcite and vaterite could be precipitated depending on the reaction conditions and dropletvolumes employed. In contrast, the crystals precipitated in the continuous flow and bulk systems comprised of a mixture of calcite and vaterite and exhibited a broad distribution of sizes for all reaction conditions investigated.

A reproducible approach to the assembly of microcapillaries for double emulsion production

“…Droplet microfluidics in particular has enabled new modes for cell sorting and analysis (Eun et al 2011;Mazutis et al 2013;Zhang et al 2013), single molecule immunoassays (Shim et al 2013), directing biomolecule evolution (Agresti et al 2010;Kintses et al 2012), and the synthesis of crystals Phillips et al 2014;Yashina et al 2012), contrast agents (Abbaspourrad et al 2013), and drug delivery particles (Leon et al 2014;Xu et al 2009)-among other advances (Casadevall i Solvas and deMello 2011; Guo et al 2012;Song et al 2006;Teh et al 2008;Theberge et al 2010). However, in spite of the great potential of microfluidics (Whitesides 2006), these devices are still not routinely used by non-specialists, due in part to the demands of device fabrication and the almost inevitable need to trouble-shoot (Whitesides 2013;Yetisen et al 2013).…”

Morphology control by flow-driven self-organizing precipitation

“…Ca [17], and that of confined spaces, where counterdiffusion leads to the evolution of rhombohedral and spherical aggregates in viscous sol [27] and of amorphous and calcite forms in membrane pores [28,29]. By introducing a density gradient in a system, an additional transport process can be exploited.…”

“…It has a growing number of industrial applications in the production of cement, glasses, cosmetics, plastics, ceramics, food additives, etc. [17]. Furthermore, it has medical and pharmaceutical use, such as in dental care products, because of its slow biodegradability and non-toxicity.…”

Aragonite crystallization in a Christmas-tree model microfluidic device with the addition of magnesium ions

“…Microfluidic system has been applied to a variety of crystallization to investigate micro-scale phenomena such as those involving proteins and organic and inorganic molecules [28][29][30][31][32][33]. Micro-chips are affected predominantly by shear force and develop laminar flow because of the very low Reynolds number in the devices [34].…”