NATURAL ZEOLITE AS A PERMEABLE REACTIVE BARRIER

Size: px

Start display at page:

Download "NATURAL ZEOLITE AS A PERMEABLE REACTIVE BARRIER"

Andrew Stevens
5 years ago
Views:

1 NATURAL ZEOLITE AS A PERMEABLE REACTIVE BARRIER PREDICTION OF LEAD CONCENTRATION PROFILE THROUGH ZEOLITE BARRIER N. Vukojević Medvidović, J. Perić, M. Trgo, M. Ugrina, I. Nuić University of Split, Faculty of Chemistry and Technology, Teslina 10/V, Split, Croatia. 5 th Serbian-Croatian-Slovenian Symposium on Zeolites

2 SOURCE AND TYPE OF GROUNDWATER CONTAMINATION

3 SCHEMATIC PRESENTATION OF PERMABLE REACTIVE BARRIER CONTAMINATE SOURCE PERMEABLE REACTIVE BARRIER PLUME GROUNDWATER FLOW REMEDIATED GROUNDWATER

4 The reactive barrier materials are classified according to the target pollutant and the mechanism of removal: - zero-valent iron (Fe 0 ) and iron based materials - organic based material (activated carbon, peat, sewage sludge, sawdust, etc.) - alkaline materials such as hydrated lime, ferrous sulphate - phosphate minerals such as hydroxyapatite and biogenic apatite (e.g. fish bone) - aluminosilicates such as clay and zeolites,... Zeolites have been recognized as an effective material for remediation of heavy-metalspolluted water due to their sorption properties, environmental compatibility, widespread deposits and simple exploitation.

5 Hydrological processes important for contaminant transport - quantity of water available for transport mass flow - degree of dispersion - variability in pore size distribution Contaminant characteristic important contaminant transport - contaminant solubility in water - adsorption / desorption onto soil and from soil (K d, R d ) - diffusive properties - degradation and volatilization - source of contaminants

6 Spread of contaminants Groundwater flow Development of a plume from a continuous source Groundwater flow Travel of a contaminants slug from a point source to t1 t2 t3

7 Distribution coefficient, K d Cs, adsorbed concentartion K d 1 tightly adsorbed Slope K d K d 2 lightly adsorbed K R d d C C S I (1+ ρ ε c ( o K c c d e e ) V m 1000) Ci, disolved concentration ADSORPTION ISOTHERM equilibrium relationship between C s and C i DISTRIBUTION COEFFICIENT K d - the slope of the line RETARDATION COEFFICIENT R d degree of retaining contaminats by soil

8 Contaminat migration in porous medium is subject to: - ADVECTION - DISPERSION - DIFFUSION Contaminat DIFFUSION Groundwater flow Contaminat dissolution into flowing groundwater Contaminat ADVECTION and DISPERSION

9 1 Piston flow c/c o Advection + Dispersion Advection + Dispersion + Diffusion 0 Breaktrought curve t, V ili BV

10 EXPERIMENTAL STUDY The zeolite sample - originating from the Vranjska Banja deposit - particle zeolite size of mm - treated with a 2 mol/l NaCl solution for five days at 37 o C Zeolite porosity and zeolite density (g/cm 3 ) were and 0.699, respectively. Batch performance Column performance Lead bearing feed Zeolite Lead Solution Zeolite Lead free effluent

11 Batch examination Single metal solutions: c o (Pb) mmol/l ( mg/l), were prepared by dissolving Pb(NO 3 ) 2 6H 2 O in ultrapure water. NaZ Pb 2+ solution The saturation of NaZ: - mixing 0,5 g of MNZ with 0,05 L of metal solution, S/L 10 g/l in the batch mode -72 hours at room temperature - the ph values and concentrations of lead were measured continuously by complexometric titration

12 2. Column examination - glass column: d u 12 mm i H 500 mm - zeolite bed lenght in column L 115 mm modelna otopina 2 - kolona 3 - instrument mjerenje vakuuma 4 - vakuum pumpa 5 - skupljanje uzoraka efluenta SERVICE CYCLE - Lead solution: c o mmol/l and Q 1 ml/min - down flow mode REGENERATION CYCLE REGENERATION CYCLE - solution of NaNO 3 - c o 15 g/l i Q 1 ml/min, - down flow mode - ph values were measured continuously, while concentrations of lead in efluent were equal to the concentration in influent

