Porous ceramsite from construction muck and wheat straw for wastewater treatment

Construction muck (CM) from an excavation project was used to prepare sintered porous ceramsite with wheat straw (WS) as a pore-forming agent. The effect of sintering parameters and the pore-forming agent on the properties and removal efficiency of chemical oxygen demand (COD) and ammonium nitrogen (NH₄⁺–N) (here called AmN) of the porous ceramsite were investigated. It was found that an increase in sintering temperature and time increased the compressive strength but decreased the water absorption. Porous ceramsite of diameter 5–10 mm, sintered at 1155°C for 20 min, with WS of length 5 mm and CM/WS ratio of 12.5%, was found to have the highest connected porosity, accompanied by satisfactory strength, voidage and hydrochloric acid solubility. This porous ceramsite had better removal efficiency for COD than for AmN. The removal efficiency of COD reached 72.3% when the ratio of porous ceramsite to wastewater was 150 g/l, with a COD concentration of 104.97 mg/l. Even after regeneration twice, the porous still had a removal efficiency of 60.2% COD. Physical adsorption was found to play a major role during the adsorption processes of COD and AmN by the pseudo-first-order model.