Hi, Vladimer,

One way is to immerse a few crystals of Dehydrated (white in colour) Copper Sulphate in the mixture, which will absorb water from oil by which the white crystals will turn blue, meaning that the salt has absorbed water. The salt will not dissolve in oil.

If the mixture is in bulk, heat the mixture say up to 80 degrees celsius so that the water will slowly but steadily evaporate.

thank you very much. water molecules are suspended into the oil make oil colour opaque, when biol the oil turns transparent and with low kinematic viscosity . in this case into the warm  and transparent iol we see that water separates from the oil on the buttom. We Pour off the oil surface layer to another vessel and left the lower aqueous layer. but when cool oil  down the room temperature  oil again became opaque. may water drops maintained into the iol.

Vladimer,

as you say water is dispersed in oil (at least most of it) not dissolved.

Never boil the oil with dispersed water because of safety. As suggested keep it below 100°C (also at bottom!).

Instead of waterless copper sulfate better to use waterless sodium sulfate (cheaper).

You may enhance separation by centrifugation. For removing traces you may use molecular sieves.

So, let's begin in detail. This oil is heat transfer oil (http://s02.static-shell.com/content/dam/shell/static/ind/downloads/lubes-b2b/other-shell-lubricants/heat-transfer-oil.pdf), 6 liter. This oil is needed to the chemical jacketed reactor for temperature control. In the system, was small water and oil pump dispersed water drops into the oil during circulation. Oil changed the color. It consists of dispersed and dissolved water into the oil. We boiled in order to remove access of water. At high temperature (80 °C) oil become transparent and I noticed sediment water droplets on bottom. We remove this bottom level but when upper level oil has cooled down the room temperature it regained its color – opaque like a “Fanta”. I think suspended water droplets remained into the main oil. I think It need several procedure of boiling with your proposed copper sulfate Or sodium sulfate technique to finally remove tiny droplets, am I right?

agree, alternatively or in addition you may use centrifugation. It seems water solubility is enhanced at 80°C. So lower temperature maybe tried as long as the viscosity is not too high for water separation.

Further you may dry it over sodium sulfate or molecular sieve.

thank you very much. we couldn't use centrifugation as oil is 6 liter and it takes much time

Dehydrated Copper Sulphate immediately takes up the water, changing its colour. If further addition of the salt doesn't change the salt colour, it means there is no water left in the mixture.

Another way is to freeze the mixture to zero degrees celsius, whereby the water freezes first, & being solid, it will be easier to separate both through an ordinary sieve.