natural polymers and adsorption properties
TRANSCRIPT
Presentation Outline
Introduction
Definition of natural polymers
Classification of natural polymers
Properties and advantages/disadvantages
Methods of preparation
General areas of application for natural polymers
Adsorption definition
Types of adsorption processes
Difference between physisorption and chemisorption
Factors affecting adsorption
Properties of natural polymers based on adsorption
Conclusion
Introduction
From the Greek word''POLYMEROS''
''Poly'' meaning Many
''Meros''meaning parts
Many Parts = POLYMER
Natural Polymers:Polymers that occur in natureproduced from living organisms
Synthetic Polymers
What are Natural polymers?
Definition:A polymer is a large molecule (macromolecules) composed of many repeated subunits, known as monomers
Thus a natural polymer is a polymer produced from living organisms and result from only raw materials that are found in nature
Why great attention for natural polymers?
Because they are biocompatible and biodegradable, so they can be hydrolysed into removable and non-toxic products.
Monomer Monomer DimerPolymer
Reapting units of monomer
Classification of Natural polymers based on source
NATURAL POLYMERS
Plants Animals Microbes
Polysaccahridee.g cellulose,starch
Proteins e.ggelatin, albumin
Polysaccahridese.g chitin,chitosan
Polyesterse.g Poly-hydroxyalkanoate
Polysaccahrides e.g Hyaluronate, pullulan
Classification of Natural polymers based on structure
NATURAL POLYMERS
Agri-Polymer Biopolyesters
Polysaccharides PolypeptidesBacterial Polyesters(microorganisms)
R1
O
OR2
Ester group
H2N CH
CH3
C
O
N
H
CH
CH3
C
O
OH
Peptide bond(Amide group)O
HO
OROH
OH
OH
Glycosidic bond
Examples1. Cellulose2. Chitin3. Chitosan4. Starch
Example Proteins made of 1. Gelatin2. Albumin
Examples1. Polyhydroxybutyrate (PHB)2. Polylactides (PLA)3. Poly--caprolactone (PCL)
Polynucleotides
Examples1. RNA2. DNA
Starch
Polysaccharides
Polypeptide
Bacterial polyesters
H O CH
CH3
CH2C
O
OH
n
polyhydroxybutyrate (PHB)
H O CH
CH3
C
npolylactic acid (PLA)
H O (CH2)5 C
Poly--caprolactone (PCL)
n
O
OH
O
OH
N
H
CH
O
H3C CH3
N
H
C
O
N
OH
C
H
O
N
H
CH3
CH
O
Tetrapolypetide (Val-Gly-Ser-Ala)
Properties and advantages/disadvantages
Due to the great properties exhibited by natural polymers, this makes them of great research interest
Natural polymers are; Readily biodegradable by showing no adverse effects on the environment or human beings. Non-toxic/ non-inflammatory due to their source in nature. Biocompatible based on positive interaction in other living organisms or tissues. Highly porous Have high molecular weight making them exhibit high viscosity Easy and cheap to prepare/produce in comparison with synthetic polymers Capable of attachment with other molecules with their varying functional groups creating easy modification Easily available and are from renewable resources:
Disadvantages: Possible microbial contamination during production due to their natural sources. Batch to batch variation as a result of difference resources and resource regions. Slow process as production rate depends upon the environment and many other factors, Potential impurities may also result in unwanted immune reactions. Heavy metal contamination often associated with herbal polymeric excipients(An excipient is a natural or synthetic substance
formulated alongside the active ingredient of a medication).
Method of preparation
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Generally most natural polymers are naturally built by condensation polymerization method. Other polymerisation methods include; free radical polymerization, grafting and photo-polymerization.
Formation of cellulose glucose units
Preparation of PLA from lactic acid
+
General Applications areas of natural polymers
NATURAL
POLYMERS
Industrial applications
Bioplastics Packaging
materials
Biomedical applications
Drug delivery Tissue engineering
Wastewater treatment
Agricultural applications
use in biocontrol Fertilizer release
Adsorption definition
Definitions:
Adsorbate: It is the the substance which is adsorbed on the surface Examples are: gases, dyes, metals.
Adsorbent: It is the substance on which surface the adsorbate is adsorbed . Examples chitosan, cellulose, Starch, PLA
Chemical Adsorption (chemisorption) Involves molecules or atoms stick to the surface of
adsorbent by forming a chemical bond ( usually covalent ), and tend to find sites that maximize their coordination number with the substrate. The distance between the surface & the closest adsorbate atom is also typically shorter for chemisorption
Example of adsorbent include functionalised polymers and their composites such as chitosan crosslinked hydrogel beads.
Adsorbate
Adsorbent surface
Van Der Waal forcebetween adsorbent and adsorbate
Physisorption model
Adsorbate sticked adsorbent surface
Adsorbent surfacaee.g Cellulose polymer
Chemisorption Model
Red and Green adsorbatePurple Adsorbent surface
Physical adsorption (Physisorption) Involves a van der Waals interaction
between the adsorbate and the substrate.
