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A review: preparation of sludge derived carbons and their performance in wastewater treatment

The tremendous pressure of annually increasing amount of sewage sludge producing from wastewater treatment plants and the imposition of more stringent legislation on its disposal and utilization prompt a drive for alternative uses of sewage sludge. Considering abundant energy embedded in sewage sludge, pyrolysis for producing biochar is deemed to be an especially promising method. In this review, preparation methods of sludge derived carbons (SDCs) including pretreatment, pyrolysis temperature and modification, coupled with its application as adsorbents and catalysts in wastewater treatment are discussed. Due to the excellent properties of well-developed porosity and various functional groups on the surface of SDCs, they have high adsorption capacities of heavy metals and organic pollutants. Besides, the metals indigenously existed in sludge are recognized as active components, which makes the SDCs excellent catalysts or catalyst supports in advanced oxidation processes. In order to sufficiently explore the sludge-based biochar, it is recommended that further studies should involve its application in practical wastewater and its environmentally-safe use as well.