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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
1 ACKNOWLEDGEMENTS Through this thesis, I would like to express the deepest appreciation to the Deparment of Oil Refining and Petrochemistry for teaching me during years at HUMG Especially, I wish to thank to my instructor, Dr Nguyen Thi Linh for her supervision, guidance and help throughout the thesis of my research work and for her valuable comments on this thesis In additon, I would like to thank my friends in laboratory and my classmatesAdvanced Program K3 They were always supporting and encouraging me with their best Finally, during implementation the thesis, due to time constraint and my limited knowledge, some flaws in the process are unvoidable So I would like to receive the help of lecturers for my thesis is more complete CONTENTS Page INTRODUCTION In these day, the industry is growing rapidly and plays a important role in economy Beside the growing, it releases a lot of pollutants to enviroment, affects directly human health and ecology Ion heavy metals in wastewater of industry are like Electroplating, Steel Processing, Metallurgy, Textile dyeing, Chemicals, when released into enviroment polluting the water source, influenced so much cause by high toxicity and can accumulate in living body Heavy metal pollution is one of the most important enviroment problems for the time being However, treatments of heavy metals in wastewater in Viet Nam from factorys still didn’t care too much Because the factorys just are not too large production scale, so they restrict investment to wastewater treatment systems.With the lack of effective wastewater treatment systems, so concentration of heavy metals releasing 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 these requirements, we need proper methods that not only tackle heavy metals in wastewater but also can restrict heavy metals’s harm to enviroment and human health With the consent of Oil & Gas Department and Dr.Nguyen Thi Linh, the thesis: ”Study on chemical modification of natural aminopolysaccharide use as absorbents to remove heavy metals in wastewater” is performed * Objectives: Study on chemical modification of natural aminopolysaccharide use as absorbents to remove heavy metals in wastewater and give a method with the optimal condition to get the best result * Contents: The thesis has chapters: Chapter 1: Literature review Chapter 2: Experimental Chapter 3: Results and discusstions CHAPTER LITERATURE REVIEW Aminopolysaccharide 1.1 Introduction of aminopolysaccaride The majority of commercial polymers and ionexchange resins are derived from petroleum-basedraw materials using processing chemistry that is notalways safe or environmental friendly Today, there is growing interest in developing natural lowcostaltematives to synthetic polymers Chitin, found in the exoskeleton of shrimp shells,the cuticles of insects, and the cells walls of fungi, is the most abundant aminopolysaccharide (also known as aminopolysaccharide) in nature [1,2] This lowcost material is a linear homopolymer composed of p(l-4)-linked N-acetyl glucosamine It is structurally similar to cellulose, but it is an aminopolymer and has acetamide groupsat the C-2 positions in place of the hydroxyl groups.The presence of these groups is highly advantageous providing distinctive absorption functions and conducting modification reactions Figure 1.1 Structures of natural Aminopolysaccharide[3] The raw polymer is only commercially extracted from marine shrimp shells primarily because a large amount of waste is available as a by-product of food processing Chitin is extracted from shimp shells (shrimps, crabs, squids) by acid treatment to dissolve the calcium carbonate CaCO followed by alkaline extraction to dissolve 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 become a major concern in the seafood processing industry So, there is a need to recycle these by-products Their use for the treatment of