The selective separation mechanisms of three textile dyes with NaCl solution by nanofiltration membranes during brine recovery at three different pH values were investigated. Tests were performed with the purpose of relating flux decline, brine recovery, and dye rejection behavior to membrane characteristics, like molecular weight cutoff, contact angle, and zeta potential, charge of the dye molecules, and solution chemistry. The salt-organic separation factor was estimated in order to rank and choose the most suitable nanofiltration membranes for brine recovery with high degree of flux.