Highly-effective phosphate removal from aqueous solutions by calcined nano-porous palygorskite matrix with embedded lanthanum hydroxide

Abstract

Abstract Efficient phosphate removal from wastewater is critical for the safety of natural water bodies against eutrophication and for the replenishment of unrenewable phosphorus resources. In order to enhance phosphate capture efficiency and exploit raw clay for high value-added products, HPAL-LaOH was fabricated by embedding lanthanum hydroxide onto calcined nano-porous palygorskite clay through a simple-green hydrothermal method where the host palygorskite with cross-linked networks providing abundant binding sites for La(OH)3 incorporation, allowing the accessibility of phosphate for the adequate crystallization of lanthanum phosphate without triggering pore blockage. Excellent phosphate adsorption capacity (109.63 mg/g) was achieved by HPAL-LaOH, over 13 times higher than that of raw palygorskite, also much higher than commercial pure La(OH)3 (69.64 mg/g) in batch runs. Interestingly, for solutions below 100 mg/L in a wide pH range of 3–11, almost complete phosphate sequestration (