Nowadays, selecting a suitable environmentally friendly and economic adsorbent has becoming oneof the most serious concerns of researchers. In this study, oil sludge from crude oil storage tanks was used to produce an activated carbon with the highest Specific surface area. Also, in order to enhance the surface and structural properties of clay absorbent, a composite was produced using oil sludge and montmorillonite clay. A series of activated carbons were prepared using physical activation withwater vapor at different temperatures. Also three series of activated carbons and three series of clay-carbon composite adsorbents were produced at different production conditions, including different activation temperature, activating agents and Impregnation ratios. Three carbon adsorbents and two composite adsorbents were selected for continuing the experiments after comparing the production efficiency, iodine number, textural properties, specific surface area, and phenol and nickel adsorption capacities. Other physical and structural properties of optimal adsorbents were analyzed by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD). Leaching testofheavy metals and determination of heavy metal concentrations were also performed. The effects of some parameters such as pH, contact time, adsorbent dose, initial concentrations of phenol, nickel and phosphate and temperature were studied to determine thermodynamics parameters, equilibrium isotherms and absorption process kinetics. The pseudo-first and pseudo-second order kinetics equations were used to determine the best adsorption kinetic models of phenol, nickel and phosphate onto the synthesized adsorbents at the optimum conditions. Also, isotherm of experimental data was evaluated using Langmuir, Freundlich and Tamkin equations. The results showed that among the four types of activated carbon prepared using physical and chemical methods, the best surface and structural properties belong to the carbons that were activated by potassium hydroxide at 800 ?C and 2: 1 ratio and by zinc chloride at 500 ?C and a ratio of 1: 1 and by iron chloride at 700 ?C and a ratio of 2: 1 with specific surface area of 2263, 1259 and 683 m 2 /g and total pore volume of 1.37, 1.22 and 0.684 m 3 /g respectively. Among the composite adsorbents, two composites activated by potassium hydroxide and zinc chloride at 500 ?C and a 2: 1 impregnation ratio were selected as the best samples with highest specific surface area (297 and 343 m 2 /g) and porosity (0.257 and 0.835 m 3 /g ).The specific surface area of carbon adsorbent without activation and montmorillonite clay were 14 and 172 m 2 /g respectively. Therefore, activation in optimal conditions could significantly increase the specific surface and pore structure. The study of batch adsorption isotherms of phenol, nickel and phosphate onto the optimal adsorbents showed that regarding the correlation coefficient, Freundlich, Langmuir and Freundlich models describe the isotherm data better, respectively. The higher correlation coefficient of Freundlich absorption with experimental data confirms the multi-layer absorption onto the adsorbents. Also, the results of fitting absorption kinetics models for all adsorbents indicate that the adsorption process follows pseudo second order model. According to this information and the results obtained from other characterization analyzes, activated carbon produced from oil sludge can be considered as an efficient and cost effective adsorbent for industrial wastewater treatment. Also, the combination of oil sludge and clay montmorillonite in the form of a composite improves significantly the quality of adsorbent in comparison with clay adsorbent from the aspects of specific surface area, pore structure, production efficiency, mechanical hardness and absorption capacity.