ADSORPTION COMPLETE REVIEW

1. ADSORPTION
Submitted to:
Professor Atif Mustafa
Environmental Engineering Department
N.E.D. UET KARACHI
Prepared By:
Abu Umeer (EN-22/2018-19)
u.ahmed8@yahoo.com
Subject:
Physico-Chemical Processes
EN-22/2018-19 1

2. Contents
1. Background
2. Treatment Methods
3. Introduction
4. Adsorption
5. Chemistry of adsorption
6. Isotherms
7. Effect of Physico-chemical parameters
8. Agricultural waste Adsorbents
9. Cost comparison
10. conclusion
11. References

3.  Textile industries consume (up to 150 l of water to dye 1 kg of
cotton)(Jadhav et al. 2010).
 Rated as high dye polluters.
 Environmental pollution, is a global concern.
Dye is a colored, aromatic organic compound.
Inert and difficult to biodegrade when
discharged into waste streams.
 Heavy metal contamination into the aqueous media
and in industrial effluents is a major ecological problem
due to their toxic nature.
BACKGROUND
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4. Treatment methods for effluents
Chemical methods
Physical methods Biological methods
Oxidation
Ozonation
Filtration
Coagulation/
Flocculation Adsorption
Anaerobic Aerobic
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5. EN-22/2018-19 5
Flexibility and
simplicity of
design,
Low operating
cost,
insensitivity to
toxic pollutants
ease of
operation.
Adsorption also
does not
produce harmful
substances
Adsorption has been found to be superior to other techniques in terms of
• Introduction

6. Adsorption processes: Applications
- SO2 from vent gases
- H2O from air, methane, N2
- Removal of solvent, odours
from air
- NOx from N2
- Organics from water solution
- Water from organic solution
- Decolourization
Purifications: Separations:
- Removal of organics from - N2/O2
vent gases
- Acetone from ventstream
- C2H4 fromvent
- Normal paraffins/ Iso praffins
- CO, CH4, CO2, N2, Ar from
hydrogen
- Normal paraffins from Iso paraffins
- Normal paraffins from olefins
gasphaseliquidphase
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7. • adsorbate does diffuse into the structure
of the adsorbent (in this case indeed the process is
called absorption).
• Adsorption is the process when a molecule, or ion, called
adsorbate present in a gaseous or liquid bulk sticks on the
surface of a solid, rarely a liquid, called adsorbent.
• The reverse process, that is, the drop of a
molecule from a solid surface, is called desorption
It is a surface process, that is, only the surface of the adsorbent
is involved,
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8. adsorbate: material being adsorbed
adsorbent: material doing the adsorbing.
(examples are activated carbon or ion
exchange resin).
Example:
If we have to remove soluble material from the solution phase, but the
material is neither volatile nor biodegradable, we often employ adsorption
processes.

