Natural Surfactants for Flotation Deinking in Paper Recycling R. - - PowerPoint PPT Presentation
Natural Surfactants for Flotation Deinking in Paper Recycling R. A. Venditti, O. J. Rojas, H. Morris, J. Tucker, K. Spence, C. Austin and L. G. Castillo Forest Biomaterials Science and Engineering, North Carolina State University, Raleigh USA
Forest Biomaterials Science and Engineering, North Carolina State University, Raleigh USA
necessitates stable foams to allow the separation of ink from fiber
added to stock at 0.02 to 0.2 % of solids
foaming agents are petroleum- based and may not be environmentally friendly
alternatives that may lessen dependence on petroleum feedstocks?
Polar Group Non-polar Group
O OH O O H O H
CH
2
OH
Surfactant
θ θ
initial state: no surfactant change in wetting Separation by shear (rolling)
substrate
water substrate ink water
+ surfactant:
θ θ θ θ Substrate
water θ θ θ θ ink
Adhesion Destabilization
attraction repulsion Distance
(1) adhered particle (2) particle separation (3) particle removal
substrate ink 1 1 surfactant adsorption/diffusion 2 2 adhesion reduction 3 3 mechanical shear separation
e
(1) (1) (2) (2)
V2
e
E
V1
(3) (3)
liquid film
gas strained area low surface tension surface tension gradient liquid flow low surface tension high surface tension
The flotation process is a complex process requiring
multiple steps to occur:
Release of the ink from fiber Attachment of ink to air bubble Air bubble to be incorporated into stable foam Foam to be separated from the liquid phase A surfactant can impact all of these steps……its effect
Introduction Materials Results and Discussion Detergency Adsorption Foamability Flotation Deinking Conclusions Questions
Alkyl phenol ethoxylate (APE) Alkyl (C10-C16) mono and
Protein-based surfactant from
soybean
Commercially formulated
surfactant blend
Recycled Xeroxcopy Paper of 92
Copied with text on both sides of the
Pulped at 3% consistency in Tappi
Preparation of films via
sublimation of tripalmitin, a fatty acid model of an ink
Exposed ink surface to
surfactant solution with shear in beaker
Measured contact angle
Condenser Vacuum Chamber Ink Source Gold Wafer Vacuum Ink Source Gold
Milli-Q Water Source Gold Wafer Light Source Measurement / Observation
Preparation of films
via sublimation of tripalmitin, a fatty acid model of an ink
Exposed ink surface
to surfactant solution with shear in beaker
Measured contact
angle of water drop on surface of treated film
10 20 30 40 50 60 70 80 90 20 40 60 80 100 120 140 160 180 200 220 10 20 30 40 50 60 70 80 90 20 40 60 80 100 120 140 160 180 200 220
Time (min) Contact Angle (degrees)
after treatment of “printed” surfaces with surfactants, before (solid symbol) and after rinsing with water (washing, open symbols)
more hydrophilic
rinsing: different surface affinity
20 30 40 50 60 70 80
50 100
Time (min) Contact angle (degrees)
Sugar-based Synthetic Protein Commercial 50 100 Sugar-based APE Protein Commercial
17 35 Sugar Based 42 40 Protein-Based 30 50 APE 15 30 Commercial
% Change on Rinsing % Change on Treatment Surfactant
Changes in contact
angle after treatment of “printed” surfaces with surfactants, before (solid symbol) and after rinsing with water (washing,
Surfactants make inks
more hydrophilic
Different response to
rinsing: different surface affinity
% Change Treat = 100%* [CA(no treat) – CA(treat)]/CA(no treat) % Change Rinse = 100%* [CA(no treat) – CA(treat/rinse)]/CA(no treat)
Piezoelectric quartz crystal, sandwiched
Measures the resonance frequency and
.9 ng/cm2 sensitivity in water
q q q q
2
Q-Sense E4 unit
