Study on chemical modification of natural aminopolysaccharide use as absorbents to remove heavy metals in wastewater and give amethod with the optimal condition to get the best result.

CONTENTS Page ACKNOWLEDGEMENTS 1 CONTENTS 2 LIST OF FIGURES 5 LIST OF TABLES 6 INTRODUCTION 7 CHAPTER 1. LITERATURE REVIEW 8 Aminopolysaccharide 8 1.1. Introduction of aminopolysaccaride. 8 1.2. Structure, physical, chemical, biological properties of aminopolysaccharide 9 1.2.1. Structure of aminopolysaccharide 9 1.2.2. Physical and chemical properties of aminopolysaccharide 11 1.2.3. Biological properties 12 1.3. Applications of aminopolysaccharide 12 1.4. Modification of amonipolysaccharide 13 1.4.1. Physical modification 13 1.4.2. Chemical modification 13 1.5. Heavy Metal in Wastewater 14 1.5.1. Heavy Metal in Wastewater 14 1.5.2. Effect of some heavy metals on living body and human 15 1.6. Some general methods in treatment heavy metals 17 1.6.1. Precipitation 17 1.6.2. Absorption 19 1.6.3. Ion exchange 20 CHAPTER 2. EXPERIMENTAL 21 2.1. Materials and Apparatus 21 2.1.1. Materials 21 2.1.2. Appartus 21 2.2. Amonipolysacharide synthesis process. 21 2.2.1. General Process( diagram) 25 2.2.2. Deacetylation process 26 2.2.3. Investigation on effect of reaction temperature 26 2.2.4. Investigation on effect of material ratio 27 2.2.5. Investigation on effect of reaction time 27 2.3. Evaluation of the ability of treating heavy metal in wastewater of APSAMS material 27 2.3.1. Investigate the effects of contact time 28 2.4. Methods of product structure analysis 29 2.4.1. Infrared spectroscopy (IR spectroscopy) analyses the components and structure of aminopolysacharide 29 2.4.2. ICPOES method to analyses the concentration of heavy metals in wastewater 30 2.4.3. Determine the degree of deacetylation (DD) 30 CHAPTER 3. RESULTS AND DISCUSSION 31 3.1. The results of systhesis amonipolysaccharide 31 3.1.1. Enzyme papain 32 3.1.2. Microwave 33 3.2. Amonipolysaccharide modification result 34 3.2.1. Effect of reaction time 35 3.2.2. Effect of reaction temperature 36 3.3. Results of the ability of absorption heavy metal in wastewater of APSAMS material 38 3.3.1. Effect of absorption amount 38 3.3.2. Effect of Cu2+ concentration 39 3.3.3. Effect of contact time 39 3.3.4. Effect of pH 40 CONCLUSION AND RECOMMENDATION 42 REFERENCE 43

Through this thesis, I would like to express the deepest appreciation to theDeparment of Oil Refining and Petrochemistry for teaching me during 5 years atHUMG Especially, I wish to thank to my instructor, Dr Nguyen Thi Linh for hersupervision, guidance and help throughout the thesis of my research work and for hervaluable comments on this thesis.

In additon, I would like to thank my friends in laboratory and my Advanced Program K3 They were always supporting and encouraging me with theirbest

classmates-Finally, during implementation the thesis, due to time constraint and my limitedknowledge, some flaws in the process are unvoidable So I would like to receive thehelp of lecturers for my thesis is more complete

