The role of four gas dispersion parameters in ink particle collection was investigated in 4" and 20" flotation columns. Gas holdup (epsilon(g)) and superficial gas velocity (J(g)) were measured on-line and bubble size (d(b)) was estimated using drift flux analysis that enabled bubble surface area flux (S-b) to be calculated. Operating with approximately zero froth depth ink recovery as a function of retention time (controlled by underflow rate) was determined. Using a mixing model, the collection zone flotation rate constant (k(c)) was estimated from the recovery-time data. The rate constant was not related to J(g) or d(b) but was linearly dependent on epsilon(g) and S-b, similar to findings in mineral flotation studies. (C) 2003 Elsevier Ltd. All rights reserved.