Qcmddemo.exe
“rigid” film “soft” film
Sensor out T-loop out Inlet Control valve T-loop
Sensor cell
speed
(ml/min) 0.25
Pump Reservoir
Crystal
A(t)=A0⋅exp(-t/τ)⋅sin(2πft+φ) D=1/ πfτ
Mathematical representation
Fitting routine; Levenberg- Marquandt’s (Numerical Recipies)
Recording Sensitivity Drive Amplitude
Surfactant solution
injected around 500 s
Rinsing with water
at about 2500 s
Commercial
surfactant had lowest affinity to model ink film
Protein had
highest affinity
Kinetics revealed
3.7 12.4 Sugar-based 3.1 13.6 Protein-based 3.0 12.8 Synthetic 11.3 10.1 Commercial Surfactant released (ng) Amount adsorbed (ng) Type
400 ml of 0.025 g/L surfactant
solution
Air flow of 185 ml/min through
air dispersing stone
Foam height recorded vs time
(0 Ross Miles Foam) (110) (42) (108)
Foam Height (cm)
5 10 15 20 500 1000 Synthetic Sugar based Protein based Commercial mixture
Time
5 10 15 20 Synthetic Sugar based Protein based Commercial mixture
5 10 15 20 25 20 40 60 80
Removal Efficiency as % of Control Max Foam Height (cm)
Synthetic Sugar based Protein Based Commercial mixture 5 10 15 20 25 20 40 60 80 Synthetic Sugar based Protein Based Commercial mixture
5 10 15 20 500 1000 Synthetic Sugar based Protein based Commercial mixture 5 10 15 20 APE Sugar based Protein based Commercial mixture
5 10 15 20 25 20 40 60 80 Synthetic Sugar based Protein Based Commercial mixture 5 10 15 20 25 20 40 60 80 Synthetic Sugar based Protein Based Commercial mixture 5 10 15 20 25 20 40 60 80 Synthetic Sugar based Protein Based Commercial mixture 5 10 15 20 25 20 40 60 80 APE Sugar based Protein Based Commercial mixture
(42) (110) (108)
Pulping 3% K, 10 min, 50 C, Tappi
Disintegrator
Flotation Wemco Lab Cell, 1% K,
RT, stopped when foam production ceased, ranged from 60-210 s
Image Analysis, Scanner system,
0.007 mm2 smallest particle size considered
( ) % *100
Control Sample Control
PPM PPM RE PPM − =
At a given surfactant charge, the removal efficiency correlates with
the foamability does not reflect selectivity of separation
Surfactant Added to Flotation Cell
10 20 30 40 50 60 70 80 90 100 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Surfactant Charge (% on OD fiber) Removal Eff. (%)
Sugar-based Commercial mixture Protein-based APE
Surfactant Added in Flotation Cell
10 20 30 40 50 60 70 80 90 100 50 55 60 65 70 75 80 85 90 95 100
Yield (%) Removal Eff. (%)
Sugar based Commercial mixture Protein based APE
significantly lower selectivity:
ink (QCM)
angle on model ink
surfactant sterically stabilizes toner in water
toner agglomeration (Berg and
coworkers, 1994; Venditti and coworkers 1999)
deposition on polyester by cationic starch (Venditti and
coworkers, 1999)
Surfactant Added in Flotation Cell
10 20 30 40 50 60 70 80 90 100 50 55 60 65 70 75 80 85 90 95 100
Yield (%) Removal Eff. (%)
Sugar based Commercial mixture Protein based APE
Methods to distinguish differences in adsorption, desorption and
detergency between different surfactants have been demonstrated
Foamability has a strong correlation with removal efficiency,
independent of yield considerations
Selectivity is related to adsorption, surface modification of toner
(contact angle) and steric stabilization of ink particles
The surfactant with the sugar moieties had similar flotation removal
efficiencies than did synthetic (APE) surfactants
NCSU Undergraduate Research Program and EPA People Prosperity and the Planet (P3). Support by University of Guadalajara for visiting
research experience of Luis Castillo at NCSU is gratefully acknowledged.
We would also like to acknowledge the assistance