Natural Surfactants for Flotation Deinking in Paper Recycling...|Flotation Wemco Lab Cell, 1% K, RT,...
Transcript of Natural Surfactants for Flotation Deinking in Paper Recycling...|Flotation Wemco Lab Cell, 1% K, RT,...
-
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
-
IntroductionThe flotation process necessitates stable foams to allow the separation of ink from fiberFoaming agents may be added to stock at 0.02 to 0.2 % of solidsCurrently, many of the foaming agents are petroleum-based and may not be environmentally friendlyAre there more green alternatives that may lessen dependence on petroleum feedstocks? How to evaluate?
-
Surfactant at Interfaces:Modification of the surface energy
Water Air or Oil
Interface
Polar Non- Polar
Surfactant
Polar Group
Non-polarGroup
OOHO
OH OH CH
2OH
Surfactant
-
Detergency
θθ
initial state:no surfactant
change in wetting
Separation by shear (rolling)
substrate
oilwater
substrate
inkwater
+ surfactant:
θθ
θθ
Substrate
oilwater
θθ
θθ
ink
A B
-
Detergency
Adhesion Destabilization
attra
ctio
nre
puls
ion
Distance
(1) adhered particle(2) particle separation(3) particle removal
substrate
ink
11 surfactant adsorption/diffusion
22 adhesion reduction
33 mechanical shear separation
e
(1)(1)
0
(2)(2)V2
e
E
V
V1
(3)(3)
-
Surfactant at Air-Water Interface: Foam Stability
liquid film
gas
strained area
low surface tension
surfacetension g
radient
liquid flow
low surface tension
high surface tension
-
IntroductionThe flotation process is a complex process requiring multiple steps to occur:
Release of the ink from fiberAttachment of ink to air bubbleAir bubble to be incorporated into stable foamFoam to be separated from the liquid phase
A surfactant can impact all of these steps……its effect on flotation can be difficult to interpret
-
Outline
IntroductionMaterialsResults and Discussion
DetergencyAdsorptionFoamabilityFlotation Deinking
ConclusionsQuestions
-
Surfactants Studied
Alkyl phenol ethoxylate (APE) Alkyl (C10-C16) mono and oligomeric D- glucopyranose Protein-based surfactant from soybeanCommercially formulated surfactant blend
-
Recovered Paper Material
Recycled Xeroxcopy Paper of 92 brightness and 30% recycled content Copied with text on both sides of the paper with a xerographic toner Pulped at 3% consistency in TappiDisintegrator
-
Detergency Analysis
Preparation of films via sublimation of tripalmitin, a fatty acid model of an inkExposed ink surface to surfactant solution with shear in beakerMeasured contact angle of water drop on surface of treated film
Condenser
Vacuum Chamber
Ink Source
GoldWafer
Vacuum
Ink Source
Gold
-
Detergency AnalysisMilli-Q Water Source
Gold Wafer
Light Source
Measurement / Observation
Preparation of films via sublimation of tripalmitin, a fatty acid model of an inkExposed ink surface to surfactant solution with shear in beakerMeasured contact angle of water drop on surface of treated film 0
10
20
30
40
50
60
70
80
90
0 20 40 60 80 100 120 140 160 180 200 2200
10
20
30
40
50
60
70
80
90
0 20 40 60 80 100 120 140 160 180 200 220
Time (min)
Con
tact
Ang
le (d
egre
es)
-
Detergency Analysis:
Changes in contact angle after treatment of “printed”surfaces with surfactants, before (solid symbol) and after rinsing with water (washing, open symbols) Surfactants make inks more hydrophilicDifferent response to rinsing: different surface affinity
20
30
40
50
60
70
80
0 50 100Time (min)
Con
tact
ang
le (d
egre
es)
Sugar-based
Synthetic
Protein
Commercial
0 50 100
Sugar-based
APE
Protein
Commercial
-
Detergency Analysis (Contact Angles):
1735Sugar Based
4240Protein-Based
3050APE
1530Commercial
% Change on Rinsing
% Change on Treatment
SurfactantChanges in contact angle after treatment of “printed” surfaces with surfactants, before (solid symbol) and after rinsing with water (washing, open symbols) Surfactants make inks more hydrophilicDifferent 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)
-
Quartz Crystal MicrobalancePiezoelectric quartz crystal, sandwiched between a pair of electrodes Measures the resonance frequency and dissipation due to adsorption on surface.9 ng/cm2 sensitivity in water
