Application of cross-linked stearic acid nanoparticles with dialysis membranes for methylene blue recovery

The interfacial properties of conjugated linoleic acid (CLA), and the ability to polymerize it, make it a potential precursor to nano-scale materials for water and wastewater treatment. Hence, the properties of CLA and of cross-linked linoleic acid micelles, which are basically stearic acid (SA) nanoparticles, were investigated in this study. The acid dissociation constant (pKa) of CLA was measured to be 4.93. The surface tension (γ) and the critical micelle concentration (CMC) of CLA (potassium salt) at different temperatures and ionic strengths were measured. Higher temperatures and ionic strengths both led to lower CMC and surface tension values. The average diameter and aggregation number of 4 mM thermally cross-linked micelles (4.55 nm and 135, respectively) were both larger than that of self-assembled 4 mM CLA micelles at 25 °C (2.83 nm and 44, respectively) in 0.1 M KOH. The pure cross-linked SA nanoparticles were obtained by repeated dialysis, and the stability of the cross-linked nanoparticles was confirmed by further dialysis and from equilibration studies in different solvents. The potential application of SA nanoparticles with dialysis membranes was tested by removing a cationic organic material, methylene blue, from water.