Adsorption of copper from aqueous solutions on synthetic zeolites produced from Greek fmy ash: Kinetic and equilibrium studies Katerina Vavouraki*, Lefteris Makratzis, Despoina Pentari, Konstantinos Komnitsas Laboratory of Management of Mining / Metallurgical Wastes & Rehabilitation of Contaminated Soils School of Mineral Resources Engineering, T echnical University of Crete Heraklion, 26-29/06/2019 1
Outline 1. Introduction 2. Experimental process synthesis batch adsorption experiments 3. Results Zeolite characterization (XRD, FTIR) Adsorption capacity of synthetic zeolites for Cu(II) ions: Kinetics (1 st , 2 nd order) Isotherms (Langmuir , Freundlich) 4. Conclusions Heraklion, 26-29/06/2019 2
Introduction I. Fly ash Coal is the second major fossil fuel source for energy production among other energy sources Fly ash (FA) used in this study: by- product of the thermoelectric power station in Megalopolis (Peloponnese, Greece) produced from coal combustion annual production: 12·10 6 tons only 10% of the produced fmy ash is (Hosseini Asl et al., J. Cleaner Prod. 2019 , 208, used in the cement industry as 1131) pozzolanic additive to improve properties of concrete 90% of fmy ash is disposed of in abandoned mining sites and causes environmental problems Heraklion, 26-29/06/2019 3
Introduction II. Zeolites Zeolites: crystalline, microporous aluminosilicates with a basic crystalline framework composed of SiO 4 and AlO 4 tetrahedra connected with shared oxygen atoms, and forming characteristic structures that result in excellent performance in multiple applications : as candidate adsorbent materials are very attractive due to cost-efgectiveness & good selectivity for Converting fmy ash into zeolites not heavy metals only partially solves the disposal problem but also converts a potentially hazardous 3 types of zeolites : natural, modifjed, & material into a value-added, marketable synthetic product Structural units of zeolite-A, sodalite & Fly ash contains signifjcant amounts of faujasite crystalline and amorphous aluminosilicates; can (Masoudian et al., Bull. Chem. React. Eng. Catal. be used for zeolite production 2013 , 8 , 54) Heraklion, 26-29/06/2019 4
State-of-the-art (After Simate et al., J. Environ. Chem. Eng. 2016, 4, 229 Several studies investigated the conversion of fmy ash to zeolites and their adsorption effjciency for heavy metals, organics & gaseous pollutants Heraklion, 26-29/06/2019 5
Aim of this study.. Production of zeolites from Greek lignite fmy ash from Megalopolis by alkaline fusion Characterization of synthetic zeolites Kinetics models Adsorption equilibrium Regeneration experiments Heraklion, 26-29/06/2019 6
Experimental process: Synthesis of zeolites XRF analysis of FA Major Fly ash components Megalop % w/ w olis (FA) SiO 2 43.13 CaO 18.74 Al 2 O 3 13.07 Fe 2 O 3(tot) 12.40 MgO 2.65 MnO 0.1 Na 2 O 1.40 Synthetic Zeolites: K 2 O 2.33 alkaline fusion (with NaOH) of FA at 600 °C for 1 h P 2 O 5 0.21 mass ratios of FA to NaOH: 1:1 ( ZFA1 ) and 1:1.5 TiO 2 1.11 SO 3 4.56 ( ZFA1.5 ) Cr 2 O 3 0.06 pulverized and mixed with H 2 O (in a constant ratio LOI 4.67 of 20% w/v) under overnight stirring Total 104.43 Si/ Al 2.91 after incubation of the suspension at low temperature (30 °C for 4 days) the synthesized zeolites were obtained after centrifugation and drying at 80 °C for 24 h Heraklion, 26-29/06/2019 7
Experimental process: Batch experiments xperimental conditions: Cu(NO 3 ) 2 solution concentration: 50-200 mg.L -1 Adsorbent (zeolite) dosage: 0.3-1.5 g.L -1 constant ionic strength NaCl 0.1 M working volume: 250 mL stirring at 600 rpm room temperature fjltration (0.45μm PTFE) Cu(II) by AAS Heraklion, 26-29/06/2019 8