wastewater from another industry could be helpful not only to the environment in solving the solid waste disposal problem, but also to the economy However, chitin is an extremely insoluble processes and uses of chitin, and so far, very few large-scale industrial uses have been found More important than chitin is its derivative, aminopolysaccharide Partial deacetylation of chitin results in the production of aminopolysaccharide which is aminopolysaccharide composed by polymers of glucosamine and N-acetyl glucosamine The ‘‘aminopolysaccharide label’’ generally corresponds to polymers with less than 25% acetyl content The fully deacetylated product is rarely obtained due to the risks of side reactions and chain depolymerization Copolymers with various extents of deacetylation and grades are now commercially available Aminopolysaccharide and chitin are of commercial interest due to their high percentage of nitrogen compared to synthetically substituted cellulose Aminopolysaccharide is soluble in acid solutions and is chemically more versatile than chitin or cellulose The main reasons for this are undoubtedly its appealing in trinsic properties such as biodegradability, biocompatibility, film-forming ability, bioadhesivity, polyfunctionality, hydrophilicity and absorption properties Most of the properties of aminopolysaccharide can be related to its cationic nature [1], which is unique among abundant polysaccharides and natural polymers These numerous properties lead to the recognition of this polyamine as a promising raw material for absorption purposes Demineralization Deacetylation Waste Shrimp Shells ────────> Chitin ──────────> Aminopolysaccharide Deproteinization Decoloration 1.2 Structure, physical, chemical, biological properties of aminopolysaccharide 1.2.1 Structure of aminopolysaccharide[4] Aminopolysaccharide is a partially deacetylated polymer obtained from the alkaline deacetylation of chitin by changing N-acetyl to amin group at C2, a biopolymer extracted from shrimp shells sources Aminopolysaccharide exhibits a variety of physico-chemical and biological properties resulting in numerous applications in fields such as cosmetics, biomedical engineering, pharmaceuticals, ophthalmology, biotechnology, agriculture, textiles, oenology, food processing and nutrition Aminopolysaccharide established from 2-amino-2-deoxy-p-Dglucosamin unit, contacted p-(l-4) glucozit Name: Poly(l -4)-2-amino-2-deoxy-β-D-glucose; poly( -4)-2-amino-2-deoxyβ- D-glucopyranose [ C6H11O4N]n Maminopolysaccharide = (161,07)n Chitin only has one practice group -OH, aminopolysaccharide has practice groups -OH,-NH2, so aminopolysaccharide is easier to take part in chemical reacti n than chitin Practical use of aminopolysaccharide has been mainly confined to the unmodified forms For a breakthrough in its utilization, chemical derivatization onto polymer chains has been proposed to produce new materials Derivatization is a key point which will introduce the desired properties to enlarge the field of its potential applications Aminopolysaccharide has three types of reactive functional groups, an amino group as well as both primary and secondary hydroxyl groups at the C-2, C-3 and C-6 positions Its advantage over other polysaccharides is that its chemical structure allows specific modifications without too many difficulties, especially, at the C-2 position These functional groups allow direct substitution reactions and chemical modifications, yielding numerous useful materials for different domains of application The most commonly used chemical activations are carboxymethylation, acetylation and grafting The variety of groups which can be attached to the polymer is almost unlimited 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 10 1.2.3 Biological properties [7] Biocompatibility • Non-toxic • Biodegradable • Adsorbable Bioactivity • Antimicrobial activity (fungi,bacteria, viruses) • Antacid, antiulcer, and antitumoral properties • Blood anticoagulants • Hypolipidemic activity • Bioadhesive 1.3 Applications of aminopolysaccharide [7] The potential industrial use of aminopolysaccharide is widely recognized This versatile material is used in biomedical engineering, pharmacy, dentistry, ophthalmology, biotechnology, chemistry, cosmetics, textile, pulp and paper, oenology, food industry, agriculture and photography 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 • Sutures/bandages • Ophthalmology, contact lenses Biotechnology • Enzyme and cell immobilization • Cell-stimulating materials • Matrix for affinity chromatography or membranes • Chemical industry • Water purification (metal chelation); water engineering (flocculation, filtration, absorption); sludge treatment • Reverse osmosis, filtration membranes; gasseparation • Production ofbiodegradable packagingfilms • Catalysis 26 To survey the effect of material ratio, during the experiment, change the APSAMS by 1: 1, 1: 2, 1:3, 1:4 Using the IR spectroscopy to determine the DD, compare the samples we get, so derive the most appropriate proportion of the material for the modification 2.2.5 Investigation on effect of reaction time Each reaction has a certain reation time in order to get the highest efect Therefore, it is necessary to survey the effect of modification Similar to survey the effect of temperature and material ratio, we change the response time to 1h, 2h, 3h, 4h Using IR spectroscopy to analysis, recalculated deacetylation and conclude the appropriate time for modification 2.3 Evaluation of the ability of treating heavy metal in wastewater of APS-AMS material The ability of treating heavy metals in wastewater of APS-AMS material is demonstrated by the ability of absorbing metals in the solution between Cu + and distilled water We have carried out the following steps: - Mix samples of copper (Cu2 +) solution with concentration 10 mg/l, 20 mg/l, 30 mg/l, 40 mg/l, 50 mg/l * Investigation of the effect of absorption amount on absorption Weight adsorbent (APS-AMS) different in 10ml solution for Cu + with concentration of 20mg/l Perform absorption under conditions like the table below Table 2.2 Effect of amount of absorbent Amount of absorbent (APS-AMS) (g) Time of contact (minutes) Concentratio n of Cu2+ (mg/l) 0.1 0.15 30 30 20 20 20 3 30 20 7 0.3 30 7 0.25 30 pH 0.2 20 7 7 * Investigation of the effect of Cu2+ concentration Weigh 0.15g of APS-AMS adsorbent in 10mls of Cu 2+ solution at different concentrations Perform absorption under conditions like the table below 27 Table 2.3 Effect of concentration of Cu2+ Amount of absorbent(AP S-AMS) (g) 0.15 Time of contact (minutes) 30 0.15 Concentratio n of Cu2+ (mg/l) 10 pH 0.15 30 0.15 30 20 7 40 30 7 0.15 30 30 50 7 7 2.3.1 Investigate the effects of contact time Weigh 0.15g of APS-AMS adsorbent in 10ml of Cu 2+ solution at concentration of 20mg/l Perform absorption under conditions like the table below Table 2.4 Effect of contact time Amount of absorbent( APSAMS)(g) Time of contact (minutes) Concentrat ion of Cu2+ (mg/l) 0.1 0.1 10 3 50 20 7 0.1 40 20 7 0.1 30 20 pH 0.1 20 20 20 7 7 * Investigate the effect of pH in solution Weigh 0.15g of APS-AMS adsorbent in 10ml solution for Cu2+ with concentration of 20mg/l The sample solution is adjusted pH with NaOH or HCl to reach different pHs Perform absorption under conditions like the table below Table 2.5 Effect of pH 28 Amount 0 of 0.1 0.1 0.1 absorben 5 t (APSAMS) (g) Time of 3 contact 30 30 30 (minutes ) Concentr 2 ation of 20 20 20 Cu2+ (mg/l) 7 pH 0 0.1 0.1 5 30 30 20 20 11 2.4 Methods of product structure analysis 2.4.1 Infrared spectroscopy (IR spectroscopy) analyses the components and structure of aminopolysacharide [16] Infrared spectroscopy (IR spectroscopy) is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light It covers a range of techniques, mostly based on absorption spectroscopy As with all spectroscopic techniques, it can be used to identify and study chemicals For a given sample which may be solid, liquid, or