Preparation and performance of artificial wetland phosphorus removal filter media based on construction wastes

Efficient and high-capacity adsorption materials are crucial for improving the phosphorus removal efficiency of constructed wetlands. This study focuses on preparing porous phosphorus removal filter media using construction wastes (mainly waste concrete and waste foam bricks) as the main raw materials. The filter material was characterized for their main chemical composition and morphological features using X-ray diffraction and scanning electron microscope. The adsorption performance of the filter material for phosphorus in water was evaluated through adsorption kinetics and adsorption isotherm experiments, static comparative experiments, and dynamic experiments. The results showed that the material had a large specific surface area and well-developed pore structure, featuring a layered pore structure of internal microstructure with a specific surface area of 22.7 m²/g. The adsorption process fitted the pseudo-second-order adsorption kinetics model and Langmuir adsorption isotherm model, with the adsorption mechanism being primarily monolayer physical and chemical composite adsorption with a maximum adsorption capacity of 693.21 mg/g. In static adsorption experiments with a total phosphorus concentration of 0.4 mg/L, the average phosphorus removal rate of the porous material within 4 hours was 65.38%, which was 4.10, 1.98, 3.52, 2.29 and 1.59 times higher than that of waste concrete, waste foam bricks, ceramic granules, diatomaceous earth, and activated carbon, respectively. In dynamic experiments simulating horizontal subsurface flow wetlands with an influent total phosphorus concentration of 0.40 mg/L and hydraulic loads of 0.48, 0.96, 1.20, and 2.40 m³/(m²·d), the average phosphorus removal rates were 95.74%, 93.56%, 80.42% and 55.34%, respectively. Under a hydraulic load of 0.96 m³/(m²·d), an influent average phosphorus concentration of 0.52 mg/L, and continuous inflow for 45 days, the average phosphorus removal rate of the porous material was 92.65%. The filter material had the advantages of a simple preparation method, excellent phosphorus removal performance, effective utilization of construction waste, and application potential as constructed wetland filler.