Crawfish shell-based biosorbents for rare earth element (Nd(III)) immobilization in aqueous solution
| Authors: | Balazs Bencsik, Jessica Davis, Thomas Elder, Yucheng Peng |
| Year: | 2026 |
| Type: | Scientific Journal |
| Station: | Southern Research Station |
| DOI: | https://doi.org/10.1016/j.jece.2026.123900 |
| Source: | Journal of Environmental Chemical Engineering |
Abstract
Pristine crawfish shell waste and shell-derived biochars produced at 500, 650, and 800 ◦C were evaluated as calcium-rich sustainable biosorbents for Nd(III) immobilization from aqueous solution. Batch experiments were conducted at 23 ◦C using 50 mL of 1000 mg L-1 Nd(III) solution and sorbent mass of 25–100 mg to investigate removal behavior, kinetics, and mechanisms. The 800 ◦C biochar exhibited the highest apparent Nd(III) removal capacity (1200 mg g-1), which was attributed to instantaneous alkaline precipitation and the formation of Nd (OH)3. In contrast, pristine crawfish shell and the 500 and 650 ◦C biochars immobilized Nd(III) primarily through a dissolution–precipitation mechanism, yielding amorphous and crystalline Nd-containing carbonate phases. Among these sorbents, pristine crawfish shell showed the highest removal capacity at a sorbent mass of 25 mg (574.8 mg g-1), followed by the 500 ◦C biochar (490.1 mg g-1), whereas the 650 ◦C biochar exhibited substantially lower performance (291.4 mg g-1). Except for the 800 ◦C biochar, for which removal was instantaneous, the Elovich model provided the best fit to the kinetic data across pristine shell, 500 ◦C, and 650 ◦C sorbent types, regardless of the sorbent mass. The strong correlation between Ca(II) release and Nd(III) removal, supported by XRD, FTIR, and SEM–EDS analyses, indicates that Nd(III) immobilization is governed by phase dependent dissolution of calcium carbonate substrates followed by reprecipitation of Nd phases. These findings demonstrate that crawfish shell waste can serve as a highly efficient sacrificial biogenic calcium carbonate precursor for Nd(III) immobilization, even under ambient conditions.