simplified (undergraduate lab-scale) "flotation de-inking" of newspaper print
DESCRIPTION
SFU Chem 317 projectTRANSCRIPT
SIMPLIFIED “FLOTATION DE-‐INKING” OF NEWSPAPER
NAUMAN MITHANI (CHEM 317 -‐ 2010 SPRING)
1
• de-‐ink newspaper as per the technique of flota%on de-‐inking
• scaled down & adapted for lab environment improvised equipment
• focus on op#misa#on of variables:
✓ duraAon of flotaAon
✓ concentraAon of flotaAon agent
-‐ temperature
-‐ consistency (cs. %)
PURPOSE
if possible
2
• paper, a ubiquitous material
• a disposable material
• 33% to 50% of solid municipal waste*
➡ a crucial parameter in the long-‐term environmental sustainability of a large populaXon centre
✤ so it must be recycled, which in turn consumes...
✤ water
✤ electricity
✤ & other (environmental) resources
✤ sustainability & expansion if:
✤ high performance & high quality of recycled paper
BACKGROUND: paper facts
0
25
50
75
100
USA (2004) Canada (2006)
4.5
50
13.5
50
pape
r (m
illion
ton
nes)
un-recoveredrecovered
* Nie et al. Environmental Engineering and Policy (1998) vol. 1 (1) pp. 47-58 3
• Paper, essenXally, is a felted sheet of cellulose fibres
• actually, it is a complex mixture of chemical addiXves, fillers, bonding agents (upto ~40 % weight)
• Cellulose: (C6H10O5)n
• bears a surfeit of O-‐ and OH groups network of H-‐bonds
• highly hydrophilic
• zero water-‐contact angle
INTRO: chemical composiXon of paper
hydrophilic and hydrophobic surfaces. The contact angle
is measured from the surface through the liquid to the
tangent of the liquid surface as indicated by the arrows. Hydrophilic Hydrophobic
4
• Ink applies to paper...
• ... by absorpXon which then dries/sets in the fibre
• ... OR... by fusing which then cools and bonds to the fibre
• different composiXon for different printed materials:
• NEWSPRINT INK: mineral/vegetable oil (45 -‐ 60%) and resin (5 to 35%)
• the oil serves as the vehicle for the pigment
• black: inorganic carbon (graphite) blacks
• colours: organic pigments
• immiscible oil + (co)polymer resin + carbon black ink is H-‐phobic
• water contact angle is >80°.
INTRO: the ink (toner)
hydrophilic and hydrophobic surfaces. The contact angle
is measured from the surface through the liquid to the
tangent of the liquid surface as indicated by the arrows. Hydrophilic Hydrophobic 5
• (froth) flotaXon de-‐inking is the more popular de-‐inking method
• bejer than wash de-‐inking (laundry-‐esque) since it can also remove larger parXcles: 10 -‐ 400 μm (diameter) in addiXon to fine ink & filler parXcles.
• overall: lesser quanXXes of water needed
• overall: higher quality of recycled paper
• schemaXc below shows industrial de-‐inking plant setup
INTRO: flotaXon de-‐inking
source: Wikipedia6
• first step -‐ pulping: the paper is disintegrated in water to form a pulp slurry
• collector (foaming agent + surfactant) is added to pulp slurry
• air (bubbles) is introduced
• the H-‐phobic ink binds to collector + air bubble
• carried to the surface -‐ REJECT stream
• forms “contaminant”-‐laden foam/froth
• which is then removed or scraped-‐off
• the flotaXon is only 1 in a series, there are 2 series
INTRO: the flotaAon de-‐inking process
7source: Wikipedia
• actuality: conXnuous FEED of pulp slurry + collector mixture into such a chamber where air is con#nuously supplied
• only 1 improvised flota#on cell shall be used here
8source: Deng et al. “SURFACTANT SPRAY”...Georgia Institute of Technology (2004)
schemaXc of industrial flotaXon cell setup
The second parameter, cleanliness efficiency, is calculated as follows:
eq. 2: Cleanliness efficiency =FEED count ! ACCEPT count( )
FEED count" 100
It has been found that the operational parameters of a flotation de-inking process must balance between high
fibre yield and high cleanliness efficiency: if a high fraction of the FEED is subjected to rejection then the remainder of
the (processed) sample may be very clean; naturally, the down side is low fibre yield; and vice versa.
