The purpose of this study was the characterization and production of carbonaceous adsorbents from oil sludge of heavy fuel oils storage tanks of Isfahan oil refinery. Carbonaceous adsorbent without activation was produced at 600 °C for 1 h in nitrogen atmosphere. For activated carbon, the same carbonization conditions was applied with adding KOH as activating agent. To determine the characteristics of the carbonaceous sorbents, several tests including concentration of heavy metals, leaching, SEM, FT-IR and BET were carried out. Leaching tests of heavy metals using distilled water and TCLP toxicity method showed that heavy metals concentrations are in the allowable range of presented standards. Specific surface area of carbonaceous adsorbent produced without activation and activated carbon was 3.6 and 304.9 m 2 /g, respectively. Thus, activation with potassium hydroxide could significantly increase the specific surface area and pore structure. Adsorption experiments of cadmium by batch method using Taguchi experimental design with four factor including initial concentration, dose adsorbent, contact time and pH in four level were performed. For cadmium adsorption by carbonaceous adsorbent produced without activation, initial concentration and for activated carbon, dose adsorbent had the most influence on the sorption. For cadmium adsorption by carbonaceous adsorbent without activation, initial pH of solution and for activated carbon, contact time showed less effect on the adsorption process. In optimal conditions, the adsorption efficiency of cadmium by carbonaceous adsorbent without activation and activated carbon were 77.7 and 98.2%, respectively, which represents a high percentage of cadmium adsorption. Adsorption isotherms studies showed that the adsorption of cadmium by carbonaceous adsorbent without activation and activated carbon are more consistent with the Freundlich and Redlich–Peterson isotherms models, respectively. The results of column experiments indicated that regeneration capabilities of both carbonaceous adsorbent by HNO 3 are high. Both of the carbonaceous adsorbent showed good efficiency for adsorption of cadmium from industrial wastewater sample. The produced adsorbents have comparable adsorbing ability with imported and internal commercial activated carbons. Keywords: Charaterization, Oil sludge, Activated carbon, Adsorption, Cadmium