The impact of contact time on pyrene sorptive behavior by a sandy-loam soil

Batch experiments with pyrene (PYR) were conducted to quantify the effect of contact time on its sorption and desorption behavior by a sandy-loam soil. Twenty-four and 48 h contact times were chosen for the nonequilibrium conditions and 240 h for the pseudoequilibrium study. All times was selected based on the kinetic results. The nonlinear, pseudoequilibrium sorption isotherm was fit to a two-stage Freundlich model: 3-7 mg/l for the first stage and 7-15 mg/l for the second stage. A substantial fraction of the sorbed PYR was not desorbed within the given desorption time. The reason of hysteresis was found to be a sorption enhancement due to soil hydration which provided more sorption sites. A desorption enhancement at 240-h desorption steps was attributed to the increased dissolved organic matter evolution. This study also found that both soil organic matter and clay materials had an equal role in PYR sorption enhancement and desorption resistance.