Brushite-infused polyacrylonitrile nanofiber adsorbent for strontium removal from water

The Fukushima Daiichi nuclear disaster and the decommissioning of over a hundred nuclear reactors worldwide led to the increase in the demand for efficient water treatment technologies to remove radionuclides, such as ⁹⁰Sr. Brushite or dicalcium phosphate dihydrate (DCPD) is a potential adsorbent to remove strontium from water. In this study, composite poly(acrylonitrile) (PAN) nanofiber (NF) adsorbents with DCPD (PAN/DCPD) were prepared, characterized, and investigated for strontium adsorption in water. Material characterization revealed mechanically suitable, hydrophilic, and macroporous composite NF adsorbents with average fiber diameters of <500 nm. As-prepared DCPD powder exhibited a superior strontium uptake capacity of 81.7 mg g^-1 at pH ≅ 10 of aqueous Sr²⁺ solution over its biogenic and synthetic predecessor, hydroxyapatite. Increased DCPD loading resulted in higher adsorption. Maximum Sr²⁺ uptake of PAN/DCPD NF with 70 wt% DCPD loading (PAN/70DCPD NF) was 146 mg g^-1 considering the Sips isotherm model. Kinetic studies revealed that Sr²⁺ removal by PAN/DCPD NF was a chemisorption process which involved ion exchange and surface complexation. PAN/70DCPD NF as a dead-end membrane filter exhibited superior removal efficiency over pure PAN NF. The overall results of this study revealed the potential application of PAN/DCPD NF adsorbent for ⁹⁰Sr removal from water.