Study on the synthesis and application of polymer containing suitable funtional groups for seperation some light rare earth elements

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY ----------------------------- HOANG THI PHUONG STUDY ON THE SYNTHESIS AND APPLICATION OF POLYMER CONTAINING SUITABLE FUNTIONAL GROUPS FOR SEPERATION SOME LIGHT RARE EARTH ELEMENTS NGƯỜI H Scientific Fied: Organic Chemistry Classification Code: 9.44.01.14 S. Nguyễn Văn Khôi DISSERTATION SUMMARY HA NOI - 2018 The dissertation was completed at: Institute of Chemistry Vietnam Academy of Science and Technology Scientific Supervisors: 1. Prof. Dr. Nguyen Van Khoi Institute of Chemistry – Vietnam Academy of Science and Technology 2. Dr. Trinh Duc Cong Institute of Chemistry – Vietnam Academy of Science and Technology 1st Reviewer : . 2nd Reviewer: . 3rd Reviewer: . The dissertation will be defended at Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay District, Ha Noi City. At hour.date.month.2018 The dissertation can be found in National Library of Vietnam and the library of Graduate University of Science and Technology, Vietnam Academy of Science and Technology. 1 INTRODUCTION 1. Background Rare earths are the special minerals, which are considered by many countries in the world and classified on material grade that can’t be replaced because they have many special properties. Rare earth elements play a very important role in development of high-tech fields, such as: electricity, electronics, optics, lasers, superconductors materials and luminescent materials. Thus, the title of dissertation was proposed: “Study on the synthesis and application of polymers containing suitable funtional groups for seperation some light rare earth elements”, to study on synthesize, characterization and application of polymers for sorption some light rare earth elements. 2. Objectives of the dissertation Successfully synthesis polymers containing suitable funtional groups to seperate the light rare earth element (La, Nd, Pr, and Ce); evaluted the efficiency of polymers on seperating light rare earth element; evaluated the ability of polymers on separating each of the rare earth metal ions on the ion exchange column. 3. Main contents of dissertation - Synthesis polymers containing suitable funtional group for the separation of the rare earth elements: + Synthesis poly(hydroxamic acid) from acrylamide (PHA-PAM). + Synthesis poly(hydroxamic acid) from acrylamide and vinyl sulfonate (PHA-VSA). - Studied on adsorption, desorption process; and evaluted the ability of two polymers on adsorpting some light rare earth metal ions (La3+, Ce4+, Pr3+ and Nd4+). - Studied and evaluted the capable of PHA resin on seperating some light rare earth elements (La3+, Ce4+, Pr3+ and Nd4+). 4. Structure of the thesis The dissertation has 138 pages, including the literature review, experiment, results and discussions, conclusions, pubblication, with 45 2 images, 45 tables and 114 references. B. CONTENTS OF DISSERTATION CHAPTER I. LITERATURE REVIEW An overview of domestic and foreign publications on rare earths, methods for seperate light rare earth metal ions; overview researchs on synthesis and application of polymers containing suitable funtional groups to separate rare earth metal ions. From there, the research orientation of the dissertation were proposed. CHAPTER II. EXPERIMENTAL 2.1. Materials and equipments 2.1.1. Materials Acrylamide (AM), Sodium vinyl sulfonate (VSA), Ammonium persulfate; N, N’ - methylene bisacrylamide hydroxylamine hydrochloride (HA); Span 80, Paraffin oil, diesel oil, Dowex HCR-s resin, Amberlite IR 120 resin, standard solution: La(NO3)3, Ce(NO3)3, Pr(NO3)3, Nd(NO3)3; solution which contain light rare earth metal ions with content: La3+ 36.76 wt%, Ce4+ 47.79 wt%, Pr3+ 4.41 wt%, Nd3+ 11.03 wt% was seperated and provided by Institute for Technology of Radioactive and Rare Elements, Vietnam. Chemicals for analysis: distilled water, NaOH, NaHCO3,HCl, H2SO4, CH3OH,C2H5OH, C20H14O4, HNO3, C6H14, CHCl3, H2C2O4, CH3COOH, CH3COONa were used without purification. 