Heavy metal ions and methyl orange adsorption by N/O atoms co-doped biomass porous carbon in sewage purification: Experimental and DFT analysis

Developing low-cost and green biomass derived carbon with high adsorption capacity is an important way to solve heavy metal and organic pollution in water. Herein, triethanolamine, potassium hydroxide, and rice straw were used as raw materials to prepare the heteroatom doping biomass carbon (RSDPC) via solvothermal avenue. The adsorption performance and mechanism of Pb 2 + , Cu 2+ , and methyl orange (MO) on RSDPC were systematically investigated via a series of experimental characterizations, adsorption kinetics, isothermal models, and density functional theory (DFT) calculations. The synthesized RSDPC exhibited the maximum adsorption capacities to Pb 2+ , Cu 2+ , and MO are of ca. 230.2, 170.0, and 346.8 mg·g −1 , respectively, originating from the developed pore structure, considerable specific surface area, and numerous N/O co-doping active sites. Basing on the evaluation of kinetic and isotherm models, the adsorption mechanism of RSDPC to the pollutants is mainly induced by semi-chemical and monolayer adsorption. The cyclic adsorption measurements presented the RSDPC possessed stable adsorption capacity after 5 cycles with the average adsorption rates of ca. 94.33 %, 98.49 %, and 99.95 % to Pb 2+ , Cu 2+ and MO, respectively. The pollutant elimination of RSDPC in different real samples were all near 100 %. Moreover, the adsorption process of Pb 2+ and Cu 2+ ions was controlled by electrostatic interaction and that of MO was controlled by π-π stacking interaction, which was verified by density function theory (DFT) calculations and XPS analysis after adsorption simultaneously. This work developed a green and versatile biomass derived carbon by structural design and N/O heteroatoms co-doping to investigate the microscopic mechanisms of pollutant adsorption via the combination of experiments and theoretical calculations, providing a new method for the resource utilization of agricultural waste in the field of complex sewage purification.