9. THE CHEMISTRY OF ADSORPTION
 When the adsorbate adheres
to the surface because of
physical forces.
 If the adsorbate molecules
hit the surface with low
energy, it is dissipated as
heat by vibration of the
lattice of solid; hence, they
are trapped on the surface.
 If the molecules hit the
surface with too much
energy, this cannot be
dissipated by the adsorbent,
and they bounce away.
 When the adsorbate is chemically bound (usually
covalent) to the adsorbent’s surface.
 It can be activated process, it requires that the
adsorbate has a minimum of E in order to be sorbed.
 This depends on the presence of an energetic barrier
between the physiosorbed and chemisorbed state
(Figure A):
 If B>E , then the adsorbate will chemically bond to
the adsorbent only if it has more energy than the
barrier, otherwise it will be desorbed.
 If B<E, all the molecules physiosorbed can quickly
form a chemical bond with the adsorbent surface and
chemisorption will occur rapidly.
Irreversible. Monolayer, ΔΗ ≥ 40 ≤ 400 kJ mol1, @ 20 ⁰C ≈ 1 h, /100 ⁰C ≈ 1 s.Reversible, Multilayer, ΔΗ≤.20kj/mol, @20 ⁰C≈108
𝑠 / -170⁰c=S
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10. Δ H c
Δ
H c
d
Δ H p Δ H p
E a,c
d
Figure (A) Diagram of energy of adsorption depending on distance (d) of adsorbate molecule from surface.
• Solid line is for physisorption, involving low enthalpy (Hp),
• Dashed for chemisorption, where the energy required is higher (Hc).
• On the left is the case of activated chemisorption: Ea,c is the activation
energy for chemisorption.
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12. • adsorption is described through a relationship independent from time between the amount of adsorbate attached to the
adsorbent and the amount in the environment (expressed as a pressure if it is a gas, a concentration if it dissolved in a solution).
• In case of dissolved adsorbate,
•
where q (mg 𝑔−1
) is the mass adsorbed per mass unit of adsorbent.
• C (mg/l) the concentration of adsorbate in the environment.
• Such relationships are called isotherms, which means that their validity is limited to the case of constant temperature.
There are several kinds of isotherms.
The most used are the isotherm of
• Langmuir
• isotherm of Freundlich.
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13. Described by the following equation:
where qm (mg/ g) is the maximum amount of adsorbate in the adsorbent.
b (l/mg) is the equilibrium constant related to the enthalpy of the process.
Four hypotheses are behind this formulation.
1. Adsorbate attach only on particular sites, that is, they establish a link with the adsorbate (by of van der Waals forces or
chemical bonds).
2. Adsorption occurs only in a monolayer, that is, once a site is occupied by a molecule, it cannot bind to another one: this leads
to the saturation shape of the isotherm.
3. Last two assumptions can be summarized stating that Adsorption occurs homogeneously (even if discreetly) on the surface.
The Langmuir isotherm
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14. Freundlich isotherm
Described by the following equation:
Where,
• a (mg/g) is the mass adsorbed with a unitary concentration.
• n is an empirical constant usually greater than 1.
• Freundlich model is not empirical but it is
theoretically based.
Assumptions:
1) Adsorption is Multilayer.
2) Energy required for adsorption is not constant, it
varies and it is exponentially distributed.
Another isotherm that fits well the data of adsorption of gases on solids is the BET isotherm (Brunauer, Emmet, Teller).
The main assumption :
 The first layer of adsorbate can adsorb on its another layer,
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15. Langmuir-Freundlich-BET
C , z
Figure (B):
They describe the amount of adsorbate expressed in term of mass fraction q (or fraction of sites
occupied for BET) depending on its concentration C (or on pressure of gaseous adsorbate relative to
Langmuir
BET
Freundlich
• Langmuir isotherm is shown in Figure B. The shape of
the curve clearly depends on parameters; however,
usually the saturation is reached quite fast
• The Freundlich curve (Figure B): the
slope decreases when concentration of
adsorbate increases.
BET isotherm implies an endless
adsorption, even if in this case the slope of
the curve increases with the pressure of
adsorbate (Figure B).
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16. • Effect of Various Physicochemical Process Parameters on Heavy Metal and Dye Adsorption:
The efficiency of liquid phase adsorption process in solids is dependent on:
 adsorbent properties (surface area, pore structure, chemistry of the surface, particle size, etc.)
 adsorbate properties (molecular weight, molecular structure, molecular size, polarity, etc.).
Solution PH
Temperature
Contact time
Initial solution
concentration
Presence of other
ions
Many physicochemical factors such as
Investigation of these parameters can give information on the
Adsorption mechanism that is of fundamental importance in
selecting (Adsorbent) and preparation conditions to be used for the
efficient adsorption of a specific Adsorbate (heavy metal or dye).
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17. Process parameters
Effects on adsorption of pollutants (heavy metals and ionic dyes)
Solution pH ↑ It enhances adsorptive removal of cationic metals or basic dyes but reduces that of anionic metals or
acidic dyes.
Initial adsorbate
concentration ↑
It increases the quantity of adsorbed pollutant per unit weight of adsorbent but decreases its removal
efficiency.
Temperature ↑ It usually enhances adsorptive removal of water pollutant by increasing surface activity and kinetic
energy of the adsorbate but may damage physical structure of adsorbent.
Adsorbent dosage ↑ It decreases the quantity of adsorbed pollutant per unit weight of adsorbent but increases its removal
efficiency.
Addition of salt ↑ It reduces adsorptive removal of adsorptive pollutant by competing with the adsorbate for binding sites
of adsorbent.
Adsorbent size ↓ It is favorable for batch process due to higher surface area of the adsorbent, but not for column process
due to its low mechanical strength and clogging of the column.
Agitation speed ↑ It enhances adsorptive removal rate of adsorptive pollutant by minimizing its mass transfer resistance
but may damage physical structure of adsorbent.
Table: Influences of physicochemical process parameters on adsorption capacity of water pollutants,
such as metals and dyes modified from (Park et al. 2010)
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18. Adsorbents Adsorbates (heavy metals and
