1. Department of Chemistry, Indian Institute of Technology (BHU), Varanasi 221005, India
2. Department of Chemical Engineering and Technology, Indian Institute of Technology (BHU), Varanasi 221005, India, Tel./Fax:
3. Institute of Environment & Sustainable Development (IESD), Banaras Hindu University (BHU), Varanasi 221005, India
4. School of Environmental Sciences, Jawaharlal Nehru University (JNU), New Delhi 110067, India