Surfactant adsorption to soil components and soils

Abstract

Soils are complex and widely varying mixtures of organic matter and inorganic materials; adsorption of surfactants to soils is therefore related to the soil composition. We first discuss the properties of surfactants, including the critical micelle concentration (CMC) and surfactant adsorption on water/air interfaces, the latter gives an impression of surfactant adsorption to a hydrophobic surface and illustrates the importance of the CMC for the adsorption process. Then attention is paid to the most important types of soil particles: humic and fulvic acids, silica, metal oxides and layered aluminosilicates. Information is provided on their structure, surface properties and primary (proton) charge characteristics, which are all important for surfactant binding. Subsequently, the adsorption of different types of surfactants on these individual soil components is discussed in detail, based on mainly experimental results and considering the specific (chemical) and electrostatic interactions, with hydrophobic attraction as an important component of the specific interactions. Adsorption models that can describe the features semi-quantitatively are briefly discussed. In the last part of the paper some trends of surfactant adsorption on soils are briefly discussed together with some complications that may occur and finally the consequences of surfactant adsorption for soil colloidal stability and permeability are considered. When we seek to understand the fate of surfactants in soil and aqueous environments, the hydrophobicity and charge density of the soil or soil particles, must be considered together with the structure, hydrophobicity and charge of the surfactants, because these factors affect the adsorption. The pH and ionic strength are important parameters with respect to the charge density of the particles. As surfactant adsorption influences soil structure and permeability, insight in surfactant adsorption to soil particles is useful for good soil management.

Adsorption of Anionic Surfactants onto Alumina: Characteristics, Mechanisms, and Application for Heavy Metal Removal

“…As can be seen in Figure 4, the adsorption efficiencies increase from 0 to 1 mM NaCl then they decrease from 1 to 200 mM. At very low salt concentration, adsorption of both SDS and STS is controlled by both electrostatic and hydrophobic interactions [31,32]. However, the desorption of surfactant is enhanced with increasing salt concentration [33].…”

Influence of surfactants and humic acids on Artemia Franciscana's embryonic phospho-metabolite profile as measured by 31P NMR

“…Two such components are metal ions as well as suspended clay and oxide particles. Overall, the roles of metal ions and clays on surfactant binding (or availability from the opposite point of view) will vary depending on the surfactant's ionic classification and can be explained by ionic and hydrophobic considerations, including the hydrophilicity of the sorbent's surface (Ishiguro and Koopal 2016). In grosso modo terms, metal ions block the cationic sorption sites within or on clays, oxides, and natural organic matter, including HAs, and hence decrease the ability of HAs to sorb cationic surfactants, while inducing aggregation and precipitation of anionic surfactants.…”

Sorption of surfactants onto sediment at environmentally relevant concentrations:independent-mode as unifying concept

“…Also more complex models like combinations of a linear and one or more Langmuir, Temkin, Toth isotherms or the non-ideal competitive adsorption (NICA)-Donnan model have been proposed. [20][21][22][23][24] The models establish a relationship between a number of data points of measured concentrations C s in soil or sediment and concentrations C w in water, at equilibrium. In the present work we refer to the ratios of such measured data, obtained from the applied experimental system, as partition coefficients, K p (L kg À1 ).…”