• Experimental overview
This series of experiments seeks to build upon the paper on lab-scale flotation de-inking by Venditti, R. [J.
Chem. Ed. 81(5), 693]: “A Simple Flotation De-Inking Experiment for the Recycling of Paper” [9]. The experimental
overview is cited as follows:
“This paper describes a laboratory exercise for the f lotation de-inking of wastepaper. The exercise consists of disintegrating
printed wastepaper in a blender and then removing the ink or toner contaminants by pumping air bubbles through the
suspension using an aquarium pump or other source of air bubbles. Foam is taken off the top of the container that is rich in
ink (the reject sample) while the cleaned fiber remains in the container (the accept sample). After the experiment the accept and
reject samples are analyzed for ink concentration and for fiber content.
Common, inexpensive equipment and no chemicals (other than a surfactant to enhance foaming) are needed for the
exercise.” [9]
Figure 3: A schematic drawing of the laboratory flotation
experiment.
6
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A Simple Flotation De-inking Experiment for the Recycling of Paper
Richard A. Venditti
Associate ProfessorNorth Carolina State UniversityDepartment of Wood and Paper ScienceRaleigh NC, 27695-8005Telephone: (919) 515-6185Fax: (919) 515-6302Email: [email protected]
Lab Summary
Flotation de-inking is used in paper recycling processes to preferentially remove hydrophobic contaminants
such as inks and toners from a slurry of fibers in an aqueous phase. In the process, fine air bubbles are
introduced into the suspension and the hydrophobic contaminants preferentially attach to the bubble-water
interfaces and float to the surface. The foam on the top of the surface laden with contaminant is skimmed
away resulting in the separation.
This paper describes a laboratory exercise for the flotation de-inking of wastepaper. The exercise consists
of disintegrating printed wastepaper in a blender and then removing the ink or toner contaminants by
pumping air bubbles through the suspension using an aquarium pump (Figure 1) or other source of air
bubbles. Foam is taken off the top of the container that is rich in ink (the reject sample) while the cleaned
fiber remains in the container (the accept sample). After the experiment the accept and reject samples are
analyzed for ink concentration and for fiber content.
Tubing Foam laden with ink
Air Pump Dispersed Wastepaper
Large Plastic Tray
Figure 1. Schematic Drawing of the Laboratory Flotation Experiment.
Common, inexpensive equipment and no chemicals (other than a surfactant to enhance foaming) are needed
for the exercise. The experiment is useful for middle/high school science courses or introductory level
college environmental, chemical engineering, or chemistry courses in need of a simple experiment that
schemaXc of the improvised flotaXon cell
(
photo of an industrial flotaXon cell using “surface surfactant spray”photo of the improvised flotaXon cell
• fibre yield, Y (%):
• based on the law of mass conservaAon: (F)EED = (A)CCEPT + (R)EJECT
• fibre yield based on (F)EED and (A)CCEPT stream:
• fibre yield based on (F)EED and (R)EJECT stream:
• fibre yield based on (A)CCEPT and (R)EJECT stream:
9
INTRO: flotaAon de-‐inking performancedry mass of accepted solids
dry mass of total solids fed into process× 100
YFA %( ) = AF× 100
YFR %( ) = F − RF
× 100
YAR %( ) = AA + R
× 100
• contaminant removal OR cleanliness efficiency:
• based on the contaminant or ink spec count of the (F)EED and (A)CCEPT streams:
cleanliness efficiency = FEED count - ACCEPT countFEED count
× 100
• household blender
• generic 1 litre aqua#c tank pump coupled with an air diffuser
• Paper: same pages from mulXple copies of a standard newspaper (SFU Peak) printed on 52/75 e-‐brite paper (NORPAC, Burnaby, BC)
• Ink: standard newspaper ink (Sun Chemical, Richmond, BC) -‐ exact formulaXon could not be known
• foaming agent (collector): “BRD2345”, a proprietary foaming agent (Buckman Laboratories, Memphis, USA)
• microscope & soQware for ink spec size and density characterisaXon:
• MoAc B-‐5 Professional Series with MoAc images Advanced 3.0 by Micro-‐OpXc Industrial group (Richmond, BC)
10
EXPERIMENTAL: notable MATERIALS (common, inexpensive)
1. cut 2.25g worth of paper into 3 × 3 cm squares and place them in blender with 400 mL of tap water (pH: 6.51) of desired temperature
2. blended for 3 min.
