Adsorption of Cationic and Anionic Surfactants on Natural Rubber Latex Particles

Abstract

Natural rubber (NR) latex consists of natural rubber particles which are mainly cis-polyisoprene and non-rubber substances such as proteins and lipids. NR particles typically exhibit a bimodal curve of particle size distribution. The small particles with submicron size can be obtained by high speed centrifugation. These particles has a point of zero charge at pH about 3.9. This enables NR particles as an amphoteric substance. Cationic surfactant, CTAB, and anionic surfactant, SDS, were selected to adsorb on NR particles at pH 8 and 3 respectively. The results showed that the adsorption isotherm of cationic surfactant is L-shape while it is S-shape for anionic one. The equilibrium time and adsorption isotherms for both conditions were determined by TOC, HPLC, and surface tension. Effect of salt on the adsorption of both surfactants were also included.