Efficient phosphate removal utilizing N, Zn-doped carbon dots as an innovative nanoadsorbent.

The primary goal of this study is to examine PO adsorption from aqueous solutions using zinc-doped carbon dots (Zn-N-CDs) as a new adsorbent and cost-effective technique. Zn-N-CDs were produced through a hydrothermal process and subsequently identified using various techniques. The effect of reaction time, temperature, pH, ionic strength, adsorbent dosage, initial PO concentration, and anion competition (NO , Cl, HCO , and SO ) on PO adsorption using Zn-N-CDs were investigated. The characterization results depicted that Zn-N-CDs have a spherical structure without obvious aggregation and revealed the amorphous nature of carbon dots with many pores. Zn-N-CDs had a high affinity for adsorbing PO , reaching equilibrium within 5 minutes. While PO adsorption reduced with an increase in temperature, it increased with pH and ionic strength. The optimal conditions for PO adsorption were determined to be pH 8, 100 mM KCl as an ionic strength, and 5 g L of Zn-N-CDs. The presence of SO and HCO as competing anions slightly decreased PO adsorption. Thermodynamic studies revealed that PO adsorption onto Zn-N-CDs was endothermic, spontaneous, and disordered, as evidenced by Δ° < 0, Δ° > 0, and Δ° > 0. The experimental data fit well with a pseudo-second-order kinetic model ( = 0.999) and the Freundlich isotherm model ( = 0.9754), signifying that PO adsorption onto Zn-N-CDs occurs through multi-layer and chemi-sorption mechanisms. Overall, Zn-N-CDs indicated a great capability to adsorb high concentrations of PO across a wide range of pH values, indicating their potential for environmental remediation.