Hamza, A., A. M. Alao, and M. S. Galadima. “Adsorption of Chromium (VI) onto Metakaolin: Isotherms, Modelling and Optimization”. Journal of Science and Technology, Vol. 11, no. 1, June 2019, pp. 45-54, https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/4101.