Droplet microfluidic encapsulation of monoethanolamine and graphene nanoplatelet for high carbon capture performance

Vigorous studies have been conducted for effective reduction of carbon dioxide (CO₂) and other greenhouse gases from anthropogenic sources as primary driver of climate change. Among a portfolio of technologies for CO₂ capture, storage and monitoring, microencapsulation of carbon solvents (MECS) has become promising and gained increasing attention in recent decade, as it can minimize the leakage of the solvent and enhance mass transfer with an increased surface area to volume ratio. In particular, encapsulation of carbon solvents via polymeric shells also circumvents the issues that carbon solvents normally encounter, such as high viscosity or corrosivity, by offering a protective layer between the solvents and absorption column. Although there has been recent progress towards microencapsulation of carbon solvents, the realization of which has focused mainly on use of polydimethylsiloxane (PDMS) devices which necessitate the use of clean room or glass capillary devices which are inherently difficult to align while fabrication. In this work, an off-shelf needle based microfluidic system has been established to form microcapsules with monoethanolamine (MEA) encapsulated in the silicone polymer shell made by TEGO RAD 2650 for carbon capture. The low-cost and facile method offers an exquisite control over the size, shape and inner structure of the microcapsules. MECS of MEA has higher absorption CO₂ rate than its neat solvent by at least a fold. Beyond that, incorporating graphene nanoplatelet (GNP) into the core solvent yields MECS of MEA with GNP, showing improved CO₂ uptake capacity by 10 and 60% when absorption was carried out at 25 and 60°C, respectively. Therefore, the off-shelf droplet-based microfluidics opens up a new avenue for ease access to versatile fabrication of microencapsulated carbon sorbents with well-tailored properties in more cost-effective way, thus benefitting their pragmatic applications for carbon capture and utilization.