Abstract
Every year, tons of precious and/or toxic metals are thrown away in industrial liquid effluents and most frequently directly in natural environment. The recovery of those metals in dilute solutions is an everyday problem associating both ecology and economy. Copper is among the most prevalent and valuable metal used by industry. Cementation is one of the most effective and economic techniques for recovering toxic and or valuable metals from industrial waste solution and from leach liquors obtained by leaching low grade copper ore. The present study was carried out to investigate the removal of copper metal ions from synthetic waste water by cementation using a rotating iron cylinder. The study covered the effect of different parameters in batch mode which are: Initial copper concentrations, pH values, rotational speed, and reaction temperature on the rate of cementation. The rate of cementation was found to increase with increasing rotational speed, temperature, and pH till a value of 2.1 and then starts to decrease .On the other hand as the initial copper ions concentration increases from 0.2 to 0.4 M the rate of copper ions removal increase. The rate of copper recovery ranged from 10% to 90% per hour depending on the operating conditions Rates of cementation which can be expressed in terms of the rate of mass transfer were correlated to the controlling parameters by dimensionless equation: Sh=0.18 SC0.33 Re0.961. This equation can be used in the design and operation of high-productivity cementation reactor.
Highlights
The importance of environmental pollution control has increased significantly in recent years
According to the electrochemical theory of cementation which postulates that cementation takes place through the galvanic cell: Fe/ electrolyte/ Cu, increasing the cathode area via copper powder formation would decrease polarization and would increase the rate of cementation
This phenomenon was observed by AH Elshazly [30] in the case of copper cementation onto zinc plates.( Figure 3) shows that the present data fit equation (2) i.e. The reaction is first order with respect to Cu++ concentration, this finding is consistent with previous studies [20,21] on extremely dilute solutions i.e the concentration range of Cu++ does not alter the mechanism of the reaction
Summary
The importance of environmental pollution control has increased significantly in recent years. Environmental lists are primarily concerned with the presence of heavy metals in aqueous effluents due to their high toxicity and impact on human and aquatic life [1]. Cementation is one of the most effective and economic techniques for recovering toxic and/or valuable metals from industrial waste solutions [8]. The main disadvantages of the technique are excess sacrificial metal consumption [10].Cementation is used as a general term to describe the process whereby a metal is precipitated from a solution of its salts by another electropositive metal by spontaneous electrochemical reduction to its elemental metallic state, with consequent oxidation of a sacrificial metal for the recovery of more expensive and more noble dissolved metal species present in aqueous solutions [11]. The general reaction for a cementation process is given by [12]
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