Process for separating oil from emulsions of oil in water

Claim 2

A single-stage process of separating oil from an oil-in-water emulsion which comprises adding a ferric salt to the emulsion, thereafter adding to the emulsion containing the ferric salt used oil and an alkali in sufficient amount to adjust the hydrogen-ion concentration of the mixture to a pH between 5.5 and 6.5, subsequently adding an aqueous solution of high-molecular weight water-soluble polymeric flocculating agent to the mixture, intimately mixing the mixture and thereafter allowing it to stand for a sufficient period for it to stratify into two phases, one phase consisting essentially of water free from oil and the other consisting of the flocculating agent and the ferric hydroxide containing the oil present in the emulsion, and finally separating the two phases.

Claim 3

A single-stage process as defined in claim 1, in which the alkali is sodium hydroxide.

Claim 4

A single-stage process as defined in claim 2, in which the mixture is adjusted to a pH of 6.2 by the addition of sodium hydroxide.

Claim 5

A single-stage process as defined in claim 2, wherein the ferric salt is ferric sulfate.

Claim 6

A single-stage process as defined in claim 2, wherein the ferric salt is ferric chloride.

Claim 7

A single-stage process as defined in claim 1, wherein said step of forming said intimate mixture comprises passing a compressed gas through the mixture to intensify the mixing.

Claim 8

A single-stage process of separating oil from an oil-water emulsion which comprises adding a ferric salt to the emulsion; adding under vigorous stirring used oil and an alkali in an amount sufficient to adjust the hydrogen-ion concentration of the mixture to a pH value between 5.5 and 6.5; subsequently adding an aqueous solution of high-molecular weight water-soluble polymeric flocculating agent to the mixture; intimately mixing the components of said mixture and thereafter allowing it to stand for a sufficient time period to separate into two phases, one phase consisting essentially of water free of oil, and the other consisting of the flocculating agent, ferric hydroxide containing the oil originally present in the emulsion together with the subsequently added oil; and finally separating the two phases.

Claim 9

A single-stage process of separating oil from an oil-water emulsion which comprises adding a ferric salt to the emulsion; adding under vigorous stirring used oil and an alkali in an amount sufficient to adjust the hydrogen-ion concentration of the mixture to a pH value between 5.5 and 6.5; subsequently adding an aqueous solution of high-molecular weight water-soluble polymeric flocculating agent to the mixture; intimately mixing the components of said mixture and thereafter allowing it to stand for a sufficient time period to separate into two phases, one phase consisting essentially of water free of oil, and the other consisting of the flocculating agent, ferric hydroxide containing the oil originally present in the emulsion together with the subsequently added oil; and finally separating the two phases.

Claim 10

A single-stage process as defined in claim 7, in which the amount of the aqueous solution of the polymer that is added to the mixture is equivalent to between 30 and 60 milligrams of polymer per liter of the mixture.

Claim 11

A single-stage process as defined in claim 7, wherein said polymer is selected from the group consisting of polyacrylic acid, polyacrylamide polyvinyl alcohol and polyethylene oxide.

Claim 12

A single-stage process as defined in claim 7, wherein said polymer consists essentially of a mixture of polyacrylamide with an alkali salt of polyacrylic acid.

Claim 13

A single-stage process as defined in claim 7, wherein said polymer consists essentially of a mixture of polyacrylamide with an ammonium salt of polyacrylic acid.

Claim 14

A single-stage process as defined in claim 7, in which the oil added is oil that was recovered from a prior batch of ferric hydroxide that was separated in a prior operation of the process.

Claim 15

A single-stage process as defined in claim 7, in which a mineral oil is added to the mixture after its adjustment to a pH value between 5.5 and 6.5 has been made, in an amount equivalent to approximately one volume of oil to each 100 volumes of the mixture.

Claim 16

A single-stage process as defined in claim 7, in which the oil-in-water emulsion is a used cutting oil.

Claim 17

A single-stage process as defined in claim 7, wherein said mixture is adjusted to a pH value of 5.5 by the addition of sodium hydroxide.

Claim 18

A single-stage process as defined in claim 7, wherein said mixture is adjusted to a pH value of 6.2 by the addition of sodium hydroxide.