dyes)
Initial concentration
range (mg L−1)
Percentage (%)
removal range
References
Tomato waste (acid treated) Cu(II) 25–125 Decrease Yargıç et al.
(2015)
Cucumber peel (chemically
modified)
Remazol black 5 5–150 94.82–21.84 Sayğılı and
Güzel
(2017)
Tomato seeds Acid red 14 50–150 89–85 Najafi et al.
(2015)
Sugarcane bagasse Basic blue 9 250–500 94–55.5 Zhang et al.
(2013)
Table (a) The effect of initial concentration of heavy metals and dyes using several agricultural
solid waste adsorbents
Adsorbents Adsorbates (heavy
metals and dyes)
pH range Percentage (%)
removal range
References
Tomato leaf powder Ni2+ 2–5.5 Increase Gutha et al. (2015)
Rice husk Zn2+ 4–8 Increase Galletti et al. (2015)
Coffee waste Toluidine blue 2.0–10.5 50–95 Lafi et al. (2014)
Cucumber peels Methylene blue 2–10 13.44–77.70 Akkaya and Güzel
(2014)
Potato peel waste Acid blue 1 2–11 Decrease Hoseinzadeh et al.
(2014)
Table (b) The effect of solution pH on the adsorption of heavy metals and dyes by different
agricultural solid waste adsorbents.
`
Adsorbents Adsorbates (heavy
metals and dyes)
Temperature
range
(°K)
Type of References
Process
Tomato leaf Ni2+ 303–323 Endothermic Gutha et al. (2015)
Tomato waste
derived biochar
Co2+ 293–313 Endothermic Önal et al. (2014)
Rice husk (nitric acid
treated)
Malachite green 303–333 Endothermic Ramaraju et al. (2013)
Sugarcane bagasse Rhodamine B 303–323 Endothermic Zhang et al. (2013)
Adsorbents Adsorbates
(heavy metals
and dyes)
Adsorbent
dosage
Percentage
(%) removal
range
References
Bagasse pith (sulfurized
activated carbon)
Zn2+ 0.5–8 g L−1
Increase Krishnan et al. (2016)
Sugarcane bagasse
(sulfuric acid treated)
Cu2+ 0.5–2 g 100
mL−1
Increase Rana et al. (2014)
Cucumber peel (modified) Direct blue 71 0.1–1.0 g 41.92–97.60 Sayğılı and Güzel (2017)
Tea waste Acid orange 7 2–20 g L−1
90–99 Khosla et al. (2013)
Table (c) Influence of solution temperature on heavy metal and dye adsorption using various
agricultural solid waste adsorbents
Table (d) The effect of adsorbent dosage on the percentage of heavy metal and dye removal
using several agricultural wastes as adsorbents
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19. • Analytical techniques & instruments are used to characterize the physicochemical surface properties of adsorbent which further decide the
effectiveness of material as adsorbent and its suitability in adsorption field.
Role of Agricultural Solid Waste Adsorbent Characteristics on Adsorption
1. Morphology and Surface Properties of Agricultural Solid Waste Adsorbents During Adsorption:
i. Scanning Electron Microscopy (SEM): Used to examine the surface micromorphological texture of adsorbent
materials.
ii. X-ray Diffraction Spectrum Study : Investigate crystalline nature of adsorbent materials.
iii. Powder X-ray diffraction (XRD) : Measure crystalline content of adsorbent materials, crystalline phases present, spacing between
lattice planes, the preferential ordering and epitaxial growth of crystallites within the material.
iv. Point of zero Charge: The pH at which the surface charge = 0. To understand the mechanism of adsorption process under
varying pH. SEM: image of
CHARCOAL
XRD patterns of Wheat Straw adsorbents. (pHpzc): (a) raw (b) NaOH treated eucalyptus sheathiana bark.
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20. v. BET Analysis : Brunauer–Emmett–Teller (BET) equation to calculate specific surface area known as BET surface area.
vi. Particle Size: adsorbent particle size affects the surface area for adsorption. It is indicator of content uniformity, dissolution,
quality and performance of absorption rates
2. Elemental and Functional Group Analysis of Agricultural Solid Waste Adsorbents.
 It is done using a CHNS/O elemental analyzer. (carbon, hydrogen, nitrogen, sulfur, and oxygen) in an adsorbent to understand the influence of
chemical properties participating in adsorption phenomenon.
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21. 3. Activation of Agricultural Solid Waste Adsorbents
Physical ChemicalBiological
i.e.: Acid and Caustic, Methanol, Formaldehyde,
etc.
boiling / heating autoclaving mechanical disruption.
Washing raw
adsorbent
with
detergents
Treatment
with organic
and inorganic
compounds
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22. Adsorbents Modifying agents Adsorbates References
Olive stone Phosphoric acid (H3PO4) Cu2+, Ni2+, and Pb2+ Bohli et al. (2015)
Leaf biomass Nitric acid (HNO3) Pb2+ Madala et al. (2015)
Sugarcane bagasse Sulfuric acid (H2SO4) Cu2+ Rana et al. (2014)
Rice husk Nitric acid (HNO3) Malachite green Ramaraju et al. (2013)
Activated agricultural solid waste adsorbents and their modifying agents used for the removal of heavy metals and dyes
Modification Treatment Advantages Disadvantages
Chemical
characteristics
Basic Enhances uptake of organics Insome cases, decrease the uptakeof
metal ions
Acidic Increases acidic functional groups on activated carbon
surface enhances chelation ability with metal species
May decrease BET surface area and pore
volume
Impregnation of foreign
materials
Enhances in-built catalytic oxidation capability May decrease BET surface area and pore
volume
Physical characteristics Heat Increases BET surface area and pore volume Decreases oxygen surface functional
groups
Biological characteristics adsorption Prolongs activated carbon bed life by rapid oxidation of
organics by bacteria before the material can occupy
adsorption sites
Thick biofilm encapsulating activated
carbon may impede diffusion of
adsorbate species
Technical advantages and disadvantages of existing modification techniques adapted from Gautam et al. (2014)
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23. • Drying ofrefrigerants,
organicsolvents,
transformeroils
• Desiccantsinpacking&
doubleglazing
• DewPointControlof
naturalGas
SILICA
GEL
• Drying ofgases,organic
solvents,transformeroils
• RemovalofHClfrom
Hydrogen
• Removaloffluorine in
Alkylationprocess
ACTIVATED
ALUMINA
• Removalofodoursfrom
gases
• Recoveryof
solvent vapours
• Nitrogenfromair
• Waterpurification
• PurificationofHe
ACTIVATED
CARBON
• WaterPurification
• Recovery&purification
ofsteroids&aminoacids
• Separationoffattyacids
fromwater&toulene
• Recoveryofproteins&
enzymes
POLYMERS
&RESINS
• Treatmentofedibleoils
• Removaloforganic
pigments
• Refiningofmineraloils
• Removalofpoly
chlorinatedbiphenyls
(PCBs)
CLAY
• Oxygenfromair
• Drying ofgases
• Drying ofrefrigerants&
organicliquids
• Pollutioncontrol
includingremovalofHg
• Recoveryoffructosefrom
CornSyrup
ZEOLITES
Commercial Adsorbents

