Co-Hydrothermal Carbonization of Sewage Sludge with Wood Chip: Fuel Properties and Heavy Metal Transformation Behavior of Hydrochars
2021
Lu, Xiaoluan | Ma, Xiaoqian | Qin, Zhen | Ke, Chuncheng | Chen, Limei | Chen, Xinfei
To further reduce the toxicity of heavy metals (HMs) in sewage sludge (SS), organic acid (oxalic acid, citric acid, acetic acid) washing was used before co-hydrothermal carbonization (co-HTC) with pinewood. The results showed the total concentrations of six HMs (As, Cu, Ni, Cr, Mn, and Zn) in hydrochar produced at 230 °C decreased obviously during co-HTC. More importantly, F1 + F2 fractions of Ni, Cr, Mn, and Zn were also lowered. With the pretreatment of citric acid, the hydrochar from co-HTC exhibited the lowest potential ecological risk among all simples. Compared with the hydrochar produced from SS, the coalification degree, higher heating values (5.61–6.19 MJ/kg), and combustion behavior of the hydrochar derived from co-HTC were upgraded and improved. These findings offered a viable technology that could lower the bioavailability of HMs and realize the energy value of SS.
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