Simultaneous production of syngas and magnetic biochar via pyrolysis of paper mill sludge using CO₂ as reaction medium

Pyrolysis of paper mill sludge (PMS) was conducted to produce syngas (H₂ 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°C) was superior to the cases of pyrolysis of acid-washed PMS (i.e., minerals-eliminated PMS) in CO₂ (2.9 mol% at 720°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. Copyright © 2017 Elsevier Ltd.