AACIMP 2010 Summer School lecture by Mårten Ericson. "Sustainable Development" stream. "Environmental Technology" course. Part 1. More info at http://summerschool.ssa.org.ua

1. Environmental technology
for
Cleaner Production
Mårten Ericson
Research engineer

2. Content
• Introduction to cleaner production
• Ion exchange
- How it works, mechanisms & generic case
- Applications
• Adsorption
• Absorption
• Catalytic reduction
• Condensation
• Membrane techniques
• Summary - What have we learned

5. Cleaner production
• Environmental technology is a tool for Cleaner
Production
• Cleaner Production strategies:
• Raw material
• Process
• Equipment
• Process control
• Management
• Separation and extraction
• Product design
• Internal/external

6. Things to concider for an engineer
to solve a environmental problem
• Current status – total flows, concentrations,
amounts, running conditions
• What should be separated? – Particles, solubles, in
water or air?
• What to do with the separated ”product”
• Efficiency
• Stability of method
• Space requirements
• Economy
• Maintenance

7. Separation operations for cleaner production
solutions
Different unit operation can be used for separation of certain
components in order to prolong the usage time of a process
solution - kidney function
Process
 stage x  Process 
stage y
 Kidney
Pollutants
Process 
 stage x

Kidney
Pollutants
Common unit operations for the separation stage are e.g.
Ion exchange, RO, UF, Stripping a.o

8. Separation operations for cleaner production
solutions
Different unit operation can be used for separation of certain
components from a process flow in order to recycle them into
the process - recovery function
Recycling of
a component


Process  Separation 
stage x stage
Common unit operations for the separation stages are:
Ion exchange
Evaporation
Membrane processes, e.g. RO and UF
Extraction
Stripping

9. Separation operations for cleaner production
solutions
Different unit operation can be used for separation of certain
components in a wastewater flow from a process in order to
protect for instance the biological stage in the external waste-
water treatment plant from toxic substances
 Process stage 

Separation stage,
e.g. adsorption, UF, 
RO a.o. Specific com-
pounds to be
handled as waste

Waste water

treatment stages Sludge
 Effluent

10. Ion exchange
• Ion exchange definition: Exchange of ions
between two electrolytes or between an
electrolyte solution and a complex.
• What is an ion?
• When can we use ion exchanger (to be
answered later)

11. Ion exchange Regeneration
Me2+  Me2+
Low conc. An- An-
 High
conc.
Cation
resin R-H+ R-2Me2+

H+
 - H+
An An-
Ion exchange reaction:
2 R–H + Me 2+   R2–Me + 2H +
Regeneration reaction:
2 R–H + Me 2+   R2–Me + 2H +

12. Classification of synthetic ion
exchange resins
Type of Functional Ion to exchange
resin group
1. Strong acid -SO3-H+ Cations in general
cation resin
2. Weak acid -COO-H+ -’’- -’’- , espec.
cation resin Ca , Mg2+, Na+
2+
O- H + Cs+ & multi-valent
cations
3. Strong base Quaternary Anions, espec. fr.
anion resin amine weak acids (CN-,
CO32-, SiO32-)
4. Weak base Primary, secon- Anions to strong
anion resin dary and ter- acids (SO42-, Cl-,
tiary amine NO3-, CrO42-,
HPO42-)
5. Chelating Cations, espec.
resins heavy metals
Typical exchange capacities for synthetic resins are
2 - 10 eq/kg resin

13. Selectivity for ions - a strong acid
cation resin and a strong base
anion resin
Cations Anions
Pb2+ 9,9 NO3- 3,0-4,0
Ca2+ 5,2 Cl- 1,0
Ni2+ 3,9 HCO3- 0,4
Mg2+ 3,3 SO42- 0,15
Na+ 2,0  F- 0,1
H+ 1,3 DecreasingOH- 0,06
selectivity
Li+ 1.0 CO3- 0,03
Notice - the relative selectivity to different
ions is depending on which ion exchange
resin that is in use.

