Heavy metals constitute a group of danger inorganic chemical for the ecosystems and human health because of their high toxicity in the industrial aqueous waste water.
Heavy metals are presenting naturally 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, ore refineries, tanneries, fertilizer industries, battery and pesticide production, metal plating 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 membrane filtration, ion exchange, chemical precipitation and electrochemical technologies 6, 7, 8, 9, 10.
Among these techniques, adsorption has revealed the flexibility in design and operation and, in many cases, it will generate high-quality treated effluent. In addition, due to the fact of the reversible nature of most adsorption processes, the biosrobents can be regenerated by appropriate desorption processes for multiple uses 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 and Temkin 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.
