Transport mechanisms of detergent ingredients through ultrafiltration membranes

• The permeation of Na4EDTA is governed by electrostatic interactions.
• The permeation of SDS depends on micelles formation.
• NaOH shields membrane charges and destabilizes the micellar layer.
• At low concentrations, it is not possible to recover both agents in the same stream.

The extensive use of anionic surfactant sodium dodecyl sulfate (SDS) and the chelating agent ethylenediaminetetraacetic sodium salt (Na4EDTA) in industrial detergent formulations suggests the need to study the possibility of their recovery and reuse from waste effluents in order to decrease the cost of the cleaning process and to avoid environmental drawbacks, as well as to save water. A lab-scale plant was provided with a 5 kDa ceramic membrane and used to study the permeation and retention of these compounds in single solutions as well as several mixtures. The presence of micelles in the concentration polarization layer plays an important role in the permeate flow rates and the retention of both compounds. Finally, the decrease in SDS and Na4EDTA retention when NaOH is added is attributed to micelles and pre-micelles destabilization and membrane charge shielding, respectively.