Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2000-09-08
2003-02-04
Cintins, Ivars (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S688000, C210S912000
Reexamination Certificate
active
06514414
ABSTRACT:
TECHNICAL FIELD
The present invention provides a process for the separation and removal of iron ions from a basic zinc solution containing said iron ions. The present invention also provides a process for preparing zinc oxide that is substantially free of iron ions.
BACKGROUND OF THE INVENTION
Zinc oxide is a commercially important compound of zinc. It is used in rubber, paint, ceramics, emollients, and fluorescent pigments. It is also used in the organic field in the manufacture of zinc-containing organometallic compounds such as accelerators for the curing of rubber, and in the photocopying industry.
In one process, it is made from zinc hydrosulfite (zinc dithionite), which is converted to sodium hydrosulfite by the action of sodium hydroxide. In this reaction, zinc oxide is a byproduct. However, there is a need to further purify it for applications in various industries such as the rubber and cosmetic industry. The present invention provides a process for obtaining zinc oxide that is substantially free of iron ions, as well as a general process for the separation and removal of iron ions from a basic zinc solution.
U.S. Pat. No. 4,071,357, Peters, Jan. 31, 1978, discloses a process for recovering a substantially pure zinc oxide product from steel-making flue dust or a similar material which comprises leaching the flue dust with concentrated ammonia and carbon dioxide to dissolve zinc and unwanted impurities, cementing the leach filtrate with zinc to remove copper, cadmium, and lead impurities, conducting a steam distillation on the cementation filtrate to precipitate basic zinc carbonate, remove the ammonia and carbon dioxide, and iron impurities, and filtering to provide a residue of essentially basic zinc carbonate, sulfur, and chromium. This residue is then washed to remove soluble sulfates, dried and calcined at high temperatures to break down the basic zinc carbonate into zinc oxide, water washed to remove chromium and the residue of the water wash dried to produce the desired impurity-free zinc oxide product. The two water washes may be combined into one step performed after the calcining step to remove both sulfur and chromium in one step.
U.S. Pat. No. 5,582,737, Gula et al., Dec. 10, 1996, and U.S. Pat. No. 5,948,264, Dreisinger et al., Sep. 7, 1999, disclose an ion exchange separation, recovery and regeneration process for the control of iron to replace the conventional bleed stream process used in copper electrowinning. The process minimizes the loss of cobalt from the electrowinning circuit and strips the iron into a sulfate based solution suitable for leach solution makeup. In addition, this process can effect a lowering of the total iron concentration in the electrolyte circuit with an associated increase in current efficiency. The process captures the iron as iron (III) on an ion exchange medium containing a plurality of —CH(PO
3
R
2
)
2
or —C(PO
3
R
2
)
2
— groups through which the divalent metal ions pass. The iron (III) is then reduced with copper(I) to form iron(II) that is freed from the exchange medium, thereby permitting regeneration of the medium.
U.S. Pat. No. 5,759,503, Myerson et al., Jun. 2, 1998, discloses a method for the recovery of high purity zinc oxide products, and optionally iron-carbon feedstocks, from industrial waste streams containing zinc oxide and/or iron. The waste streams preliminary can be treated by adding carbon and an ammonium chloride solution, separating any undissolved components from the solution, displacing undesired metal ions from the solution using zinc metal, treating the solution to remove therefrom zinc compounds, and further treating the zinc compounds and the undissolved components, as necessary, resulting in the zinc products and the optional iron-carbon feedbacks. Once the zinc oxide has been recovered, the purification process is used to further purify the zinc oxide to obtain zinc oxide which is at least 99.8% pure and which has a predeterminable purity and particle characteristics.
SUMMARY OF THE INVENTION
The present invention provides a process for the separation and removal of iron ions from a basic zinc solution comprising said iron ions, said process comprising the steps of:
(a) contacting an aqueous basic zinc solution that comprises said iron ions with a solid ion exchange resin comprising an insoluble cross-linked polymer, said polymer comprising at least one pendant phosphonate group;
(b) maintaining said contact at a pH of from about 8 to about 12, and a temperature of from about 10° C. to about 90° C., for a time period sufficient to form solid phase-bound iron ions and a liquid phase containing the aqueous basic zinc solution having an iron ion concentration that is substantially reduced compared to the solution from (a);
(c) separating the solid phase-bound iron ions and the liquid phase; and
(d) contacting the solid phase-bound iron ions with an aqueous acidic solution under conditions sufficient to regenerate the solid ion exchange resin.
The present invention also provides a process for preparing zinc oxide that is substantially free of iron ions, said process comprising the steps of:
(a) contacting ammonium carbonate and zinc oxide to form a mixture comprising a zinc ammonia carbonate complex and metal impurities comprising iron, lead, and cadmium, and optionally sulfur compounds;
(b) optionally filtering the mixture from step (a) to produce a residue comprising mostly sulfur and a filtrate comprising mostly the zinc ammonium carbonate complex and metal impurities comprising iron, lead and cadmium;
(c) treating the filtrate from step (b), or the mixture from step (a) with zinc(0) to remove the lead and cadmium and to form a cementation product, and filtering the cementation product to form a cementation residue comprising mostly zinc, lead and cadmium and a cementation filtrate comprising mostly zinc and iron ions;
(d) contacting the cementation filtrate from step (c) with an ion exchange resin comprising an insoluble cross-linked polymer, said polymer comprising at least one pendant phosphonate group, and maintaining said contact for a time period sufficient to form solid phase-bound iron ions and a liquid phase containing the cementation filtrate having an iron ion concentration that is substantially reduced compared to the concentration of iron ions in the cementation filtrate in step (c);
(e) heating the liquid phase from step (d) to remove ammonia and to precipitate zinc ions in solution as mostly zinc carbonate;
(f) calcimining the zinc carbonate precipitate of step (e) at a temperature of from about 200° C. to about 1100° C. to convert the zinc carbonate to zinc oxide.
DETAILED DESCRIPTION OF THE INVENTION
The first step in the present process for the separation and removal of iron ions from a basic zinc solution involves contacting an aqueous basic zinc solution that contains iron ions with a solid ion exchange resin comprising an insoluble cross-linked polymer.
In a preferred embodiment, the iron ions to be removed are iron(III) ions although iron ions of other oxidation states such as Fe(II) or Fe(I) are also within the scope of the present invention.
The basic zinc solution is prepared in a similar way to that of U.S. Pat. No. 4,071,357 in that a zinc oxide wet cake is dissolved in a solution that contains ammonia and carbon dioxide bubbled into it to produce ammonium carbonate. A zinc-ammonia-carbonate complex is formed. The ammonium carbonate that forms the zinc-ammonia carbonate complex is preferably an ammoniacal-ammonium carbonate solution which can be prepared by feeding gaseous carbon dioxide into a concentrated ammonium hydroxide solution with vigorous stirring, as disclosed in U.S. Pat. No. 5,204,084. While the basic zinc solution of the present invention preferentially contains ammonium hydroxide, the present process may also employ other basic zinc solutions such as those containing sodium hydroxide.
The insoluble crosslinked polymer of the solid ion exchange resin comprises at least one pendant phoshonate (—PO
3
R
2
) group. In one embodiment, the pendant phosphonate g
Cintins Ivars
Clariant Finance (BVI) Limited
Silverman Richard P.
LandOfFree
Process for separation and removal of iron ions from basic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for separation and removal of iron ions from basic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for separation and removal of iron ions from basic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3141333