Page

ACKNOWLEDGEMENTS 1

CONTENTS 2

LIST OF FIGURES 5

LIST OF TABLES 6

INTRODUCTION 7

CHAPTER 1 LITERATURE REVIEW 8

Aminopolysaccharide 8

1.1 Introduction of aminopolysaccaride 8

1.2 Structure, physical, chemical, biological properties of aminopolysaccharide 9

1.2.1 Structure of aminopolysaccharide 9

1.2.2 Physical and chemical properties of aminopolysaccharide 11

1.2.3 Biological properties 12

1.3 Applications of aminopolysaccharide 12

1.4 Modification of amonipolysaccharide 13

1.4.1 Physical modification 13

1.4.2 Chemical modification 13

1.5 Heavy Metal in Wastewater 14

1.5.1 Heavy Metal in Wastewater 14

1.5.2 Effect of some heavy metals on living body and human 15

1.6 Some general methods in treatment heavy metals 17

1.6.1 Precipitation 17

1.6.2 Absorption 19

1.6.3 Ion exchange 20

CHAPTER 2 EXPERIMENTAL 21

2.1.1 Materials 21

2.1.2 Appartus 21

2.2 Amonipolysacharide synthesis process 21

2.2.1 General Process( diagram) 25

2.2.2 Deacetylation process 26

2.2.3 Investigation on effect of reaction temperature 26

2.2.4 Investigation on effect of material ratio 27

2.2.5 Investigation on effect of reaction time 27

2.3 Evaluation of the ability of treating heavy metal in wastewater of APS-AMS material 27

2.3.1 Investigate the effects of contact time 28

2.4 Methods of product structure analysis 29

2.4.1 Infrared spectroscopy (IR spectroscopy) analyses the components and structure of aminopolysacharide 29

2.4.2 ICP-OES method to analyses the concentration of heavy metals in wastewater 30 2.4.3 Determine the degree of deacetylation (DD) 30

