Oil-absorbing polymers are natural elements that absorb oil from water without damage to the water. A polymer is a multi-unit set of molecules with a complex structure. As of 2011, polymer chemistry is being tested as a means of cleaning up major oil spills and maintaining industrial oil contamination. It is thought that the polymer molecules "eat" the oil molecules and restructure themselves to accommodate them; then the polymer substance is either removed from the water or dissipates naturally.
Partially freezing a mixture of oil and water will separate the oil from the water in segments. The oil is staved off by pouring out one-quarter of the unfrozen water and repeating the freezing cycle again; this process can be repeated up to four times. The complicated structure of the frozen water, with multiple hydrogen bonds criscrossing throughout, doesn't allow the oil molecules to fit inside.
Epsom salts coagulate oil that has already begun to emulsify in the water; the salts also reduce the solubility of the oil. When the oil has clumped together it can be removed from the water by straining. However, the salts themselves will leave residue in the water, so the water will not be completely clean after the oil is removed.
Oil skimming is meant to remove oil from the surface of water. A strip of chemically enhanced oil-skimming material moves through the water and attracts the oil resting on top; the water does not bond to the oil-skimming material and is left behind. Oil skimming is commonly used with major industrial machinery, such as steel mills and food processing plants. The oil used to operate the machinery in these plants can leave behind a residue that contaminates coolants.