Deinking recycled paper using column flotation

The degree of waste paper recycling has been increasing steadily in North America over the last decade. Flotation is a popular method for removing ink from fibres (deinking) and is traditionally performed in mechanical cells. Column flotation has been proposed as an alternative to mechanical cells. In this work, open and packed laboratory and pilot-scale columns were operated to determine their relative merits and how they compare to a circuit of mechanical cells.It was found that the type of sparger was critical for obtaining high flotation efficiencies. Fine porous stainless steel spargers (0.5 $ mu$m) produced flotation efficiencies which were equal to those of the mechanical cells. Packing was effective in increasing flotation efficiency when the coarse porous stainless steel sparger (100 $ mu$m) was used in the laboratory column and when the variable gap sparger was used in the pilot column.The organic loss from all column configurations (laboratory and pilot-scale) was less than 3%.The scale up procedure was evaluated using data from the laboratory column and pilot column dimensions. Finally, using data from the laboratory column, industrial columns were designed