Membrane-assisted removal of hydrocarbons from laboratory test results contaminated soils

The effectiveness of soil remediation process, consisting of the soil washing, microfiltration and pervaporation process to remove iso-octane (VOC) was investigated. The several different parameters influencing the washing process were investigated: type of the soil (sand and sandy clay), time of the washing process as well as an addition of surfactants to the washing solution. The MFenhanced soil washing allowed for the removal of iso-octane from the contaminated soil. Efficiency of iso-octane removal depended on the type of soil and was worse for the sandy clay, because of its higher stickiness and plasticity. The addition of a surfactant enhanced iso-octane removal; however, its optimal concentration in washing solution should not be higher than 0.1 Á 0.3 wt.%. A substantial excess of a washing solution to the soil (at least 100:1) was needed to obtain a good removal of volatile organic compounds (VOCs) from contaminated soil. Iso-octane extracted from the contaminated soil was subsequently removed by pervaporation process with several types of hydrophobic membranes. Prior to pervaporation process, the washing solutions underwent microfiltration to remove all suspended particles from the feed. The best pervaporative properties were found for the PDMS-PAN membrane. An addition of the surfactant increased the solubility of iso-octane in water during the washing step of remediation process but simultaneously dramatically decreased the efficiency of the final removal of VOCs from water by pervaporation.

MF-enhanced soil washing allowed for the removal of hydrocarbons from the contaminated soils. Efficiency of iso-octane removal depended on the type of the soil and was worse for the sandy clay soils. The addition of a surfactant enhanced iso-octane removal; however, its optimal concentration in washing solution should not be higher than 0.1 Á 0.3 wt.%. A substantial excess of washing solution to soil (i.e. 100:1) was needed during remediation to obtain a good removal of VOCs from the soil. VOCs extracted from the contaminated soils by washing process can be subsequently removed by pervaporation with hydrophobic membranes. Prior to pervaporation process, the washing solutions must undergo microfiltration to remove all suspended particles from the feed. It was found that the PDMS-PAN membrane was the most efficient in pervaporation removal of VOCs from water. An addition of the surfactant increased the solubility of iso-octane in water during the washing step of remediation process but simultaneously dramatically decreased the efficiency of the final removal of VOCs from water by pervaporation. This fact indicates that the soil washing step of the remediation procedure should be performed without any surfactant addition, as its removal from the system for further recycling seems to be very complicated and could create another pollution problem. Fig. 12 presents the layout of the suggested MF Á PV integrated remediation system to treat soils contaminated with such VOCs like petroleum hydrocarbons.