Structure and adsorption properties of sewage sludge-derived carbon with removal of inorganic impurities and high porosity

Purified sludge carbon (PSC) with removal of inorganic ‘impurities’ (Si, Al, etc.) is prepared from sewage sludge. Morphological structure, textural properties, surface elements and functional groups of sludge carbon (SC) and PSC are compared. SBET and pore volume of PSC are about three times higher than those of SC. PSC with large fluffy cavities remains some memory of SC parent structure. Removed fractions can be considered as a natural template for producing a hierarchical porous structure in PSC. Abundant oxygen-containing groups including hydroxyl and epoxide are generated in PSC, which are favorable for organic contaminant removal from wastewater. Diffraction peaks at 2θ = 45°, bending modes of Si–O–Si and Na1s peaks (1070.5 eV) jointly confirm that only a trace of adsorbed impurities (Na2O·(SiO2)x (x ⩾ 1)) is retained on PSC surface. PSC is superior to SC and comparable to commercial activated carbon for rhodamine B and phenol adsorption capacity.