1. DST-CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa
2. Department of Chemical Sciences, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa
3. Water Pollution Monitoring and Remediation Initiatives Research Group, School of Chemical and Minerals Engineering, North West University, P. Bag X6001, Potchefstroom 2520, South Africa