2.1.2. Equipments Equipments for suspension polymerization with three-liter of volume, ion exchange column, vacum dry cabinet, thermostatic tank, analytical balance, magnetic stirrer instrument, thermometer, flasks, the condenser system, triangular flasks, pipette,...IR spectrometer, Perkin Elmmer emission spectrometer, thermogravimetric analyze instrument, FESEM scanning electron microscope, pH measuring equipment. 2.2. Methods 2.2.1. Synthesis poly(hydroxamic acid) based on acrylamide Processes of synthesize cross-linking polyacrylamide (PAM gel) and 3 synthesize poly(hydroxamic acid) (PHA) based on cross-linking polyacrylamide were presented in figure 2.4-2.6. Figure 2.4. Synthesis of PAM-gel Figure 2.6. Sythesis of poly(hydroxamic axit) based on modification of Filtered - Acrylamide: C% - MBA - APS Dispersed Phase V2 (ml) Continuous Phase V1 (ml) - Diesel - Span 80 Feed speed: 10ml/min Reaction flask with 3 liters of volume Cross-linking PAM Washed by n- hexane Cross-linking PAM (granulate form with same size) Dried at 60oC long in 5 hours Invesstigated the factors: - AM Concentration - Temperature and time - Content of MBA - Content of ABS - Content of Span 80 - The stirrier speed - Monomer phase/oil phase ratio PAM-gel (10 g PAM + 50 g H2O) Add NH2OH.HCl solution with concentration: 1-3.5 M, pH:10-14 Stirred: 100 rpm Time: 30 minutes Reation mixture: temperature T (oC), time t (min) Filtered Washed by water to pH=7 Dried: 60oC, in 5 hours Polyhydroxamic acid (granulate form had similar size and light yellow of colour) Reaction flask with 3 liters of volume Invesigated the factors - Temperature and time of reation - pH of medium -Concentration of NH2OH.HCl 4 PAM-gel 2.2.2. Synthesis poly(hydroxamic acid) from acrylamide and sodium vinyl sulfonate 2.2.2.1. Co-polymerization process of acrylamide and sodium vinyl sulfonate To investigated the coefficient of copolymerization process, controlled the conversion of reactions ≤ 10% (by reacting at very low concentration condition, experimented several times to conversion reached ≤ 10%). Synthesis 5 samples of copolymer with difference of VSA/AM molar ratio: 10/90, 30/70, 50/50, 60/40, 70/30 and 90/10; other conditions of reaction didn’t change. 2.2.2.2. Synthesis cross-linking P(AM-co-VSA) by suspension polymerization Process of synthesize cross-linking P(AM-co-VSA) was similar the suspension polymerization of AM; monomer were AM and VSA with VSA/AM weight ratio was 60/40. 2.2.2.3. Modification of P(AM-co-VSA) to poly(hydroxamic acid) modified processes of copolymer of AM and VSA (P[AM-co-VSA]- gel) were carried out similarly the modification of PAM-gel to PHA-PAM. 2.2.3. Adsorption and de-adsorption the rare earth matal ions by PHA-PAM and PHA-VSA Adsorption: take 0.15 g PHA-PAM (or PHA-VSA) to reation flask containing 50 ml each of ion solution: La3+, Ce4+, Pr3+ and Nd3+ with research concentration, strirred at room temperature. After reation time, measured the remaining concentration of each metal ion in solution using ICP-OES method. * Investigated the factors that effect on adsorption process: pH, time, initiator concentration of metal ions. * Adsorption isotherms: From the results obtained when investigated of factors on the adsorption process, Langmuir isotherm models was constructed. 