Microfluidic fabrication of porous polydimethylsiloxane microparticles for the treatment of toluene-contaminated water

In this paper, pristine and two types of porous polydimethylsiloxane (PDMS) microparticles were fabricated using oil-in-water (O/W) single emulsion template by the needle-based microfluidic multiphase system. By manipulating the flow rate of either the dispersed or continuous phase, microparticles of various sizes were obtained. The capillary number of the continuous phase for all flow conditions applied in this study was less than 0.1, suggesting that the flow regime was dripping. The coefficients of variation (CV) of sizes under different flow conditions were less than 1.5% which indicates the particles to be highly monodispersed. The surface morphology and particle size were characterized by optical microscope and scanning electron microscope. Pristine PDMS microparticles (PDMS-P) and PDMS microparticles templated from tetrachloromethane (CCl 4 ) and white granulated sugars (PDMS-C and PDMS-S, respectively) were prepared under the same flow conditions. Subsequently, the microparticles were adopted for treatment of a synthetic wastewater that contained organic compounds such as toluene under static and dynamic states for comparison. The effects including the releasing amount, size of particles, porosity of microparticles and initial concentration of pollutants were investigated based on the toluene concentration variation, which was quantified by a gas chromatograph-headspace sampler (GC-HS). It has been found that 50 mg of porous PDMS microparticles are capable of realising over 65% of toluene removal efficiency of 200 ppm toluene aqueous solution within 2 h. The microparticles were collected and reused 30 times with unchanged treatment capacity.