The present invention relates to new processes useful for separating whey proteins from whey protein-containing solutions using a novel anion exchanger which comprises a water insoluble, hydrophilic, water swellable, hydroxy (C₂-C₄) alkylated and cross-linked regenerated cellulose, derivatized with quaternary amino (QA) groups where the level of substitution of the QA groups is 1.4 milli-equivalents per dry gram of anion exchanger (meq/g) or greater.