Nanofiltration removal of chlorinated organic compounds from alkaline bleaching effluents in a pulp and paper plant

Three commercial nanofiltration membranes were used for the removal of chlorinated organic compounds from the first alkaline extraction effluent originated from a kraft mill, using eucalyptus wood as raw material. The assays were carried out at the following operating conditions: pressure = 20 bar, TEMPERATURE = 20°C and circulation VELOCITY = 2 m/s. The results show the nanofiltration feasibility. For the three membranes the rejection factors of chlorinated organic compounds are greater than 95% and two of them present permeate fluxes of approx. 42 kg/hm². Several reference solutes with a wide range of molecular weights and functional groups were also permeated. Their results compared with those of mill effluent allow us to conclude that the effluent tannic compounds are not in a fouling form and that the majority of the organochlorinated matter has a molecular weight greater than 500 Da.