Deinking in bubble column and airlift reactors: Influence of wastewater of Merox unit as pulping liquor

Abstract

Deinking efficiency of recycled fibers was investigated in bubble column reactor (BCR) and in internal loop airlift reactor (ALR). The brightness and intensity of ink spot of deinked fibers were reported as deinking efficiencies. A four-step process involving pulping, washing, flotation, and secondary washing was used. Employing ALR instead of BCR resulted in an increase of 1–4% in brightness, and a decrease of 3–14% in number of ink spot. Subsequently, in separate experiment the wastewater obtained from a Merox unit was used in pulping step instead of sodium hydroxide solution as pulping liquor. Compared to sodium hydroxide, industrial wastewater rendered more brightness gain. Comparison of both experiments suggests that using industrial wastewater in the pulping step and ALR in flotation step gives satisfactory results for industrial applications, yields a quality product with reduced capital investment and operation costs while considerably preserving the environment.