Separation of pulp and inorganic materials from paper sludge using ionic liquid and centrifugation

Pulp and inorganic materials were recovered from paper sludge (PS) using 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and centrifugation. Two types of PS with particle sizes 12 μm and 1 mm were used. Each type was mixed with [BMIM]Cl (PS:[BMIM]Cl = 1:20, w/w) in a polytetrafluoroethylene beaker at 100 °C. The inorganic materials were obtained by centrifugal separation of the [BMIM]Cl solution of pulp components and the solid phase, and the pulp dissolved in [BMIM]Cl was regenerated by addition of ethanol. The amount of pulp components recovered from PS with the smaller particle size was almost 100%, and was greater than from PS with the larger particle size. The recovery rate of inorganic materials from PS with small particle size was lower than that from PS with large particle size. [BMIM]Cl recovered by vacuum distillation and dehydration could be re-used for dissolution of pulp components of PS.

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► Using [BMIM]Cl and centrifugation we separated inorganic materials from paper sludge.
► Separation depended on paper sludge particle size and [BMIM]Cl solution viscosity.
► After ethanol removal [BMIM]Cl was recyclable.
► Recycled [BMIM]Cl could repeatedly dissolve the pulp component of paper sludge.