Synthesis of Highly Ordered Crystalline Wurtzite (ZnO) Membrane for Selenium-Chromium Separation

Abstract

Pure ZnO and composite ZnO-CeO2 coated thin films on titania substrates were prepared using a chelating sol-gel method under controlled conditions to be used in the separation and/or rejection of Se(IV) and Cr(VI). XRD and SEM studies confirmed the formation of highly ordered arrays of crystalline wurtzite microstructure with mixed orientation. An increase in average particle size of the prepared membranes from 1.25 to 3 µm with increasing CeO2 percent was observed indicating the vital role of CeO2 as secondary phase in improving the crystallinity of the coated films formed. Detailed study of the separation performance of the selected membranes toward Se(IV)-Cr(VI) was studied. A high separation performance for the different membranes prepared was observed toward Se(IV) with respect to Cr(VI). The polar characteristic of ZnO thin films played an essential role in Se(IV) separation. However, a high permeation flow of Cr(VI) through the membranes was governed by the capillary pressure induced within the porous structure of the membranes.

Keywords

• Rutile substrate
• Pure and composite ZnO membranes
• Polymeric sol-gel
• SeIV separation
• CrVI permeation.