Results I. Characterization of synthetic zeolites FTIR XRD 1440 1630 440 631 874 976 FAM 3500 1090 680 ZFAM1 ZFA1.5 ZFAM1.5 Absorbance (a.u.) ZFA1 FA 500 1000 1500 2000 2500 3000 3500 4000 Q: Quartz, SiO 2 -1 ) Wavenumber (cm Al: Albite, NaAlSi 3 O 8 3500cm -1 : stretching vibration (-OH, G: Gehlenite, Ca 2 Al 2 SiO 7 HOH) An: Anhydrite, CaSO 4 1630cm -1 : bending vibrations (HOH) Η: Hematite, Fe 2 O 3 1440cm -1 : stretching vibrations (O-C-O) L: Lime, CaO 1090, 976cm -1 : asymmetric stretching C: Calcite, CaCO 3 vibration X: Zeolite X, NaAlSi 1.23 O 4.46 ·3.07H 2 O 874, 680, 631cm -1 : symmetric stretching vibrations (Si-O-Si, Al-O-Si) A: Zeolite A, NaAlSi 1.1 O 4.2 ·2.25H 2 O 440cm -1 : bending vibration (Si-O-Si and S,Al: Sodium aluminium silicate hydrate, O-Si-O) Heraklion, 26-29/06/2019 9 Na 6 Al 6 Si 10 O 32 ·12H 2 O S: Sodalite, Na Al Si O Cl
Results II. Kinetic studies Efgect of initial Cu(II) concentration Efgect of initial Cu(II) concentration on the adsorption capacity of ZFA1 and ZFA1.5 (dosage 0.5 g·L -1 , pH 4.4). C 0 , C t : initial and measured Cu(II) concentrations in solution C 0 , C t : initial and measured Cu(II) concentrations in solution during adsorption during adsorption ZFA1 ZFA1. ZFAM7 ZFAM15 5 100 100 90 90 The adsorption capacity 80 80 decreases when the initial 70 70 Cu(II) concentration 60 60 increases until the system % AD 50 50 reaches equilibrium At Cu(II) 200mg.L -1 %AD 40 40 (ZFA1) was greater to -1 -1 30 30 C 0 = 45 mg.L C 0 = 45 mg.L %AD (ZFA1.5) -1 -1 C 0 = 100 mg.L 20 C 0 = 100 mg.L 20 -1 -1 C 0 = 140 mg.L C 0 = 140 mg.L 10 10 -1 -1 C 0 = 200 mg.L C 0 = 200 mg.L 0 0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 t (min) t (min) Heraklion, 26-29/06/2019 10
Results II. Kinetic studies Efgect of the adsorbent dosage Efgect of adsorbent dosage (g·L -1 ) on the adsorption effjciency of ZFA1 (initial Cu(II) concentration of 140 mg·L -1 ; pH 4.4) ZFA1 ZFAM7 Increase of adsorbent dosage 100 resulted in increase of Cu(II) 90 adsorption due to the increase 80 of the number of available 70 adsorption sites 60 At low dosage (0.3 g·L -1 ) the % AD 50 adsorption degree of ZFA1 40 decreased by 55% compared 30 -1 ZFAM7 1.5 g.L to the adsorption capacity at -1 1 g.L 20 higher dosage (1.5 g·L -1 ) -1 0.5 g.L Kinetic modelling at dosage of 10 -1 0.3 g.L 0.5 g·L -1 0 0 10 20 30 40 50 60 t (min) Heraklion, 26-29/06/2019 11
Results II. Kinetic modelling Pseudo-fjrst & pseudo-second-order adsorption of Cu(II) onto 0.5 g.L -1 ZFA1 (a, c) and ZFA1.5 (b, d) synthesized zeolites 1 st order 2 nd -order Pseudo-fjrst-order ZFAM7 ZFA1 ZFAM15 ZFA1.5 3 3 The experimental data a b 2 2 fjt well the pseudo- 1 1 second order kinetic log (q e -q t ) 0 0 model -1 -1 -1 C 0 = 45 mg.L -1 The rate constant k 2 , C 0 = 45 mg.L -2 -1 -2 C 0 = 90 mg.L -1 C 0 = 90 mg.L however, depended on -1 C 0 = 140 mg.L -1 C 0 = 140 mg.L -3 -3 -1 C 0 = 190 mg.L -1 C 0 = 200 mg.L the initial concentration -4 -4 0 10 20 30 40 50 60 0 10 20 30 40 50 60 of Cu(II) ions in solution, 1.0 1.0 d c C 0 = 45 mg.L-1 -1 C 0 = 45 mg.L indicating that surface C 0 = 90 mg.L-1 -1 0.8 0.8 C 0 = 90 mg.L difgusion instead of C 0 = 140 mg.L-1 t/ q t (min.g/ mg) -1 C 0 = 140 mg.L C 0 = 190 mg.L-1 chemisorption of Cu(II) 0.6 -1 0.6 C 0 = 200 mg.L ions at the adsorption 0.4 0.4 sites of synthetic 0.2 0.2 zeolites is the rate 0.0 determining step 0.0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Heraklion, 26-29/06/2019 12 t (min) t (min) Pseudo-second-order
Results III. Equilibrium isotherms Experimental and modelled Cu(II) adsorption isotherms for synthetic zeolites, ZFA1 and ZFA1.5 using Langmuir and Freundlich equations (Cu(II) concentration of 50 to 200 mg.L- 1 , dosage 0.5 g.L -1 ; θ 25 °C; stirring speed 600 rpm; time 60 min; pH 4.4) Freundlich isotherms Langmuir isotherms 0.30 3.0 ZFAM7 ZFA1 ZFAM7 ZFA1 ZFA1. ZFAM15 ZFAM15 ZFA1. 0.25 5 5 0.20 2.5 -1 ) e (g.L e logq Langmuir Langmuir 0.15 C e / q Freundlich Freundlich 0.10 2.0 0.05 0.00 1.5 0 10 20 30 40 50 60 -2 -1 0 1 2 -1 ) C e (mg.L logC e the adsorption data is best fjtted by Langmuir isotherm Freundlich isotherm the Langmuir equation. Langmuir q m k l R 2 R L k f n R 2 mg·g -1 L·mg -1 g·L -1 model suggests a monolayer adsorption of Cu(II) on the outer ZFA1 310.6 1.7 0.99 0.005 198. 7.5 0.825 surface of zeolites ( ZFA1 and 4 2 7 ZFA1.5 ). ZFA1. 295.9 3.4 0.99 0.004 152. 5.6 0.904 The highest equilibrium 5 9 9 2 adsorption capacity obtained Heraklion, 26-29/06/2019 13 for Cu(II) was 311 and
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