## 4 Conclusions  
In this study, MnFe\({}_{2}\)O\({}_{4}\)/GO nanocomposite was synthesized and characterized through the in-situ method for applying water treatment from Pb\({}^{2+}\) ions and NR dye. Different techniques were used for the nanocomposite characterization, including SEM, TEM, FT-IR, XRD, Raman, and XPS to determine its size, composition, and morphology. The optimal conditions for Pb\({}^{2+}\) and NR dye adsorption over MnFe\({}_{2}\)O\({}_{4}\)/GO nanocomposite were determined by studying different factors, including initial concentration, dose, pH, and contact time. The initial concentration-effect study indicated that the increased concentration of pollutants led to the increase of adsorption capacity from 63 to 625 mg/g and from 20 to 90 mg/g for Pb\({}^{2+}\) ions and NR dye removal, respectively. The dose-effect study indicated that the increased adsorbent dose led to increased removal efficiency from 39% to 98.8% and from 63% to 94% for Pb\({}^{2+}\) and NR dye, respectively, due to the increased number of active adsorbent sites. The pH effect study indicated that the optimum pH for both pollutants' adsorption was found to be 6.0. The contact time effect study indicated that Pb\({}^{2+}\) ions and NR dye's adsorption capacity increased quickly at the first stage and then gradually became slower. The first stage was observed for Pb\({}^{2+}\) ion and NR dye adsorption at the first 15 and 20 min, respectively. The tremendous available numbers of adsorption sites over MnFe\({}_{2}\)O\({}_{4}\)/GO nanocomposite are responsible for this rapid increase of adsorption capacity at the first stage. After this stage, the surface saturation was reached, and hence the equilibrium reached with no further significant increase in the adsorption capacity. The optimum contact times for Pb\({}^{2+}\) ions and NR dye were 120 and 30 min, respectively. The monolayer adsorption was concluded for Pb\({}^{2+}\) and NR dye adsorption over the synthesized nanocomposite that indicated from experimental fitting to Langmuir isotherm. The adsorption capacities are 636.94 and 46.08 mg/g for the adsorption of Pb\({}^{2+}\) and NR dye, respectively according to Langmuir isotherm. The reusability study of this adsorbent for up to five cycles indicated that this nanocomposite is reusable and stable, reducing the overall cost of treatment. We can conclude that MnFe\({}_{2}\)O\({}_{4}\)/GO nanocomposite is a promising adsorbent for removing Pb\({}^{2+}\) ions and NR dye from water.  
Conceptualization, N.S.A.; K.M.MK., F.M.A., and M.A.T.; investigation, M.A.T.; data curation, M.A.T., and S.M.S.; writing--original draft preparation, M.A.T. and S.M.S.; writing--review and editing, N.S.A.; K.M.MK., and F.M.A.; supervision, M.A.T. and S.M.S.; project administration, S.M.S. All authors have read and agreed to the published version of the manuscript. This research was funded by the Deanship of Scientific Research at King Khalid University. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Acknowledgments: The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through research groups program under grant number R.G.P.2/111/42. Also, this research was funded by the Deanship of Scientific Research at Princess Nourah bint Abdulrahman University through the Fast-track Research Funding Program. Conflicts of Interest: The authors declare no conflict of interest.