in-situ immobilization of contaminants and sealing of soil ... · pdf filesealing of soil and...

In-situ immobilization of contaminants and sealing of soil and rock by crystallization processes from supersaturated solutions

Dr. Gerald Ziegenbalg

IBZ-Freiberg

www.ibz-freiberg.de 2

IBZ-Freiberg: Main working fields

Technologies for in-situ remediation of areas polluted by organic and inorganic compounds.

In-situ heavy metal fixation by directed precipitation processes.

Encapsulation of polluted areas, waste rock dumps and tailings.

Sealing of porous/fractured rock.

Contract research in chemical engineering / raw material processing.

Contract research in hydrometallurgy and water treatment.

Development of construction materials.

Geochemical research and modeling.

Training courses in Chemical Engineering and Advanced Inorganic Chemistry.

www.ibz-freiberg.de 3

Copying of natural crystallization processes for:

Stabilization of porous and fractured rock

Immobilization of heavy metals

Overlaying of reactive mineral surfaces to prevent formation of acid rock drainage

Sealing of inflows into mines

Creation of conditions favorable for natural degradation / attenuation of organic contaminants

Use of solutions leading to directed crystallization processes

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Fundamentals: Preparation of mineral forming solutions

Without precipitation inhibitor:

CaCl2 + MgSO4 + 2 H2O CaSO4*2H2O + Mg2+ + 2Cl-

Ba(OH)2 + H2SO4 BaSO4

spontaneous, quantitative precipitation

In the presence of suitable precipitation inhibitors:

CaCl2 + MgSO4 Ca2+ + SO42- + Mg2++ 2Cl-

Ba(OH)2 + H2SO4 Ba2+ + SO42- + H2O

temporary stable solutions

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Delayed gypsum crystallisation after inhibitor addition to 0.5 molar CaSO4 solutions

Immeaditely after mixing

after one hour

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Delayed gypsum crystallisation after inhibitor addition to 0.5 molar CaSO4 solutions

after 3 hours

after 24 hours

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Action of inhibitors

A B C

time

CaS

O4 c

oncentr

ation

Inhibitor concentration: A < B < C

Retardation time

Equilibrium concentration

without inhibitor

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Minerals that can be formed from supersaturated solutions

CaSO4*2H2O

CaSO4

BaSO4

CaCO3

Ca(OH)2

Calcium phosphates

Calcium silicates

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Gypsum formed during the flow of supersaturated solutions through pipes

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Use of CaSO4 solutions to seal

fractures

well with TRG

growing gypsum layers

favoured gypsum growth on places with high turbulency

mixing zone(only limited gypsum crystallisation, mainly dilution)

DB brine DB-brine

mixing zone

CaSO4-solution

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Grouting station at Mosaic Potash Esterhazy Ltd. (Canada)

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Development of inflow

brine composition and inflow rate (inflow#107)

50

75

100

125

150

1751

2.

Ju

l

14

. Ju

l

16

. Ju

l

18

. Ju

l

20

. Ju

l

22

. Ju

l

24

. Ju

l

26

. Ju

l

28

. Ju

l

30

. Ju

l

inflo

w [

GP

M]

0

0,2

0,4

0,6

0,8

1

1,2

SO

4,

Mg

[w

t.-%

]

# 107

SO4-107

Mg - 107

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Sealing of brine inflows in the Merkers mine of K+S Kali GmbH, Germany

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Sand solidified by gypsum

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Gypsum crystals blocking porous sandstone

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Permeability change and effluent composition

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14 16 18

Injected volume of CaSO4 forming solution [litre]

kf [

m/d

ay]

0

2

4

6

8

10

12

14

16

Ca

SO

4 in

dis

cha

rge

d

solu

tio

n [

g/l]

CaSO4 [g/l]

kf [m/d]

Break for 12 hours

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In-situ immobilization of heavy metals

inthe „Koenigstein“ mine

Former uranium mine which is situated in an ecological sensitive area (near to the river Elbe and on the border to the National park „Saxon Switzerland“.

Uranium production was carried out by in-situ leaching of porous sandstone formation with diluted sulfuric acid

Flooding of the mine will lead to the discharge of large amounts of contaminated water into ground water horizons

Step by step flooding and treatment of the flooding water

Immobilization by BaSO4 forming solutions

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Characteristics of BaSO4

(Barite)

Solubility product: 10-10 mol2/l2

Solubility: 2 mg/l at 25 °C Coprecipitation:

K+>Na+>NH4+>Rb+=Cs+=Li+

Ca2+>Mg2+=Zn2+=Cd2+=Hg2+

Fe3+ > Al3+

NO3- > Cl- > Br-

Formation of solid solutions with:RaSO4 , PbSO4 , SrSO4 und Hg2SO4

Adsorption of ions: Ba2+>Hg2+>Pb2+>Cd2+>Mn2+>Zn2+>Cu2+>Ni2+>Mg2+>Al3+

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BaSO4-crystals formed on the surface of sand particles

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Immobilization of heavy metals in a former uranium mine in Germany

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Discharge of uranium during immobilization in comparison with flushing with water

0

5

10

15

20

25

30

35

1. immobilisation 2. immobilisation flushing with

water

Uranium

[kg]

Discharged uranium during

immobilization

Uranium output during

flushing with water

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Summary: Action of mineral forming solutions

formation of layers

formation of singlecrystals

precipitation as result of mixing with presentpore water

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We offer:

a unique technology to immobilize contaminants by crystallization of natural minerals from metastable, supersaturated solutions.

a unique technology to seal porous soil and rock formations as well as to stop water inflows into mines.

development of remediation and technology concepts.

consultancy concerning geochemical processes. contract research concerning raw material

processing and handling of waste materials. analytical services. synthesis of inorganic materials.

www.ibz-freiberg.de 24

Thank you very much !