CHAPTER 3 RESULTS AND DISCUSSION 31

3.1 The results of systhesis amonipolysaccharide 31

3.1.1 Enzyme papain 32

3.1.2 Microwave 33

3.2 Amonipolysaccharide modification result 34

3.2.1 Effect of reaction time 35

3.2.2 Effect of reaction temperature 36

3.3 Results of the ability of absorption heavy metal in wastewater of APS-AMS material 38

3.3.1 Effect of absorption amount 38

3.3.2 Effect of Cu2+ concentration 39

3.3.3 Effect of contact time 39

3.3.4 Effect of pH 40

CONCLUSION AND RECOMMENDATION 42

REFERENCE 43

Figure 1.1 Structures of natural Aminopolysaccharide 10

Figure 1.2 Some compounds of Aminopolysaccharide and Chitin 13

Figure 2.1 Shrimp shells after washing and drying 28

Figure 2.2 Shrimp shells after treating with HCl(enzyme method) 29

Figure 2.3 Chitin (enzyme method) 30

Figure 2.4 Aminopolysaccharide(enzyme method) 30

Figure 2.5 Shrimp shells afer washing and drying 31

Figure 2.6 Shrimp shells after treating with HCl(microwave method) 32

Figure 2.7 Chitin (microwave method) 33

Figure 2.8 Aminopolysaccharide (microwave method) 33

Figure 3.1 Image of Aminopolysaccharide is dissvolved in CH3COOH 41

Figure 3.2 Image of Aminopolysaccharide product(enzyme method) 42

Figure 3.3 FT-IR spectroscopy of aminopolysaccharide(enzyme method) 42

Figure 3.4 Image of Aminopolysaccharide product(microwave method) 43

Figure 3.5 FT-IR spectroscopy of aminopolysaccharide(microwave method) 43

Figure 3.6 FT-IR spectroscopy of APS-AMS 1:1 ratio 44

Figure 3.7 FT-IR measurement result of APS-AMS 1:2 ratio 44

Figure 3.8 FT-IR spectroscopy of APS-AMS 1:3 ratio 44

Figure 3.9 FT-IR spectroscopy of APS-AMS 1:4 ratio 45

Figure 3.10 FT-IR spectroscopyof APS-AMS 1h reaction time 46

Figure 3.11 FT-IR spectroscopyof APS-AMS 2h reaction time 46

Figure 3.12 FT-IR spectroscopyof APS-AMS 3h reaction time 46

Figure 3.13 FT-IR spectroscopy of APS-AMS 4h reaction time 46

Figure 3.14 FT-IR spectroscopy of APS-AMS 50ºC reaction temperature 47

Figure 3.15 FT-IR spectroscopy of APS-AMS 60ºC reaction temperature 47

Figure 3.16 FT-IR spectroscopy of APS-AMS 70ºC reaction temperature 48

Figure 3.17 FT-IR spectroscopy of APS-AMS 80ºC reaction temperature 48

Figure 3.18 Effect of absorption amount on absorption 49

Figure 3.19 Effect of cencentration of Cu2+ on absorption 50

Figure 3.20 Effect of contact time on absorption 51

Figure 3.21 Effect of pH on absorption 52

LIST OF TABLES

Table 1.1 pH at the starting point of the precipitation of the metals 22

Table 2.1 Effect of amount of absorbent 35

Table 2.2 Effect of concentration of Cu2+ 36

Table 2.3 Effect of contact time 36

Table 2.4 Effect of pH 37

Table 3.1 The result of Degree of Crosslinking of APS – AMS(material ratio) 44

Table 3.2 The result of Degree of crosslinking of APS – AMS(reaction time) 46 Table 3.3 The result of Degree of crosslinking of APS – AMS reaction temperature 47

In these day, the industry is growing rapidly and plays a important role ineconomy Beside the growing, it releases a lot of pollutants to enviroment, affectsdirectly human health and ecology Ion heavy metals in wastewater of industry are likeElectroplating, Steel Processing, Metallurgy, Textile dyeing, Chemicals, whenreleased into enviroment polluting the water source, influenced so much cause by hightoxicity and can accumulate in living body

Heavy metal pollution is one of the most important enviroment problems forthe time being However, treatments of heavy metals in wastewater in Viet Nam fromfactorys still didn’t care too much Because the factorys just are not too largeproduction scale, so they restrict investment to wastewater treatment systems.With thelack of effective wastewater treatment systems, so concentration of heavy metalsreleasing to enviroment will exceeds acceptance limit

Consequently, Study to come up with a new method working more effective,more environmentally friendly and cheaper is really necessary.According to theserequirements, we need proper methods that not only tackle heavy metals in wastewaterbut also can restrict heavy metals’s harm to enviroment and human health With theconsent of Oil & Gas Department and Dr.Nguyen Thi Linh, the thesis: ”Study onchemical modification of natural aminopolysaccharide use as absorbents to removeheavy metals in wastewater” is performed

* Objectives:

Study on chemical modification of natural aminopolysaccharide use asabsorbents to remove heavy metals in wastewater and give a method with the optimalcondition to get the best result

* Contents:

The thesis has 3 chapters:

Chapter 1: Literature review

Chapter 2: Experimental

Chapter 3: Results and discusstions

CHAPTER 1 LITERATURE REVIEW

Aminopolysaccharide

1.1 Introduction of aminopolysaccaride.

The majority of commercial polymers and ionexchange resins are derived frompetroleum-basedraw materials using processing chemistry that is notalways safe orenvironmental friendly Today, there is growing interest in developing natural low-costaltematives to synthetic polymers Chitin, found in the exoskeleton of shrimpshells,the cuticles of insects, and the cells walls of fungi, is the most abundantaminopolysaccharide (also known as aminopolysaccharide) in nature [1,2] This low-cost material is a linear homopolymer composed of p(l-4)-linked N-acetylglucosamine It is structurally similar to cellulose, but it is an aminopolymer and hasacetamide groupsat the C-2 positions in place of the hydroxyl groups.The presence ofthese groups is highly advantageous providing distinctive absorption functions andconducting modification reactions

Figure 1.1 Structures of natural Aminopolysaccharide[3]

The raw polymer is only commercially extracted from marine shrimp shellsprimarily because a large amount of waste is available as a by-product of foodprocessing Chitin is extracted from shimp shells (shrimps, crabs, squids) by acidtreatment to dissolve the calcium carbonate CaCO3 followed by alkaline extraction todissolve the proteins and by a decolorization step to obtain a colorless product

Since the biodegradation of chitin is very slow in waste shrimp shells,accumulation of large quantities of discards from processing of shrimp shells has

recycle these by-products Their use for the treatment of wastewater from anotherindustry could be helpful not only to the environment in solving the solid wastedisposal problem, but also to the economy However, chitin is an extremely insolubleprocesses and uses of chitin, and so far, very few large-scale industrial uses have beenfound More important than chitin is its derivative, aminopolysaccharide.

