Droplet columns are used for their ability to greatly enhance liquid-liquid interfacial areas. The use of a droplet column for the two-phase epoxidation of cyclooctene by oxone in aqueous solution was studied as an application of pollution prevention, i.e., the replacement of hazardous solvents with water. The dispersion of alkene droplets in aqueous oxone solution was generated by pumping the organic phase through a sparger at the bottom of the column. Then, organic droplets rise to the top of the aqueous phase. As the alkene droplets rise, they are oxidized by the oxone solution to form epoxide. The study of aqueous epoxidation in a droplet column shows that the epoxidation of alkenes can be represented as a first-order reaction in alkene and a first-order reaction in oxone under mass transfer limiting conditions. By recycling the cyclooctene, over 60% yield of cyclooctene epoxide can be achieved in 3 h. However, due to epoxide crystals formation, a second reactor is needed to remove the solid and to bring the yield up to 80%. we found that a stirred tank reactor, which avoids the need to put the crystallized mixture through the small holes of a sparger, performed well in this application as a second reactor.