How Dissolved-Air Flotation Recovers Paper Fibers from Paper Mill White Water
Application to Paper Mill White Water
Dissolved-air flotation has been applied as a separation technique to recover suspended solids from the paper mill white water system. [S1]
Material Recovered: Suspended Solids and Reject-Derived Fibers
Fibers obtained from dissolved air flotation rejects were oxidized using a TEMPO oxidation system to prepare oxidized recovered fibers. [S2]
Between 10% and 20% of the fibers in the dissolved air flotation rejects are also lost (Chaiarrekij et al.). [S2]
Processing of the Recovered Material
Dissolved air flotation rejects, 150 g (wet weight), were mixed with 10 L of distilled water and then screened using a 100-mesh sieve. [S2]
Fifteen grams of the collected fibers and 1500 mL distilled water were combined in a 2000 mL 3-neck flask equipped with a stirring apparatus. [S2]
Then 3-chloro-2-hydroxypropyl–trimethyl ammonium chloride (10%, 20%, 30%, or 50% of fiber dry basis) was put into the beaker flask, the mixture was stirred for 10 min, the beaker flask was put into the 70 °C stove for 4 h, then 60 mL distilled water was combined in the beaker flask. [S2]
The mixture was filtered off by filter paper, washed four times with 100 mL distilled water, and dried in air. [S2]
A portion of the paper samples were immersed in water at room temperature for 24 h, then disintegrated and without further addition of chemicals, the pulp samples were formed again into recycled handsheets in accordance with China GB standard methods (Wang et al.). [S2]
Performance of the Recovered Fibers
SEM micrographs showed that fibers were integrated more closely in the paper sheet, benefiting from the addition of the oxidized recovered fibers. [S2]
When the dosage of oxidized recovered fibers amount exceeded 3%, the physical properties of paper sheets became worse, probably because of the increasing of negative charge, which would increase the repulsive force among the fibers. [S2]
It is thus clear that the oxidized recovered fibers also can be effective for the production of recycled paper (Weise 1998; Hubbe et al.). [S2]
Oxidized recovered fibers obtained from dissolved air flotation rejects can be used effectively to improve paper physical properties. [S2]
Optimization of the Flotation Process
The main aim of this research was to modify, optimise and evaluate the performance of a continuous process using dissolved air flotation. [S4]