Studies on the performance of functionalized Fe₃O₄ as phosphate adsorbent and assessment to its environmental compatibility

Background: The pressing demand to increase agricultural productivity amid the rapidly growing population has exponentially boosted fertilizers usage. Phosphate (Pi) runoff from fertilizers induces eutrophication in water sources and severely affects its surrounding ecosystems. To cope with Pi accumulation problem, this study reported the synthesis of an environmentally friendly magnetic adsorbent, namely Fe₃O₄/thiamine (thF). 
Method: A one-step chemical oxidation and functionalization technique for thF synthesis was developed. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), nitrogen (N₂) sorption, and superconducting quantum interference device (SQUID) analysis were conducted to ensure the formation of Fe₃O₄, confirm the successful incorporation of thiamine, and gain insight into the factors influencing the adsorptivity of thF-363. 
Significant Findings: The thF synthesized at 363 K (thF-363) produces an adsorbent with the highest Pi removal efficiency compared to other synthesis conditions. The thF-363 showed up to 1.51-fold higher adsorption capacity than the unmodified Fe₃O₄. The large surface area and occurrence of thiamine functional groups are the contributing factors in enhancing its adsorption capacity for Pi removal. The thF-363 did not adversely affect the growth of the model plant, Arabidopsis thaliana; demonstrating its suitability as an environmentally friendly adsorbents for Pi removal from eutrophicated water with the feasibility of magnetic separation from an aqueous system.