nfC
nf
fnf
ftm qqqq Δ−=
Δ−=
Δ−=Δ 2
0 02
νρρ
Q-Sense E4 unit
-
QCM-D ping principle
Frequency change (Δf): related to the mass of the attached film
Disipation (ΔD): related to the viscoelasticity
Qcmddemo.exe
“rigid” film “soft” film
-
Sensor out
T-loop out
Inlet
Control valve
T-loop
Flow with T-loop – Liquid Transport
Sensorcell
speed(ml/min) 0.25
Pump
Reservoir
-
QCM: Measurement principleCrystal
A(t)=A0⋅exp(-t/τ)⋅sin(2πft+φ)
D=1/ πfτ
Mathematical representationof the decay curve
Fitting routine; Levenberg-Marquandt’s (Numerical Recipies)
•Decay recording – electronics unit•Decay fitting - PC
Recording SensitivityDrive Amplitude
-
QCM ResultsSurfactant solution injected around 500 sRinsing with water at about 2500 s Commercial surfactant had lowest affinity to model ink filmProtein had highest affinityKinetics revealed
3.712.4Sugar-based
3.113.6Protein-based
3.012.8Synthetic
11.310.1Commercial
Surfactantreleased (ng)
Amountadsorbed (ng)Type
-
Dynamic Foamability
400 ml of 0.025 g/L surfactant solutionAir flow of 185 ml/min through air dispersing stoneFoam height recorded vs time
-
Dynamic Foamability
(0 Ross Miles Foam)
(110)
(42)
(108)
Foam
Hei
ght (
cm)
0
5
10
15
20
0 500 1000
Synthetic
Sugar based
Protein based
Commercial mixture
Time
0
5
10
15
20
Synthetic
Sugar based
Protein based
Commercial mixture
0
5
10
15
20
25
0 20 40 60 80
Removal Efficiency as % of ControlM
ax F
oam
Hei
ght (
cm) Synthetic
Sugar basedProtein BasedCommercialmixture
0
5
10
15
20
25
0 20 40 60 80
SyntheticSugar basedProtein BasedCommercialmixture
0
5
10
15
20
0 500 1000
Synthetic
Sugar based
Protein based
Commercial mixture
0
5
10
15
20
APE
Sugar based
Protein based
Commercial mixture
0
5
10
15
20
25
0 20 40 60 80
SyntheticSugar basedProtein BasedCommercialmixture
0
5
10
15
20
25
0 20 40 60 80
SyntheticSugar basedProtein BasedCommercialmixture
0
5
10
15
20
25
0 20 40 60 80
SyntheticSugar basedProtein BasedCommercialmixture
0
5
10
15
20
25
0 20 40 60 80
APESugar basedProtein BasedCommercialmixture
(42)
(110)
(108)
-
Flotation Deinking Experiments
Pulping 3% K, 10 min, 50 C, TappiDisintegratorFlotation Wemco Lab Cell, 1% K, RT, stopped when foam production ceased, ranged from 60-210 sImage Analysis, Scanner system, 0.007 mm2 smallest particle size considered
( )% *100Control Sample
Control
PPM PPMRE
PPM−
=
-
Flotation Results: Efficiency vs surfactant charge
At a given surfactant charge, the removal efficiency correlates with the foamability does not reflect selectivity of separation
Surfactant Added to Flotation Cell
0
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)
Rem
oval
Eff.
(%)
Sugar-based
Commercial mixture
Protein-based
APE
-
Flotation Results: SelectivitySurfactant Added in Flotation Cell
0
10
20
30
40
50
60
70
80
90
100
50 55 60 65 70 75 80 85 90 95 100
Yield (%)
Rem
oval
Eff.
(%)
Sugar based
Commercial mixture
Protein based
APE
-
Flotation Results: SelectivityProtein-based surfactant has significantly lower selectivity:
highest adsorption onto model ink (QCM)largest decrease in contact angle on model inkHigher MW, charged material
Indication that the protein-based surfactant sterically stabilizes toner in water
Cationic starch interference of toner agglomeration (Berg and coworkers, 1994; Venditti and coworkers 1999)
Acrylate adhesive anti-deposition on polyester by cationic starch (Venditti and coworkers, 1999)
Surfactant Added in Flotation Cell
0102030405060708090
100
50 55 60 65 70 75 80 85 90 95 100
Yield (%)
Rem
oval
Eff.
(%)
Sugar based
Commercial mixture
Protein based
APE
-
Conclusions
Methods to distinguish differences in adsorption, desorption and detergency between different surfactants have been demonstratedFoamability has a strong correlation with removal efficiency, independent of yield considerationsSelectivity 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
-
Acknowledgements
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 of Dr. Xavier Turon with the QCM experiments.