13 RESULTS AND DISCUSION

14 Equilibrium amount and percentage of the retained lead on zeolite vs. initial lead concentration 1 0,8 a) 1,0 0,8 q e (c o c e ) V m qe, mmol/g. 0,6 0,4 0,6 α, - α c ( o c c o e ) 100 0,2 qe, NaZ α 0, c o, mmol/l 0,2 Results from the batch study

15 Distribution coefficients (K d ) and retardation coefficients (R d ) vs. initial lead concentration 2,0 Kd Rd Kd Rd b) , Kd, l/g 1,0 0, Rd, - 0, c o, mmol/l 0 K d co c V ρ e ( ) R d (1+ Kd 1000) c m ε e

16 Results from the column study c/co, - SERVICE CYCLE 1,0 0,8 0,6 0,4 0,2 0,0 co1.026 mmol/l co1.759 mmol/l co2.513 mmol/l Time, min a) q c E e K R d d V 0 E n (c 0 c)dv ρ H A T n V c ( o E V q t E E (1+ c c e ρ ε e n ) E m K V m d 1000) Distribution and Retardation Coefficients estimation. c o mmol/l q e mmol/g c e mmol/l V l K d l/g R d -

17 Estimation of hydrodynamic dispersion coefficients 1,0 0,8 1,0 0,8 Brigham method c/co, - 0,6 0,4 0,2 co1.026 mmol/l co1.759 mmol/l co2.513 mmol/l c/co, - 0,6 0,4 0,2 0, U, l Number of effluent pore volume, U U V V V A L ε where: V- volume of effluent discharge over time, cm 3 V p - pore volume, cm 3 A-cross sectional area of the column, cm 2 L-length of the zeolite bed, cm ε-porosity. p 0, (U-1)/(U 1/2 ) v L (c0.84 c 8 ε 0.16 DL where: v is the discharge linear velocity (m/min), c 0.84 and c 0.16 correspond to the relative concentration c/c o of 0.84 and 0.16, respectively. )

18 Hydrodynamic dispersion coefficients estimation c o mmol/l q e mmol/g c e mmol/l V l K d l/g R d - D L 10 4 m 2 /min D LR 10 8 m 2 /min The transport of lead from the point source through the barrier can be analyzed by a simple analytical pulse model, in which the input pulse contamination has been injected at x0, and the spreading of contaminate can be predicted according to the following equation: c(x, t) c o 4 π D LR t exp( x is the distance within the barrier (m) (x v 4 D r LR t) t D LR is the retardation hydrodynamic dispersion (D LR D L /R d ) Note: v r is the groundwater velocity (v r m/min). 2 )

19 POSSIBLE SOLUTION OF SPREADING OF CONTAMINANT DUE TO ADVECTION, DIFFUSION AND DISPERSION

20 c(pb), mmol/l x 0.3 m co co1.026 mmol/l co co1.759 mmol/l co co mmol/l c(pb), mmol/l x 0.4 m x 0.5 m x 0.6 m c(pb), mmol/l c(pb), mmol/l t, min t, min Effect of lead initial concentration on the lead concentration profile through the zeolite barrier at 0.3 m, 0.4 m, 0.5 m and 0.6 m.

21 CONCLUSION Natural zeolite can be effectively used as a permeable reactive barrier for lead removal from contaminated water. The values of the distribution and retardation coefficient evaluated from the batch and column studies indicate the ability of the zeolite barrier to retain the contaminant. The hydrodynamic dispersion coefficient was evaluated from the column study by applying the Brigham method. The lead concentration pattern through the zeolite barrier is predicted for distances of 0.3, 0.4, 0.5 and 0.6 m within the barrier. The results indicate that certain dimension of the barrier is required to ensure an adequate contact time between the contaminants and the zeolite, which depends on groundwater velocity and the initial concentrations of contaminates.

22 Thank you for your attention

23 QUESTIONS?

Design of Fixed Bed Column for Lead Removal on Natural Zeolite Based on Batch Studies

Design of Fixed Bed Column for Lead Removal on Natural Zeolite Based on Batch Studies N. VUKOJEVIÆ MEDVIDOVIÆ et al., Design of Fixed Bed Column, Chem. Biochem. Eng. Q. 27 (1) 21 28 (2013) 21 Presented at 3 rd International Symposium on Environmental Management, SEM Towards Sustainable