PHOTOCATALYTIC DEGRADATION AND REMOVAL OF HEAVY METALS IN PHARMACEUTICAL WASTE BY SELENIUM DOPED ZNO

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Journal for Research | Volume 02 | Issue 05 | July 2016 ISSN: 2395-7549

Photocatalytic Degradation And Removal of Heavy Metals in Pharmaceutical Waste by Selenium Doped ZnO Nano Composite Semiconductor L Shruthi Research Scholar DOS in Environmental Science University of Mysore

Shyni Student DOS in Environmental Science University of Mysore

K Jagadish Research Scholar Centre for Materials Science and Technology University of Mysore

Dr.S.Srikantaswamy Associate Professor DOS in Environmental Science University of Mysore

M.R Abhilash Research Scholar DOS in Environmental Science University of Mysore

Abstract In recent years pharmaceutical wastes (PW) deposal of has become a major difficulty for the environment. Therefore, pharmaceutical waste removal is very necessary before its discharge from the pharma industry. The separation of drugs containing organic compounds in wastewater streams is failed by convectional and biological treatments. Thus, the reduction of harmful effects of pharmaceutical compounds is possible by heterogeneous photocatalysis process. Herein we reported the degradation of pharmaceutical concentration in pharmaceutical waste by heterogeneous photocatalyst ZnO doped with Selenium prepared by cost effective hydrothermal method. In addition the heavy metals in pharmaceutical waste were also removed by ZnO/Se nanocomposite. The average band gap of nanocomposite (~2.5 eV) increase the photocatalytic activity and degrade the organic compounds in pharmaceutical waste. The heavy metals get adsorbed on the high surface area of nanocomposite and removed completely by filtration method. The Selenium doped ZnO photocatalyst semiconductor was characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDAX) and also the characteristic crystalline forms of ZnO/Se nanocomposite was confirmed by XRD. The functional groups and particle size distribution of ZnO/Se nanocomposite was characterized by FTIR and DLS respectively. The reduction of organic compounds in the pharmaceutical waste was confirmed by COD analysis and removal of heavy metals was performed by AAS analysis. Keywords: Sol-gel, Hydrothermal, Nanocomposite, Pharmaceutical, Water Purification _______________________________________________________________________________________________________ I.

INTRODUCTION

The investigation of visible-light active semiconductor photocatalysts has gained huge applications in environmental nanotechnology. The degradation of organic compounds in pharmaceutical wastewater using ZnO and its composites is becoming the most extensive photocatalyst. The primary step in photocatalysis is the creation of pairs of Electron - hole further increasing excitation of band-gap ZnO. Oxidizing species will yield by migration of these pairs interface. Among various semiconductor photocatalysts (Fe2O3, ZnO, WO3, ZnS, CdS and SrTiO3) used, ZnO has emerged to be more efficient catalyst because it’s higher rate mineralization and efficient generation of more number of H 2O2 [1]. ZnO nanoparticle has more number of active sites with high surface activity. Among the various semiconducting materials, the investigation of TiO2 is widely employed, however for the degradation of organic compounds in aquatic systems ZnO exhibits better efficiency than TiO2 [2]. ZnO Doped with metal ions can influence the performance and affects the interfacial charge transfer of the photocatalysts. The largest enhancement of photoactivity through doping can be found in nanosized particles. However, ZnO has a wide band-gap (~3.37 eV) [3] and is excited by sun-light irradiation. Charge separation distances within the ZnO semiconductor particle, recombination speed of e─/h+ is too fast and resulting very less quantum yield [4]. A good photocatalyst ZnO nanocomposite has efficiency of e─/h+ pair separation and many research developed with focusing on increasing the photocatalytic efficiency in visible region. The modification of ZnO with metal, non-metal ion, rare earth metals and surface modificatio [5-16]. Transition metal ions like Fe3+, Cr3+, Co2+ and Mo2+ are usually employed to lower the band-gap and enhance the photocatalytic activity of

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