Document 0LqKbeK9m8odo1ZB3nGrb8Vx

1 3 : 10 'U 4 'y <>2*1 en ' /; Evidence that Dibenzoruran Acts as a Precursor for the Chi oritutted Dlbeuzoturana Formed IXir'ng Pulp Bleaching g) ooi ooi t)^ f o n \ C. f f fl > c 4* l'f R.K* Voss* C-F. Luthe, R.T* Fleming, R.M. Berry and L-H. Allen Pulp and Piper Research Institute of Canada 570 St- John's Boulevard Pointe Claire, Quebec H9R 3J9 ABSTRACT ov levels of chlorinated dioxins furans (collect!*-- , referred to as dioxins) have recently been discovered 1n the waste *trv ;*ns and products ol certain bleached krait puJ p mills. Paprican has >*es; A. by initiating a r search program t.o determine how and under what rendJtions dioxins are *rmed in pulp and paper processes with a ''lew re ininizins; or eliminating their formation. imirary findings from this investigative research program have 'detUified oil-based defoa-ers as a potential source of unchlorin- ated furan and dioxin precursor compounds which caa be converted to their chlorinated forms in the chlorination stage of pulp t aching. As a follow t-r> these initial findings, some additional selected defoaners and dofearner bvse oils have been examined for their dlbenzofuran (DBF) content and for their cauacitv r.c contribute to chlorinated dioxins/ furans formation when added to brown stock pulp prior to bleaching. From these mor^ recent studies it is clear that significant differences exist between the various types of oils used by deioamer compounders. Certain types of oils appear to he free of dibonzofuran precursor; these are premium oils which have been specially treated to eliminate aromatic constituents. The absence of dioxin/furan precursors in this grade of oil v a c o n f i r m e d by the observation that chlorination of brown stock pulp spiked with a defoataer based upon such oil did not lead to an enhancement of chlorinated dioxins and furans. This paper will aLso include a general discussion on the various mechanisms whereby chlorinated dioxins and furans can be formed in pulp bleaching and the role that precursor compounds Such as the unchlortnated dibenzofuran (rp:-") play in such a process* 83