Production of sorptive granules from incinerated sewage sludge ash and upcycling in cement mortar

This paper describes a method to produce sorptive granules solely from solid waste. The produced granules can remove multi-toxic heavy metal(loid)s from wastewaters and be upcycled as lightweight aggregates in cement mortars. Specifically, kilogram-scale production of millimeter-sized granules was obtained via the thermal treatment of green bodies prepared from phosphorus-stripped incinerated sewage sludge ash (ISSA), peanut shell and waste bentonite at a mass ratio of 1:1:2 at 1050 °C under a N₂ atmosphere. The synthesized granules with good mechanical strength (4.9 MPa) exhibited excellent adsorption capacities towards As(V), Cr(VI), Cu(II) and Pb(II) at respectively 14.11, 5.79, 14.12 and 23.52 mg/g at an initial solution pH of 3.0 via mechanisms including redox reactions, complexation, (co)precipitation, and cation exchange. Moreover, the potentially hazardous spent granules could be environmental safely reused as a partial river sand replacement in cement mortars based on the Toxicity Characteristics Leaching Procedure.