Purification of solid waste phosphogypsum by various cationic collectors: Experimental study and theoretical calculation.

Phosphogypsum (PG), a byproduct of phosphate fertilizer production, poses environmental pollution risks due to the potential release of impurities such as phosphorus, fluoride, and organic compounds, necessitating effective treatment and remediation. Among various methodologies, flotation has emerged as a key technique for separating impurities from PG. Although extensive research has been conducted on the separation and reuse of PG, studies focusing specifically on organic impurity separation and collector optimization are still limited. This study utilized a reverse flotation method with various cationic collectors-dodecyl trimethyl ammonium chloride (DTAC), dodecyl amine (DDA), octadecyl dimethyl benzyl ammonium chloride (ODBC), and dodecyl benzyl dimethyl ammonium chloride (DDBAC)-to whiten PG (whiteness from 29.88% to 66%) by removing organic impurities, quartz, etc. Results indicated varying adsorption effects on impurities with the following trend: DDA < DTAC < ODBC < DDBAC. Density functional theory (DFT) and molecular dynamics (MD) calculations confirmed that the adsorption between the collectors and quartz primarily occurs through hydrogen bonding and dipole-dipole interactions, while DDBAC and ODBC also demonstrated π-π interactions with compounds containing benzene rings. This study provides insights for collector selection in reverse flotation and a theoretical basis for PG recycling.