Partial deacetylation of chitin results in the production of aminopolysaccharidewhich is aminopolysaccharide composed by polymers of glucosamine and N-acetylglucosamine The ‘‘aminopolysaccharide label’’ generally corresponds to polymerswith less than 25% acetyl content The fully deacetylated product is rarely obtaineddue to the risks of side reactions and chain depolymerization Copolymers with variousextents of deacetylation and grades are now commercially available.Aminopolysaccharide and chitin are of commercial interest due to their highpercentage of nitrogen compared to synthetically substituted cellulose.Aminopolysaccharide is soluble in acid solutions and is chemically more versatile thanchitin or cellulose The main reasons for this are undoubtedly its appealing in trinsicproperties such as biodegradability, biocompatibility, film-forming ability,bioadhesivity, polyfunctionality, hydrophilicity and absorption properties Most of theproperties of aminopolysaccharide can be related to its cationic nature [1], which isunique among abundant polysaccharides and natural polymers These numerousproperties lead to the recognition of this polyamine as a promising raw material forabsorption purposes

Aminopolysaccharide established from 2-amino-2-deoxy-p-Dglucosamin unit,contacted p-(l-4) glucozit.

Name: Poly(l β-D-glucose; poly( 1 β- D-glucopyranose

-4)-2-amino-2-deoxy-[ C6H11O4N]n Maminopolysaccharide = (161,07)n

Chitin only has one practice group -OH, aminopolysaccharide has 2 practicegroups -OH,-NH2, so aminopolysaccharide is easier to take part in chemical reacti nthan chitin Practical use of aminopolysaccharide has been mainly confined to theunmodified forms For a breakthrough in its utilization, chemical derivatization ontopolymer chains has been proposed to produce new materials Derivatization is a keypoint which will introduce the desired properties to enlarge the field of its potentialapplications Aminopolysaccharide has three types of reactive functional groups, anamino group as well as both primary and secondary hydroxyl groups at the C-2, C-3and C-6 positions Its advantage over other polysaccharides is that its chemicalstructure allows specific modifications without too many difficulties, especially, at theC-2 position These functional groups allow direct substitution reactions and chemicalmodifications, yielding numerous useful materials for different domains of application.The most commonly used chemical activations are carboxymethylation, acetylationand grafting The variety of groups which can be attached to the polymer is almostunlimited

Figure 1.2 Some compounds of Aminopolysaccharide and Chitin[6]

1.2.2 Physical and chemical properties of aminopolysaccharide [7]

• Linear aminopolysaccharide with high nitrogen content

• RigidD-glucosamine structure; high crystallinity; hydrophilicity

• Capacity to form hydrogen bonds intermolecularly; highviscosity

• Weak base; the deprotonated amino group acts a powerfulnucleophile

• Insoluble in water and organic solvents; soluble in dilute aqueous acidicsolutions as acetic acid 2%, formic acid, lactic acid

• Numerous reactive groups for chemical activation and crosslinking

• Forms salts with organic and inorganic acids

• Chelating and complexing properties

• Ionic conductivit

• Polyelectrolytes (at acidic pH)

• Cationic biopolymer with highcharge density (one positive charge per glucosamineresidue)

• Flocculating agent; interacts withnegatively charged molecules

• Entrapment and absorption properties; filtration and separation

• Film-forming ability; adhesivity

• Materials for isolation of biomolecules

• Antimicrobial activity (fungi,bacteria, viruses).

• Antacid, antiulcer, and antitumoral properties

Agriculture

• Protection of plants

• Increase of crop yields (reduces the growth of phytopathogenic fungi)

• Seed and fertilizer coating; soil treatment Biomedical engineering

• Biological activities (antifungal, antimicrobial, antiinfectious); antitumor agent

• Hemostatic effects; enhances blood coagulation

• Promotes tissue growth; stimulates cell proliferation; artificial skin

• Water purification (metal chelation); water engineering (flocculation,

filtration, absorption); sludge treatment

• Reverse osmosis, filtration membranes; gasseparation

• Production ofbiodegradable packagingfilms

• Catalysis

Cosmetics and toiletries

• Hair spray, lotion; hand and body creams;shampoo, moisturizer

• Food industry

• Diet foods and dietary fiber;hypocholesteroiemic activity (bindscholesterol, fatty acids andmono glycerides)

