DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on 12/3/25 has been entered.
Claim Status
The claims are newly amended.
Response to Arguments
The remarks filed are persuasive. However, part of the rejection from prior action dated 3/10/25 is partly re-iterated here. Therefore, the argument in response to this action is responded to here below.
The remarks dated 6/10/25 argued the following:
Applicant notes that Examiner appears to have conflated aspects of the Cited References, in particular with Nie, against features as recited in the claims. A feature of the claims as presented is to remove organic material prior to screening, by mixing the ore with sulfuric acid. Nie merely discloses exemplary conditioning of the ore using either sulfuric acid or sodium hydroxide prior to flotation. Such conditioning is meant to provide a certain pH to increase the effectiveness of the flotation reagent that is used after conditioning. However, the Cited References (especially Nie), do not disclose or suggest alone or in any combination removing organic matter from the ore using sulfuric acid prior to screening in view of any applicable deemed common knowledge. Notably, in Nie, its English translation states the following: *cites to Nie reference.
The remarks are respectfully not persuasive. Nie describes the same process steps of combining sulfuric acid at ambient temperature with the ore while mixing using ore whose particle size has been reduced in particle size. Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the same process steps used with the same components would have the same effect. Applicant argues that Nie describes conditioning. However, Nie describes the same process steps claimed, which would be effective to remove the same contaminants.
Claim Rejections - 35 USC § 112
The following is a quotation of the first paragraph of 35 U.S.C. 112(a):
IN GENERAL.—The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.
The following is a quotation of the first paragraph of pre-AIA 35 U.S.C. 112:
The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention.
Claims 1-12, 20-27 are rejected under 35 U.S.C. 112(a) or 35 U.S.C. 112 (pre-AIA ), first paragraph, as failing to comply with the written description requirement. The claim(s) contains subject matter which was not described in the specification in such a way as to reasonably convey to one skilled in the relevant art that the inventor or a joint inventor, or for applications subject to pre-AIA 35 U.S.C. 112, the inventor(s), at the time the application was filed, had possession of the claimed invention.
Claims 1 and 20 recite the features “where the mixing is conducted without externally heating the ore”. The specification describes instances where sulfuric acid and ore are combined without heating, but the reference does not state that the mixture should not be heated.
Claims 1 and 20 also recite that “the ore may subsequently be processed for further removal of organics”. Paragraph 64 describes further processing of the ore, but does not specifically state that the ore is process for the further removal of organics.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claim(s) 1, 2, 20 is/are rejected under 35 U.S.C. 103 as being unpatentable over Duyvesteyn (US Pub.: 2016/0153070) and in view of Gradl (EP 0131876) and in view of Rissanen (WO 2014/118436) and in view of Pingitore (US Pub.: 2016/0138133).
Duyvesteyn describes a system and method for acid leaching scandium-bearing ores (title). The ore can be a laterite ore (para. 13). The process uses sulfuric acid to leach the ore to separate some metal compounds from the rest of the ore (para. 52). More specifically, Duyvesteyn describes treating ore with sulfuric acid at room temperature (para. 80) to remove impurities (abstract). Impurities can include silicates (para. 36, 56).
As to the sulfuric acid removing organic contaminants, since the process uses the same reagents together, in the same way, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that they would react in the same way.
Nonetheless, this feature is taught by Gradl.
Gradl explains that in the prior art, it is known to use sulfuric acid to treat contaminants and it can be used as an adsorbent for organic contaminants (see “Description”, para. 4).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the same compound would be effective in the same way.
As to the screening step, Rissanen describes a method for recovering metals from ores (title). The process involves combing the ore in a slurry (page 4, lines 6-12) and then acidified (page 5, lines 11-15). Rissanen then states that the grains have a size of from 0.6 to 1.2mm (page 7, lines 10-13). Furthermore, Rissanen states that the largest grains consist of silicates and these grains can be slurried and then screened off from the rest of the ore ranging in size from 0.6 to 0.7mm by using a screen (pg 7, lines 10-16).
As to the screening step, Rissanen describes a method for recovering metals from ores (title). The process involves combing the ore in a slurry (page 4, lines 6-12) and then acidified (page 5, lines 11-15). Rissanen then states that the grains have a size of from 0.6 to 1.2mm (page 7, lines 10-13). Furthermore, Rissanen states that the largest grains consist of silicates and these grains can be slurried and then screened off from the rest of the ore ranging in size from 0.6 to 0.7mm by using a screen (pg 7, lines 10-16).
A prima facie case of obviousness exists where the claimed ranges and prior art ranges overlap or are close enough that one skilled in the art would have expected them to have the same properties. See MPEP 2144.05 I.”
