Remediation Of Polycyclic Aromatic Hydrocarbons Contaminated Loess By Washing With Rhamnolipid

Polycyclic aromatic hydrocarbons(PAHs) pollution in soil has become one of the important directions of environment pollution and control of soil at present. It is important to investigate distributing and transferring rules, mechanism, destination and control technology for ensuring the safety of soil environment.Firstly,this paper studied the solubilization of biosurfactant rhamnolipid(RL) to PAHs and the effect of rhamnolipid elution to single or combined phenanthrene and pyrene contaminated loess by batch experimental methods.And then, this paper also studied the efficiency of rhamnolipid to phenanthrene by the soil column leaching. The influenc e factors of surfactant concentrations, p H value, temperature and inorganic salts had a further investigated. Thus, this proves that the results of our study have great significance on the remediation of PAHs contaminated soils. The major findings were observed as following:(1) The solubilization of biosurfactant RL to PAHs, and the factors influencing solubilization were investigated by batch experimental methods. The results of this study demonstrate that the solubility of PAHs in aqueous solution increases with oncentration growth of the surfactant when the concentration of RL is higher than its c ritical micelle concentration(CMC). Also, the solubility folds( S*w/Sw) increase greatly. The molar solubilization ratio(MSR) decreases as the solute molecular weight increases. The micellewater partition coefficient(Km) increases as the the hydrophobicity of PAHs increase. In addition, the experiments show that factors such as p H value, temperature and ionic strength have influence on the solubilization of RL to PAHs. The solubility of phenanthrene and pyrene in RL solution increase with decreasing of p H value and temperature rising. The effect of ionic strength for solubilization is strongly dependent on cationic type. Increasing K+ ionic strength in solution can enhance the PAHs solubilization potential. However, the opposite effect is observed for Ca2+ ionic.(2) The effect of rhamnolipid elution to phenanthrene contaminated loess, and the factors influencing elution were investigated by batch experimental methods.The results shows that the effect of elution to phenanthrene changes with the time growth. When the washing time of phenanthrene reaches 12 h the washing effic iency achieves the balance.The washing efficiency of phenanthrene increases with the increase of surfactant concentrations. The elution rate of phenanthrene increases as the temperature increase.The elution rate of phenanthrene increase at first and then decrease s with the increasing of p H.And the maximum elution rate for phenanthrene from contaminated loess is obtained at p H=7.0. K+ and low concentration of Ca2+ ionic strength in solution can enhance the elution rate of RL to phenanthrene from contaminated loess.(3) The effect of rhamnolipid elution to combined phenanthrene and pyrene contaminated loess, and the factors influencing elution were investigated by batch experimental methods.It is shows that the elution rate of phenanthrene and pyrene increases with the increase of surfactant concentrations, the elution rate of phenanthrene is much higher. For mixed contaminated loess soil, the elution rate of phenanthrene and pyrene increases at first and then decreases with the increasing of solution p H value, the maximum elution rate for phenanthrene and pyrene from contaminated loess is obtained at p H=7.0. Temperature has a little effect on elution rate of rhamnolipid for phenanthrene and pyrene. K+ and low concentration of Ca2+ ionic strength in solution can enhance the elution rate of RL to phenanthrene and pyrene from contaminated loess, but the Ca2+ concentrations also have a little effect on elution rate of RL to PAHs from combined phenanthrene and pyrene contaminated loess.(4) The effect of RL on leaching of phenanthrene from contaminated soil, and the factors influencing leaching effiiciency were studied by soil column leaching. The results that the elution curve is regular patterns in which the phenanthrene concentrations in elutant increases, achieving maximum and then decreases with the porous volume numbers of eluting solutions.The removal percentages of RL for phenanthrene increases with the increase of surfactant concentrations. The leaching efficiency of RL for phenanthrene increases with increasing of p H value. K+ and low concentration of Ca2+ ionic strength in solution can enhance the effiiciency of phenanthrene.