• Preservation of foods from microbialdeterioration

• Bioconversion for the production of valueadded food products

• Recovery of waste material from foodprocessing discards

• Clarification and deacidification of fruitjuices and beverages

• Emulsifying agent; colour stabilization

• Animal feed additive Pharmaceutics

• Controlled drug delivery carriers

• Microcapsules (forming gels and capsules with anionic polymers)

• Dermatological products (treats acne)

Others

• Textiles (anti-bacterial properties)

• Pulp and paper (wet strength)

• Enology (clarification, deacidification)

• Dentistry (dental implants)

of application in the form of powder, flakes and foremost as gels: beads, membranes,sponge, fibers, hollow fibers, etc Flake and power forms of chitosan are not suitable to

be used as adsorbents due to their low surface area and no porosity Chitosan flakesmodified into beads are essential for the enhancement of absorption performance.There are many studies describing the preparation of chitosan gels Manufacturing ofgel beads allows an expansion of the polymer network improving access to internalsorption sites and enhancing diffusion mechanisms

1.4.2 Chemical modification

The chemical modification of chitosan is of interest as the modification wouldnot change the fundamental skeleton of chitosan but bring new or improved properties

A great number of chitosan derivatives have been obtained with the aim of adsorbingmetal ions by grafting new functional groups on the chitosan backbone The newfunctional groups are incorporated to increase the density of sorption sites, to changethe pH range for metal sorption and to change the sorption sites in order to increasesorption selectivity for the target metal The chemical modification affords a widerange of derivatives with modified properties for specific and use applications indiversified areas mainly of pharmaceutical, biomedical and biotechnological fields.

1.5 Heavy Metal in Wastewater[9]

1.5.1 Heavy Metal in Wastewater

Heavy metal is metals that has the density greater than 5mg/cm3 Metals exist inwastewater affecting human health and living bodies such as : Zn, Cu, Pb, Cd, Hg, Ni,

Cr, As, Wastewater contains heavy metals is mainly released into enviroment cause

by industrial productive processes, mining process, refining ore, metals, Moreover,heavy metal compounds are widely used in industrial processes such as coloring anddyeing, in tanning, rubber, textile and paper products, is a major source of heavymetal pollution in water There is also the existence of heavy metals in domesticsewage by agents in cosmetics used to make-up, wash face and some chemicals used

in agriculture also cause this pollution

Ions of heavy metals in water often combine with other components to move to

a more stable state and often hydrated to form shells that made by water molecules tohelp protect it with non-water molecules around to return to a more stable state Thishydrating shell is usually a sphere which has the metal ion is centered, the watermolecules that surround it are called the shell The molecules that are closest to themetal ions are most likely to interact with the strongest metal ions, the next ones beingweaker, and at some distance there will be no interaction

Hydration process can be considered as a creating complex process with thecentral are metal ions and ligands being water molecules Usually, the number ofcoordinates of most metals is 6

Metallic ions carry a positive charge, so under the effect of electrostaticrepulsion, the hydrogen atoms of water molecules closing to the metal ions are ejected,

so the water molecules closing to the water molecules have higher acidic metal ions(higher yields of protons) than water molecules outside the solution The process ofceding this proton has formed hydroxide complex, oxo or metal oxo hydroxide such ashydroxide, oxide or oxide hydroxide mixtures This process is called hydrolysis ofmetal, metal ions with water

1.5.2 Effect of some heavy metals on living body and human

1.5.2.1 Coppper(Cu)

* Source:

The main waste source of copper in industrial waste water is the wastewaterfrom the process of plating and wastewater from the washing and soaking process inthe tanks containing copper.Copper and brass tanks are often subjected to strong acids,

in their containment processes, containing solutions, which oxidize copper into thesolution In copper plating processes, copper is used as the main material or as acoating for metals such as gold, silver, Copper in wastewater usually exists in theform of: Cu2+ salts such as CuCl2, CuSO4 or exist as complex salts For example,when copper is combined with NaOH it produces: Na2[Cu(OH)4][10]

* Toxicity:

