Study on preparation of porous water treatment fillers from fly ash by foaming

Fly ash is one of the most troublesome industrial solid wastes in China, and the large amounts stockpiled in many regions urgently need value‐added utilization. Owing to its honeycomb structure and high surface area, fly ash shows potential as a water treatment material. However, the commonly used ceramic‐particle preparation process suffers from high energy consumption and low porosity. This study explored the process optimization of foamed fly ash filler, aiming to develop a non‐sintered, porous substrate for water treatment. The results showed that using a certain power plant's fly ash as the raw material, with a ratio of 70% fly ash, 30% cement, and a 60% water to cement ratio, animal protein was used as the foaming agent; the foamed fly ash filler had the best performance. Its apparent density was 762.8 kg/m 3 , specific surface area was 8.75 m 2 /g, 1‐hour water absorption rate was 37.25%, and the combined crushing and wear rate was 4.23%. In nitrogen and phosphorus adsorption tests, the non‐sintered filler achieved removal rates of 66.58% for phosphorus and 52.59% for ammonia nitrogen, outperforming the commonly used substrates of sintered ceramic particles and natural quartz sand. The non‐sintering route can promote large‐scale resource utilization of fly ash and deliver environmental benefits by reducing waste and energy use.