Removal of dissolved heavy metals from aqueous waste effluents

Claim 2

An environmentally-compatible process for removal of toxic heavy metals from an aqueous effluent comprising the steps of: (a) contacting a bed of at least 50% by weight pure iron in particulate form, 50% or more of which has a mesh size in the range of about 21/2 to 200 (U.S. Standard Sieve Series), with an oxygen-containing medium and an aqueous medium at a temperature in the range of about 40° F. to 140° F. and a pH in the range of about 7 to 10 under conditions providing an oxygen-water-iron interface without agitation of said bed for a period sufficient to react at least a substantial portion of the exposed iron surfaces of the particulates in said bed with the oxygen and water so as to produce active surfaces on the iron particles having enhanced adsorption for said heavy metals; (b) thereafter, without allowing the active adsorptive surfaces so formed to dry, inundating the particulates with said aqueous effluent at a temperature in the range of about 40° F. to 140° F. and a pH in the range of about 7 to 10 so as to bring about intimate contact of the aqueous effluent and adsorptive surfaces to effect adsorption of at least a substantial portion of said heavy metals in the aqueous effluent on to said adsorptive surfaces; and (c) separating the contacted aqueous effluent having reduced amounts of heavy metal from the bed of iron particulates having heavy metals adsorbed thereon.

Claim 3

The process of claim 1 including the step of periodically replacing the bed of spent iron particulates having adsorbed heavy metals thereon with a bed of fresh at least 50% by weight pure iron in particulate form and repeating steps (a), (b) and (c).

Claim 4

The process of claim 1 wherein said oxygen-containing medium is air.

Claim 5

The process of claim 1 wherein said aqueous medium is said aqueous effluent.

Claim 6

The process of claim 1 wherein said active surfaces having enhanced adsorption comprise ferric oxyhydroxide.

Claim 7

The process of claim 1 including the step of charging the spent iron having adsorbed heavy metal thereon as raw material to a steelmaking process.

Claim 8

An environmentally-compatible process for removal of toxic heavy metals from an aqueous effluent comprising the steps of: (a) contacting a bed of at least 50% by weight iron particles, 50% or more of which has a mesh size in the range of about 21/2 to 200 (U.S. Standard Sieve Series), with air and said aqueous effluent at a pH in the range of about 7 to 10 and a temperature in the range of about 40° F. to 140° F. and under conditions providing an oxygen-water-iron interface without agitation of the iron particles in said bed for a period sufficient to react at least a substantial amount of the iron with the oxygen and water so as to produce active surfaces on the iron particles having enhanced adsorption for said heavy metals; (b) thereafter, without allowing the active adsorptive surfaces so formed to dry and without agitation of the iron particles in said bed, inundating the activated iron particles so as to bring about intimate contact of the adsorptive surfaces and said aqueous effluent at a temperature in the range of about 40° F. to 140° F. and at a pH in the range of about 7 to 10 for a period sufficient for at least a substantial portion of said heavy metals to be adsorbed on to said adsorptive surfaces; (c) separating the contacted aqueous effluent having reduced amounts of heavy metals from the bed of iron particles having the heavy metals adsorbed thereon; (d) periodically replacing the bed of iron particles after exhaustion with a fresh bed of at least 50% by weight iron particles, 50% or more of which has a mesh size in the range of about 21/2 to 200 (U.S. Standard Sieve Series), and repeating steps (a), (b) and (c) with same.

Claim 9

An environmentally-compatible process for removal of toxic heavy metals from an aqueous effluent comprising the steps of: (a) contacting a bed of at least 50% by weight iron particles, 50% or more of which has a mesh size in the range of about 21/2 to 200 (U.S. Standard Sieve Series), with air and said aqueous effluent at a pH in the range of about 7 to 10 and a temperature in the range of about 40° F. to 140° F. and under conditions providing an oxygen-water-iron interface without agitation of the iron particles in said bed for a period sufficient to react at least a substantial amount of the iron with the oxygen and water so as to produce active surfaces on the iron particles having enhanced adsorption for said heavy metals; (b) thereafter, without allowing the active adsorptive surfaces so formed to dry and without agitation of the iron particles in said bed, inundating the activated iron particles so as to bring about intimate contact of the adsorptive surfaces and said aqueous effluent at a temperature in the range of about 40° F. to 140° F. and at a pH in the range of about 7 to 10 for a period sufficient for at least a substantial portion of said heavy metals to be adsorbed on to said adsorptive surfaces; (c) separating the contacted aqueous effluent having reduced amounts of heavy metals from the bed of iron particles having the heavy metals adsorbed thereon; (d) periodically replacing the bed of iron particles after exhaustion with a fresh bed of at least 50% by weight iron particles, 50% or more of which has a mesh size in the range of about 21/2 to 200 (U.S. Standard Sieve Series), and repeating steps (a), (b) and (c) with same.

