Carboxymethyl cellulose binding to mineral substrates: characterization by atomic force microscopy-based force spectroscopy and quartz-crystal microbalance with dissipation monitoring.

The attachment of the sodium salt of carboxymethyl cellulose (CMC) onto iron oxide and various silicate substrates in aqueous solution as a function of salt concentration and pH was studied by atomic force microscopy-based force spectroscopy (AFM) and quartz-crystal microbalance with dissipation monitoring (QCM-D). Both ionic strength and cation valency were found to influence substrate binding. Notably, QCM-D experiments strongly suggested that the solubility of CMC is directly impacted by the presence of CaCl2. Such data are critical for the design of new molecules for stabilizing mineral floc dispersions and for assessing the mobility of CMC-coated particles in the subsurface. Modeling of AFM data with an extended Ohshima theory showed that van der Waals and steric forces played a major role in the interactions between CMC and mineral substrates, and that hydration forces were also important.