Soil organic polluted matter phenol migration characteristics in modified loessial soil

Abstract: In order to prevent and control longitudinal migration of pollutants in soil and protect the groundwater from pollution, saturated soil column transport experiments were conducted，and the software CXTFIT2.1 was used for fitting the parameters from the experiments. This study aimed to explore retarding effect of the cetyltrimethylammonium bromide (CTMAB) modified soil and raw soil on migration of phenol, and to investigate the effect of modification ratio, pH, ionic strength on phenol migration in soil column. The results showed that with the software CXTFIT2.1, the deterministic equilibrium CDE (EM) model can be used to simulate breakthrough curves of Cl-, and the deterministic non-equilibrium CDE (NEM) model can be used to simulate breakthrough curves of phenol well. Non-reactive Cl- was used to determine the soil column parameter dispersion coefficient when average pore water velocity v was fixed. Then the average velocity of pore water and dispersion coefficient were used to calculate the transport parameter retardation factor of the reactive solute phenol. Clay layer of Lou soil modified by CTMAB significantly enhanced the retardant ability of soil for phenol migration. The greater the modification ratio was, the later the flow time of phenol was, and the greater the retardation coefficient was. With the modification ratio increasing from 0 to 100%, the flow time of phenol was delayed by 3.90 to 82.65 pv, and the retardation coefficient increased from 0.48 to 12.51. So the increase of modified soil proportion can block phenol transportation, and increase the retention quantity of phenol. In other words, the retention ratio more than 25% modification ratio soil samples reached about 50% for phenol, while the retention ratios of CK and 10% modification ratio soil samples for phenol were only about 20%. The pH values ranging from 6.0 to 8.0 had almost no effects on blocking phenol migration in the modified soils. The flow time of phenol in raw soil remained at around 0.45 pv, and the retardation coefficient was about 2.00. The flow time of phenol in 100% modified soil remained at around 12.30 pv, and the retardation coefficient was about 60.50. The larger ionic strength was, the earlier the flow time of phenol was, and the smaller the retardation coefficient was. With the ionic strength increasing from 0.001 to 0.1 mol/L, the flow time of phenol in raw soil was advanced from 4.07 to 3.42 pv, and the retardation coefficient dropped from 0.56 to 0.37. The flow time of phenol in 100% modified soil was advanced from 130.47 to 55.27 pv, and the retardation coefficient dropped from 17.57 to 8.71. So the rise of ionic strength can decrease retardant ability of raw soil and 100% modified soil. Therefore, increasing ionic strength can promote the migration of phenol, and decrease retardant ability in raw soil and modified soil. The retarding effect of the 100% modified soil for phenol migration in neutral environment was best when ionic strength was 0.001 mol/L. This study has an important significance for the repair or control of the organic modified soil on soil and groundwater pollution.