الفهرس 
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Abstract
The aim of the present work is to study the effect of a stationary wiper almost touching a rotating zinc cylinder on the rate of Cu +2 ions cementation; the following parameters have been investigated:
(I) Initial Cu +2 concentration
(2) rpm
(3) the effect of the presence and absence of a wiper
(4) the effect of different additives on the rate of Cu+2 cementation
.:. cationic and anionic surfactant
.:. Drag Reducing Polymer
The rate ofCu+2 cementation was expressed by the mass transfer coefficient which was determined under different investigated parameters.
The present study revealed the following results:
.:. The mass transfer coefficient increases as rpm increaSes for zinc rotating cylinder in absence and presence of a wiper
.:. The mass transfer coefficient increases as initial Cu +2 ions concentration increases in case of absence and presence of a wiper
.:. The presence of a wiper enhances the rate of Cu +2 ions cementation by a factor ranges from (1.59 to 64%) depending on the different investigated parameters .
• :. The enhancing effect of the stationary wiper extents to include a wide range of rpm, whereas in case of rotating cylinder without a wiper the rate of cementation begins to decline at high rpm due to surface blocking by the Cu deposits .
• :. The presence of a wiper has also an economic advantage as for a certain % Cu recovery a lower mechanical power is required compared to rotating cylinder without wiper.
.:. The mass transfer data of the present study have been correlated for the condition of
326<Re<6191
2779<Sc<3244
For rotating zinc cylinder without a wiper as