Preparation of polysulfone microcapsules containing 1-octanol for the recovery of caprolactam.

Polysulphone (PSF) microcapsules containing 1-octanol were prepared with solvent extraction method for the recovery of caprolactam. One-step and two-step processes were, respectively, applied to prepare microcapsules. In order to get high extractant loading, a loading method with the assistance of ultrasound has been developed. With the two-step preparation process the extractant loss can be avoided. A very high extractant loading ratio of 5.96 g g(-1) and the maximum uptake to caprolactam of 65.6 mg g(-1) were achieved. Under the action of ultrasound the extractant loading efficiency is greatly intensified. With the one-step process 1-octanol loading ratio is highly limited. Only 1.74 g g(-1) loading ratio and 29.9 mg g(-1) uptake to caprolactam were realized. Meanwhile the extractant loss in the one-step process is serious. Considering extraction capacity and extractant loss in the preparation process, it is suggested that PSF microcapsules containing 1-octanol should be prepared with the two-step process. To fasten mass transfer rate, microcapsules with relatively smaller size are desired.