14. Important parameters to concider
• When can we use ion exchange?
• Load
• Concentration
• Contaminants – particles, other metals?

15. Applications
• Applications in biochemistry, chemistry
• Metal plating – chromating (Cr3+, Cr2O72-,
CrO42-)
• Wastewater containing NH4+ (nitrogen)

16. Using ion exchange in order to
increase the recovery of metals
from an economy rinse
Product
Water
 Water
   
Process bath  Economy  Rinse
rinse
Drag out To waste
 water
Ion H+ treatment
exchanger 
Concentrate

17. Using ion exchange as a kidney
in order to clean the rinsing water
Product
Water

  
Process bath  Rinse 1  Rinse 2
Drag out
  H+
To waste water
treatment Ion 
exchanger
To waste water
treatment
 2+
Me

18. Ion exchanging as a polishing method after
a chemical metal precipitation stage
Flocculating Ion exchange
OH-
agent
Waste water
containing
metals
Precipitation
Flocculation
Sludge Effluent
Settling
The ion exchanger will give a very clean water. Since the ion
exchanger is in use as a polishing stage the ion exchanger doesn´t
have to be regenerated so often.

19. Movie 1

20. Absorption
• Definition: The process by which one
substance, such as a solid or liquid, takes up
another substance, such as a liquid or gas,
through minute pores or spaces between its
molecules. A paper towel takes up water, and
water takes up carbon dioxide, by absorption.

21. Physical absorption
• Physical absorption involving such factors as
solubility and vapor-pressure relationships
• Examples: Acetone can be recovered from an acetone–air
mixture by passing the gas stream into water in which the
acetone dissolves while the air passes out
• Ammonia may be removed from an ammonia–air mixture by
absorption in water
• Particles can be removed from a particle-air mixture by
absorption in water

22. Chemical absorption
• Chemical absorption involving chemical
reactions between the absorbed substance
and the absorbing medium
• Examples: Oxides of nitrogen can absorbed in water to give
nitric acid
• Carbon dioxide is absorbed in a solution of sodium hydroxide
• Removal of SOx using CaO/CaCO3 slurry or Na2SO3

23. Design of equipment
• In considering the design of equipment to
achieve gas absorption, the main requirement
is that the gas should be brought into intimate
contact with the liquid, and the effectiveness
of the equipment will largely be determined
by the success with which it promotes contact
between the two phases.

24. Equipment

25. Equipment
Spray scrubber Counter cross flow Spray scrubber with
spray scrubber rotating air flow

26. Equipment
Venturi scrubber Cascade scrubber

27. Adsorption
• Adsorption definition: adhesion of molecules
to a solid surface
• Two types of adsorption: physical /chemical

28. Chemisorption
Chemisorption is characterized by strong
interaction between adsorbate and substrate
surface (chemical bond between reactant and
surface)
Binding energy: 1-10 eV

29. Physisorption
Physisorption is characterized by mainly Van der
Waals bonds between adsorbate and
substrate surface
Binding energy: 10-100 meV

30. Desorption/Regeneration
• Chemical desorption
- Using an acid
- Using a base
- Using an organic solvent
• Thermal regeneration
- The carbon is heated in an oven and the adsorbate is driven
off as gas – the adsorbate is oxidized and destroyed

31. Thermodynamics
ΔG = Δ H - T Δ S
Spontaneous: ΔG < 0
Non-spontaneous: ΔG > 0
Δ H (enthalpy): heat content of a system
Δ S (entropy): measure of how
organized/disorganized a system is
Adsorption = exothermic
How will the temperature affect the adsorption?