3. added desired amount of foaming agent to the pulp slurry and sXrred gently at length (> 5 min.)
4. divided the pulp slurry into two beakers labelled FEED stream & ACCEPT-‐to-‐be stream
5. filled the ACCEPT-‐to-‐be stream beaker to desired volume (maintained temperature) to control consistency (cs. %)
6. placed the ACCEPT-‐to-‐be stream into a relaXvely large plasXc tray
7. the air diffuser connected to the air pump (by tubing) was placed into the beaker
8. the pump was turned on to mark the start of the flotaXon
11
EXPERIMENTAL: METHOD (overview)
9. the generated foam was periodically scraped off (REJECT stream)
10. arer a certain, desired Xme the pump was turned off to mark the end of the flotaXon
11. the contents of the plasXc tray (REJECT stream), the remnants in the ACCEPT-‐to-‐be beaker (now the ACCEPT stream) & the contents of the FEED stream were filtered (Whatman 1: 110 mm)
12. the contents of each stream were dried overnight at 105 °C
13. the mass of the contents (fibres) of each stream was measured
14. contaminant (ink spec) characterisaXon was ajempted using the microscope setup
12
EXPERIMENTAL: METHOD (overview)(contd.)
The second parameter, cleanliness efficiency, is calculated as follows:
eq. 2: Cleanliness efficiency =FEED count ! ACCEPT count( )
FEED count" 100
It has been found that the operational parameters of a flotation de-inking process must balance between high
fibre yield and high cleanliness efficiency: if a high fraction of the FEED is subjected to rejection then the remainder of
the (processed) sample may be very clean; naturally, the down side is low fibre yield; and vice versa.
• Experimental overview
This series of experiments seeks to build upon the paper on lab-scale flotation de-inking by Venditti, R. [J.
Chem. Ed. 81(5), 693]: “A Simple Flotation De-Inking Experiment for the Recycling of Paper” [9]. The experimental
overview is cited as follows:
“This paper describes a laboratory exercise for the f lotation de-inking of wastepaper. The exercise consists of disintegrating
printed wastepaper in a blender and then removing the ink or toner contaminants by pumping air bubbles through the
suspension using an aquarium pump or other source of air bubbles. Foam is taken off the top of the container that is rich in
ink (the reject sample) while the cleaned fiber remains in the container (the accept sample). After the experiment the accept and
reject samples are analyzed for ink concentration and for fiber content.
Common, inexpensive equipment and no chemicals (other than a surfactant to enhance foaming) are needed for the
exercise.” [9]
Figure 3: A schematic drawing of the laboratory flotation
experiment.
6
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2
A Simple Flotation De-inking Experiment for the Recycling of Paper
Richard A. Venditti
Associate ProfessorNorth Carolina State UniversityDepartment of Wood and Paper ScienceRaleigh NC, 27695-8005Telephone: (919) 515-6185Fax: (919) 515-6302Email: [email protected]
Lab Summary
Flotation de-inking is used in paper recycling processes to preferentially remove hydrophobic contaminants
such as inks and toners from a slurry of fibers in an aqueous phase. In the process, fine air bubbles are
introduced into the suspension and the hydrophobic contaminants preferentially attach to the bubble-water
interfaces and float to the surface. The foam on the top of the surface laden with contaminant is skimmed
away resulting in the separation.
