Study On Agglormeration And Magnetic Deinking For Mixed Office Waste

A major problem in recycling Mixed Office Waste (MOW) is the difficulty in removing toner inks. The purpose of this study was to develop an effective agglomeration-magnetic separation process for deinking of MOW and to study the agglomeration mechanism of toner using magnetic seeds.Magnetic seeds, hydrophobicly modified with surfactant, was introduced into this deinking process, facilitating the separation of magnetic agglomerate consisting of toner and magnetite. Kerosene, also being used in the agglomeration-magnetic process, serves a distinct function during the chemical agglomeration, promoting the agglomeration of toner and magnetic seeds into larger particles.Hydrophobic magnetic seeds was prepared by surface modification method using mixture of sodium oleate and stearic acid. Results of orthogonal experiments showed that optimum effects of modification were obtained with the condition that sodium oleate/stearic acid weight ratio of7:1, temperature of70℃, time of100min, pH of8and modifer dasages of6%. Analysis of SEM and FTIR indicated that the mixed acid change the magnetite surface from hydrophilic to hydrophobic and adsorb to the magnetite through chemical bond.After the modified magnetic seeds had been prepared, the interference of agglomeration and magnetic separation conditions on the deinking of MOW with magnetic seeds was studied. It is manifested that Kerosene plays an essential role as cohesioner and certain agglomeration time, pH and stir intensity need to be assured in order to promote the contact and cohesion of toner to magnetic seeds. It is as well as revealed an ideal deinking result that pulp ISO brightness from88.6%to94.2%, residual ink from59412mm2/kg to1638mm2/kg and ink recovery over97.2%, with the optimum experimental conditions.As to the study of the mechanism of agglomeration process, coagulation experiments using pure toner were conducted and energy model of this process was proposed, as well as the thermodynamics calculation. Experimental results indicate that a kerosene to toner weight ratio of1/16is sufficient for agglomeration of toner ink.With the results of agglomeration experiments and electronic microscope analysis, the interaction among toner, magnetic seeds and kerosene during agglomeration process can be envisioned to go through following phases.1) Kerosene, as liquid agglomeration agent, will spread on the surface of magnetic seeds and toner inks.2) Agglomeration agents attached to the toner particles and magnetic seeds respectively.3) Toner and magnetic seeds packed with kerosene bond together to form initial agglomerates by the liquid bridge mechanism. Then the agglomerates formed grow to an extent of size with stability and magnetism.Thermodynamics calculation based on energy model of agglomeration process demonstrated the possibility of toner condensation with magnetic seeds at a low energy imput.