32. About adsorbents
• Adsorbents used today:
- Activated carbon
- Zeolites
- Polymeric adsorbents
• Tomorrow?
- Super activated carbon (>3000 m2/g)
- Magnetic adsorbents

33. Activated carbon
Specific surface area: 500-1500 m2/g
Capacity: 100-200 g/kg
Activated carbon is used for wastewater treatment and
the substances should have the following properties:
- High molecular weight
- Low solubility in water
- Low polarity
- Low temperature
Notice: when adsorption of many substances in a water the
adsorption capacity of any individual compound is lower than
if this compound is alone in the water. But the total
adsorption may be higher

34. • Activated carbon
- High adsorption efficieny, even when the substance has a low
concentration in the water
- High adsorption capacity
- Difficult to regenerate
- Flat breaktrough curve
• Polymeric adsorbents:
- Lower adsorption capacity
- Easy to regenerate
- Low adsorption efficiency at low concentrations
- Steep breakthrough curve
• Conclusion:
- Activated carbon – polishing method
- Polymeric adsorbent – recovery

35. Characteristic comparison
Adsorbent Specific Pore volume Mean pore Relative
surface area (cm3/g) diameter (Å) cost
(m2/g)
Activated carbon (granular) 700-1300 1 30-59 1
Activated carbon
(powdered) 800-1800 1 40-60 3
Zeolite 700 0.3 3-10 5
Polymeric (PS, DVB) 350 0.4 90 7
Polymeric (acrylate esther) 450 0.4 80 7

36. Adsorption
Important parameters to concider:
• Partition coefficient (distribution coefficient)
• Concentration
• Flows
• Temperature
• Polarity
Liquid containing organic substances at low
concentrations!

37. Applications I
• Domestic water cleaning – to remove substances
givin water a bad taste or odour
• Municipal wastewater treatment (when a high
cleaning efficient is necessary)
• Industrial wastewater treatment especially to get a
toxicity reduction
• Process internal cleaning
• Wastewater treamtent with the PACT-process
(activated sludge + activated carbon)

38. Important to remember!
• Adsorption is usually a polishing method and
is not used to recover substances!

39. Movie 2

40. Condensation
• Condensation is the change in the phase of
matter from the gaseous phase into liquid
droplets or solid grains of the same element/
chemical species.
• Condensation commonly occurs when a vapor
is cooled and/or compressed to its saturation
limit (dew point) when the molecular density
in the gas phase reaches its maximal
threshold.

41. Equipment
• Heat exchangers (tubes)
• Scrubbing with water

42. Applications
• Separation of water soluble Hg in flue gases
• Lots of different salts will go out with the
condensed water
• Energy!!! Lots of energy in water vapour
• Recovery/separation of solvents with high
boiling point (why high boiling point?)

43. Catalytic reduction
• Reduction of compounds – many toxic
compound can be transformed to less toxic
for example NOx  N2
• Oxidation of HC, CO (catalyst in cars most
common)  CO2 & H2O
• NOx - where, what, when

44. SNCR
• SNCR – selective non catalytic reduction
• Use ammonia (NH3) for the reduction of NOx
• Directly spray NH3 into the furnace
• Important reactions can be described with
these formulas
4NO + 4NH3 + O2  4N2 + H2O
6NO2 + 8NH3  7N2 + 12H2O

45. SCR
• SCR – selective catalytic reduction
• Chemical reactions in a reactor with a catalyst
(TiO2/V2O5)

46. SNCR vs SCR
• Investment
• Cost
• Reduction %
• Pollution/de-activation
• Placement
• Running conditions

47. Introduction to membrane
filtration
• Oldest separation technique? Separation
technique – sieving or diffusion
• Many applications
Feed water Retentate
Semipermeable membrane
Permeate

48. Microfiltration (MF)
• Separation mechanism: Sieving
• Separates: Particles with diameter 0.2-10 µm
• Pressure: 0.01-0.1 MPa

49. Applications
• Last stage after chemical precipitation of
waste water from surface coating industry.

50. Ultrafiltration (UF)
• Separation mechanism: Sieving
• Separates: Particles with diameter 0.001-0.1
µm
• Pressure: 0.2-1.5 MPa

51. Ultrafiltration
• Ultrafiltration for good purification of waste
water. Can also be used for pre-concentration
and then as a ”recovery function”

52. Applications
• Treatment of alkaline degreasing bath
(kidney)
• Treatment of oil emulsions
• Electrodip painting industry

