g-C3N4 modified natural low-grade dolomite-palygorskite: Removal capacity and adsorption mechanism for Gd3+

Rare earth elements (REEs) pose significant environmental challenges due to the wastewater generated during their extraction. Developing efficient adsorbents with simple, economical and eco-friendly methods for removing and recovering REEs from wastewater is highly demanded but full of challenges. This study creates a novel adsorbent ( g -C 3 N 4 /0.5DPal) for efficient REEs removal and recovery by integrating the low-grade mineral dolomite-palygorskite with g -C 3 N 4 through a "one-pot" calcination method. Characterization techniques including SEM, XRD , FT-IR, XPS , etc., were employed to analyze the structure of the g -C 3 N 4 /0.5DPal composite. Batch adsorption experiments focusing on Gd 3+ from among the REEs were conducted to evaluate the adsorption performance. The results reveal a remarkable 3.34 times increase in Gd 3+ adsorption capacity of g -C 3 N 4 /0.5DPal (192.46 mg/g) compared to raw dolomite-palygorskite (57.62 mg/g) at 298 K, highlighting the effectiveness of the modification. The adsorption mechanism involves electrostatic interactions , surface complexation, and cation-π interactions. It is worth noting that g -C 3 N 4 facilitates the conversion of dolomite to calcite during the preparation process, enhancing the Gd 3+ adsorption of g -C 3 N 4 /0.5DPal. This work offers a promising solution for the removal and recovery of REEs and the high-value utilization of low-grade minerals, addressing both environmental concerns and resource sustainability.