2.2.4. Studied on desorption and repeated use of poly(hydroxamic acid) resin Conducted six adsorption - desorption cycles using 0.15g of adsorbent material. After each cycle, measured the percentage of metal adsorbed, the percentage of metal desorbed and the loss weight of 5 absorbent. 2.2.5. Absorbed the light rare earth ions on column by PHA-PAM Process of seperation light rare earth metal ions was showed in figure 2.8 Figure 2.8. Process of seperation light rare earth metal ions from rare earth metal solution by PHA resin CHAPTER III. RESULTS AND DISCUSSION 3.1. Study on synthesis of poly(hydroxamic acid) based on acrylamide 3.1.1. Study on synthesis of cross-linked polyacrylamide (PAM-gel) Eluted by HCl: 0,6M Eluted by HCl: 0,1M Eluted by HCl: 0,2M Eluted by HCl: 0,4M Light rare earth metal ions composition: La3+, Nd3+, Pd3+ và Ce4+ - Concentration: 500mg/l -pH=6; acetate buffer: 0.5 M Ion exchange column - Dcolumn : 20mm - Lcolumn : 800mm - Lresin : 500mm Quantitative pump - : 130 ml/minute Adsorbed in 180 minutes Washed with HCl 0.5M - Flow: 3-7 ml/minute - Vr/Vn: 3/1 – 18/1 Nd3+ rich fraction Pd3+ rich fraction Ce4+ rich fraction Adsorbed and desorped each fraction on ion exchange column 6 In this study, the continuous phase used was diesel oil. Factors influencing product properties were investigated such as temperature (70- 95oC) and time (60-240 min), monomer concentration (15-35%), APS concentration (0, 5-1.75), crosslinker concentration (7-11%), monomer / oil phase ratio (1 / 5-1 / 3), surfactant span 80 concentration (0.1-0, 35) and stirring speed (200-400 rpm). The results are presented in tables 3.1- 3.6) Table 3.1. Effect of temperature and reaction time on characterization of PAM-gel Temp. (oC) Time (min) Gel1 (%) D2TB (m) Product characteristics 70 180 91,4 - Granular, block 240 95 - Granular, block 80 60 94,8 ~ 180 Granular, block 90 98,6  187 Discrete round granular 90 60 99,5 230 Discrete round granular 95 60 - - block Reaction efficiency reached the maximum value at 90oC, 60 minutes. Thus, the condition of 90oC and 60 minutes was chosen as the reaction condition for the next study. Figure 3.1. Effect of monomer concentration and reaction time on gel content of PAM-gel When the monomer concentration increases from 15% to 30%, the gel content increases and the reaction time decreases. However, when monomer concentration is high (35% sample), the polymerization process is very fast, difficult to control the reaction process. Therefore, 30% monomer was chose for optimal reaction temperature and time. 1Gel content of products 2 Average granular diameter of the product 0 20 40 60 80 100 G el c o n te n ts ( % ) Time (min) 35% 30% 25% 20% 15% 7 Table 3.2. Effect of initiator concentration on gel content and swelling capacity of PAM-gel KPS concentration, % 0,5 0,75 1,0 1,25 1,5 1,75 Gel content, % 93,2 96,8 99,5 98,4 98,0 97,3 Swelling capacity, g/g 3,2 3,9 4,7 4,2 3,8 3,6 Results showed that the optimum KPS concentration for PAM-gel synthesis was 1.0%. Table 3.3. Effect of crosslinker concentration on swelling capacity and gel content of PAM-gel MBA concentration (%) 7 8 9 10 11 Swelling capacity (g/g) 6,2 5,8 5,5 4,7 4,1 Gel content (%) 98 98 98,4 99,5 99,5 Increasing of crosslinker concentration from 7 to 11%, reduce the swelling capacity from 6,2 to 4,1 g/g. Chosen MBA content is 10% for next study. Table 3.4. Effect of ratio of monomer/oil phase on particle characteristics Ratio of monomer/oil phase Average diameter of granular` DTB(m) Characteristics and separability of granular 1/5  225 Round granules, evenly 1/4  230 Round granules, evenly 1/3 - partially blocked At a monomer/oil phase ratio of 1/4, the granulation process is better, distributing the particle size more uniformly than the rest. Table 3.5. Effect of suspension stabilizer on particle