The disposal of sludge processes accounts for 60% of the total operation and 40% of total emissions of greenhouse gas from wastewater treatment plants operations. Moreover, sludge contains pathogenic microorganisms, organics, inorganics, trace metals and emerging micropollutants, which can be a public health menace. To comply with the Environmental Protection Agency standards, sludge must be stabilized and detoxified before being disposed or reused. This study focuses on the use of sludge biochar (adsorbent) from the pyrolysis of wastewater treatment sludge for the removal of selected trace metals (copper, cobalt and nickel) in aqueous solution by optimization of the temperature and adsorbent particle sizes. The morphology of the surface at increased temperature (400, 500 and 600 oC) showed an enhanced surface with space and structure (pores) that promoted the adsorption of metal ions. A decreased of adsorbent particle size from 250 μm to 100 μm and an increased in pyrolyzed biochar temperature from (400, oC, 500 oC and 600 oC) resulted in the removal of the trace metals (77.86%, 75% and 56.25% of copper, cobalt and nickel respectively) from the aqueous solution. Biochar produced from sludge can be an alternative adsorbent for the removal of trace metal in wastewater treatment processes.