Treatment of nitrate containing wastewater by adsorption process using polypyrrole-modified plastic-carbon: Characteristic and mechanism

Polypyrrole-modified plastic-carbon (PET-PPy) composite was prepared by using high porosity plastic-carbon materials and a special doping mechanism of polypyrrole to remove nitrate from water to achieve waste recycling. As a result, PET-PPy-500 showed remarkable nitrate adsorption in both acidic and alkaline wastewater. The pseudo-second-order kinetic and Langmuir isotherm models were fit for the nitrate adsorption by PET-PPy-500, and the maximum adsorption capacity predicted by the Langmuir model was 10.04 mg NO3-N/g (45.18 mg NO3/g) at 30 degrees C. The ion exchange and electrostatic attraction were the main mechanisms of removing NO3 by PET-PPy-500, which was demonstrated by the interface characterization and theoretical calculation. The doped ions (Cl) and/or other anions produced by charge transfer interaction were the main exchange ions in the process of NO3 adsorption. The main binding sites in the electrostatic adsorption process were nitrogencontaining functional groups, which can be confirmed by the results of XPS and density functional theory (DFT). Furthermore, DFT results also showed that the adsorption of nitrate by PET-PPy was a spontaneous exothermic process, and the adsorption energy at the nitrogen site was the lowest. The findings of this study provide a feasible strategy for the advanced treatment of nitrate containing wastewater.

Automated summary

In this study, a polypyrrole-modified plastic-carbon (PET-PPy) composite was prepared by using high porosity plastic-carbon materials and a special doping mechanism of polypyrrole. It showed remarkable nitrate adsorption in both acidic and alkaline wastewater. The main mechanisms of removing nitrate by PET-PPy were ion exchange and electrostatic attraction. The findings provide a feasible strategy for the advanced treatment of nitrate containing wastewater.