How can you separate oil from water with cheap materials?

Answer 1

Assuming the oil and water physically separate in a short time when standing still: If you would like to save the oil, cut the bottom off a plastic bottle and leave the cap on (for small samples a sixteen ounce or one liter bottle, for a gallon at a time use a three or five gallon jug with a pour spout on the bottom, they usually have a fill spout so you don't have to cut holes and they sit flat on a table to make draining easier) fill the bottle with the mixture, let stand on its cap until they separate (the longer you can let it separate the better the results), loosen the cap slightly so the water leaks out, what's left is fairly pure oil. If you have larger samples (like a 50 gallon drum or larger) siphoning becomes more feasible and the shape of the bottom of the container becomes more important. If it is flat try to shim one side up so there is one low spot and smooth drainage to it. Insert the siphon hose down to the low spot, and siphon until the water is gone (a safer siphon arrangement is an intermediate bottle between your mouth and the oil). If they don't separate easily, you may still have an option: if the oil has a high vapor temperature like cooking oils, you can try distillation. Slow cook the mixture until the water evaporates, at low enough temperature that it doesn't boil or burn the oil when the water is gone. If you need to recover the water, run the outflow gas through a long coiled tube to condense. If the oil is more complex like crude oil (has components that have lower evaporation temperature than water), the time, effort and expense go much higher. That would be a different question.