characteristics Span 80 content (%) Gel content , % Average diameter of granular DTB(m) Characteristics and separability of particles 0,10 99,2 - Unround granules, block 0,20 99,6 - Unround granules, block 0,30 99,5  230 Round granules, evenly 0,35 98,5 - Granular and partially emulsified 8 Results in table 3.5 showed that, with 0,3% span 80, product are round granules, evenly. Table 3.6. Effect of stirring speed on particle size distribution Stirring speed (rpm) Particle size distribution (%) 500(m) 200  7  55  38 300  4 92 4 400  38  57 5 With 300 rpm, the product is more uniform, with a particle size of 100-500m is 92% (Average diameter of granular is about 230 m). Thus, the optimal conditions for PAM-gel synthesis are: Reaction temperature 90oC for 60 minutes, 30% of monomer, 10% of crosslinker (in monomer), 1% of initiator, 0,3% of Span 80 at 300 rpm and ¼ of the phase ratio monomer/oil. + Characteristic of PHA-gel: Particle size distribution with D ~230 µm, swelling capacity: 4.7 g/g and gel content of 99.5%. 3.1.2. Sythesis of poly(hydroxamic axit) based on modification of PAM-gel To study the modification of PAM-gel into poly(hydroxamic acid) (PHA-PAM) by hydroxylamine, PAM-gel are 100-500 µm in size, humidity <58%. Study on factors affacting the modification of acrylamide group to hydroxamic acid group such as temperature (25-40oC), time (0-24 hours), pH (pH=10-14) and concentration of NH2OH.HCl (1.0-3.5M). The results are shown in figure 3.6 and tables 3.9-3.10. Figure 3.6. Effect of reaction temperature and time on funtional group content When the temperature increases form 250C to 300C, -CONHOH content increases from 9,8 to 11,4 mmol/g after 24h. Table 3.9. Effect of pH on funtional group content pH -CONH2 (mmol/g) - COOH (mmol/g) - CONHOH (mmol/g) 0 2 4 6 8 10 12 0 6 12 18 24 -C O N H O H ( m m o l/ g ) Time (hrs) 25 0C 30 0C 40 0C 9 10 12,93 1,25 1,14 11 12,57 1,50 1,25 12 8,54 1,75 5,03 13 3,94 1,70 9,68 14 2,30 1,68 11,34 Table 3.9 shows that the pH in the 10-11 range, the modification is very slow (low -CONHOH content). In the pH range of 12-14, the content of -CONHOH group increased gradually and reached the maximum value at pH=14. Table 3.10. Effect of NH2OH.HCl concentration on funtional group content NH2OH.HCl Concentration (M) -CONH2 (mmol/g) -COOH (mmol/g) -CONHOH (mmol/g) 1,0 5,38 1,45 8,49 2,0 4,39 1,57 9,36 3,0 3,09 1,61 10,62 3,3 2,30 1,68 11,34 3,5 2,26 1,72 11,34 Table 3.10 shows that at the concentration of NH2OH.HCl 3.3M, the content of -CONHON group is the highest. ➢ Physical and chemical characteristics of PHA-PAM Characteristic properties of PHA-PAM are evaluated by FTIR spectroscopy, thermo gravimetric analysis (TGA), scanning electron microscopy (SEM). The results are shown in Tables 3.11-3.12 and Figures 3.9-3.10. Table 3.1. FTIR characteristic of groups in PHA-PAM Wavenumber (cm-1) Bending Funtional group 3436-3190 N-H, -OH Amine (-NH2), -COOH 2928 C-H Alkyl (-CH2) 2857 C=N -CONHOH (enol form) 1668 C=O Cacbonyl (-C=O) 1009 N-O -CONHOH 10 Hình 3.9. TGA curves of PHA-PAM Hình 3.10. SEM image of PHA-PAM Table 3.12. The PHA-PAM thermal analysis data Stage Range of temp. oC TMax, oC Loss weight, % 1 Tp-220 186 9,33 2 220-340 307 17,81 3 340-450 385 35,15 The optimal conditions for the modification of PAM-gel into PHA- PAM are 3.3 M hydroxylamine hydrochloride, at 30oC for 24 hours at pH 14. PHA-PAM contains -CONH2 group content of 2.3 mmol/g, -COOH group 1.68 mmol/g and -CONHOH group 11.34 mmol/g. 3.2. Synthesis of poly(hydroxamic axit) based on acrylamide and sodium vinyl sulfonate 3.2.1. Copolymerization of acrylamide và sodium vinyl sulfonate 3.2.1.1. Effect of reaction temperature, time and initiator concentration The temperatures were studied 65, 70, 75oC, time range of 60-24 minutes, initiator concentration: 0,5; 0,75; 1; 1,2%. The results are shown in figure 3.11-3.12. 