摘要：AbstractIn an effort to seek a new technical platform for disposal of drinking water treatment sludge (DWTS: alum sludge), pyrolysis of DWTS was mainly investigated in this study. To establish a more sustainable thermolytic platform for DWTS, this study particularly employed CO2as reactive gas medium. Thus, this study laid great emphasis on elucidating the mechanistic roles of CO2during the thermolysis of DWTS. A series of the TGA tests of DWTS in CO2in reference to N2revealed no occurrence of the heterogeneous reaction between CO2and the sample surface of DWTS. As such, at the temperature regime before initiating the Boudouard reaction (i.e., ≥700 °C), the mass decay patterns of DWTS in N2and CO2were nearly identical. However, the gaseous effluents from lab-scale pyrolysis of DWTS in CO2in reference to N2were different. In sum, the homogeneous reactions between CO2and volatile matters (VMs) evolved from the thermolysis of DWTS led to the enhanced generation of CO. Also, CO2suppressed dehydrogenation of VMs. Such the genuine mechanistic roles of CO2in the thermolysis of DWTS subsequently led to the compositional modifications of the chemical species in pyrolytic oil. Furthermore, the biochar composite was obtained as byproduct of pyrolysis of DWTS. Considering that the high content of Al2O3and Fe-species in the biochar composite imparts a strong affinity for As(V), the practical use of the biochar composite as a sorptive material for arsenic (V) was evaluated at the fundamental levels. This work reported that adsorption of As(V) onto the biochar composite followed the pseudo-second order model and the Freundlich isotherm model.Graphical abstractDisplay OmittedHighlights•Valorization of alum sludge was achieved via a thermolytic platform.•Carbon dioxide was used to establish the more sustainable thermolytic platform for alum sludge.•The use of CO2resulted in the enhanced formation of CO and suppression of dehydrogenation.•The biochar composite could be used as a sorptive material for As(V).
