Ever-increasing of world population, water resources limitations, lack of rainfall, water crisis in the country, and inappropriate distribution of fresh water in temporal and spatial scales on one hand, and increase of surface and groundwater pollution by industrial wastewaters on the other hand, requires using modern and environmentally-acceptable methods for removing these contaminants. Methods such as chemical precipitation, electrode ratification, and ion exchanging have been used for treatment of industrial wastewaters. But one of the cheapest and most efficient methods is using surface adsorption by the low-cost adsorbents. In this study, two plant residues (sunflower and cotton residues) and one industrial adsorbent (activated carbon) were applied for eliminating heavy metals from artificial and natural wastewaters. Plant residues with size of 0.5-0.7 mm were used. For characteristic modification, the plant residues were treated by 0.1 mol NaOH and also anionic surfactant (sodium dodecyl sulfate, SDS). But activated carbon was just treated with this surfactant. Modifications have been done in three levels of surfactant including 1, 2 and 3 times of critical micelle concentration (CMC). Adsorption was done in suspensions containing 0.5 gr adsorbent in 100 cc wastewater solution. Optimization of four effective factors on adsorption (i.e. pH, initial concentration, adsorbents’ dose and contact time) of Pb and Ni via sunflower residues has been done by using Minitab software. The capacity of the three aforementioned adsorbents was assessed for removing the heavy metal cations of Cr(III), Cd(II) and Ni(II). Some of the adsorbents’ characteristics were determined by FTIR spectrum and Scanning Electron microscopy (SEM), at modified and nonmodified states, and before and after the adsorption. The results showed that pH, initial wastewater concentration, and adsorbent dose are effective factors in adsorption, but contact time was insignificant. The best pH for adsorption of Pb and Ni was 7. The optimum dose of adsorbent was 0.5 gr. The optimum initial concentration for Ni and Pb was achieved as 100 mg/L and 200 mg/L, respectively. The results of FTIR demonstrated that adding surfactant has resulted in hemistal structure in SDS environment and reduction in carbonyl concentration. Freundlich, Langmuir, and Langmuir-Freundlich isotherms were used to model the adsorption equilibrium data. The Langmuir-Freundlich model performed relatively better than the other models due to its high R 2 in capturing the non-linear relationships of the variables. Activated carbon had the highest rate of adsorption in all the treatments. In plant residues treatments, sunflower and cotton residues had the highest adsorption of Ni and Cr, respectively. Both plant residues had the same adsorption rate for Cd. The most adsorption amount was 17, 60 and 32 mg/gr by cotton and sunflower residues for Cd, Cr and Ni, respectively. Among heavy metals, Cr had the highest adsorption equilibrium rate and Ni and Cd were next. In surfactant-modified treatments, the 0.5 CMC solution had significant effect (due to not forming the micelles in the solution) as compared to other treatments.