Pyrolysis of paper mill sludge (PMS) was conducted to produce syngas (H-2 and CO) and fabricate magnetic biochar (PMS biochar) for use as an adsorbent for As(V). The enhanced generation of CO was observed in the CO2 atmosphere due to reactions triggered by CO2. Particularly, the generation of syngas from pyrolysis of PMS in CO2 (9.6 mol% at 720 degrees C) was superior to the cases of pyrolysis of acid-washed PMS (i.e., minerals-eliminated PMS) in CO2 (2.9 mol% at 720 degrees C), which evidences catalytic effects attributed by Fe and Ca species contained in PMS. Based on the results of X-ray diffraction (XRD), pyrolysis of PMS in CO2 led to the conversion of Fe species into magnetite (Fe3O4) solid phase that imparted the magnetic property to the biochar (saturation magnetization: 28.4 emu g(-1)). The PMS biochar exhibited high As(V) adsorption capacity of 34.1 mg g(-1) in a given condition, which could be attributed to the great adsorption affinity of Fe3O4/CaCO3 mixture toward As(V). The integrated approach for the utilization of PMS could satisfy growing demand for renewable energy and environmental sustainability. (C) 2017 Elsevier Ltd. All rights reserved.