gaseous, the method or technique of infrared spectroscopy uses an instrument called an infrared spectrometer (or spectrophotometer) to produce an infrared spectrum A basic IR spectrum is essentially a graph of infrared light absorbance (or transmittance) on the vertical axis vs frequency or wavelength on the horizontal axis Typical units of frequency used in IR spectra are reciprocal centimeters (sometimes called wave numbers), with the symbol cm-1 Units of IR wavelength are commonly given in micrometers (formerly called "microns"), symbol µm, which are related to wave numbers in a reciprocal way A common laboratory instrument that uses this technique is a Fourier transform infrared (FTIR) spectrometer Two-dimensional IR is also possible as discussed below The infrared portion of the electromagnetic spectrum is usually divided into three regions: the near-, mid- and far- infrared, named for their relation to the visible spectrum The higher-energy near-IR, approximately 14000—4000 cm -1 (0.8-2.5 µm wavelength) can excite overtone or harmonic vibrations The mid-infrared, approximately 4000-400 cm-1 (2.5-25 µm) may be used to study the fundamental vibrations and associated rotational-vibrational structure The far-infrared, 29 approximately 400-10 cm~l (25-1000 pm), lying adjacent to the microwave region, has low energy and may be used for rotational spectroscopy The names and classifications of these subregions are conventions, and are only loosely based on the relative molecular or electromagnetic properties 2.4.2 ICP-OES method to analyses the concentration of heavy metals in wastewater [17] The ICP-OES technique is the method that determination of a large number of elements The detection limits for these elements are generally in the µg/L (ppb) range As in many techniques, the detection limit is regarded as the lowest concentration at which the analyst can be relatively certain that an element is present in a sample Measurements made at or near the detection limit, however, are not considered to be quantitative For purposes of rough quantitation (±10%), it is recommended that an element’s concentration should be at least five times higher than the detection limit For accurate quantitation (±2%), the concentration should be greater than 100 times the detection limit In ICP-OES method, the light emitted by the excited atoms and ions in the plasma is measured to obtain information about the sample Because the excited species in the plasma emit light at several different wavelengths, the emission from the plasma is polychromatic This polychromatic radiation must be separated into individual wavelengths so the emission from each excited species can be identified and its intensity can be measured without interference from emission at other wavelengths The separation of light according to wavelength is generally done using a monochromator, which is used to measure light at one wavelength at a time, or a polychromator, which can be used to measure light at several different wavelengths at once The actual detection of the light, once it has been separated from other wavelengths, is done using a photosensitive detector such as a photo-multiplier tube (PMT) or advanced detector techniques such as a charge-injection device (CID) or a charge-coupled device (CCD) 2.4.3 Determine the degree of deacetylation (DD) The degree of deacetyiation is the ratio of replacing -NHCOCH3 group in chitin with - NH2 group • Infrared spectra make the KBr disks, at a frequency range of 4000-400cm -1 DD (%) = 100 – [(A1650/A3540) 100/1.33] Where, A1655 and A 3450 are the absorbencies at 1655 cm-l(N-acetyl content) and 3450 cm-1 (hydroxyl group) respectively If: DD < 50% : chitin DD > 50%: aminopolysaccharide The methods to determine DD: - Proton nuclear magnetic resonance - IR spectroscopy - Total number nitrogen 30 CHAPTER RESULTS AND DISCUSSION 3.1 The results of systhesis amonipolysaccharide After performing methods : enzyme papain and microwave,we obtained