STUDIES ON THE TREATMENT OF WASTEWATERS CONTAINING Cr 6+ WITH IRONOXIDE-SILICA COMPOSITE MATERIALS PREPARED BY DIFFERENT METHODS A dissertation submitted in partial fulfillment of the requirements for the degree of M.Phil. in Chemistry By Biplob Kumer Deb Registration No. 100703207P Roll No. 100703207P Session: October,2007 Physical Chemistry Research Laboratory Department of Chemistry BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY, DHAKA. Bangladesh. June,2012.