LAUSR

Abstract The surface chemical properties of quartz containing iron species and pyrite in the presence of sodium alginate (ALG) as well as bulk solution studies of Fe were experimentally and theoretically investigated. The adsorption of ALG onto pyrite and quartz containing iron species was observed to decrease with increase in pH. The binding energy calculations at BP86/6-311++g/def2-TZVP level of theory indicated that the most stable structure for Si ( O H ) 5 - ∙∙∙ FeOH+∙∙∙ALG complex had a complexation energy of −834.5 kJ/mol on the singlet (S = 0) potential energy hypersurface. Additionally, FeOH+∙∙∙ALG and Si ( O H ) 5 - ∙∙∙FeOH+ complexes were the most stable on the quintet (S = 2) potential energy hypersurface with complexation energies of −2352.9 and −1596.4 kJ/mol, respectively. The nature of interaction in the complexes was further probed by using various quantum chemical tools namely quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analysis. The results indicated that the interactions O Fe∙∙∙O in FeOH+∙∙∙ALG and Si ( O H ) 5 - ∙∙∙FeOH+ as well as O H∙∙∙O hydrogen bond in Si ( O H ) 5 - ∙∙∙FeOH+∙∙∙ALG were partially covalent in nature. In the presence of 2000 g/t of ALG at pH 5.3, the grade and recovery of Fe obtained was 44.7% and 97.2% with a selectivity index of 35.8.