Thermodynamics of monochlorophenol isomers and pyrite interfacial interactions in the activation state

Thermodynamic parameters of the activation state for phenol and three monochlorophenol (MCP) isomer–pyrite complexes, i.e., MCP isomers used were 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 4-chlorophenol (4-CP), have been derived from the temperature-dependent kinetic data. Both the initial rate and adsorption density values increased in the order phenol < 2-CP < 3-CP < 4-CP. This suggests that the presence of chlorine substituent on the aromatic ring results in enhanced CP adsorption on pyrite. The activation energy (Ea)(Ea), Gibbs free energy (ΔG#)(ΔG#), entropy (ΔS#)(ΔS#), and enthalpy (ΔH#)(ΔH#) of the activation stage for MCP adsorption on pyrite were calculated by Arrhenius and Eyring models. Always ΔS#ΔS# values approximate to zero and −TΔS#−TΔS# values are positive, which indicates that the activation state of MCP adsorption process is entropy-controlled, and the observed linear dependence of ΔH#ΔH# on −TΔS#−TΔS# signals an entropy–enthalpy compensation effect of the MCP adsorption process. The ΓMCPΓMCP data were quantified well both by 1−pK1−pK diffused double layer (1−pK1−pK DLM) and Langmuir models.