This paper describes a laboratory exercise for the flotation de-inking of wastepaper. The exercise consists
of disintegrating printed wastepaper in a blender and then removing the ink or toner contaminants by
pumping air bubbles through the suspension using an aquarium pump (Figure 1) or other source of air
bubbles. Foam is taken off the top of the container that is rich in ink (the reject sample) while the cleaned
fiber remains in the container (the accept sample). After the experiment the accept and reject samples are
analyzed for ink concentration and for fiber content.
Tubing Foam laden with ink
Air Pump Dispersed Wastepaper
Large Plastic Tray
Figure 1. Schematic Drawing of the Laboratory Flotation Experiment.
Common, inexpensive equipment and no chemicals (other than a surfactant to enhance foaming) are needed
for the exercise. The experiment is useful for middle/high school science courses or introductory level
college environmental, chemical engineering, or chemistry courses in need of a simple experiment that
• a schemaXc of the experimental setup is shown here
• the ink specs were too small & numerous for the naked eye
• could not carried out with the microscope: two sample photos from different experiments are shown below
• even at 10X, the specs are too small and numerous for a manual count -‐ the sorware did not have the ability to conduct a parXcle/spec count
• at >10X, there was insufficient light for any viewing 13
RESULTS & DISCUSSION: INK SPEC COUNT FAILURE
• consistency, cs. % is defined as: where ρ(water) = 1 g/mL
14
RESULTS & DISCUSSION: effect of CS. %
cs. %( )= mass of solids (grams)volume of water (mL)
× 100
T (°C) cs. (%)vol. (mL)
conc. (mL/g)
time (min.)
avg. Y (%)
σ (%)
23 0.296 5.00 2.22 10.023 0.468 5.00 2.22 10.0
48.9 4.728.5 19.2
• as the cs. % is raised by 58%, the yield falls by the same number: ΔY(%) / Δcs.(%) = 1
• expectedly, since there is a greater amount of fibre per unit volume of water...
• ... there is more that may be carried off into the REJECT stream.
• results are inconclusive since there are insufficient data points.
0
10
20
30
40
50
60
0.20 0.26 0.32 0.38 0.44 0.50
average Y (%) vs. cs. (%)
avg
. Y (%
)
cs. (%)
• as the temperature is raised by 52%, the fibre yield falls by 26%: ΔY(%) / ΔT (°C) = 0.5
• expectedly, as there is greater convecXon and greater thermal moXon...
• ... there is a greater amount that goes up & out as REJECT stream
• results are inconclusive since there are insufficient data points
15
RESULTS & DISCUSSION: effect of TEMPERATURE
T (°C) cs. (%)vol. (mL)
conc. (mL/g)
time (min.)
avg. Y (%)
σ (%)
23 0.468 5.00 2.22 10.0
35 0.468 5.00 2.22 10.0
28.5 0.6
21.2 20.5
0
10
20
30
40
50
20 25 30 35 40
average Y (%) vs. temperature (°C)
avg
. Y (%
)
temperature (°C)
16
RESULTS & DISCUSSION: effect of TIME (min.)
T (°C) cs. (%)vol. (mL)
conc. (mL/g)
time (min.)
avg. Y (%)
σ (%)
23 0.468 5.00 2.22 10.023 0.468 5.00 2.22 5.023 0.468 5.00 2.22 3.023 0.468 5.00 2.22 2.023 0.468 5.00 2.22 1.523 0.468 5.00 2.22 1.0
28.5 19.2
35.8 18.4
40.9 31.1
51.6 20.6
54.4 15.1
64.2 0.2
0
10
20
30
40
50
60
70
80
0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
R² = 0.99
average Y (%) vs. time (min.)
avg
. Y (%
)
time (min.)