white sample and want to check whether this is aminopolysaccharide or not So, we put sample into CH3COOH and stir It’s totally dissoveled after 5-10 minutes Accoring to physical properties of aminopolysaccharide, we can determine that the sample is aminopolysaccharide Figure 3.11 Image of Aminopolysaccharide is dissvolved in CH3COOH So, this is the results of methods of treating aminopolysaccharide: 3.1.1 Enzyme papain 31 Figure 3.12 Image of Aminopolysaccharide product(enzyme method) • Characterization of amonipolysaccharide product by FT-IR method Figure 3.13 FT-IR spectroscopy of aminopolysaccharide(enzyme method) As shown in the figure 3.1, FT- IR spectrum of Aminopolysaccharide showed strong band at 1030, 1081 and 1381 cm-1 characteristic of saccharide structure ( due to O-H bending, C-H stretching, C-N stretching) The strong band at 3475 cm -1 could be assigned to the extension vibration of -NH of amino polysaccharide The absorption band at 1643 cm-1 characteristic of unconverted acetyl group of chitin Depend on the absorption bands of amin group and acetyl group of aminopolysaccharide from FT-IR spectrum, we can determine Degree of Deacetylation (DD) of aminopolysaccharide product: Aminopolysaccharide use enzyme papain method has DD= 82,3 % 32 3.1.2 Microwave Figure 3.14 Image of Aminopolysaccharide product(microwave method) • Characterization of amonipolysaccharide product by FT-IR method Figure 3.15 FT-IR spectroscopy of aminopolysaccharide(microwave method) Aminopolysaccharide use microwave method has DD= 79,2 % 33 3.2 Amonipolysaccharide modification result * The results of investigation on effect of material ratio Figure 3.16 FT-IR spectroscopy of APS-AMS 1:1 ratio Figure 3.17 FT-IR measurement result of APS-AMS 1:2 ratio Figure 3.18 FT-IR spectroscopy of APS-AMS 1:3 ratio Figure 3.19 FT-IR spectroscopy of APS-AMS 1:4 ratio 34 The FT- IR spectrum of APS- AMS showed strong band at 1055 and 1029 cm -1 characteristic of stretching vibration of sulfate group This sign could be determined present of sulfate group in APS-AMS material That mean is reacted crosslinking The strong band at 3475 cm-1 could be assigned to the extension vibration of -NH2 of amino polysaccharide The absorption band at 1643 cm-1 characteristic of unconverted acetyl group of chitin Table 3.6 The result of Degree of Crosslinking of APS – AMS(material ratio) Sample APS-AMS Temperature(ºC) Reaction DD(%) Degree of ratio time(h) crosslinking of APSAMS 1:1 60 68.22 17.37 1:2 60 58.53 28.91 1:3 60 33.24 59.61 1:4 60 39.65 51.88 As a result, we can derive that the sample with APS-AMS ratio 1:3 has the highest degree of crosslinking of APS-AMS = 59.61% 3.2.1 Effect of reaction time Figure 3.20 FT-IR spectroscopyof APS-AMS 1h reaction time Figure 3.21 FT-IR spectroscopyof APS-AMS 2h reaction time 35 Figure 3.22 FT-IR spectroscopyof APS-AMS 3h reaction time Figure 3.23 FT-IR spectroscopy of APS-AMS 4h reaction time Table 3.7 The result of Degree of crosslinking of APS – AMS(reaction time) Sample APS-AMS Temperature(ºC) Reaction DD(%) Degree of ratio time(h) crosslinking of APSAMS 1:3 60 40.52 50.76 1:3 60 33.24 59.61 1:3 60 36.24 55.96 1:3 60 37.95 53.88 As a result, we can derive that the sample with reaction time 2h has the highest degree of crosslinking of APS-AMS = 59.61% 3.2.2 Effect of reaction temperature Figure 3.24 FT-IR spectroscopy of APS-AMS 50ºC reaction temperature 36 Figure 3.25 FT-IR spectroscopy of APS-AMS 60ºC reaction temperature Figure 3.26 FT-IR spectroscopy of APS-AMS 70ºC reaction temperature Figure 3.27 FT-IR spectroscopy of APS-AMS 80ºC reaction temperature Table 3.8 The result of Degree of crosslinking of APS – AMS reaction temperature Sample APS-AMS Temperature(ºC) Reaction DD(%) Degree of ratio time(h) crosslinking of APSAMS 1:3 50 45.96 44.16 10 1:3 60 33.24 59.61 11 1:3 70 52.15 36.63 12 1:3 80 47.71 42.03 37 As a result, we can derive that the sample with temperature 60°C has the highest degree of crosslinking of APS-AMS = 59.61% From