Adsorption mechanisms of crude oil onto polytetrafluoroethylene membrane: Kinetics and isotherm, and strategies for adsorption fouling control

In this work, a polytetrafluoroethylene (PTFE) membrane was experimentally studied to examine the mechanisms of adsorption fouling of crude oil on the microfiltration membrane. Isotherm and kinetics models were fit to the adsorption data. Scanning electron microscopy–energy dispersive spectroscopy and Fourier–transform infrared spectroscopy were conducted, and the effects of the initial concentration of crude oil, contact time, solution pH, ionic strength, and temperature were examined to understand the adsorption mechanism. Our results revealed that the Temkin model and pseudo–first–order model fit the adsorption data for crude oil on the PTFE membrane well, with R2 values of >0.98. The adsorption behavior was physical, as indicated by the value of the heat of adsorption BT (0.028 kJ/mol) and ΔrHmθ (–16.24 kJ/mol). Moreover, the values of ΔrGmθ (4.21–6.31 kJ/mol), ΔrHmθ (–16.24 kJ/mol), and ΔrSmθ (–0.06981 kJ/(mol·K)) indicated that the adsorption followed a spontaneous, exothermic, and less random process. Furthermore, the adsorption fouling was mitigated by slowing down the diffusion rate, decreasing the initial concentration of crude oil, reducing the adsorption time, increasing the solution temperature, and maintaining a pH value between 4.0 and 10.0. These results provide theoretical support for mitigating the adsorption fouling of the PTFE membrane during oily wastewater treatment.