A re-entrainment prevention apparatus (18) for use in a settler area (12) of a mixer-settler, the re-entrainment prevention apparatus (18) comprising: at least one panel (28, 30) of generally vertical linearly-spaced barrier elements (31), an upper barrier element (24) and a lower barrier element (26), wherein the upper and lower barrier elements (24, 26) are arranged relative to the generally vertical barrier elements (31) so as to constrain a fluid flow (32) that impinges thereon such that it is directed through fluid flow channels defined between the generally vertical linearly-spaced barrier elements (31).