S. C. Olu, P. E. Dim, and J. O. Okafor, “REMOVAL OF CU (II) FROM DYE EFFLUENT USING NATURAL AND PHOSPHATE-MODIFIED NIGERIAN KAOLINITE CLAY”, Int. J. Res. Granthaalayah, vol. 7, no. 8, pp. 402–414, Aug. 2019.