Biosurfactants have different effects on different organic substances in soil

2022-05-30 09:15:36

In recent years, because some industrial and domestic wastewater is used for farmland irrigation, soil pollution tends to be serious. The solubilization and elution of surfactants to other organic pollutants and enhanced adsorption have been paid more and more attention. Surfactants and organic pollutants in soil mainly have the following modes of action: 1) surfactants and organic pollutants compete for adsorption sites on the soil surface. The result of this competitive adsorption can lead to the decrease of the adsorption amount of organic pollutants on the soil, thus increasing the concentration of organic pollutants in the soil solution. 2) The organic pollutants adsorbed on soil are dissolved into surfactant micelles, thus increasing the solubility of organic pollutants in soil solution.

These two points are reflected in the solubilization of surfactants. 3) Due to the amphiphilic nature of surfactants, surfactants adsorbed on the soil can further adsorb organic pollutants through hydrophobic groups, that is, organic pollutants form a second layer of adsorption on the soil, which will increase the adsorption capacity of organic pollutants on the soil. 4) Some surfactants can disperse the soil colloid after adsorption on the soil, which will increase the soil surface area and adsorption sites, thus possibly increasing the adsorption capacity of organic pollutants. Points 3 and 4 show the enhanced adsorption of surfactants. The interaction between surfactants and pollutants in soil greatly affects the transport and degradation characteristics of pollutants in soil. Therefore, it is of great practical significance to deeply understand the interaction mechanism between surfactants and pollutants.

Biosurfactants have different effects on different organic substances in soil. Scheibenbogen et al. Found that rhamnolipid produced by P. aerugino2sa can effectively remove hydrocarbons in sandy soil. The removal rate depends on the type of organic pollutants and the concentration of surfactants. Desch ê NES et al. Proved that rhamnolipids produced by the same genus enhance the solubility of tetracyclic aromatic hydrocarbons more than tricyclic aromatic hydrocarbons. It can be seen that biosurfactants have certain selectivity for organic pollutants, so it is necessary to select good biosurfactants for different pollutants, which is also the focus in the future application of soil remediation.

Pesticides can ensure the normal growth of crops, but also continue to accumulate in the soil, resulting in the decline of soil quality. Many foreign scholars have studied the removal of pesticides in soil, and investigated the effects of biosurfactants on the desorption and transport of pesticides in soil. Juan c.mata-sandoval et al. Made a series of studies. They estimated the effect of rhamnolipid on the distribution of organic pesticides in the soil water micelle system by establishing the Langmuir adsorption model, and came to the conclusion that when the concentration of the adsorbed surfactant is lower than the critical micelle concentration (CMC), the hydrophobicity of the soil and the adsorption of pesticides will be increased. When the concentration exceeds CMC, Surfactants act as cosolvent, and pesticides in soil can be effectively desorbed without the influence of soil dry humidity.