1

Use of biosurfactants and nanomaterials as novel

agents for mining effluent remediation

Catherine N. Mulligan, Director

Concordia Institute for Water, Energy and Sustainable Systems

Concordia University, Montreal, Quebec

Email: mulligan@civil.concordia.ca

2

Background

Objectives

Methods (2 approaches-biosurfactants and nanoparticles)

Results and Discussion

Conclusions

Overview

Introduction

Mine tailings are by-products of the process of

extracting valuable minerals from the ores.

In Yellowknife, gold is embedded in

arsenopyrite ore.

Mine tailings from the historical gold mine,

Giant Mines (Yellowknife, NWT), are stored in

tailing ponds near the shores of The Great

Slave Lake.

3Geol. Marco Barsanti (1975)

Arsenic

A primary pollutant in water

Among the list of priority substances

(CEPA, 1996)

A group 1 carcinogen

www.sos-arsenic.net

4

Mine tailings’ threats to the

environment

5

High concentrations of heavy metals are found in

mine tailings.

Can be major environmental contamination

sources into the surrounding soil, air, ground or

surface water.

Accidental release of mine tailings to the

surrounding due to:

malfunctioning of chambers

contaminated water seeping from storage

areas.

6

www.toxiclegacies.com1920 × 1349

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Chromium

Sources: Metal finishing industry, leather tanning,

Iron and steel industries, dyes,

Electroplating, metal cleaning,

photography, wood treatment, mines

Cr (VI) is toxic to human, animals and plants

Associated with the development of various chronic health

disorders

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Copper

Adults acute lethal dose is 4 - 400 mg of copper (II) ion per kg

of body weight. Children could be affected with lower levels.

Many sources can supply copper to rainwater runoff which

enters water bodies such as breakdown of chemicals, landfills

as seepage, mining residues or through the use of copper

algaecides in lakes.

Remediation methods

Capping, excavation

Stabilization/solidification

Chemical extraction

Washing/ flushing

Bioremediation

Phytoremediation

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10

Surfactants

Surface active agents (surfactants) are chemical compounds

Hydrophobic Chain or Tail Hydrophilic Head Group

(linear or branched hydrocarbon portion) (polar or ionic portion)

Surfactant monomer

11

General Classification of Surfactants

Generally, surfactants classification depends on head group

charge:

Cationic surfactants

Anionic surfactants

Nonionic surfactants

Amphoteric and zwitter-ionic surfactants

Surfactants (Surface active agents)

Chemical compounds with a hydrophobic tail (linear or

branched hydrocarbon) and a hydrophilic head (polar or

ionic)

– Surface tension reduction due to molecular film at interface

– CMC: minimum concentration necessary to initiate micelle

formation

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13

Critical Micelle Concentration (CMC)

-Critical value of concentration where the surfactant solution monomers start to form micelles.

ABOVE CMC

(SPHERICAL MICELLES)

BELOW CMC

(MONOMERS)

Biosurfactants

Produced either on the surfaces of microbial cell or

excreted extracellularly

Advantages

– Higher biodegradability and lower toxicity

– More economic than the other surfactants

– Potential to decrease the environmental impacts of oil sands

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Rhamnolipid Biosurfactant

Pseudomonas aeruginosa species has the ability to produce

four different rhamnolipids (R1 – R4)

Anionic and capable of lowering the water surface tension

from 72 to 29 mN/m

Rhamnolipid important environmental applications are:

Biodegradation of petroleum hydrocarbons and (PAHs)

Removal of heavy metals and organics

Dispersing oil in contaminated water

RhamnolipidAn anionic biosurfactant produced by Pseudomonas aeruginosa

species

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Rhamnolipids type I or mono-rhamnolipids contain one rhamnose group while

rhamnolipids type II or di-rhamnolipids; contain two rhamnose groups (El

Zeftawy and Mulligan 2011)

Sophorolipids Glycolipid

Main producers: yeasts of

Candida sp.

Primary producer: Candida

bombicola

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Structure of

sophorolipid

produced

by C.

bombicola(Mulligan, 2005).

