Mitigation of phosphorus contamination from livestock farms with La-containing hydrochar adsorbent

[Display omitted] •Novel mechanochemical synthesis of La-HC and La-HCN.•Urea-La rice straw recovers farm phosphorus from wastewater.•High-capacity, quick-acting La-containing adsorbents for phosphorus.•La-containing hydrochar: few resources and low CO2 emissions. Phosphorus releases from livestock and poultry farms cause environmental contamination that must be mitigated through robust and effective recycle technologies. Lanthanum-modified hydrochars (La-HCN) prepared via mechanochemical modification had 96.8 mg g−1 phosphorus adsorption capacities and unprecedented fast uptake rates (half-maximum absorption capacity in 1.5 min). Presence of nitrogen in the hydrochars enhanced ion electrostatic interactions between lanthanum and carbon and accelerated phosphorus adsorption, which was confirmed theoretically with density functional theory calculations. Life cycle assessment (LCA) on a one-animal one-year basis revealed that production of La-containing hydrochar required fewer resources, had lower greenhouse gas emissions (171 kg CO2) and lower environmental impact than comparable adsorbent materials. Phosphorus removal levels achieved using the La-HCN adsorbent on actual wastewater from livestock and poultry breeding farms reached an adsorption rate of 93.6 %, exceeded sewage effluent standards of China, US EPA and EU, thus, demonstrate the practicality and scope of the developed technology.