GEORGE ALEXANDRU POPA, DANIELA FLORENTINA POPA (ENACHE), DUMITRA DANIELA SLAVE(CLEJ), ION DIN SPIRIDON, CRISTINA MONICA MIREA, ADRIAN CIOCANEA ULTRAFILTRATION OF AQUEOUS SOLUTIONS OF FOOD DYE IN THE PRESENCE OF SURFACTANTS The objective of the study is the low-pressure membrane process for treating aqueous solutions containing food dyes and surfactants. The influence of surfactants (SDS – sodium dedecil sulphate, SO – sodium octanoate) in the separation of synthetic food dyes (E104 – quinoline yellow) was analyzed. Polysulfone and polysulfone-polyaniline membranes were used. Dye and surfactant concentrations used were 10% (equivalent to 100g/m3). The pressures used in the ultrafiltration process were 0.1, 0.2 and 0.3 MPa. When dye containing solutions were passed through the membranes, an increase in their flux was observed. The presence of surfactants in the solutions lead to a decline in flux when pressures of 0.1 and 0.2 MPa were used, but an improvement could be seen as the pressure increased to 0.3 MPa, for both dead-end and cross-flow filtration. Using only dead-end alternative, higher fluxes were achieved for both membranes, but it decreases with time due to accumulation on the membrane surface. The use of cross-flow filtration did not allow accumulation on the membrane surface so that the flux was constant in time.The use of anionic surfactants improved the food dye retention. The interactions between membranes and surfactants can be an important factor supporting the efficiency of the ultrafiltration.