Facile synthesis of lattice-defective and recyclable zirconium hydroxide coated nanoscale zero-valent iron for robust arsenite removal

A novel core-shell structured adsorbent, zirconium hydroxide coated nanoscale zerovalent iron (NZVI@Zr(OH)(4)), was developed for aqueous arsenite (As(III)) removal. The effects of water content and Zr dose for the coating process on the coating efficiency, anti-corrosion stability, and As(III) removal were investigated to optimize the performance of NZVI@Zr(OH)(4). The Zr(OH)(4) shell with a coating ratio of 200 wt% (Zr/Fe) was demonstrated to completely cover the NZVI surface, which can protect the NZVI core from aqueous corrosion in aerobic conditions and maintain its ferromagnetism. Due to the strong ferromagnetism of NZVI, a magnetism saturation value of 32.3 emu/g could be obtained with a high Zr content of 44.5 wt%, which could concurrently guarantee the quick magnetic separation for recycling and the high As(III) adsorption capacity. The Zr(OH)(4) shell synthesized at room temperature possesses a weak crystalline and mesoporous structure. Abundant oxygen lattice defects with the uncoordinated Zr(IV) on the surface of Zr(OH)(4) shell could be utilized for the As(III) removal via chemisorption. As a result, the NZVI@Zr(OH)(4) performed a much higher capacity (380.0 mg-As.g(-1) or 853.2 mg-As.g-Zr-1) than commercial Zr(OH)(4) and other magnetic Zr-based materials, which was not affected by the pH variation and the co-existed environmental anions and natural organic matters. Therefore, NZVI@Zr(OH)(4) is a promising material that can be applied and recycled to remove As(III) under diverse aqueous conditions.

Automated summary

In this study, a novel core-shell structured adsorbent was developed for efficient removal of aqueous arsenite. The adsorbent exhibited excellent corrosion resistance, high adsorption capacity, and was not affected by environmental factors, making it suitable for various water conditions.