The Ni-zero-valent iron magnetic biochar composites (Ni-ZVI-MBC) were synthesized from paper mill sludge and used as an adsorbent for the removal of pentachlorophenol (PCP) from the synthetic and real paper mill effluent. The synthesized Ni-ZVI-MBC was characterized and analyzed for the stability of Ni and ZVI particles in the biochar matrix. The Ni-ZVI-MBC involves simultaneous adsorption and dechlorination mechanism resulting in higher PCP removal efficiency. The presence of Ni as a catalyst in Ni-ZVI-MBC enhances the dechlorination rate and the adsorption of PCP by preventing the accumulation of PCP in the biochar matrix. The effect of operating parameters (solution pH, Ni loading, initial PCP concentration in the solution and temperature) on adsorption and dechlorination efficiency was studied. The exhausted Ni-ZVI-MBCs were used for the brick formation and the bricks showed good compressive strength and negligible heavy metal and PCP leaching. (C) 2015 Elsevier B.V. All rights reserved.