한국물환경학회 ․ 대한상하수도학회 2012 공동학술발표회 논문집 3월 21~22일(일산 킨텍스) P-262 A Review on Surfactant Adsorption onto Solid-Liquid Interface and its Fundamentals † Sohan Shrestha ·Prajwal Shrestha·Rahman Rafique·Guntae Son·Jeyeon Moon·Seunghwan Lee † School of Civil and Environmental Engineering, Kumoh National Institute of Technology, Gumi 730-701, Korea 1. Introduction Surfactants represent an important category of contaminants in industrial effluents (Gupta, 2005). A continued surfactant pollution of natural water is connected with the distinct colloid-chemical property of surfactants, namely their surface-activity or ability to form foams, emulsions, and micelles, as well as their ability to form structures in the volume and stabilize other pollutants in water. These properties hinder decontamination of surfactant-containing sewage. Various techniques have been used and developed to remove surfactants from wastewaters. Among them, adsorption process seems to be an effective method for the removal of surfactants because adsorption process is found to be superior for water re-use in terms of initial cost, simplicity of design, ease of operation and insensitivity to toxic substances (Forgacs et al., 2005). This review is mainly focused on the study of various operating parameters influencing surfactant adsorption on solid–liquid interface. 2. Factors Influencing Adsorption of Surfactants With increase in hydrocarbon chain length of the surfactant, the surfactant molecule becomes more hydrophobic, which leads to the change in bulk properties of the solution due to predominance of hydrophobic forces in adsorption mechanism. This in turn, enhances the surfactant adsorption onto solid-liquid interface (Wu et al., 2001). The structure of adsorbed layer depends on the ‘packing of the molecules’ which in turn depends on mutual repulsion and steric constants among adsorbate species. And the position of functional group greatly influences mutual repulsion and steric hindrance among adsorbate species. Similarly, presence of electrolyte decreases CMC of non-ionic surfactant and increases lateral interactions between the polar chains (Denoyel and Rouqerol, 1991). An increase in electrolyte concentration leads to an increase of adsorption capacity of surfactants. With increase of NaCl concentration, electrical double layer on the surface of adsorbent is compressed and electrostatic repulsion between adsorbed surfactant species decreases which results in increment of adsorption capacity (Pethkar et al., 1998). Solution pH alters adsorbent surface charge i.e. adsorbent surface becomes positively charged at lower pH and vice-versa. So from electrostatics perspective, negatively charged surface is unfavorable for anionic surfactants adsorption and vice-versa. An increase in temperature leads to considerable decrease in adsorption of ionic surfactants. With increase in temperature, kinetic energy of the adsorbate species increases. Consequently, there is an increment in entropy of adsorbent-adsorbate system that results in decrease of aggregate organization on adsorbent surface Seunghwan Lee · E-mail : dlee@kumoh.ac.kr