The presence of cobalt(II) in wastewater is an emergent concern because of its toxicity at elevated concentration. Co(II) is a non-biodegradable, carcinogenic and mutagenic pollutant released from natural, industrial and manmade sources. In recent years, the control of water that has been polluted with Co(II) has been an emergent issue. The release of Co(II) into waterways is undesirable because ingestion of high levels of Co(II) may cause severe health issues including cancer. The current review discusses the different adsorbents such as carbonaceous and activated carbon materials, nanosized metal oxides, low-cost natural materials, clay minerals and nanocomposites employed by researchers to treat Co(II)-polluted water. The systems used have been assessed in terms of overall Co(II) sorption capacity. Special emphasis has been given to the environmental conditions such as contact time, solution pH, initial Co(II) concentration, temperature, and mineral dosage. Moreover, empirical and surface complexation modeling (SCM) of the sorption systems is summarized. Natural materials, agricultural waste materials, and bio sorbents exhibited outstanding Co(II) sorption performance. The current investigation provides an overview of the state of the Co(II) removal studies performed by using various adsorbents.

1. Contents lists available at ScienceDirect
Environmental Nanotechnology, Monitoring
& Management
journal homepage: www.elsevier.com/locate/enmm
Opportunities and constraints of using the innovative adsorbents for the
removal of cobalt(II) from wastewater: A review
Md. Aminul Islama,⁎
, David W. Mortona
, Bruce B. Johnsona
, Biplob Kumar Pramanikb
,
Bandita Mainalib
, Michael J. Angovea,⁎
a
Colloid and Environmental Chemistry (CEC) Research Laboratory, Department of Pharmacy and Applied Science, La Trobe Institute for Molecular Science (LIMS), La
Trobe University, Bendigo, Australia
b
School of Engineering and Mathematical Sciences, La Trobe University, Bendigo, VIC, 3550, Australia
A R T I C L E I N F O
Keywords:
Adsorbent
Cobalt (II)
Sorption
Removal
Isotherm
Wastewater
A B S T R A C T
The presence of cobalt(II) in wastewater is an emergent concern because of its toxicity at elevated concentration.
Co(II) is a non-biodegradable, carcinogenic and mutagenic pollutant released from natural, industrial and
manmade sources. In recent years, the control of water that has been polluted with Co(II) has been an emergent
issue. The release of Co(II) into waterways is undesirable because ingestion of high levels of Co(II) may cause
severe health issues including cancer. The current review discusses the different adsorbents such as carbonac-
eous and activated carbon materials, nanosized metal oxides, low-cost natural materials, clay minerals and
nanocomposites employed by researchers to treat Co(II)-polluted water. The systems used have been assessed in
terms of overall Co(II) sorption capacity. Special emphasis has been given to the environmental conditions such
as contact time, solution pH, initial Co(II) concentration, temperature, and mineral dosage. Moreover, empirical
and surface complexation modeling (SCM) of the sorption systems is summarized. Natural materials, agricultural
waste materials, and bio sorbents exhibited outstanding Co(II) sorption performance. The current investigation
provides an overview of the state of the Co(II) removal studies performed by using various adsorbents.
1. Introduction
Pollution caused by metal ions is a foremost environmental concern
worldwide due to their acute toxic and bio-accumulative nature (Hu
et al., 2018; Mohammed et al., 2011; Saleem et al., 2015). The ex-
cessive use of metal ions in different industrial processes and the release
of polluted-water into the environment has contributed to an increased
quantity of metal ions contamination of waterways (Luo et al., 2018;
Mohammed et al., 2011; Saleem et al., 2015; Tchounwou et al., 2012).
Metals such as cobalt (II), cadmium (II), chromium(VI), lead (II), nickel
(II) and mercury (II) are considered as priority pollutants due to their
high toxicity at elevated concentrations (Ali et al., 2016; Bhuyan et al.,
2017; Hu et al., 2018). The US Environmental Protection Agency (EPA)
as well as the International Agency for Research on Cancer (IARC) has
grouped these ions as known human carcinogens even at low con-
centration (Tchounwou et al., 2012). According to World Health Or-
ganization (WHO), the maximum permissible concentration of cobalt
(II) in drinking water is 0.05 mg/L.
Cobalt (atomic number 27) is a naturally occurring element and is
the 24th
most rich heavy metal in the earth’s mantle. It has one stable
isotope (59
Co) and 26 known radioactive isotopes (Kim et al., 2006).
Although cobalt exists in three oxidation states (0, +2 and +3), the
most prevalent oxidation state is +2 under environmental condition
(Kim et al., 2006). It is highly susceptible to corrosion by alkali, water,
and air, and as a result, it has been used for various purposes including
electroplating, as a component in stainless and magnet steels in the
manufacture of batteries and paints pigments, and in mineral proces-
sing and forging (Uddin, 2017).
The extensive use of Co(II) in industries and its radionuclides 60
Co
and 58
Co in nuclear power plants and medicine suggests that significant
amounts of Co(II) are released into the environment. At low levels, Co
(II) is beneficial for human and plants nutrients; however, exposure to
Co(II) beyond permissible levels may damage human health and cause
vomiting, asthma, pneumonia, nausea, vision difficulties, heart pro-
blems, thyroid damage and so on (Kim et al., 2006; Luo et al., 2018;
Zhu et al., 2016). In addition, radioactive Co(II) isotopes cause hair loss,
bleeding, sterility, diarrhoea, coma and even death (Kim et al., 2006;
Liu et al., 2011a; Luo et al., 2018). A significant level of Co(II) in the
soil can be also caused acute toxicity to the plant kingdom (Dinh et al.,
2018). Therefore, it is essential that harmful Co(II) ions are removed
https://doi.org/10.1016/j.enmm.2018.10.003
Received 12 July 2018; Received in revised form 24 August 2018; Accepted 6 October 2018
⁎
Corresponding authors.
E-mail addresses: a.islam@latrobe.edu.au (Md. A. Islam), m.angove@latrobe.edu.au (M.J. Angove).
Environmental Nanotechnology, Monitoring & Management 10 (2018) 435–456
2215-1532/ © 2018 Published by Elsevier B.V.
T