The study focuses on “treating waste with waste” through the removal of toxic metals from gold mine wastewater using polysulfone (PSF) membrane infused with waste plastic derived-multi-walled carbon nanotube (MWCNTs) as an innovative approach. MWCNTs synthesized from waste polypropylene (PP) plastics by the chemical vapour deposition (CVD) method were purified in oxidizing acid, and different loadings (0, 0.05, 0.10, and 0.15 wt%) were incorporated into the PSF membrane to form mixed matrix membranes (MMM) via phase inversion technique. Fabricated pristine and nanocomposite membranes’ properties: hydrophilicity, thermal stability, and morphology, were ascertained by the water contact angle measurement, thermogravimetry analysis, and scanning electron microscopy, respectively. Results show that incorporating plastic-derived-MWCNTs into the matrices of PSF polymer significantly enhanced the properties of all fabricated MWCNTs/PSF nanocomposite membranes compared to pristine PSF. The flux and rejection of metals increased with MWCNTs loading. Iron (Fe) and nickel (Ni) removal by pristine PSF were 70.2% and 11.4%, respectively, while optimal Fe and Ni rejection of 91% and 74%, respectively, were obtained with 0.10 wt% MWCNT loading. The results obtained in this work revealed that incorporating different loadings of plastic-derived-MWCNTs onto the PSF polymer matrix impacted its surface properties, and improved flux, and removal efficiency. Therefore, utilizing waste plastics as a precursor in CNTs production will save on the cost of CNTs and provide a sustainable plastic waste management option, as well as open up vast prospects at the industrial scale in the potential for application in environmental remediation (such as in membrane separation).