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1. aqueous waste water. Heavy metals are

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1.   INTRODUTION

Heavy metals constitute a group of
inorganic chemical hazards for the ecosystems and human health because of their
high toxicity in the industrial aqueous waste water. Heavy metals are naturally occurring elements that have a
high atomic weight and a density at least 5 times greater than that of water 1.  

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For
decades, water pollution has been studied because of the rapid industrial
development which increased the production and use of heavy metals, resulting
in high concentrations of heavy metals often being discharged into water
bodies. Industries such as mining 2, 3, tanneries, metal plating, fertilizer
industries, battery and pesticide production, ore refineries and the paper
industry 4 are the major contributing sources of heavy metal. Heavy metals,
such as zinc (Zn), lead (Pb), copper (Cu), iron (Fe), nickel (Ni), and cadmium
(Cd) are toxic, carcinogenic, persistent in nature and tend to bioaccumulate 5. La source : Article 1

 

Several
methods have been proposed for efficient heavy metal removal from water,
including but not limited to chemical precipitation, ion exchange, membrane
filtration and electrochemical technologies 6, 7, 8, 9, 10. Among these
techniques, adsorption has proven the flexibility in design and operation and,
in many cases it will generate high-quality treated effluent. In addition,
owing to the reversible nature of most adsorption processes, the adsorbents can
be regenerated by suitable desorption processes for multiple use 11, and many
desorption processes are of low maintenance cost, high efficiency, and ease of
operation 12. Therefore, the adsorption process has come to the forefront as
one of the major techniques for heavy metal removal from water/wastewater.

 

This technology is cheap and
environmentally friendly if low cost adsorbents are used. In the search for low
cost adsorption materials over the past years, many researchers shifted their
interests into the use of animal wastes, such as chicken feathers, animal
bones, Ensis siliqua Shell, snail
shells, …  13, 14, 15 ,16 . Since the cost of an
adsorbent depends on its abundance, availability and effectiveness, animal wastes
have been extensively studied.

 

There are many parameters that affect the efficiency of an adsorption
process, such as pH, temperature, adsorbent dosage and initial metal
concentration. For instance, pH may affect the metal availability, functional
groups on the surface of the adsorbents and ionic strength17. In case of
adsorbent dosage and metal concentration, the efficiency mainly depends on the
availability of active sites and the competition for active sites 18.  Article1

 

The purpose of the present review is to
study the feasibility of valorization and
develop a new cost low biosorbent to remove heavy metals from wastewaters by
adsorption technique using Calcined Cow Leather as a new abundant material and
an eco-friendly biosorbent for the removal of Cu, Zn
and Ni from metal contaminated wastewater and evaluate the effects of pH,
contact time, adsorbent dosage and initial metals concentration on metal uptake
and removal efficiencies.

 

The biosorption behavior was
analyzed using the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich
adsorption isotherms. The experimental data of adsorption kinetics were
analyzed using the pseudo-first and pseudo-second order kinetic models and the
thermodynamics of this process were also studied.

 

 

2.   Materials and methods

 

2.1. heavy metal ions preparation

Unless otherwise stated, all chemical
reagents used in this study were of analytical grade.    Synthetic stock solutions of heavy metals (Cu
(II), Zn (II) and Ni (II)) of 1000 mg/L were prepared in 1L of 0.5% HNO3
distilled water by dissolving respectively, 3.97g, 4.40g, and 4.52g of CuSO4.5H2O,
ZnSO4.7H2O, and NiSO4.6H2O from
Merck (Germany). HNO3 was used as an electrolyte to control the
ionic strength of metal ions.
 Desired test solutions of heavy metal ions
were prepared using appropriate subsequent dilutions from stock solutions. The resulting stock solutions were stored in air tight
bottle. HCL and NaOH were obtained from Merck and used for pH value adjustment.

 

2.2.Biosorbent preparation

Cow leathers
(CLs) were kindly supplied by a slaughterhouse’s management waste service
located in Casablanca city. Cow leathers were cleaned from blood and other
dirt, and salted immediately after that with common marine salt, in order to
avoid degradation processes and development of micro-organisms and bacteria. Then
let dry in open air for many days helping to a partial removal of water. After
this operation, the CLs were transferred to an oven at 70°C for drying.

Dried leathers
were showed a high resistance for grinding, the reason why we opted to cut it
into small pieces, then calcined for 4 hours at 525 °C.

The materials were ground to a fine powder
and rinsed with deionized water until the pH of the filtrate reached 7 and then
dried for 24hours at 105°C.

The final material was kept in plastic container and
preserved in a desiccator for further use and the Calcined Cow Leathers were
abbreviated (CCL).

 

 

 

 

 

2.3.Apparatus

 

Iductively coupled argon plasma  Spectromètre ICP-OES iCAP 6000 (in)-
Australian, was used for the determination of Copper, Zinc, Nickel concentrations
respectively at 324 nm, 213 nm and 231 nm.

The pH was measured using a Metrohm pH meter 691,
SWISS, provided with a glass electrode. The shaking of solutions was carried
out with a 3500 VWR, USA digital shaker. Stirring of solutions was carried out
with a magnetic stirrer Model Jenway 1000, England.

 

3.   Characterization of CCL adsorbent

 

Chemical analyzes of the CCL powder were
performed using a fluorescence spectrometer (Wavelength dispersion spectrometer
– Axios type). (Table 1)

Fourier transform infrared spectroscopy
(FTIR) analysis was performed in the 450-4000cm-¹, using a
FT/IR-Vertex 70 spectrometer (Germany). (Figure 1)

The morphology of the CCL powder, was
observed using a FEI Quanta 200 instrument (USA) scanning electron microscope
(SEM), the images of the microstructure have been obtained with a maximum
voltage of 10 kV.(Figure 2)

The elemental composition of our material, has
been determined by Energy Dispersive X-rays Spectroscopy (EDXS): X’Pert Pro MPD
Panalytical (Netherlands) with Cu anode as the source of X-rays at wavelength ?=1.54 Å. (Figure 3)

The specific surface area was measured by
the BET method using a Pore Size using a Micromeritics ASAP 2020 apparatus
(USA).

 

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