Preparation, characterization of fish scales biochar and
their applications in the removal of anionic indigo carmine
dye from aqueous solutions
George O. Achieng, Chrispin O. Kowenje, Joseph O. Lalah
and Stephen O. Ojwach
ABSTRACT
The preparation and applications of Tilapia (Oreochromis niloticus) fish scale biochars (FSB) as
an adsorbent in the removal of indigo carmine dye (ICD) from aqueous solutions is described.
The biochars were prepared through pyrolysis over a temperature range of 200
C–800
C and
characterized for surface charge, functional groups, thermal stability, particle size and morphology,
elemental composition, crystallinity, and surface area by using pH
pzc
, Fourier transform infrared
(FTIR) spectroscopy, thermo-gravimetric analysis (TGA), transmission electron microscopy/scanning
electron microscopy (TEM/SEM), energy dispersive X-ray (EDX) spectroscopy, powder X-ray
diffraction (PXRD) and Brunauer-Emmett-Teller (BET) techniques, respectively. Batch experiments
were carried out to determine the variation of adsorption process with initial dye concentration,
contact time, initial solution pH, adsorbent load, temperature and adsorbent pyrolysis temperature
on the removal of the dye. The percentage removal increased with increase in initial dye
concentration and adsorbent dosage. A pH of 2 was the most appropriate for the adsorption
experiments. The equilibrium data fitted pseudo-first-order kinetics and Freundlich models, while the
thermodynamic parameters confirmed that the adsorption process was endothermic.
George O. Achieng
Chrispin O. Kowenje
Department of Chemistry,
Maseno University,
P.O. Box 333-40105, Maseno,
Kenya
Joseph O. Lalah
Department of Geochemistry and Environmental
Chemistry, School of Chemistry and Material
Science,
Technical University of Kenya,
P.O. Box 52428-00200, Nairobi,
Kenya
Stephen O. Ojwach (corresponding author)
School of Chemistry and Physics,
University of KwaZulu-Natal,
Private Bag X01, Scottsville, Pietermaritzburg
3209,
South Africa
E-mail: ojwach@ukzn.ac.za
Key words | adsorption, fish scale biochar, indigo carmine, kinetics
INTRODUCTION
A number of carbon materials are derived from either plant
or animal biomass, which are naturally abundant and renew-
able materials (Xiu et al. ). Important focus has been
given to a variety of plant biomass such as energy crops, agri-
cultural remains, and woody biomass (Xie et al. ; Okello
et al. ). Numerous researches have been done on plant
biomass (Ngeno et al. ) while a very diminutive under-
standing exists on the feasibility of animal biomass. For
example, fish scales are viewed as wastes that do not have
a clear economic significance in the environment (Rustad
; De Gisi et al. ; Nnaemeka et al. ; Nia et al.
; Temesgen et al. ; Fegousse et al. ; Lafi et al.
), despite their sustainable abundance. However, fish
scales have been applied as adsorbents for the removal of
copper from water in some countries (Huang ). Huang
() utilized Tilapia niloticus Linnaeus fish scales instead
of Atlantic cod scales, alluding to the fact that tilapia is
cheaper and more available compared to Atlantic cod. In
addition, it has been shown that applying fish scales as an
adsorbent would be a better substitute for removal of
metals from waste water compared to wool since fish
scales are already a waste generated resource material
from fish markets and households (Villanueva-Espinosa
et al. ; Huang ). Rustad () reported that about
91 million tons of fish and shellfish from both inland and
marine waters were captured worldwide and 50–60% were
consumed by humans and the rest were discarded as
waste. Despite the increase in the world’s human population
and fish aquaculture, statistics have shown that there is no
significant change in fish captured (FAO ), and this sup-
ports the sustainable availability of fish scales as a resource
for production of commercial adsorbents.
2218 © IWA Publishing 2019 Water Science & Technology | 80.11 | 2019
doi: 10.2166/wst.2020.040
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