When the copper content in the human body is 10 g/kg (can be fatal), the dose

of 60-100 mg/kg cause of vomiting For fish, when the concentration of Cu was 0.002mg/l, 50% of the fish died With cyanobacteria, when the concentration of Cu is 0.01mg/l, it died For plants, when the concentration of Cu is 0.1 mg/l was toxic[10]

* Concentration limit allowed[10][11]:

 With drinking water and reservoir: 0.02-1.5 mg/l and depends on country standards

 Agricultural irrigation water: 0.2 mg/l, particularly for very poor soil, can use water

up to 5 mg/l for short time

 In industrial wastewater according to Vietnam Quality Standards 2005: 2mg/l

Institute-5945-1.5.2.2 Lead(Pb)

* Source:

The main source of lead is wastewater from lead ore mining such as leadsulphide (PbS), lead carbonate (PbCO3) and lead sulphate (PbSO4) , refining lead,battery manufacture using lead electrodes, using leaded gasoline, steel, pesticides usinglead [10]

* Toxicity:

When the lead concentration in drinking water is 0.042-1.0 mg/l, symptoms ofchronic poisoning in humans occur In irrigation water, if the lead concentrations aregreater than 5 mg/l, plants are poisoned [11]

* Concentration limit allowed:

PTWI standard = 0.025-0.05 mg Pb/kg body weight/week The maximumallowed concentration of lead in drinking water of WHO is 0.05 mg/l The allowedconcentration of lead in domestic water of Vietnam is 0.05 mg/l [8], [10]

In industrial wastewater according to Vietnam Quality Standards 2005: 0.5mg/l

Institute-5945-1.5.2.3 Crom(Cr)

* Source:

The main source of chromium is wastewater from coloration, electroplating, andelectroplating In plating processes in the automotive industry, the automotive industryproduces the most chromium-plated products The main source of chromiumcompounds is the chromium that is used in the coating process [10]

* Concentration limit allowed:

According to WHO standards, the allowed concentration of chromium indrinking water is 0.05 mg/l In Vietnam, the allowed chromium concentration indomestic water is 0.05 mg/l According to Vietnam Quality Standards Institute-5945-

2005, the allowed chromium (III) in industrial wastewater : 1mg / l [11]

1.5.2.4 Cadimi(Cd)

* Source:

Industrial activities are the main source for the generation of containing wastes: metallurgy, plating, ore mining, electronics, batteries, batteries,refining, burning coal and solid wastes, mechanical operations using cadmium [10]

cadmium-* Toxicity:

Cadimi penetrates the body through the respiratory, eating and drinking In highconcentration of Cd can cause anemia, kidney failure and bone marrow damage.Concentration of Cd cause nephrotoxic effects is roughly : 0.2 mg / l [11]

* Concentration limit allowed:

TWI standard = 0.025-0.05 mg Cd/kg body weight/wk The WHO standard formaximum concentration in drinking water is 0.005 mg/l The Vietnamese standardallows the concentration of cadmium in domestic water to be 0.005 mg/l According toVietnam Quality Standards Institute-5945-2005, the allowed concentration in industrialwastewater: 0.01 mg/l [10], [12]

1.6 Some general methods in treatment heavy metals

1.6.1 Precipitation [12][13]

Heavy metal treatment by precipitation is the most common and popular method

in Vietnam today With the advantages of being inexpensive, the ability to processmultiple metals in the wastewater at the same time and the efficient handling of heavymetals is acceptable, this method is the number one choice for industrial plants inVietnam

* Mechanical Method:

Mn+

+ Am- = MmAn( precipitation )

[ M]m [A]n > Tt MA

(Mn+ : Metal ion Am- : Precipitating agent Tt : solubility)

In this method, it is possible to use many agents to precipitate with metals suchas: S2-, SO42-, PO4 , Cl- , OH but just S2-, OH- is used the most because it canprecipitate with most metals, and ions PO43-, SO4 , Cl- only precipitate with certainmetal ions so that they are only used when the wastewater contains monometallic or afew certain metals

Cr3+ + 3OH- = Cr (OH)3

Fe3+ + 3OH- = Fe (OH)3

Zn2+ +2OH- = Zn (OH)2Principle of creating precipitation is [Mn+].[OH-]n > Tt M(OH)

