Enhanced Solar Photocatalytic Activity of Thermally Stable I:ZnO/Glass Beads for Reduction of Cr(VI) in Tannery Effluent oleh Ambreen Ashar, Ijaz Ahmad Bhatti, Muhammad Mohsin, Maryam Yousaf, Humera Aziz, Adeeba Gul, Tausif Hussain, Zeeshan Ahmad Bhutta