53. UF for alkaline degreasing
• Using an UF in order to clean a degreasing
bath results in a longer life time for the bath
(4-5 times longer). That means:
- Decreased chemical consumption
- Decreased water consumption
- Decreased waste production (40-50 times lower)

54. Movie 3

55. Nanofiltration (NF)
• Separation mechanism: Sieving + membrane
diffusion
• Separates: Molecules with diameter 0.001-
0.01 µm
• Pressure: 2-4 MPa

56. Nanofiltration (NF)
• Nanofiltration ranges somewhere between
ultrafiltration and reverse osmosis
• Relative new technology
• Lower pressure as compared with RO which
reduces the operation cost significantly
• However, problem with fouling

57. Applications
• Used for removal of contaminants from water
• Desalination of water.

58. Reverse osmosis (RO)
• Separation mechanism: Membrane diffusion
• Separates: Molecules with diameter 0.0001-
0.002 µm
• Pressure: 2-10 MPa

59. Reverse osmosis

60. Reverse osmosis

61. Applications
• Surface coating industry – preconcentration of
cromic acid bath
• Chemical or galvanic industry that works with
Ni, Cu, Zn etc… use RO instead of IE
• Desalination
• Polishing method for ultra-pure water
• Leechate water from landfills

62. Important!
• RO is mainly a cleaning technology NOT for
pre-concentration. This is because the
osmotic pressure over the membrane is very
large if the concentration gradient is large.
• In the example with cromic acid is the level of
pre-concentration not that high…

63. Electrodialysis (ED)
• Similar to electrolysis. In principle, two
membranes (cationic and anionic specific)
that only let positive or negative charged ions
pass through. The ions are drawn to two
electrodes.
• Is a pre-concentration method
• Limitations: working best at removing low
molecular weight ionic components

65. Applications
• Desalination and production of salt
(economically favorable if not ultra pure
water is required)
• Can chose ion selective membranes so that
one can separate several cationic/anionic ions
(not 100% selective though)
• Acid retardation. ED also take the acid which
are in complex thus a better method
compared to ion exchange

66. Running conditions
• Velocity over membrane surface
- Increased velocity -> higher flux
• Pre-treatment
- Better pre-treatment minimize the clogging of filter
• Temperature
- For most liquids does the flux increase with higher temp. (viscocity)
• Pressure
- The flux increase linear to the pressure up to a certain level
• Concentration
- The flux decreases with increasing concentration

67. Membrane properties
• Cut off – The molecule weight of the smallest
material rejected by the membrane (how
“thick” is the membrane and the pores)
• NaCl retention – Describes the removing
properties of a RO membrane (how much is
going through)
• Flux – Volume or mass rate of transfer
through a membrane: RO = 50 l/m2,h. UF=
200-250 l/m2, h

68. Membrane properties
• Temperature – New types of materials in the
membranes that can handle temperatures
above 100 degrees celcius
• pH – Today there are membranes that works
at all pH (1-14)

69. Comparison
Process Operating Energy consumption,
pressure, kPa kWh/m3
Microfiltration 100 0.4
Ultrafiltration 525 3
Nanofiltration 875 5.3
Reverse osmosis I 1575 10.2
Reverse osmosis II 2800 18.2

70. Summary – what have we learned
• Ion exchange – how it works, mechanisms,
generic case and applications
• Absorption - how it works, mechanisms,
generic case and applications
• Adsorption - how it works, mechanisms,
generic case and applications

71. Summary – what have we learned
• Different membrane techniques and when to
use them
• Membrane properties and how to affect the
flux
• SCR/SNCR

72. Summary – what have we learned

73. Further reading
• Coulson & Richardson Vol 2. Particle Technology and
Separation Processes (membrane techniques, absorption,
adsorption, ion exchange)
• Atkins/de Paula, Physical chemistry (for understanding the
theory behind adsorption, RO etc)
• Per Olof Persson et al. Chapter 2-6 from the "Environmental
Technology - strategies and technical solutions for a
sustainable environmental protection". Can be ordered
through Industrial Ecology, KTH.