Competitive adsorption of phthalate esters on marine surface sediments: kinetic, thermodynamic, and environmental considerations

Mohammadian, Somaye; Ghanemi, Kamal; Nikpour, Yadollah

Competitive adsorption of phthalate esters on marine surface sediments: kinetic, thermodynamic, and environmental considerations

2016

Mohammadian, Somaye | Ghanemi, Kamal | Nikpour, Yadollah

In this study, the sorption behavior of six widely used phthalate esters (PEs) on marine sediments was investigated. The adsorption of PEs was fast and reached the equilibrium within 6 h. The forward and backward rate constants of all PEs on sediments were calculated. Several kinds of kinetic and thermodynamic models have been investigated; the pseudo-second-order model and the partition isotherm model were best fitted to the adsorption behavior of PEs. The rate-limiting step of sorption was controlled by the film diffusion mechanism. After treating sediments with H₂O₂, the partition coefficients of all PEs were significantly reduced and indicated that the amorphous organic carbon has a major role in adsorption process. The negative values of ΔH° and ΔG° for these compounds showed that the sorption process is exothermic and spontaneous. The adsorption capacities of all PEs were slightly influenced by increasing the salinity from 0 to 40 g L⁻¹. These research findings have a prime importance on assessment of the fate and transport of PEs in seawater-sediment systems.

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