In the current study, the photodegradation of brilliant green (BG) dye has been studied in relation to the comparative photocatalytic activity of pure ZnO and Ni-doped ZnO/CSAC (cotton stalk activated carbon), which was produced using a chemical precipitation method. The structural, optical, morphological, and functional characteristics of Ni-doped ZnO/CSAC have been investigated. The XRD patterns demonstrated the hexagonal wurtzite structure of the Ni-doped ZnO/CSAC sample. The XPS scan supported a Ni2+ oxidation state for the Ni ions incorporated into the ZnO lattice. The optical features of the Ni-doped and loaded sample demonstrated a red shift in the light absorption and reduced the recombination rate of charge carriers. The FE-SEM was used to examine the morphology of the synthesized all the samples, and EDAX spectroscopy was used to determine their composition. In comparison to pure ZnO, Ni doped, and Ni (0.075 M) doped ZnO/CSAC exhibited a greater photocatalytic degradation of 91.47 % after 120 min under visible light irradiation. This result suggests that Ni-doped ZnO/CSAC may be an effective wastewater treatment material.