Examples of adsorbents involve activated carbon and alumina
Adsorpton phenomenonTypes of adsorption
processes
Physisorptiona. Not very Specific b. No electron transfer , although polarization of adsorbate c. Rapid, non-activated & reversible d. No dissociation of adsorbed species e. Monolayer or Multilayer f. Only significant at relatively low temperatures g. Enthalpies are in the region of -20 kJ/molh. As the temperature increases, Physisorption decreases
Chemisorptiona. Highly Specific b. Electron transfer may occur leading to bond formation between adsorbate & adsorbent c. Activated , may be slow & irreversibled. May involve dissociatione. Monolayer or Multilayerf. Possible over a wide range of temperaturesg. Enthalpies are in the region of -200 kJ/molh. With the increase in temperature, Chemisorption first increases & then decreases
Difference between physisorption and chemisorption
Factors affecting adsorption
Factors Effect on adsorption
Nature of Adsorbate Gas, liquid or solid (↑↓)
Mass of adsorbent (↑) Amount (↑)
Pore size of adsorbent (↑) Micro or macrospores (↑)
Solubility of adsorbate (↑) Polarity (↓)
Size of adsorbent (↓) Particle size (↑)
Number of carbon atoms (↑) Depending on adsorbate or adsorbent (↑↓)
Temperature Depends on enthalpy and entropy
pH Depends on extent of ionization of species
Affinity between adsorbent and adsorbate (↑) Interaction (↑)
Degree of ionization of adsorbate (↑) (↑)
Contact time (↑) (↑)
Crosslinking density (↑) Swelling, pore size (↓)
↑= increase ↓= decrease
Properties of natural polymers based on adsorption
Based on literature so much research work has been performed on natural polymers for adsorption application in various area. And most of the natural polymers use are of polysaccharide origin.
Case study natural based polymers;
Chitosan polymers (Animal polysaccharide)
Gelatin (Polypeptide or protein)
Starch( Plant polysaccharide)
Chitosan:
Introduction: Chitin is a macromolecule found in the shells of
crabs, lobsters, shrimps and insects Chitosan is obtained by partial deacetylation of
chitin. Chitin and chitosan are insoluble in water
Chemistry:
Linear co-polymer of β(1-4) linked glucosamine and N- acetyl-D-glucosamine.
P
Physiochemical properties:BiodegradableBiocompatibleNon toxicChelates many transitional metal ions A cationic polysaccharide of which in acidic pH, it gets solubilized due to protonation of free amino groups and
the resultant soluble polysaccharide is positively charged.hydrophilic in nature thereby it has the ability to form gels at acidic pH. Exhibit good swelling properties
Chitosan product Area of application
Substance adsorbed
Adsorption capacity (mg/g)
Reference
Chitosan/bentonite composite
Dye removal Methyl orange 224.8 (Huang, Liu, Zhang, & Yang, 2015)
Chitosan hydrogel beads Dye removal Congo red 223.35 (Chatterjee, Lee, Lee, & Woo, 2009)
Chitosan film Dye removal Tartrazine and amaranth
413.8 and 278.3 (Rêgo, Cadaval Jr, Dotto, & Pinto, 2013)
Hydroxyapatite chitosan Metal removal
Pb(II) 264.42 (Lei et al., 2015)
Gelatin:
Introduction:
Gelatin is a natural water soluble functional polymer (protein) that is derived by partial hydrolysis of collagen (chief protein component in skin, bones and white connective tissues of the animal body).
It is commonly used for biomedical and other suitable applications due to its biodegradability and biocompatibility in physiological environments.
Physicochemical properties:
Forms of thermo-reversible gels in water: When gelatin granules are soaked in cold water they hydrate into discrete, swollen particles. On being warmed, these swollen particles dissolve to form a solution.
Soluble in aqueous solutions of polyhydric alcohols such as glycerol and propylene glycol.
Insoluble in less polar organic solvents such as benzene, acetone, primary alcohols and dimethylformamide.
It gives typical protein reactions and is hydrolyzed by most proteolytic enzymes to yield its peptide or amino acid components.
Gelatin product Area of application Substance adsorbed
Adsorption capacity (mg/g)
References
PVA/gelatin hydrogel beads
Metal removal Pb(II) 203.4 (Hui, Zhang, & Ye, 2015)
Gelatin microspheres
Dye removal Direct red 81Direct blue 78
584.2566.5
(He, Wang, Xue, & Hao, 2011)
Gelatin-starchmicrosphere
protein Bovine serum album 120 (He, Song, Zhang, You, & Tu, 2015)
Starch:Introduction:Carbohydrate polysaccharide, occurring naturally in green plants as energy store.Consist of large number of glucose units joined by glycosidic bondsConsist of a mixture of linear amylose (15-20%) and branched amylopectin (80-85%) units
Chemistry: The glucose units are linked by of α(1→4) glycosidic bonds linked for amylose and α(1→6)-linked branches for amylopectin.
(1-6) Linkage
(1-4) Linkage
Properties: BiodegradableBiocompatibleNon-toxicNon- immunogenicNon-inflammatoryVery hydrophilicReadily soluble in water at temperature of 50-70 °CExhibits good swelling properties in aqueous media
Starch product Area of application Substance adsorbed
Adsorption capacity (mg/g)
Reference
Porous starch Xanthate
Metal removal Pb(II) 109.4 (Ma, Liu, Anderson, & Chang, 2015)
Cationic starch clay composite
Dye removal Brilliant blue X-Br 122 (Xing, Liu, Xu, & Liu, 2012)
Chitosan-starch Dye removal Direct red 80 345.23 (Asabuwa thesis; 2011)
Starch/acrylic acid Metal removal Pb(II) and Hg(II) 123.2 and 131.2 (Huang, Xiao, & Chen, 2011)
Conclusions
Based on literature studies natural based polymers still remain one of the suitable available polymeric material for enhance adsorption process based on their
Ready availability from renewable sources
Low cost
Distinguishable physicochemical properties of;
Biodegradability
Biocompatibility
Non toxicity,
High swelling due to their hydrophilicity
Available modifying functional groups and
Ready solubility in various solvent make these natural polymers very advantageous for the adsorption of metal, dyes, other organic solvent and gases from aqueous media and the environment.
As a research perspective is concern enormous works are still been performed using natural polymers for various applications of adsorption, biomedical and other suitable application both at the industrial and academic research institutes.