18Removal of Mn, Fe, As, Cr, Ni, Cu & Pb with

different concentrations of SL from mining

residues

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Objectives

To determine the feasibility of using biosurfactant

(rhamnolipid JBR 210) to enhance the removal and

reduction of hexavalent chromium both in water

To evaluate rhamnolipid (JBR 425) capability to

removal of various metals (arsenic, copper,

chromium) from aqueous solutions

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Results

Water media: Effect of pH on reduction of Cr (VI)

Experimental Conditions:

pH: 6-10

Cr (VI) conc: 10 ppm

Rhamnolipid conc: 0.5%

Temperature: 25 C

Time: 24h

0

10

20

30

40

50

60

6 7 8 9 10

pH

Cr

(VI)

Re

du

cti

on

(%

)

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ResultsWater media: Effect of rhamnolipid concentration

on reduction of Cr (VI)

Experimental Conditions:

pH: 6

Cr (VI) conc: 10 ppm

Rhamnolipid conc: 0.05- 5%

Temperature: 25 C

Time: 24h

0

20

40

60

80

100

120

0.05 0.1 0.2 0.4 0.5 1 2 4 5

Concentration of Rhamnolipid (%)

Cr

(VI)

Re

du

cti

on

(%

)

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Results

Experimental Conditions:

pH: 6

Cr (VI) conc: 10 – 400 ppm

Rhamnolipid conc: 2%

Temperature: 25 C

Time: 24h

Water media: Effect of initial Cr (VI) concentration

on reduction of Cr (VI)

0

20

40

60

80

100

120

10 50 100 200 400

Initial Cr(VI) concentration in water (mg/L)

Cr

(VI)

Re

du

cti

on

(%

)

Effect of Rhamnolipid

Concentration on Cr (VI) Reduction

pH 6, T= 23℃ and Cr (VI) = 10 mg/L

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Result and Discussion

Effect of Different Initial Concentrations of Hexavalent

Chromium on Reduction of Cr (VI)

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Result and Discussion

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Flow diagram of the micellar enhanced

ultrafiltration system

Feed reservoir

Sampling/Drain

ball valve

Feed sampling

stream

Peristaltic pump

Pressure

gauge

Pressure

gauge

Retentate

stream

Permeate

stream

Flow meter Membrane

cartridge

Back pressure

control valve

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Biosurfactant Role

Hollow Fiber Membrane Characteristics Nominal Molecular Weight Cut-Off (NMWC): 5000

Cartridge Membrane Area (cm2):140Nominal

Fiber ID (mm): 0.5 Nominal

Number of Fibres: 30

Nominal Flow Path Length: 30 cm

Increasing the contaminant size to be larger than membrane

pore size by:0

Solubilizing organics inside the micelle (hydrophobic core)

Attracting heavy metals on the micelle hydrophilic surface

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Micellar-Enhanced Ultrafiltration (MEUF)

It’s when the micellar solution is passed through a membrane having pore sizes small enough (2 –10 nm) to reject the micelles

Flow direction

Copper ion

Rhamnolipid

monomer

Micelle containing

solubilized benzene

molecules and attracted

copper ions

Ultrafiltration

membrane

Membrane pore

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Determination of molar ratio (MR) of 100 %

rejection

Rejection (R) = 1 - ( Cp / Cf )

Cp = Permeate Concentration ; Cf = Feed Concentration

100%Rejection MR=number of rhamnolipid moles (Cp=0)

number of contaminant moles

Effect of Rhamnolipid Concentration

on Cr Rejection

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Result and Discussion

Rhamnolipid Behavior in Presence

of Chromium

pH 6, T= 23 ℃, TMP= 70 kPa

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Result and Discussion

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Rhamnolipid rejection of

rhamnolipid-copper aqueous

solution

Surface tension of permeate of

rhamnolipid-copper aqueous

solution

99.8

99.9

99.2

99.3

99.4

99.5

99.6

99.7

99.8

99.9

100.0

158.9 317.8

Rhamnolipid Feed Conc. (mg/l)