11 Figure 3.10. Effect of reaction temperature and time on conversion Figure 3.11. Effect of initiator cocentration on conversion The react condition was chosen: temp. 70oC, time 180 minutes and 1% initiator. 3.2.1.2. Determine the reactivity ratios of monomers Determination of intermediate coefficients  and  in the Kelen- Tudos equation. The results are shown in Table 3.14. Table 3.14. Determination of coefficients  và  Mẫu M1 0,111 0,175 0,07 -0,52 0,88 0,07 -0,55 M2 0,429 0,630 0,29 -0,25 0,25 -0,21 M3 1,000 1,070 0,93 0,07 0,51 0,04 M4 1,500 1,580 1,42 0,55 0,97 0,40 M5 2,333 2,380 2,29 1,35 0,72 0,43 M6 9,000 7,310 11,08 7,77 0,93 0,65 From equation  = 1,3883 – 0,6197 with α = 0,88 extrapolation to  = 0 so rVSA = 0,547,  = 1 so rAM = 0,768. 3.2.2. Copolymerization of acrylamide and sodium vinyl sulfonate by suspension polymerization In this study, continuous phase is diezen oil. Factors influencing product properties were investigated such as temperature (70-90oC) and time (60-240 min), monomer concentration (4,63-40%), APS concentration (0, 5-1.75), crosslinker concentration (7-11%), monomer / oil phase ratio (1 /5-1/3), surfactant span 80 concentration (0.1-0, 35) and stirring speed (200-400 rpm). The results are presented in tables 3.15-3.20) 0 20 40 60 80 100 0 60 120 180 240 C o n v er si o n ( % ) Time (min) 65 oC 70 oC 75 oC 0 20 40 60 80 100 0 60 120 180 240 0,50% 0,75% 1,00% 1,20%C o n v er si o n ( % ) Time (min) x M M = ][ ][ 2 1     y Md Md = 2 1 y x F 2 = y yx G )1( − = maxminFF= F F + =   F G + =   12 Table 3.15. Effect of reaction time and temperature Temp. (oC) Time (phút) Gel3 (%) D4TB (m) Characteristics of product 700C 180 93 - Granular, block 240 100 175 Granular, unblock 800C 60 - - Granular, adhesive 90 100  230 Even round granules, separately 900C 60 100 232 Even round granules, separately Table 3.16. Effect of crossliker concentration on gel content and swelling capacity of copolymer P[AM-co-VSA] MBA concentration (%) 7 8 9 10 11 Gel content, (%) 99 99 99 99 99 Swelling capacity (g/g) 12,6 9,5 7,2 5,4 4,3 Table 3.17. Effect of monomer concentration on product characteristics Monomer concentration (%) Gel5 (%) Time D6TB (m) Product characteristics 4,63  100 180 85 Small granules 10  100 150 115 Small granules 20  100 90 175 granularly 30  100 60 232 Even round granules, separately 40  100 50 325 Uneven granules, separately Table 3.18. Effect of monomer/oil ratio Ratio of monomer/oil Average granular diameter DTB(m) Product characteristics 1/5 215 Round granules, good dispersion 1/4 232 Round granules, good dispersion 1/3 - Partially blocked 3Gel content of products 4 Average granular diameter of the products 5 Gel content of products 6 Average granular diameter of the products 13 Table 3.19. Effects of surfactant span 80 concentration Span 80 (%) Average granular diameter DTB(m) Product characteristics 0,10 - Unround granules 0,20 - Unround granules 0,30 232 Evenly, round granules 0,35 - Granular and partially suspenion Table 3.20. Effect of stirring speed Mix speed (rpm) Gel content (%) Average granular diameter DTB(m) 500 200 >99  8  50  42 300 >99  5 90 5 400 >99  45  50 5 The result was a optimum synthetic condition: reaction temperature 90oC for 60 minutes, 30% of monomer, 8% of crosslinker (in monomer), 0,3% of Span 80 at 300 rpm. 3.2.3. Sythesis of poly(hydroxamic axit) based on modification of P[AM- co-VSA] In this study, Study on factors affacting the modification of P(AM- co-VSA) to poly(hydroxamic acid) (PHA-VSA) were investered such as temperature (25-50oC), time (0-24 hours), pH (pH=10-14) and concen