Efficient and stable adsorption uranium from wastewater by P-ZBCT composite adsorbent at low dosage

In this research, a new synthesis approach was developed for an adsorbent, namely the phosphorylated ZIF-8/bamboo charcoal/chitosan/tannic acid (P-ZBCT) composite, for the efficient adsorption of uranyl ions from wastewater at low dosages. Impressively, the uranium adsorption rate of P-ZBCT reaches up to 98 % at a low dosage of 0.056 g/L in a 10-mg/L uranium solution, outperforming most reported uranium adsorption materials. The theoretical maximum adsorption capacity of P-ZBCT for uranium at 308 K and pH 6.0 is 2357.69 mg/g, with uranium adsorption being a spontaneous endothermic chemical reaction. Mechanistic analysis reveals that surface functional groups such as PO, amino group, and CN play a pivotal role in uranium adsorption. A competitive adsorption experiment shows that zinc is the most competitive with uranium adsorption; however, the partition coefficient of U is 11 times that of zinc, indicating that the absorption of uranium is more selective than that of other metal ions, such as zinc. Adsorption treatment using P-ZBCT successfully reduces the uranium content in real uranium tailings-containing pond wastewater to 34 μg/L. P-ZBCT demonstrates exceptional recycling performance, maintaining an adsorption rate of 85 % even after 10 sorption-desorption cycles. Therefore, P-ZBCT exhibits significant potential for efficiently extracting uranium from low-concentration uranium-containing wastewater.