Investigation of adsorption of copper, zinc and cadmium metals by polymeric coagulant polyaluminum chloride based on density functional theory

There are different types of suspended metal materials in wastewater and municipal water, and high-cost coagulants must be used to remove them in water refinery. polyaluminum chloride (PAC) is one of the newest coagulants. Due to the high cost and long preparation time of PAC, it is more economical to use simulation methods instead of experimental tests. In this paper, the adsorption process of copper, zinc and cadmium on PAC coagulants has been studied using the density functional theory (DFT) by Quantum Espresso calculation code. The calculations are based on the flat wave method with quasi-potential using the generalized gradient approximation (GGA). The pseudopotential used is also generated by the ultra-soft method. Analysis of the band structure and density of electron states showed that the PAC materals are semiconductor with an energy gap of 5.4 eV. Also, the results obtained from adsorption calculations showed that copper, zinc and cadmium metals are adsorbed with PAC coagulant adsorption energy of -4.56, -8.79 and -13.25, respectively. According to these results, increasing the conductivity of the PAC compound, which is the result of reducing the energy gap during the adsorption process, can be a factor in identifying suspended metals in water.