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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.  

 

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

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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.

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