Claim 10

The process of claim 7, including the step of recycling at least a portion of the separated aqueous effluent from step (c) back to step (b) so as to increase the amount of toxic metals removed.

Claim 11

The process of claim 7 wherein a plurality of beds of said iron particles are provided in parallel flow relationship and steps (a), (b) and (c) are carried out in each bed.

Claim 12

The process of claim 9 wherein the replacement of a bed of exhausted iron particles with a fresh bed of at least 50% by weight iron particles of step (d) is carried out in at least one bed while steps (a), (b) and (c) are carried out in the other of said plurality of beds.

Claim 13

The process of claim 7 wherein a plurality of beds of said iron particles are provided in series flow relationship and steps (a), (b) and (c) are carried out in each bed whereby the toxic metal content of the effluent is progressively lowered.

Claim 14

The process of claim 11 wherein the replacement of a bed of exhausted iron particles with a fresh bed of at least 50% by weight iron particles of step (d) is carried out in at least one bed while steps (a), (b) and (c) are carried out in the other of said plurality of beds.

Claim 15

An environmentally-compatible process for the removal of toxic heavy metals from aqueous effluent comprising the steps of: (a) providing a bed of iron particulates having at least 50% by weight pure iron, 50% or more of the particulates having a mesh size in the range of about 10 to 80 (U.S. Standard Sieve Series); (b) flowing an aqueous medium at a temperature in the range of about 40° F. to 140° F. and a pH in the range of about 7 to 10 upwardly through said bed in the presence of air so as to form an upwardly rising interface of iron particulates, air and aqueous medium for a period sufficient to react at least a substantial portion of the iron particulates with oxygen and water so as to form active iron surfaces having enhanced adsorptive properties for said heavy metals, the flow rate of said aqueous medium being insufficient to cause agitation of said bed or entrainment of said iron particulates in said aqueous medium; (c) thereafter and without allowing the adsorptive surfaces so formed to dry, flowing the aqueous effluent to be treated through the bed at a temperature in the range of about 40° F. to 140° F. and a pH in the range of about 7 to 10, whereby the iron particulates with adsorptive surfaces intimately contact the effluent and toxic heavy metals are adsorbed on said adsorptive surfaces; (d) periodically discontinuing the flow of aqueous effluent through the bed, replacing the exhausted bed with a fresh bed of particulates as in step (a), and repeating steps (b), (c) and (d); and (e) disposing of the exhausted bed having adsorbed heavy metals thereon as a scrap iron charge to other processing.

Claim 16

An environmentally-compatible process for the removal of toxic heavy metals from aqueous effluent comprising the steps of: (a) providing a bed of iron particulates having at least 50% by weight pure iron, 50% or more of the particulates having a mesh size in the range of about 10 to 80 (U.S. Standard Sieve Series); (b) flowing an aqueous medium at a temperature in the range of about 40° F. to 140° F. and a pH in the range of about 7 to 10 upwardly through said bed in the presence of air so as to form an upwardly rising interface of iron particulates, air and aqueous medium for a period sufficient to react at least a substantial portion of the iron particulates with oxygen and water so as to form active iron surfaces having enhanced adsorptive properties for said heavy metals, the flow rate of said aqueous medium being insufficient to cause agitation of said bed or entrainment of said iron particulates in said aqueous medium; (c) thereafter and without allowing the adsorptive surfaces so formed to dry, flowing the aqueous effluent to be treated through the bed at a temperature in the range of about 40° F. to 140° F. and a pH in the range of about 7 to 10, whereby the iron particulates with adsorptive surfaces intimately contact the effluent and toxic heavy metals are adsorbed on said adsorptive surfaces; (d) periodically discontinuing the flow of aqueous effluent through the bed, replacing the exhausted bed with a fresh bed of particulates as in step (a), and repeating steps (b), (c) and (d); and (e) disposing of the exhausted bed having adsorbed heavy metals thereon as a scrap iron charge to other processing.

Claim 17

The process of claim 13, including the step of recycling at least a portion of the treated aqueous effluent to step (c) so as to increase the amount of toxic metals removed.

Claim 18

The process of claim 13 wherein a plurality of beds of said particulates are provided in parallel flow relationship and steps (b), (c) and (d) are carried out in each bed.

Claim 19

The process of claim 15 wherein bed replacement of step (d) and step (a) are carried out in at least one bed while steps (b) and (c) are carried out in the other of said plurality of beds.

Claim 20

The process of claim 13 wherein a plurality of beds of said particulates are provided in series flow relationship and steps (b), (c) and (d) are carried out in each bed whereby the toxic metal content of the effluent is progressively lowered.

Claim 21

The process of claim 17 wherein bed replacement of step (d) and step (a) are carried out in at least one bed while steps (b) and (c) are carried out in the other of said plurality of beds.