The use of magnetic lanthanum-based materials for phosphate removal from river water has gained increasing attention. However, challenges to produce and use lanthanum-based materials in large-scale or pilot-scale studies remain. In this work, a kilogram-scale Fe3O4/La(OH)3 magnetically recyclable composite for removing phosphate from river water was developed through a low-temperature precipitation route. The composite was used to remove phosphate from river water at both bench- and pilot-scales. Based on the bench-scale tests, the developed Fe3O4/La(OH)3 composite was found to have excellent magnetic particle separation efficiency (>98%) and a sorption capacity of 11.77 mg/g for phosphate. A 1.0 g/L dosage of the composite in the river water sample was able to selectively reduce the phosphate level from 0.089 to 0.005 mg/L in 60 min over five consecutive adsorption cycles. At the pilot-scale, the Fe3O4/La(OH)3 composite only achieved 36.0% phosphate removal efficiency, which is considerably different from the bench-scale results over an operational time of five months and a total treatment volume of 300 m3. This significantly reduced removal efficiency is mainly attributable to turbidity, suspended solids, and organic matter in the river water and the deteriorated magnetic separation efficiency. This study revealed potential challenges and shed new insights on moving magnetic nanocomposite-based technology from the bench-scale to the pilot-scale, which can inspire new designs for the application of similar technology.

Pilot-scale study is a critical step towards practical application. In this work, a pilot-scale adsorption system was established to validate and to evaluate the performance of phosphorus (P) polishing removal using the lanthanum-based polymeric nanocomposite La@201, with an average treatment capacity of 10 m(3)/day over a period of 8 months. The adsorption system effectively reduced the P concentration to below the eutrophic limit (0.02 mg/L), achieving an average removal efficiency of 91.23% for orthophosphate and 78.51% for total phosphorus. The adsorption system exhibited high stability, robustness, and resilience towards external stimuli such as the fluctuating influent P concentration, varying turbidity, and competing ions. The limited dissolution of La from the La@201 adsorbent was caused by the accumulation of organic matter in the two adsorption columns, indicating the material's high stability. In general, the river water complex matrix collectively affected the P removal efficiency by La@201 through synergistic effects in which the turbidity, conductivity, and fluoride ions contributed the most. Post characterization of adsorbents after the operation identified multiple La-P phases, which are drastically different from the observation in lab-scale experiments, however still indicating the dominating role of the La-P interaction for selective P removal. The regeneration process was used to transform the used La@201 to its pristine state reversely. We believe this study indicates the excellent potential of La@201 for practical applications, offers new insights into the design and scaling-up of novel adsorbents and adsorption technology for polishing phosphate treatment from natural waters and wastewater.