Development of SLL equilibrium
speciation and data fitting tool and
its application to P recovery process
from sludge
Z.A. Shariff, L. Fraikin, A. Léonard, A. Pfennig
za.shariff@uliege.be
Products, Environment, and Processes (PEPs)
Department of Chemical Engineering
University of Liège
https://www.chemeng.uliege.be
Jahrestreffen der ProcessNet-Fachgruppen
agenda
Introduction to P recycling
PULSE process
SLLE tool
results
summary
introduction
• essential element for all forms of life
• finite resource
• EU imports more than 90% of P
• sewage has potential to cover more
than 20% of P demand in
North-West Europe
PULSE (Phosphorus University of Liege
Sludge Extraction) process
acid
organic
solvent
base/Ca
drying
leaching
filtration
reactive
extraction
re-extraction
CaP
solid
waste
metals
precipitation
dewatered
sludge
waste
water
re-extraction
agent/NH
3P + impurities
~20% DM
≥95% DM
PULSE process
leaching of P and metals from sludge
𝐹𝑒𝑃𝑂
4
+ 3𝐻𝐶𝑙 → 𝐹𝑒
3+
+ 𝐻
3
𝑃𝑂
4
+ 3𝐶𝑙
−
Reactive extraction of metals with organic solvent
Fe
3+
+ 4Cl
−
↔ FeCl
4
−
𝑅
3
𝑁𝐻𝐶𝑙 + 𝐹𝑒𝐶𝑙
4
−
↔ 𝐹𝑒𝐶𝑙
4
𝑅
3
𝑁𝐻 + 𝐶𝑙
−
Precipitation of CaP
why SLL equilibrium modelling
process development
evaluation of unit operations
deeper understanding
process optimization
charge balance (CB)
0 = σ
𝑖=0
𝑛
𝑐
𝑖
𝑧
𝑖
mass balance (MB)
𝐶𝑡𝑜𝑡
𝑗
= σ
𝑖=0
𝑛
𝜈
𝑖,𝑗
𝑐
𝑖
law of mass action (LMA)
𝑙𝑜𝑔𝐾
𝑚
= σ
𝑖=0
𝑛
𝜈
𝑖,𝑟
𝑙𝑜𝑔 𝑎
𝑖
FeCl
3liquid phase speciation
FeCl
3Fe
3+Cl
-FeCl
2+FeCl
2+FeCl
4-FeOH
2+FeOH
2 +FeOH
3OH
-H
+FeOH
4-FeOH
3(s)𝑎
𝑖
=
γ
𝑖
𝑐
𝑖
a
i
= activity of ith species
γ
𝑖
= activity coefficient
𝑐
𝑖
= concentration
𝐴𝐵
𝑠𝑜𝑙𝑖𝑑
↔ 𝜈
1
𝐴 + 𝜈
2
𝐵
from law of mass action
𝐾
𝑠𝑝
= 𝑎
𝐴0
𝜈
1𝑎
𝐵0
𝜈
2(at equilibrium)
Ion Activity product: 𝐼𝐴𝑃 = 𝑎
𝐴
𝜈
1𝑎
𝐵
𝜈
2(actual)
Saturation Index: 𝑆𝐼 = log 𝐼𝐴𝑃 – 𝑙𝑜𝑔 𝐾
𝑠𝑝
•
SI = 0:
IAP =
𝐾
𝑠𝑝
→
equilibrium
•
SI < 0:
IAP <
𝐾
𝑠𝑝
→
undersaturated (dissolution)
•
SI > 0:
IAP >
𝐾
𝑠𝑝
→
supersaturated (precipitation)
SLE MATLAB tool results
-1 0 1 2 3 4 5 6 7 8 9 1E-6 1E-5 1E-4 0.001 0.01 0.1 1CaHPO
4FeCl
4-FeHPO
Fe
2+PO
43-CaHPO
4(S)
AlPO
4(S)
FePO
4(S)
CaH
2PO
4+FeH
2PO
42+H
3PO
4H
2PO
4-HPO
42-FeH
2PO
4+Ca
2+Cl
-Al
3+Fe
3+con
cen
tra
tion
mo
l/l
pH
experimental v/s SLE speciation results
-1 0 1 2 3 4 5 6 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 de gr ee of P lea ching equilibrium pH HCl H2SO4 HNO3 HCl+HNO3 HCl+H2SO4 HNO3+H2SO4 H3PO4 modelnon-linear data fitting
deviation of modelling results
complex nature of sludge
P and metals bound to organic matter
lack of thermodynamic data
fitting of multiple parameters - equilibrium
constants and reaction stoichiometry
metal extraction from sludge liquor
TBP 10%; Exxal 3%; diluent – Ketrul;
0 2 4 6 8 10 0.0 0.2 0.4 0.6 0.8 1.0 Pb Zn P Hg Fe Cu Cd As de gr ee of ext ra ction
0.01 0.1 1 0.0 0.2 0.4 0.6 0.8 1.0 E (experimental) E (model)
de
gr
ee
of
ext
ra
ction
(E)
Alamine 336 conc. mol/L
LLE - non-linear data fitting
𝐹𝑒𝐶𝑙
𝑚−+
𝑛𝑅
3𝑁𝐻
+𝐶𝑙
−=
𝐹𝑒𝐶𝑙
𝑚(𝑅
3𝑁𝐻)
𝑛+
𝑛𝐶𝑙
−𝐿𝑜𝑔 𝐾 = 3.616
summary
MATLAB tool for simulation of SLLE with precipitation of
multiple solid phases
data fitting – lack of thermodynamic data and nature of
sludge
further development of the model
incorporate activity models for IS>1 mol/L
incorporate temperature dependence for logK
acknowledgements
we are thankful to
BTC Europe GmbH – BASF for providing
samples of Alamine336
TOTAL Belgium for providing samples of Ketrul
UGhent and Prayon for ICP analyses
Development of SLL equilibrium
speciation and data fitting tool and
its application to P recovery process
from sludge
Z.A. Shariff, L. Fraikin, A. Léonard, A. Pfennig
za.shariff@uliege.be
Products, Environment, and Processes (PEPs)
Department of Chemical Engineering
University of Liège
https://www.chemeng.uliege.be
Jahrestreffen der ProcessNet-Fachgruppen
References
http://www.nweurope.eu/projects/project-search/phos4you-phosphorus-recovery-from-waste-water-for-your-life/
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Morel, F., & Hering, J. G., 1993. Principles and applications of aquatic chemistry. New York (N.Y.): Wiley
Carrayrou , J., Mosé , R., & Behra, P., 2002. New efficient algorithm for solving thermodynamic chemistry. AIChE, 894-904.
Andalibi, M.R., Kumar, A.S., Srinivasan, B., Bowen, P.L., Scrivener, K.L., Ludwig, C.H., & Testino, A., 2018. On the mesoscale mechanism of synthetic calcium– silicate–hydrate precipitation: a population balance modeling approach. J. Mater. Chem. A, 6, 363
