Microwave Stabilization of a Dynamic Membrane Layer

Abstract

Dynamic membranes have been obtained by depositing a polystyrene (PS) layer onto a nylon substrate. The dynamic membrane layer of PS particles on the nylon substrate has been treated using 2450-MHz microwave radiation of a 350 W power in air. It has been found that as a result of the microwave irradiation of the membranes in atmospheric air, the membrane mass decreases to 0.69% of the initial value depending on the treatment time. Scanning electron microscopy examination has shown the formation of agglutinated polystyrene particles and melted and compacted regions on the membrane surface. According to the scanning electron microscopy data, the microwave treatment of the membrane has decreased the roughness of its surface layer by a factor of 8. According to IR data, the action of microwave radiation on the nylon–PS membrane leads to a decrease in the intensity of peaks in a range of absorption bands from 1500 to 3500 cm–1. An observed increase in the membrane flux by microwave irradiation for up to 10 min has been associated with the etching of membrane surfaces, whereas a decrease in the flux after irradiation for 20 min is explained by the compaction and melting of particles in the dynamic layer. The stability of the dynamic layer has been established by examining the flux of the membrane and changes in its mass after backwashing with a detergent solution. It has been found that the stability of the dynamic layer of the nylon–PS membrane is achieved with microwave irradiation for 5 min. An increase in the treatment time increases the degree of surface etching and leads to the formation of defective areas in the dynamic membrane layer. The microwave-irradiated dynamic nylon–PS membrane has been used to separate a water–oil emulsion. The degree of separation of the emulsion was 96.1% at a membrane flux of 19.1 dm3 m–2 h–1.