• downward trend is expected
• trend is exponenXal: as Xme goes by...
• ... fibre + water are REJECTED
• the layer of foam becomes thicker & thicker -‐ reaches deeper into the beaker
• acts as physical filter/barrier for remaining fibres...
• ... slows further fibre REJECTION
• as per the trend, ideal flotaXon duraXon: 0 < t (min.) ≪ 1 -‐ unrealisXc
• table shows a significant increase below 3 min. -‐ the 1.5 -‐ 2.0 min. region
17
RESULTS & DISCUSSION: effect of CONCENTRATION of FOAMING AGENT
T (°C) cs. (%)vol. (mL)
conc. (mL/g)
time (min.)
avg. Y (%)
σ (%)
23 0.468 5.00 2.22 1.5
23 0.468 4.00 1.78 1.5
23 0.468 3.00 1.33 1.5
23 0.468 2.00 0.89 1.5
23 0.468 1.00 0.44 1.5
23 0.468 0.50 0.22 1.5
23 0.468 0.25 0.11 1.5
54.7 15.3
58.8 0.2
58.2 0.8
48.9 4.7
58.3 5.8
53.8 41.5
57.2 40.9
0
10
20
30
40
50
60
70
80
90
100
0 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00
R² = 0.0001
Y (%) vs. vol. of BRD2345 foaming agent
avg.
Y (%
)
volume of BRD2345 (mL)
• fibre yield is not affected by concentraXon of foaming agent
• a volume as low as 0.25 mL in 240 mL of water may be sufficient for flotaXon
• 1:1000 of foaming agent:water
• lower cost of operaXon
18
FURTHER DISCUSSION• individual high error margins: fibre loss
• wet fibre sXcks to every container/vessel -‐ difficult to wash down -‐ scrubbing down is not possible during an experiment
• ∴ fibre loss in every transfer/step e.g. division into separate FEED and ACCEPT streams
• compounded with each subsequent step -‐ the further a step is from the FEED stream, the higher the loss (reason for the significantly different YFR)
• suggesAon: use a flotaXon vessel with rough interior walls or Teflon
• other a^empts at ink spec count: failure
• pulped and intact squares were placed in various solvents to ajempt a leeching-‐out for subsequent UV-‐Vis spectroscopic analysis
• ... benzene, toluene, xylenes, DMSO, acetonitrile, polypropylene glycol, glycerol, methanol & ethanol...
• graphite is virtually insoluble -‐ all ajempts failed
• suggesAon: dedicated system e.g. flatbed scanner/CCD camera + image analysis sorware e.g. Apogee Spec*Scan 2000
19
CONCLUSION• cs. %: higher fibre loss with higher cs. %
• temperature: higher fibre loss with higher temperature
• dura#on: a realisXc opXmum of 1.5 min. was determined with a fibre yield of 54.4%
• concentra#on of foaming agent BRD2345: has no effect on fibre yield
• suitable concentraXon: 1:1000 in water
• results are only par#ally valid: only one of two performance criteria could be obtained
• effect of experimental variables on contaminant count could not be ascertained
• dedicated, proper equipment is needed
20
ACKNOWLEDGEMENTS
• Dr. Richard Vendie of the Wood & Paper Science Dept. of North Carolina State University for his guidance and provision of the foaming agent BRD2345.
• Dr. Dev Sharma, for his general assistance
• SFU Dept. of Chemistry for their generous funding and making this only a 2-‐credit course
• Tahir, for his ears
• Jasbir, for his complete experimental failure thereby reassuring my that parXal failure is not so bad
• Yuen, for never being here -‐ the extra benchspace was invaluable
• Neil Draper, for reminding me that pH of water slowly decreases in open air
• ... Dr. Goyan, for the ?-‐grade...
21
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