US 5,635,071 AGranted

Recovery of carboxylic acids from chemical plant effluents

AssigneeZenon Airport Enviromental, Inc.

InventorRiad A. Al-Samadi

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Abstract

Provided is a method of removing carboxylic acids from effluent streams comprising the steps of pretreatment which may include chemical conditioning, clarification and filtering the effluent stream to remove suspended solid particles to provide a filtered stream. The filtered stream is subjected to membrane filtration to remove organic compounds having a molecular weight of greater than 150 while simultaneously permitting permeation of the membrane by the carboxylic acids to provide a membrane filtered stream. A reverse osmosis membrane is provided having a high pressure side and a low pressure side, and the membrane filtered stream is introduced to the high pressure side of the reverse osmosis membrane. The carboxylic acids are concentrated in the high pressure side of the reverse osmosis membrane. In a preferred embodiment, purified liquid (permeate) is neutralized and passed to the high pressure side of a second pass reverse osmosis membrane, producing a high-purity final permeate for plant reuse or discharge to surface water.

Claims19

Dependent claims

A method of removing low concentrations of carboxylic acids from aqueous effluent streams comprising the steps of:

(a) filtering said effluent stream to remove solid particles to provide a filtered stream;
and
(b) introducing said filtered stream to the high pressure side of a first nanofiltration membrane to concentrate organic compounds having an average molecular weight of greater than 150 in the high pressure side to provide a first organic concentrate stream while simultaneously permitting permeation of said membrane by said carboxylic acids to provide a first nanofiltration membrane permeate stream containing carboxylic acids;
thereafter
(c) introducing said first organic concentrate stream to a high pressure side of a second nanofiltration membrane to provide a second organic concentrate stream containing organic compounds having a molecular weight of more than 150 while simultaneously permitting permeating of said second nanofiltration membrane by said carboxylic acid to provide a second nanofiltration membrane permeate stream containing carboxylic acids;
(d) providing a first reverse osmosis membrane having a high pressure side and a low pressure side;
(e) introducing said first and second nanofiltration membrane permeate streams to the high pressure side of said first reverse osmosis membrane;
(f) concentrating said carboxylic acids in the high pressure side of said reverse osmosis membrane to provide a concentrated carboxylic acids retentate and passing a purified aqueous stream to the low pressure side of said reverse osmosis membrane to provide a purified aqueous stream;
(g) recirculating a portion of said purified aqueous stream from the low pressure side of said first reverse osmosis membrane to the high pressure side of said second nanofiltration membrane;
and
(h) treating said concentrated carboxylic acids retentate to recover carboxylic acids therefrom.

8 more elements

A method of removing organic acids including acetic acid and/or formic acid from an aqueous waste stream comprising the steps of:

(a) pretreating said aqueous waste stream to remove suspended solid particles therefrom to provide a substantially solid-free filtered stream;
(b) introducing said filtered stream to the high pressure side of a first nanofiltration membrane to concentrate organic compounds having an average molecular weight of greater than 150 in the high pressure side to provide an organic concentrate stream while simultaneously permitting permeation of said membrane by an organic acid selected from the group consisting of acetic and formic acid to provide a membrane filtered stream containing said organic acid;
(c) providing a first reverse osmosis membrane having a high pressure side and a low pressure side;
(d) introducing said membrane filtered stream to the high pressure side of said first reverse osmosis membrane;
(e) concentrating said organic acid in the high pressure side of said first reverse osmosis membrane to provide a concentrated aqueous retentate and passing a purified aqueous stream containing a residual of said organic acid to the low pressure side of said first reverse osmosis membrane to provide a recovered aqueous stream;
(f) adjusting the pH of said purified aqueous stream from said low pressure side of said first pass reverse osmosis membrane to a pH in the range of 5.5 to 9.5 to provide a neutralized aqueous stream;
(g) introducing said neutralized aqueous stream to a high pressure side of a second reverse osmosis membrane to provide a retentate stream and simultaneously therewith providing a high purity effluent permeate on a low pressure side of said second reverse osmosis membrane;
(h) introducing said organic concentrate stream from the high pressure side of said first nanofiltration membrane to a high pressure side of a second nanofiltration membrane to provide a second smaller organic concentrate stream of organic compounds having an average molecular weight greater than 150 and simultaneously therewith permitting permeation of said second nanofiltration membrane by said acetic acid or formic acid to provide a second nanofiltration membrane filtered stream;
(i) recirculating a portion of said purified aqueous stream from the low pressure side of said first reverse osmosis membrane to the high pressure side of said second nanofiltration membrane;
(j) adding said second nanofiltration membrane permeate stream to the high pressure side of said first reverse osmosis membrane;
and
(k) removing organic acids from said concentrated aqueous retentate of said first reverse osmosis membrane.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/375,789Filed 20 Jan 1995
Granted: 3 Jun 1997
Term ends: Not estimatedThe source records don’t support an estimate.

Classification13 codes

C07C 51/42
Preparation of carboxylic acids or their salts, halides or anhydrides: separation; Purification; Stabilisation; Use of additives
B01D 61/029
Reverse osmosis; Hyperfiltration ; Nanofiltration: multistep processes comprising different kinds of membrane processes selected from reverse…
B01D 61/04
Reverse osmosis; Hyperfiltration ; Nanofiltration: feed pretreatment
C02F 1/441
By dialysis, osmosis or reverse osmosis: by reverse osmosis