A novel process for the growth of hexagonal ZnO nano rods on porous carbon surfaces by microwave assisted technique for the photocatalytic degradation of textile dyeing wastewater

摘要

A novel approach for the growth of hexagonal ZnO nanorods on porous carbon matrix was carried out by a combined wet impregnation and microwave process using certain precursors. Porous carbon (PC) was prepared from an agricultural feed stock by two step chemical activation method. Surface area, porosity and surface functional groups of PC were tailored to ease the wet impregnation of zinc precursor at its active sites. A microwave power of 750 Watts for 10 min was employed for the growth of the ZnO nanorods on its surface. The powder XRD pattern of ZnO nanorods supported PC (ZSPC) in Fig. 1. show the diffraction peaks corresponding to the hexagonal würtzite structure of ZnO and SP2 hybridized graphitic carbon planes. A broad diffraction peak corresponding to crystobalite phase is an indicative that silica is also present in the framework, which was one of the non carbonaceous constituent of the feed stock. The morphologies obtained from scanning electron micrograph revealed that the grown ZnO nanorods were hexagonally patterned as shown in the inset of Fig. 2. It was also remarkable to notice that the nanorods well preferred to grow on the external surface of PC rather than inside the pore cages as shown in the Fig. 2. The prepared ZSPC was tested for the photocatalytic degradation of textile dyeing wastewater collected from a textile dying unit located at Tiruppur, Tamil Nadu, India. An UV radiation of 365nm was employed throughout the study. The study was performed at different pH, time intervals and initial concentration to arrive at the optimal conditions for an efficient photocatalytic degradation. The stability and the reusability of ZSPC was also studied. A 98% degradation was achieved at higher alkaline pH. All the results suggested that the ZSPC prepared by a simple and new methodology, is a potential photocatalyst enrolling in the area of advanced wastewater treatment technologies.