Optimization of Removal Process of Petroleum Hydrocarbons from Soil Using Microwave Radiation and Its Effect on Some Soil Biological Characteristics

Such thermal methods as MicroWave (MW) radiations are considered as fast and efficient approaches in removal of organic pollutants from aquatic and terrestrial environments. This study was carried out to find the optimum conditions for oil removal from contaminated soils treated by MW irradiation. Following soil sampling from Tehran Refinery surroundings, the samples were treated under various conditions for including MW power intensity (770, 1100 and 1250 w) and frequency of 2.45 GHz, time of irradiation (5, 10 and 15 min), soil moisture (1, 10 and 15 % w/w) and added activated carbon (0, 2.5 and 5 % w/w). The optimum conditions of oil removal were obtained from results of Taguchi L9 orthogonal array. Besides, the effect of MW irradiation on some chemical and biological properties of soil was also investigated. Results indicated that the optimum conditions of the investigated parameter ranges were as follows: MW power (1100 w), irradiation time (15 min), soil moisture (1 % w/w) and added activated carbon (5 % w/w). About 70 % of petroleum hydrocarbons were dissipated within optimum conditions. Although the method exhibited some negative effects on respiration and population and respiration of soil microorganisms, still it can be used as an effective and fast approach for remediation of highly polluted soils considering the economic feasibility.