Rh

am

no

lip

id R

eje

cti

on

%

Rh Feed =

317.8 mg/l Rh Feed =

158.9 mg/l

62.0

62.1

62.2

62.3

62.4

62.5

62.6

62.7

62.8

62.9

63.0

0.29 0.31

Rhamnolipid Permeate Conc. (mg/l)

Su

rface T

en

sio

n (

mN

/m)

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Copper rejection at molar

ratio = 5.41

92.889.1

74.2

0

20

40

60

80

100

120

3.1 6.4 9.6

Copper Concentration (mg/l)

Re

jec

tio

n %

Copper rejection at molar

ratio = 6.25

0

20

40

60

80

100

120

3.1 6.4 9.6

Copper Concentration (mg/l)

Re

jec

tio

n %

Adsorption

Adsorption is among the most widely used technologies for arsenic

removal.

Different types of adsorbent materials include:

- Activated alumina (AA)

- Activated carbon (AC)

- Copper-zinc granules

- Granular ferric hydroxide

- Surfactant modified zeolite

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nZVI with granular activated

carbon

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Adsorption of pollutants by nanoparticles

High ratio of surface to the volume provide nanoparticles with more

adsorption sites.

Nanoparticles are mobile in the environment and can reach to the

point of pollution.

The possible removal pathways

- Adsorption

- Complexation

- (Co)precipitation

- Surface-mediated chemical

reduction

35Li et al.,2006, Critical Reviews in Solid

State and Materials, 31, pp. 111–122

Iron bimetallic nanoparticles

Iron reacts with oxygen and forms a layer of oxyhydroxide on the

nZVI surface.

Formation of mixed metal hydroxides layer may inhibit further

electron transfer from the Fe0 core at later reaction times.

Through combination of iron with a more noble metal (e.g. Pd, Pt,

Ag, Ni, Cu), reactivity will improve.

Iron is oxidized more rapidly when it is attached to a less active

(noble) metal.

Therefore, the transformation and reduction of contaminants can be

enhanced.

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Objectives of research

To evaluate the efficiency of nZVI/GAC

or iron/copper nanoparticles as new

adsorbents for arsenic removal from

water.

To evaluate the critical parameters in

order to enhance removal efficiency.

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Adsorption of As(III) and As(V) on nZVI/GAC. Initial

As(III)/As(V) concentration: 5000 µg/L, nZVI/GAC: 1g/L in

0.1M NaCl , Equilibrium time: 12 h

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Sorption Isotherms for Fe/Cu nanoparticles

The adsorption isotherm follows the Langmuir model.

Equilibrium isotherm model for arsenic adsorption (method 1)

As(III) As(V)

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Effect of initial concentration and adsorbent dose

Effect of adsorbent dose on the removal of arsenic (nanoparticle

method 2)

As(III) As(V)

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Conclusions

Biosurfactants are a promising agent for the

removal of arsenic and other heavy metals from

soil and mine tailings.

Rhamnolipid can reduce Cr(VI) to Cr(III).

Effectiveness was influenced by rhamnolipid

concentration, pH and chromium concentration

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Conclusions-MEUF

The formed rhamnolipid micelles have hydrophilic surfaces where the copper or chromium ions have been bound

Micelles are large enough to be retained by the hollow fibre membrane filter and rejected by a separate stream

Biosurfactants and metals are in the retentate

Clean water with acceptable concentrations of rhamnolipid monomers and contaminants is in the permeate.

Nanoparticle conclusions

Arsenite adsorption capacity by nZVI-GAC

varies from 0.800 to 1.400 mg/g over the pH 2-

11. Arsenate adsorption was higher (3.0-3.7

mg/g) over the acidic pH range 2-6.5. Among

competitive ions had insignificant impact.

Fe/Cu nanoparticles are able to remove arsenic

from aqueous solutions.

The Langmuir sorption capacity for As(III) and

As(V) were 19.68 mg/g and 21.32 mg/g for Fe-

Cu nanoparticles.

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ACKNOWLEDGEMENTS:

Financial support of NSERC and Concordia University and the

work of a number of my graduate students

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Thank you