Display omitted •Tannic acid was used as precursor to modify lanthanum oxide based nanoadsorbent.•La/C nanorods doped membrane with dual functions was synthesized.•Simultaneous removal of suspended solids and phosphate was achieved by the membrane.•Phosphorus in practical diluted wastewaters can be readily reduced to <0.1 mg/L. Finding effective ways to control eutrophication issue and achieve phosphate recycling remains a long-term challenge. Here, a composite membrane with dual functions of adsorption and filtration was proposed to remove phosphorus from diluted wastewaters. Firstly, a new adsorption material, lanthanum oxide-doped carbon material (La/C), was synthesized to selectively remove phosphorus ions from aqueous solution. Batch-experiment results revealed that the maximum adsorption capacity of La/C reached 48.8 mg-P/g at pH 7.0 with simulated phosphorus solution, which was superior to that of La compounds without C doping (37.4 mg-P/g). Combining with a serial of characterizations, ligand exchange involved multilayer adsorption was the main mechanism for the phosphorus removal. With a moderate doping amount of La/C into casting solution, the composite porous membrane was fabricated and applied to remove the particles and phosphorus from the diluted wastewaters such as secondary effluent and surface waters. Carbon component in La/C material was found to be beneficial for the pores development and hydrophilicity improvement of membrane, which resulted in a higher water flux and better anti-fouling performance. This work may provide the valuable information for the feasible application of phosphorus adsorption material and enlighten the technical development for the low phosphorus polluted wastewater remediation.