Exceptional adsorption properties of amino-carboxylic acid chelating fibers for calcium, magnesium, and strontium ions.

In the chlor-alkali industry, the thorough purification of calcium (Ca²⁺), magnesium (Mg²⁺), and strontium ions (Sr²⁺) presents a considerable challenge. In this context, we developed novel amino carboxylic acid fibers in this study by using laboratory-synthesized polyacrylonitrile-polyethyleneimine amino fibers as the matrix. The amino carboxylation process was achieved by introducing chloroacetic acid under mild alkaline and heating conditions, resulting in the desired amino carboxylic acid fibers (PAN-C-Na). Adsorption experiments demonstrated that the PAN-C-Na fibers reached adsorption equilibrium within 30 s. Additionally, they effectively adsorbed Ca²⁺ and Mg²⁺ ions at ultralow concentrations (<0.02 mg/L), exhibiting outstanding adsorption capacities of 0.40 and 0.36 mmol/g, respectively, and exceeding 50% of their saturation adsorption capacities. Moreover, compared to amino-phosphonic acid fibers, which are another type of calcium-magnesium adsorptive fibers, the PAN-C-Na fibers exhibited twice the selectivity for Sr²⁺ adsorption and proved effective in eliminating residual Sr²⁺ in brine. These findings highlight the potential of PAN-C-Na fibers as a promising material for the thorough purification of Ca²⁺, Mg²⁺, and Sr²⁺ ions in the chlor-alkali industry. [ABSTRACT FROM AUTHOR]