Journal of Hazardous Materials 192 (2011) 1539–1547
Contents lists available at ScienceDirect
Journal of Hazardous Materials
jou rn al h om epage: www.elsevier.com/loc ate/jhazmat
Surface engineered magnetic nanoparticles for removal of toxic metal ions and
bacterial pathogens
Sarika Singh, K.C. Barick
1
, D. Bahadur
∗
Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076, India
a r t i c l e i n f o
Article history:
Received 15 February 2011
Received in revised form 27 June 2011
Accepted 27 June 2011
Available online 1 July 2011
Keywords:
Nanoparticles
Magnetic
Surface functionalization
Toxic metal ions
Bacterial pathogens
Waste-water
a b s t r a c t
Surface engineered magnetic nanoparticles (Fe
3
O
4
) were synthesized by facile soft-chemical approaches.
XRD and TEM analyses reveal the formation of single-phase Fe
3
O
4
inverse spinel nanostructures. The func-
tionalization of Fe
3
O
4
nanoparticles with carboxyl (succinic acid), amine (ethylenediamine) and thiol
(2,3-dimercaptosuccinic acid) were evident from FTIR spectra, elemental analysis and zeta-potential
measurements. From TEM micrographs, it has been observed that nanoparticles of average sizes about
10 and 6 nm are formed in carboxyl and thiol functionalized Fe
3
O
4
, respectively. However, each amine
functionalized Fe
3
O
4
is of size ∼40 nm comprising numerous nanoparticles of average diameter 6 nm.
These nanoparticles show superparamagnetic behavior at room temperature with strong field dependent
magnetic responsivity. We have explored the efficiency of these nanoparticles for removal of toxic metal
ions (Cr
3+
, Co
2+
, Ni
2+
, Cu
2+
, Cd
2+
, Pb
2+
and As
3+
) and bacterial pathogens (Escherichia coli) from water.
Depending upon the surface functionality (COOH, NH
2
or SH), magnetic nanoadsorbents capture metal
ions either by forming chelate complexes or ion exchange process or electrostatic interaction. It has been
observed that the capture efficiency of bacteria is strongly dependent on the concentration of nanoad-
sorbents and their inoculation time. Furthermore, these nanoadsorbents can be used as highly efficient
separable and reusable materials for removal of toxic metal ions.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
Development of novel and cost-effective nanomaterials for envi-
ronmental remediation, pollution detection and many others has
attracted considerable attention in recent past. Contamination of
water with toxic metal ions (Cr
3+
, Ni
2+
, Co
2+
, Cu
2+
, Cd
2+
, Ag
+
, Hg
2+
,
Pb
2+
and As
3+
) and microorganisms (Escherichia coli (E. coli), Sarcina
lutea (S. lutea) and Staphylococcus aureus (S. aureus)) is becoming
a severe environmental and public health problem [1,2]. In order
to achieve environmental detoxification, various techniques like
adsorption, precipitation, ion exchange, reverse osmosis, electro-
chemical treatments, membrane filtration, evaporation, flotation,
oxidation and biosorption processes are extensively used [3–5].
Among these, adsorption is a conventional but efficient technique
to remove toxic metal ions and bacterial pathogens from water.
Numerous adsorbents have been developed for the purification
of waste-water [6–8]. In most cases, these adsorbents are highly
porous materials, providing ample surface area for adsorption.
However, the existence of intraparticle diffusion may lead to the
∗
Corresponding author. Tel.: +91 22 2576 7632; fax: +91 22 2572 3480.
E-mail address: dhirenb@iitb.ac.in (D. Bahadur).
1
Present address: Chemistry Division, Bhabha Atomic Research Centre, Mumbai
400085, India.
decrease in available space and adsorption capacity. Thus, the
development of efficient biocompatible adsorbent having large sur-
face area, active surface sites and low intraparticle diffusion rate is
of great significance in practical engineering applications.
Recently, magnetic nanoparticles (MNP) such as Fe
3
O
4
and
-Fe
2
O
3
have been investigated to resolve various environmen-
tal problems, such as removing toxic metal ions and radioactive
elements, capturing of microbial pathogens and organic dyes,
accelerating the coagulation of sewage, and remediation of con-
taminated soils [9–13]. The magnetic nanoparticles possess high
surface area and optimal magnetic properties, which lead to high
adsorption efficiency, high removal rate of contaminants, and easy
and rapid separation of adsorbent from solution via magnetic
field. The magnetic nanoparticles can be reusable after mag-
netic separation by removing the adsorbed toxic contaminants
[10]. Furthermore, magnetic nanoparticles functionalized with
biorecognition molecules such as antibody, bioprotein and car-
bohydrates [14,15] or biocompatible organic/inorganic molecules
[16,17], polymers and dendrimers [17–19] are more effective since
the free functional groups present on the surface provide large
number of active sites as well as aqueous stability, which is neces-
sary for the successful adsorption of toxic metal ions and bacterial
pathogens [20,21]. In order to achieve this, new and effective aque-
ous stabilized surface engineered/surface functionalized magnetic
nanoparticles with low regeneration cost are needed. However, the
0304-3894/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jhazmat.2011.06.074