Recovery of elemental phosphorus from phosphorus sludge

A method of recovering elemental phosphorus from a sludge that contains water, dirt, and elemental phosphorus as a discontinuous phase comprising, in a batch process, (A) melting said sludge; (B) forming a mixture of said sludge and about 0.5 to about 3 wt % of an oxidizing agent, based on the weight of said elemental phosphorus in said sludge, and about 75 to about 400 wt % water, based on the weight of said sludge; (C) stirring said mixture until a continuous elemental phosphorus phase forms then stopping said stirring before a phosphorus-in-water emulsion forms; and (D) separating said continuous elemental phosphorus phase from said mixture.

A method of recovering elemental phosphorus from a sludge that contains water, dirt, and about 5 to about 80 wt % elemental phosphorus as a discontinuous phase comprising, in a batch process, (A) melting said sludge at a temperature of about 55 to about 75.degree. C.; (B) forming a mixture of said sludge and, in an amount about 1 to about 4 times the amount of sludge, an aqueous solution containing about 0.5 to about 3 wt % chromic acid; (C) stirring said mixture until said elemental phosphorus forms a continuous phase then stopping said stirring before a phosphorus-in-water emulsion forms; and (D) separating said elemental phosphorus continuous phase from said mixture.

A method of recovering elemental phosphorus from a phosphorus sludge comprising, in a batch process, (A) melting a phosphorus sludge that contains about 5 to about 80 wt % elemental phosphorus in a discontinuous phase in a reactor at a temperature of about 55 to about 75.degree. C.; (B) forming a mixture of said sludge and, in an amount about 1 to about 4 times the amount of sludge, an aqueous solution containing about 0.5 to about 3 wt % chromic acid; (C) stirring said mixture for about 15 minutes to about 30 minutes at about 150 to about 300 rpm whereby said elemental phosphorus forms a continuous phase but does not form a phosphorus-in-water emulsion; (D) permitting said mixture to settle; (E) separating said lemental phosphorus continuous phase from said mixture; and (F) filtering or centrifuging said separated elemental phosphorus continuous phase.