Study On Deinking Behaviors Of ONPs From Different Regions

There are many kinds of deinkable ONP among the recycled paper. Howere, the deinking efficiency is not only affected by pulping and deinking process, but also affected by printing methods and types of ink. Due to the waste paper from different regions have different printing methods, and their deinking behaviors may be different, there is an adverse effect on the reuse of recycled paper. Otherwise, the reducing of deinkable of ONP which contain flexo-ink will increase the difficulty to the treatment of deinking effluent. This paper will carry out the research on deinking behaviors for local ONP, American ONP and European ONP, including the investigation of deinking efficiency, and characteristics of deinking effluent, and then explore the membrane technology for the treatment of deinking effluent.Firstly, the pulping process have been optimized as follows: 10% of consistency、10min of pulping time and no retention time after pulping. It also has been investigated that effective evaluated methods of deinking efficiency and different methods of preparation of the testing medias for the optical properties testing. The results showed that the filter pad is better for the retention for inks, and then it could reflect the pulp’s optical property more exactly. The combination of ink detachment(ID) and ink elimination(IE) to evaluate deinking efficiency has also been discussed.Secondly, the characteristics of three types of ONP were studied. The results showed that the L-ONP fiber length is shorter than that of A-ONP and E-ONP, but the ash content is higher. The deinking efficiency in alkaline conditions was also compared among them. The results showed that the brightness of L-ONP increased about 10% compared to the blank,whereas the brightness of E-ONP and A-ONP increased less than 5%. After flotation deinking and hyperwashing process, lower of ERIC, higher ink detachment and ink elimination can be abtained for L-ONP than those for both A-ONP and E-ONP in conventional alkaline deinking conditions.Thirdly, the lower-alkaline(Na2SO3 and Mg O replace of Na OH) and neutral deinking conditions have been applied to A-ONP and E-ONP, and deinking efficiency have been compared with conventional alkaline deinking conditions. The results showed that brightness and deinking efficiency for A-ONP is better in conventional alkaline deinking conditions, whereas the deinking efficiency for E-ONP is better at lower-alkaline(Na2SO3) conditions. Then the COD of deinking effluent have been measured, the results showed that the COD of alkaline deinking effluent(699 mg/L) is higher than that of the lower-alkaline deinking effluent(569 mg/L). Then the deinking efficiency of the M-ONP which is the mixture of 70% of L-ONP and 30% of E-ONP in various deinking conditions were studied. The results showed that M-ONP is also suitable for conventional alkaline deinking conditions.Finally, the optical of deinking effluent have been analyzed, and make a simply discussion of the treatment of deinking effluent with ultrafiltration membrane technology. The results of optical showed that the method of using deinking effluent mixed BKP to prepare filter pads can measure the ink concentration in deinking effluent accurately. While there is water-based ink in deinking effluent, it is better to add some CPAM during prepared pads. Meanwhile, the ink size distribution in deinking effluent was analyzed. The results showed that the size of ink particles in E-ONP deinking effluent is smaller than that in L-ONP. It has also discovered that the ink size in E-ONP mostly distributed in 0.05~0.4 μm, while the ink size in L-ONP mostly distributed in 0.6~50 μm. And the ink size in M-ONP is between L-ONP and E-ONP. The results after ultrafiltration membrane treatment showed that there is a good effect for deinking effluent, and the CODCr can be reduced about 80%. Compared with deinking efficiency and the costs, it reveals that the optimized condition is L-ONP and E-ONP use membrane with molecular weight cut-off 30 K and 10 K, respectively, thus, the reducing of COD can reach 75.1%, 68.6%, and the flux is 16.8 L/(m2·h), 24.6 L/(m2·h), respectively.