Table 1.1 pH at the starting point of the precipitation of the metals

of the OH-precipitation method Table 1.1 only shows the minimum pH possible toprecipitate heavy metals At this pH, the precipitation of the metals is not maximized

 Sulfite precipitation:

Cu2+ + S2-= CuS

Cd2+ + S2- = CdS

Ni2+ + S2- = NiS  Pb2+ + S2- = PbS  Zn2+ + S2- = ZnS

The same with OH precipitation for precipitation, [Mn+]2.[S2-]n > Tt MSn/2 (if ndivided by 2)

If not, [Mn+]2.[S]n >TtM2Sn

* Pros and Cons of the method:

Pros:

 Simple, cheap, easy to use and find materials

 Water quality after treatment meets Vietnam Quality Standards

 When making OH precipitation, it is difficult to adjust the pH for wastewatercontaining amphoteric heavy metals such as Zn

1.6.2 Absorption [14][15]

The absorption method is one of the most common methods of treatingwastewater in general and wastewater containing heavy metals in particular Themethod is used when processing waste water containing toxic levels are not high Theprocess of heavy metal absorption occurs between the liquid surface of the heavy metalsolution and the solid surface of the adsorbent

Currently, many materials have been found to absorb heavy metals such asactivated carbon, peat, inorganic materials such as iron oxide, manganese oxide, flyash, coal slag,

 Chemical absorption:

Absorption of chemistry occurs due to the reaction to form chemical bondsbetween heavy metal ions and functional groups of absorption site Normally, the

heavy metal ions react complexation with functional groups in absorbents Thisbonding is usually very durable and difficult to break, so it is difficult for thedeabsorption process.

After the absorption to treat the toxins in water in general and heavy metals inparticular, it is often carried out absorption for reconstitution, recycling (for valuableadsorbents, and must have a size that is large enough to reproduce) the adsorbent and

in many cases the precious constituents can be recovered

1.6.3 Ion exchange [14][15]

Ion exchange method is one of the most common methods for treating heavymetal ions in wastewater such as Ni2+, Fe2+, Fe3+, Cu2+, Zn2+ The method is quiteeffective in treating heavy metals, especially able to effectively recover some preciousmetals Ion exchange process takes place between the two liquid-solid phases, the ions

in the solution and the ions in the solid phase

Ion exchangers are very rich and varied, depending on the processingrequirements and conditions of use that people can choose from Ion exchangers haveinorganic sources such as: mineral metal, clay, silica, pecmutite, oxide & hydroxide ofsome metals such as chromium, aluminum, zirconium and inorganic sources such as:humic acid of humus and coal

* Mechanical Method:

In fact, the ion exchange method is a part of the absorption method, but theabsorption process is accompanied by the ion exchange between the adsorbent and theion of the solution It can be said that ion exchange is a process in which ions on thesurface of solids exchanged with ions have the same electric charge in solution whenthey contact with each other These are called ionic (ion exchange) substances, whichare completely insoluble in water

between the solution and the ion exchanger.

CHAPTER 2 EXPERIMENTAL

2.1 Materials and Apparatus

2.1.1 Materials

 Shrimp shells

 Acid chlohydric , Sodium hydroxide

 Amonium persulfate, enzyme papain, copper sulfate

 Distilled water

2.1.2 Appartus

 Thermometer

 Three neck round bottom flask, erlenmeyer flask, condenser

 Measuring cylinder & beaker

 Magnetic Stirer & stirring bar

2.2 Amonipolysacharide synthesis process.

We did this process in 2 methods

* Method 1: Use emzyme papain

Step 1:Wash the shrimp shells and dry in the oven.

Figure 2.3 Shrimp shells after washing and drying

Step 2: Demineralization

Weigh 40 g dried shimp shells and put in the cup of 1 litre, then put slowly 200

ml of 10% HC1 into immersed shimp shells It has phenomena of strong foaming, soreaction occurs (check the pH = 1-2), immerse it for about 12 hours (ovemight in roomtemperatures), stirring occasionally so that the reaction occurs rapidly (until no foam,gas escapes, pH still acid)