Heated kaolinite-La(III) hydroxide complex for effective removal of phosphate from eutrophic water

Eutrophication has long been a serious environmental problem in global water bodies, and phosphate has been considered as one of the key factors causing water eutrophication. Aiming to develop a low-cost and eco-friendly absorbent for phosphate removal, a type of heated kaolinite‑lanthanum hydroxide complex (HKL-LaOH) was prepared via an in-situ synthesis method. In the complex, a large number of nanoscale lanthanum hydroxide flakes were observed on the heated kaolinite surface. The HKL-LaOH with a relatively low lanthanum oxide content (4.42 wt%) exhibited a high phosphate adsorption capacity of 26.15 mg g−1. Such a high utilization rate of lanthanum in HKL-LaOH was attributed to the unique two-dimensional flake shape of heated kaolinite, which achieved the effective dispersion of La(OH)3 on the complex. Furthermore, a great quantity of LaPO4 nanoparticles on the heated kaolinite surface of the HKL-LaOH complex were observed, which indicated chemical adsorption of phosphate followed by precipitation of LaPO4. In summary, the high dispersion of La(OH)3 in HKL-LaOH and the resulted formation of LaPO4 nanoparticles leads to high phosphate removal from eutrophic water bodies, which shows excellent application potential in the treatment of eutrophic water. [Display omitted] •La(OH)3 synthesized in-situ on heated kaolinite to obtain hydroxide complex.•La(OH)3 was well dispersed in complex and provides abundant active surface sites.•The complex with 4.42% La2O3 showed a high phosphate removal rate (90.54%).