Adsorption behavior of naphthalene sulfonate formaldehyde condensate with different molecular weights on the cement particle surface

摘要

Naphthalene sulfonate formaldehyde condensate (FDN) is a kind of anionic surfactant which is consists of the hydrophobic naphthalene groups and hydrophilic sulfonate groups. Four FDN fractions with different molecular weights were prepared by using ultrafiltration and were determined by Electro Spray Ionization-Mass Spectroscopy (ESI-MS). The adsorption behavior of different fractions was investigated by means of ultraviolet spectrophotometer (UV spectroscopy), ZetaPlus and X-ray photoelectron spectroscopy (XPS). The results show that the adsorption of FDN with high molecular weight follows Langmuir model and belongs to monolayer adsorption on cement surface. However, the adsorption characteristic for FDN without ultrafiltration displays the multilayer adsorption. The greater adsorption amount and the adsorption layer thickness of FDN with higher molecular weight can provide sufficient steric hindrances between the particles. The electrostatic repulsion of particle surface has been found to increase with increase in the molecular weight of FDN.