Removal of natural uranium from groundwater by means of weakly basic anion exchangers

Transkript

1 X 28 Removal of natural uranium from groundwater by means of weakly basic anion exchangers Marcel Riegel Wolfgang W. Höll Riegel ITC - WGT

2 utline Introduction Equilibrium of sorption Sorption kinetics Sorption dynamics Riegel ITC - WGT

3 otivation - Uranium Occurrence Seldom up to 1 µg/l In few cases up to / higher than 1 µg/l Standards for uranium Drinking water No standards appointed ecommendation: 1 3 µg/l Mineral water Standard of 2 µg/l (GER) suitable for the preparation of infant food Chemical toxicity Removal Riegel ITC - WGT

4 peciation of uranium 1 2+ UO 2 UO2CO3 UO ( CO ) UO ( CO ) Fraction of total uranium, % UO OH ( UO ) ( OH) CO ( UO2 ) ( OH 2 ( UO ) ( OH) ph delling with MINEQL, c(u) = 1 µg/l, c(hco 3- ) = 24 mg/l 2 2 Riegel ITC - WGT

5 echanism of sorption Application of weakly basic anion exchanger + - ( ) 2- ( + ) ( ) NH OH + UO CO R NH UO CO + 2 O ( ) NH OH + SO R NH SO + 2 OH ph Protonation 2-2- N + UO CO R N + UO CO ( ) ( ) Riegel ITC - WGT

6 actors influencing the sorption (De-) Protonation of the functional groups ph Competitive sorption SO 2-4, HCO 3-, Cl -, NO 3-, NOM Change of speciation HCO 3-, Ca 2+, Mg 2+, ph Riegel ITC - WGT

7 quilibrium Experimental setup Sorption isotherms Solutions: Pure water + HCO 3 - Tap water + imidazole buffer + imidazole buffer H H N H N c(u) = 1 µg/l V L = 4 ml m IEX =,1 1 g t > 6 h Evaluation with Langmuir Freundlich K L c q = q n max 1+K c q = KFc L Riegel ITC - WGT

8 n exchangers Lewatit MP 62 Matrix: Styrene - DVB - copolymer Exclusively tertiary amine groups Amberlite IRA 67 / PWA 8 Matrix: Acrylic - DVB - copolymer Secondary and tertiary amine groups Riegel ITC - WGT

9 quilibrium - Influence of sulfate q(u), µmol/g mg/l sulfate 1 mg/l sulfate 2 mg/l sulfate q(u), mg/g c(u), µg/l ) = 1 µg/l, ph = 7.1 : Lewatit MP 62, matrix: deionised water spiked with 24 mg/l of HCO - 3 Riegel ITC - WGT

10 quilibrium - Influence of calcium Fraction of total U, % q(u), µmol/g ph Without mg/l calcium 5 mg/l calcium 1 mg/l calcium 1 mg/l calcium ph 5 UO2 CO3 2 2 Ca 2 UO 4 2 (CO 3 ) UO CO3 c(u), µg/l UO CO ) = 1 µg/l, ph = 7.5 ( ) 2-1 : Lewatit MP 62, matrix: deionised water + 24 mg/l HCO 3- + CaCl odelling with MINEQL, c(u) = 1 µg/l, c(hco 2 3- ) = 24 mg/l UO 2 ( ) q(u), mg/g

11 quilibrium - Influence of ph / IEX 35 Amberlite IRA ph = 7. ph = q(u), µmol/g ph = 7.8 ph = 6.9 ph = 7.1 Lewatit MP 62 ph = q(u), mg/g 5 ph = 8.3 ph = 9.6 ph = c(u), µg/l = 1 / 2 µg/l, matrix: tap water Amberlite IRA 67: ACRYLIC copolyme Lewatit MP 62: STYRENE copolymer

12 inetics odel: Film / Surface Diffusion c U, q U c U q U * R. n U c U * δ r Transport in the film: n& U n& U = β ( c L = ρ P U D s c * U Transport in the particle: q r U ) Profiles of concentration and loading

13 netics Determination of the transport coefficients External mass transfer coefficient ß L Short fixed bed reactor Surface diffusions coefficient D s Rotating basket reactor Short fixed bed reactor

14 inetics Mass transfer coefficient ß L 6 5 ph = 7.5 ph = 7.2 ß L, 1-5 m/s d P =.8 mm v F, m/h : Amberlite IRA 67 & Lewatit MP 62, matrix: tap water, c(u) = 1 µg/l

15 netics Determination of the transport coefficients Rotated basket reactor External mass transfer coefficient ß L Short fixed bed reactor Surface diffusions coefficient D s Rotating basket reactor

16 inetics Diffusion coefficient D s c (U), µg/l c (U) Ds s = 2 xx1e-13 x 1 m²/s DDs s = 32e-13 x 1-13 m²/s DDs s = 43e-13 x 1-13 m²/s t, min : Lewatit MP 62, ph = 7.3, d P =.6 mm, matrix: tap water

17 olumn experiments Laboratory scale CO 2 ph Effluent Sampling Analytics IEX-Column V = 25 ml ph

18 olumn breakthrough curve Laboratory scale c(u), µg/l 8 6 c(u) ph 4 Prediction 6. 2 ph 5.5 1, 2, 3, 4, 5, 6, Throughput, BV : Amberlite IRA 67, c(u) = 1 µg/l, V = 2 BV/h, matrix: tap water. 5.

19 olumn breakthrough curve Pilot plant scale Water purification plant c(u), µg/l c(u) feed c(u) effluent Prediction 2, 4, 6, 8, 1, 12, Throughput, BV. : Amberlite IRA 67, V IEX = 7.5 L, V = 28 BV/h, ph = 7.2

20 olumn breakthrough curve Full plant scale 1 c(u), µg/l Extended effectiveness test catalogue for water treatment substances c(u) feed c(u) effluent.1 1, 2, 3, 4, 5, 6, Throuhgput, BV. : Amberlite IRA 67, V IEX = 3 L, V = 2 BV/h, ph = 6.9

21 stallation of the first technical plant in GER IEX: Amberlite IRA 67 c(u) = 37 µg/l V IEX = 5 m³. V av = 32 m³/h = 6,5 BV/h ph = 7,3 After half a year (3, BV): c(u) <,1 µg/l Expected operation time: at least 1½ years (9, BV)

22 onclusions Equilibrium of sorption Elimination of uranium is possible with weakly basic anion exchangers Influencing factors: ph and water matrix Sorption kinetics Combined film / surface diffusion input for modelling of column performance Sorption dynamics Very long operation time Technical implementation already accomplished

23 cknowledgement Sibylle Heidt Volker Schlitt - TZW Karlsruhe Günther Mann - GUTec Klaus Hagen - Krüger Wabag GmbH BMBF DVGW Thank you very much for your attention

24 dd on

25 odel to predict column performance Assumptions Single component Plug flow Film / surface diffusion Basics Equilibrium at exchanger surface Mass balance of the liquid column phase Kinetic approach of film / surface diffusion Mathematics 3 coupled differential equations

26 quilibrium Influence of ph q(u), µmol/g ph = 7,2 2 ph = 7,5 ph = 8,5 4 8 c(u), µg/l ) = 1 µg/l : Lewatit MP 62, matrix: deionised water spiked with 24 mg/l of HCO - 3