Experimental study on the separation of quartz from pyrite using alginate as a selective depressant substantiated by theoretical analysis on intermolecular bonding

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(OH)-5 center dot center dot center dot FeOH+center dot center dot center dot ALG complex had a complexation energy of -834.5 kJ/mol on the singlet (S = 0) potential energy hypersurface. Additionally, FeOH+center dot center dot center dot ALG and Si(OH)-5 center dot center dot center dot 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 center dot center dot center dot O in FeOH+center dot center dot center dot ALG and Si(OH)-5 center dot center dot center dot FeOH+ as well as O-H center dot center dot center dot O hydrogen bond in Si(OH)-5 center dot center dot center dot FeOH+center dot center dot center dot 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.

Automated summary

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 investigated experimentally and theoretically. Results show that the adsorption of ALG onto pyrite and quartz containing iron species decreased with increasing pH, and the interactions in the complexes were partially covalent in nature.