Phosphorus-doped porous carbon particles based on biomass for efficient adsorption performance of Cu2+ and Zn2+ from aqueous solutions: thermodynamics, isotherms, kinetics, and mechanism

In this study, the fabrication of two-step phosphorus-doped porous carbon particles for adsorbent design based on low-cost biomass is performed for heavy metal removal. In the first step, activated carbon is produced from pistachio shells as biomass by activation of potassium hydroxide (KOH) (PSAC/KOH). In the second step, as a result of the activation of the obtained PSAC/KOH with phosphoric acid (H3PO4), phosphorus (P)-doped PSAC/KOH is obtained. Removal of Cu2+ and Zn2+ ions from environmental waters is carried out with P-doped PSAC/KOH. EDS, ICP-OES, and FTIR analyses showed that the P atom was doped on the AC surface. It is possible that the absorption of Cu2+ and Zn2+ will increase with the complexes that may form between the phosphorus-containing groups of the modified sample and the metal ions. For P atoms are less electronegative than C atoms, in possible C-P bonds, the P atom will have a positive charge density and the carbon atoms will have a negative charge density. Thus, Lewis base sites are formed on carbon atoms. Lewis base sites serve as important active sites in this adsorption application. The maximum adsorption capacities (Qm) of 136.38 mg/g and 12.57 mg/g at 30 degrees C of Cu2+ and Zn2+ removal are obtained with P-doped PSAC/KOH, respectively.