DFT benchmarking for adsorption energy in wastewater treatment

Despite its potential importance, the computational chemistry of adsorption processes for wastewater treatment has received negligible attention. Exploring the literature shows several limitations in applying quantum chemistry to study adsorption processes in wastewater treatment. The choice of suitable functionals of density functional theory (DFT) is one of the critical limits of the current application of quantum chemistry in wastewater treatment. Therefore, in this work, we performed a benchmark study of sixteen DFT functionals (including dispersions) to select the most suitable one. The def2-TZVP basis set has been used with the sixteen DFT functionals. The sixteen DFT functionals are benchmarked to the CCSD(T)/CBS level of theory. We used four different pollutants (p-aminobenzoic acid, aniline, p-chloro phenol, and phenol) adsorbed on coronene to perform this benchmarking. In addition to the coronene and the pollutant, four explicit water molecules are used to consider the environmental effects. The results show that the functional MN15 and PW6B95-D3 have the lowest mean absolute deviation relative to the CCSD(T)/CBS adsorption energies. Overall, the functionals MN15, PW6B95-D3, & omega;B97X-V, M05-2X-D3, M05-D3, and M06-2X-D3 are recommended for studying the adsorption processes.