Spectrometric study of crystal violet in presence of polyacrylic acid and polyethylenimine and its removal by polyelectrolyte enhanced ultrafiltration

Removal of crystal violet (CV) from aqueous solutions by continuous polymer-enhanced ultrafiltration (PEUF) was investigated. Two water-soluble polymers, namely polyacrylic acid (PAA) and polyethyleneimine (PEI) were selected for this study. The permeate flux profile and observed retention of CV were studied as a function of dye and polyelectrolyte concentrations, transmembrane pressure, ionic strength and pH.Experimental results showed that polyacrylic acid allowed retention of CV in the order of 99%. The enhancement is primarily due to the formation of some complexes between the anionic polymer and dye molecules. This result was confirmed by the change of the maximum absorption wavelength. However, when the PEI was applied, the CV removal can reach around 60%. In the case of PAA, the retention of CV decreases with ionic strength, a high retention was obtained at pH above 4. The ionic strength and pH have a negligible effect on the removal of CV in the case of PEI. The permeate flux depended slightly on polyelectrolytes concentrations, transmembrane pressure, ionic strength and pH.