24. 4. Adsorption with Activated Carbon Adsorbents Derived from Agricultural Biomass
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Activated carbons from biomass
Carbonization
(to enrich the carbon content and to create an initial poro
Chemical
Activation
(to enhance the pore structure of the selected adsorben
Physical
activation
Activatio
n
process
• lower temperature
• Greater carbon yield
Activation

25. EN-22/2018-19 25
Chemical and physicochemical methods Physical methods Biological methods
Explosion:
 Steam, ammonia, CO2, SO2, and acids
Alkali:
 CaO, ZnCl2, NaOH, NH3, and (NH4)2SO3
Acid:
 H2SO4, HCl, HNO3 and H3PO4 acids
Oxidizing agents:
 H2O2
 O3
-Wet oxidation
Solvent extraction of lignin: -
Ethanol–water extraction
 Benzene–water extraction
 Butanol–water extraction
Milling:
 Ball milling
 Two-roll milling - Hammer
milling
Irradiation:
 Ultrasound irradiation
 Gamma-ray irradiation
 Electron-beam irradiation -
Microwave irradiation
Others:
 Hydrothermal
 High pressure steaming
 Extrusion
 Pyrolysis
Fungi and actinomycetes:
 Lignin peroxidase, manganese peroxidase,
laccase
 White-rot and brown-rot fungi
The classification of pre-treatment methods for the production of activated adsorbents modified from source (Gautam et al. 2014)

