Abstract
Digested sludge, as the main by-product of the sewage sludge anaerobic digestion process, still contains considerable organic compounds. In this protocol, we report a facile method for preparing digested sludge-derived self-doped porous carbon material for high-performance supercapacitor electrodes via a sustainable pyrolysis/activation process. The obtained digested sludge-derived carbon material (HPDSC) exhibits versatile O-, N-doped hierarchical porous framework, high specific surface area (2103.6 m2 g−1) and partial graphitization phase, which can facilitate ion transport, provide more storage sites for electrolyte ions and enhance the conductivity of active electrode materials. The HPDSC-based supercapacitor electrodes show favourable energy storage performance, with a specific capacitance of 245 F g−1 at 1.0 A g−1 in 0.5 M Na2SO4; outstanding cycling stability, with 98.4% capacitance retention after 2000 cycles; and good rate performance (211 F g−1 at 11 A g−1). This work provides a unique self-doped three-dimensional hierarchical porous carbon material with a favourable charge storage capacity and at the same time finds a high value-added and environment-friendly strategy for disposal and recycling of digested sludge.
Highlights
With the yearly increase in sewage sludge generation [1], various sewage sludge treatment and disposal technologies have been developed and implemented to protect the environment and human health
We report a facile method for preparing digested sludge-derived self-doped porous carbon material for high-performance supercapacitor electrodes via a sustainable pyrolysis/activation process
DSC-600 displays irregular porous structures. These porous structures stem from the particular compositions of digested sludge and can be derived from the following three factors: (i) the reserved abundant intrinsic pores in digested sludge after vacuum freezing drying; (ii) SiO2 in digested sludge acting as a built-in template, which avoids agglomeration and promotes the generation of the unique pore diameter distribution; and (iii) carbonization and graphitizing of 3 mm (c)
Summary
With the yearly increase in sewage sludge generation [1], various sewage sludge treatment and disposal technologies have been developed and implemented to protect the environment and human health. Of the most widely used treatment methods because it can reduce the amount of sewage sludge for 2 disposal and generate renewable energy by converting biodegradable material into methane [2,3]. Only 20–30% of the organic materials in sewage sludge are mineralized through standard anaerobic digestion technologies [4]. The most common methods for disposing of digested sludge are land application, combustion and landfilling. Combustion is difficult because of the high ash and moisture content of digested sludge [7], and landfilling can be very challenging given the dwindling availability of land in developed cities [8]. It is necessary and important to explore more cost-effective and environmentally benign reuse of digested sludge
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