Evaluating the effectiveness of using ClO_2 bleaching as substitution of traditional Cl_2 on PCDD/F reduction in a non-wood pulp and paper mill using reeds as raw materials

The effectiveness of ClO_2 bleaching as a replacement for conventional Cl_2 bleaching,which is intensively practiced in developing countries,to reduce polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)in non-wood pulp and paper mills has not been field tested.The first field study was performed to investigate PCDD/F variations when ClO_2 bleaching was used as a substitute for conventional Cl_2 bleaching in a non-wood pulp and paper mill.It was found that the PCDD/F toxic equivalents(TEQs)in solid and effluent samples were approximately 1.3–14.9 times lower when ClO_2 bleaching was used instead of the conventional Cl_2 bleaching.2,3,7,8-Substituted tetrachlorinated dibenzofurans(2,3,7,8-TCDF)were the dominant contributors to total PCDD/F TEQs in samples from the investigated mill when using conventional Cl_2 bleaching.The formation amounts of 2,3,7,8-TCDF were reduced from 1.56–2.76 pg TEQ/g to 0.02–0.32 pg TEQ/g in solid samples when ClO_2 bleaching was used instead of the conventional Cl_2 bleaching.The replacement of Cl_2 with ClO_2 might decrease the chlorination reactions of dibenzofuran as potential precursors,and thus reduce the formation amounts of 2,3,7,8-TCDF.The results could provide important knowledge for suggesting the best available technique for PCDD/F reduction for non-wood pulp and paper mills in developing countries.