26. EN-22/2018-19 26
AC from agricultural waste materials
Heavy metals and dyes
Maximum adsorption capacity
− (qm (mg g 1))
References
Almond shell Reactive red 2 1639.9 Thitame and Shukla (2016)
Egg shell wastes Acid blue 25 109.80 Tovar-Gómez et al. (2015)
Coconut shell Malachite green 214.63 Bello and Ahmad (2012)
Rice husk Basic green 4 511 Guo et al. (2003)
Pine cone Congo red 435 Dawood et al. (2014)
Bamboo dust Methylene blue 143.2 Kannan and Sundaram (2001)
Groundnut shell and pine Methylene blue 164.9 Kannan and Sundaram (2001)
Adsorption capacities qm (mg g 1) for activated carbon (AC) materials prepared from agricultural solid wastes

27. EN-22/2018-19 27
Eggshell Pb2+ 90.90 Putra et al. (2014)
Mango seeds Methylene blue 25.36 Senthil Kumar et al. (2014)
Rice husk Crystal violet 44.87 Chakraborty et al. (2011)
Adsorbents Adsorbates (heavy metals and dyes) Maximum adsorption capacity References
−1 (qm (mg g ))
Langmuir maximum adsorption capacities qm (mg g−1) of raw agricultural solid wastes used as adsorbents

28. EN-22/2018-19 28
Modified adsorbents Heavy metals and dyes
−
Maximum adsorption capacity (qm (mg g 1)) References
Sugarcane bagasse Cu2+ 30.9 Rana et al. (2014)
Rice husk Malachite green 26.6 Ramaraju et al. (2013)
Bagasse Methylene blue 69.93 (60 °C) Low et al. (2013)
Rice straw Malachite green 256.41 Gong et al. (2007)
Adsorption capacities (qm (mg g)) for modified agricultural waste adsorbent materials

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31. EN-22/2018-19 31
Cost Comparison
Pollutant to be
removed (dye/metal)
Adsorbent −
qmax (mg
g 1)
Relative cost of
− adsorbent (US$ kg 1)
References
Cu2+ Acid-modified sugarcane bagasse 5.35 4.76 Gupta et al. (2018)
Commercial activated carbon 5.62 56.06
Zn2+ Peanut husk charcoal 0.3681 0.4 Salam et al. (2011)
Fly ash 0.1806 0.2
Natural zeolite 1.3189 0.34
Commercial activated carbon – 0.57
Cr6+ Activated tamarind seeds 29.7 0.57 Gupta and Babu (2008)
Activated neem seeds 62.9 1.25
Sawdust 21.5 0.068
Commercial activated carbon 71.7 7.68
Hg2+ and Ni2+ Chitosan 815 and 164 16 Babel and Kurniawan (2003)
Commercial activated carbon – 20–22
Pb2+ and Zn2+ Lignin (extracted from black liquor) 1865 and 95 0.06 Srivastava et al. (1994)
Commercial activated carbon – 0.1
Methylene blue Fuller’s earth (FE) FE < CAC 0.04 Atun et al. 2003)
Commercial activated carbon (CAC) 20
Methylene blue Activated carbon prepared from rice husk (RHC)
Activated carbon prepared from straw (SC)
37.57
42.60
RHC and SC nearly
5 times cheaper than
CAC
Kannan and Sundaram (2001)
Cost comparison of low-cost adsorbents with commercially activated carbons as reported in literature

32. EN-22/2018-19 32
Association of adsorbate-adsorbent particles for a good adsorption is mostly influenced by their
individual physical and chemical characteristics together with some process settings such as
solution pH, initial adsorbate concentration, adsorbent mass, solution temperature, and ionic
load of the system.
Adsorption processes are still at the stage of laboratory scale batch studies. Thus, much more
work in this area is necessary to demonstrate its possibilities on an industrial scale by
conducting pilot plant studies and designing packed bed column for continuous flow systems.
More research are needed for the sustainable valorization of post-sorption materials as
alternative other green chemical products such as fertilizers, catalyst, feed additives, etc.
Conclusion

33. EN-22/2018-19 33
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References

34. Thank You