The combined use of magnetic field and iron-based complex in advanced treatment of pulp and paper wastewater

A new method for the advanced treatment of pulp and paper wastewater was presented by combining the magnetization with iron-based complex. The iron-based complex was prepared by ferric sulfate and polycarboxylic acid (PA), forming the Fe–PA complex. Effect of magnetization conditions (magnetic intensity and water velocity) on the physical and chemical properties of wastewater were measured. Results indicated that the conductivity and surface tension of wastewater have been greatly changed after the magnetization process, and the optimal magnetizing conditions were determined as magnetic intensity of 750 mT and water velocity of 4.4 m/s. Parameters of the flocs indicated that the properties of flocs formed by Fe–PA complex were enhanced by magnetization. What's more, the pretreatment of wastewater by magnetization accelerated the removal of CODCr and cut down about 7.7% of the Fe–PA complex dosage. In addition, the pilot scale test (1000 m3/d) was designed and the combined use of magnetization and Fe–PA complex demonstrated the excellent performance for the advanced treatment of pulp and paper wastewater, with the cost only 0.84 RMB/m3 (0.13 US$/m3) for the whole pilot scale system.

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► Magnetization changes the physicochemical characteristics of the wastewater.
► The properties of flocs formed by Fe–PA complex are enhanced by magnetization.
► Magnetization accelerates the removal of CODCr and cuts down the Fe–PA complex dosage.
► Combined use of magnetization and Fe–PA complex demonstrates the excellent performance in pilot scale system.