all of results above, we can get the best result of APS-AMS modification is APS-AMS ratio 1:3, reaction time 2h, teamperature 60ºC and using it to remove Cu2+ in wastewater 3.3 Results of the ability of absorption heavy metal in wastewater of APS-AMS material 3.3.1 Effect of absorption amount We survey the change of amount APS-AMS from 0,1g -> 0,3g and keep stable concentration of Cu2+=20mg/l, contact time = 30 minutes, pH = The result is illustrated in figure 2.14 Figure 3.28 Effect of absorption amount on absorption From the chart, we can see that if we increase the amount of APS, so the reaction efficiency will increase Initially, the Cu 2+ treatment efficiency was only about 54.4% when treated with a 0.1 g APS-AMS, increasing the amount of APS-AMS from 0.1g -> 0.15g, so the reaction efficiency will be increased remarably from 54.4% to 71.6% and slightly from 0.15g-> 0.3g( 71.6% -> 76.85%) We realize that the efficiency of water treatment with amount of APS-AMS is 0.15 g and 0.3 g is not much different Because the certain processing efficiency has been reached, the extra absorption capacity is very little(the balance between the adsorbent and the adsorbent is reached) 3.3.2 Effect of Cu2+ concentration We survey the change of Cu2+ concentration from 10mg -> 50mg and keep stable amount APS-AMS = 0,15g, contact time = 30 minutes, pH = The result is illustrated in figure 2.15 Figure 3.29 Effect of cencentration of Cu2+ on absorption From the chart, we can see that if we increase the concentration of Cu 2+, so the amount of Cu2+ absorbed will decrease.It decreased slightly from 10 mg to 30 mg(79.7% -> 69.2%) and remarkably from 30mg to 50mg(69.2% -> 48.62%) It’s clear because amount of APS-AMS using is just 0,15g, so it’s easy to absorb wastewater with concentration is 10 mg/l and more difficult to absorb at higher levels because absorption sites are filled with Cu 2+, so it will be absorbed little Cu 2+ at high concentration 38 3.3.3 Effect of contact time We survey the change of contact time from 10 mintes -> 50 minutes and keep stable amount APS-AMS = 0,15g, concentration of Cu 2+=20mg/l , pH = The result is illustrated in figure 2.16 Figure 3.30 Effect of contact time on absorption From the chart, we can see that the reaction efficiency increased remarkably from 10 minutes -> 20 minutes(58.25% -> 71.6%) and very slightly from 20 minutes-> 50 minutes(71.6% -> 74.75%) From the results above, the fastest rate of Cu 2+ absorption at 20 minutes this is very important when applied in industrial wastewater treatment because short stirring time does not take up much power and therefore can save processing costs Reaction efficiency increases over time, but when the process is almost equilibrated, it will slows down because the absoprtion sites are filled with Cu2+ 3.3.4 Effect of pH We survey the change of pH from 3->11 and keep stable amount APS-AMS = 0,15g, concentration of Cu2+=20mg/l , contact time = 20 minutes The result is illustrated in figure 2.17 Figure 3.31 Effect of pH on absorption From the figure, the effect of absorption is rather low in the presence of strong acidic media At pH=3, the yield was only 32.6% and at pH = was 36.6% This is clear because in acidic environments, H+ ions will compete with Cu2 + ions to combine with the –NH2 group of aminopolysaccharide at the same link site with aminopolysaccharide Thus, the higher the acid concentration (or higher the concentration of H +), the lower the absorption capacity because the NH group changes to NH3+ as much as the lechatelier principle On the other hand, when the pH is low, the aminopolysaccharide also partially dissolves into the membrane, which interferes with the filtration process after absorption, making filtering process very slow In alkaline, neutral and weak acids, the groups -OH and -CH2OH divide H+ and become negatively charged, thus enhancing their ability to combine with Cu 2+ ions This is clearly shown on the chart, in the alkaline medium, neutral acidity is weak, so the efficiency of the absorption process is quite high pH=7 was 71.6 %,pH=9 was 67.15%, pH=11 was 65.6 % Optimal pH to perform the absorption process: pH = 39 CONCLUSION AND RECOMMENDATION * Conclusion: Chitin is transformed from shrimp shells to aminopolysacchride (APS) by enzyme and microwave methods Results showed that APS was metabolized by enzyme has higher DD = 82.3 % but need more much time to perform( roughly days) In contrast, the microwave method has a little bit less degree of deacetylation than enzyme method with DD= 79,2%, but it just takes hours to obtain aminopolysaccharide The results of methods is relatively high Some conditions affecting the APS-AMS modification have been investigated The results show the appropriate process at APS-AMS ratio 1:3, time reaction 2h, temperature 60ºC Initial evaluations of the ability of heavy metal absorption in waste water by APS-AMS material was quite good * Recommendation: The results of this study are the first step towards the introduction of APSAMS material However, for practical purposes, the thesis needs to study other methods to improve the ability to modify APS-AMS with higher metabolism The thesis also needs to study the influence of other conditions that affect the ability of absorbing heavy metals in wastewater of APS-AMS material 40 REFERENCE [1] Synowiecki J, Al-Khateeb NA Production, properties, andsome new applications ofchitin and its derivatives Crit Rev Food Sci Nutrition [2] Struszczyk MH Chitin and aminopolysacharide—part I Propertiesand production Polimery [3] https://www.researchgate.net/figure/263324738_fig2_Figure-2-Chitosan-chemicalstructure [4] Thi Luyen Tran Huynh Nguyen Duy Bao and a port number is "Improving production processes chitin - a Sosan aminopolysacharide and Processing industrial products from scrap shrimp-crab" Scientific reports, detai ministry Nha Trang, 2000 [5] http://www.mpikg-golm.mpg.de/kc/scripts/Polysaccharide.pdf “Supramolecular Biopolymers II - Polysaccharides” [6] Application of aminopolysacharide, a natural aminopolysaccharide, for dye removal from aqueous solutions by absorption processes usingbatch studies: A review of recent literatureGre 'gorio Crini [7] Hg(II) removal from water by chitosan and chitosan derivatives: A review P Miretzkya,∗, A Fernandez Cirelli [8] http://www.sciencedirect.com/science/article/pii/S1878535210001334 [9] Doan Van Kiet (2005), Some common trace elements in water and their influence, Agricultural Publishing House [10] Trinh Thi Thanh (2003), Toxicology, Environment and Human Health, National University Publisher, Hanoi [11] Nguyen Thu Thuy (2008), Research and exploration of the use of bio-based adsorbents derived from fish waste (aminopolysaccharide) for heavy metal treatment (Cr6+ ), Thesis , Hanoi Polytechnic University [12] https://www.chem.info/blog/2016/10/current-methods-removing-heavy-metalsindustrial-wastewater [13] Le Van Cat (2002), absorption and ion exchange in wastewater and wastewater treatment techniques, Statistical Publishing House, Hanoi [14] Tran Van Nhan, Ngo Thi Nga (1999), Wastewater Treatment Technology, Science and Technology Publishing House [15]https://www.researchgate.net/publication/233379998_Is_Aminopolysaccharide_a_ New_Panacea_Areas_of_Application [16]https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/Spectrpy/InfraRed/infrar ed.htm [17] https://www.perkinelmer.com/lab-solutions/resources/docs/GDE_Concepts-ofICP-OES-Booklet.pdf ... 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 n divided by 2) 17 n+ ]2. [S]n... precipitated metal hydroxide 2+ - Cu + 2OH = Cu(OH )2 2+ Cd + 2OH = Cd(OH )2 2+ Ni + 2OH = Ni (OH )2 3+ Cr + 3OH = Cr (OH)3↓ 16 3+ - Fe + 3OH = Fe (OH)3↓ 2+ Zn +2OH = Zn (OH )2 n+].[OH-]n > T Principle... aminopolysaccharide Figure 2. 10 Aminopolysaccharide (microwave method) 2. 2.1 General Process( diagram) 25 2. 2 .2 Deacetylation process The reaction produce amino polysaccharide by deacetylation chitin[16] By deacetylation