Therefore, since Duyvesteyn explains that silicates are some of the impurities in the ore Rissanen describes a smaller size of 0.6 to 0.7mm that can be used to eliminate silicates larger than this size range, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to use a screen with a size range of 0.6 to 0.7mm, in order to separate these grains in this size range from the larger grains, as taught by Rissanen for use in the process of Lowe because Rissanen explains that the larger silicate particles are not desirable.
As to the initial size of the ore, the references do not teach that the initial ore size is 4mm or less.
As to the size, Pingitore teaches a method of extracting and recovering rare earth elements (title) from ores (para. 10). Scandium is a rare earth element (para. 21). The process of Pingitore contacts the ore with sulfuric acid to recover the metals (para. 8, 10). Prior to contacting the ore with sulfuric acid, the reference explains that the ore can be crushed to a size of 2-20mm (para. 10).
A prima facie case of obviousness exists where the claimed ranges and prior art ranges overlap or are close enough that one skilled in the art would have expected them to have the same properties. See MPEP 2144.05 I.”
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to crush the ore down to a size of from 2-20mm, as taught by Pingitore for use with the leaching process of Duyvesteyn, Gradl and Rissanen because crushing the ore down to this size prior to leaching with sulfuric acid would lead to predictable and expected leaching results.
As to Claim 2, Duvesteyn teaches that after leaching with sulfuric acid, the mixture is subjected to solid-liquid separation and washing to yield a tailing and a leachate (para. 108).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the tailing would contain all the contaminants in the ore, to include any organic contaminants.
Claim(s) 1, 11, 20 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie (CN 108672102) and in view of Gradl (EP 0131876) and in view of Rissanen (WO 2014/118436).
Nie describes a method of processing a phosphorous-containing ore (title). The process crushes and mills the ore (abstract “Novelty”). The mixture is in a solution while milled (abstract, “Novelty”) and ground until the particles are less than 0.074mm in size (abstract, “Novelty”). The pH of the solution is adjusted using sulfuric acid (abstract, “Novelty”). The mixture is stirred (abstract, “Novelty”). Since the pH is adjust to the desired level using acid, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that this can be considered “maintaining the pH level in the slurry to a pH range”, while mixing the slurry.
As to the sulfuric acid removing organic contaminants, since the process uses the same reagents together, in the same way, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that they would react in the same way.
Nonetheless, this feature is taught by Gradl.
Gradl explains that in the prior art, it is known to use sulfuric acid to treat contaminants and it can be used as an adsorbent for organic contaminants (see “Description”, para. 4).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the same compound would be effective in the same way.
Although Nie describes obtaining a particle size of 0.074 mm or smaller, Nie does not describe screening the particles after mixing with sulfuric acid using a screen having a size from 1mm to 0.6mm.
As to the screening step, Rissanen describes a method for recovering metals from ores (title). The process involves combing the ore in a slurry (page 4, lines 6-12) and then acidified (page 5, lines 11-15). Rissanen then states that the grains have a size of from 0.6 to 1.2mm (page 7, lines 10-13). Furthermore, Rissanen states that the largest grains consist of silicates and these grains can slurried and then screened off from the rest of the ore ranging in size from 0.6 to 0.7mm by using a screen (pg 7, lines 10-16).
Therefore, since Nie describes reducing the particles sizes, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to use a screen with a size range of 0.6 to 0.7mm, in order to separate these grains in this size range from the larger grains, as taught by Rissanen for use in the process of NIe because Rissanen explains that the larger silicate particles are not desirable.
As to the features in the preamble, the method is effective for removing or releasing organics from ores because the same process used the same way with the same compounds would have the same effect.
A preamble is generally not accorded any patentable weight where it merely recites the purpose of a process or the intended use of a structure, and where the body of the claim does not depend on the preamble for completeness but, instead, the process steps or structural limitations are able to stand alone. See In re Hirao, 535 F.2d 67, 190 USPQ 15 (CCPA 1976) and Kropa v. Robie, 187 F.2d 150, 152, 88 USPQ 478, 481 (CCPA 1951).
Claim(s) 2, 3, 4 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie, Gradl and Rissanen as applied to claim 1 above, and further in view of Drechsel (US Pat.: 4393032).
The references do state that the rock is a phosphate ore (Claim 4), but they not state separation of the two phases (Claim 2) or use of an attrition scrubbing device (Claim 3).
Drechsel describes a process for processing phosphate rock (abstract). The process combines the rock (col. 6, line 26) with sulfuric acid (col. 6, lines 33-35). The product is then fed to a crystallizer (col. 6, lines 35-37) and then is filtered (col. 6, lines 57-58). The solution is then recycled (Fig. 2, 16 and 20).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to separate the streams into a solids stream and a liquid stream (due to filtration), as taught by Dreschel for use with the process of Nie, Gradl and Rissanen because the liquid stream can be recycled for further use.
As to Claim 3, Nie describes ball milling the ore (see above), but not use of an attrition scrubbing device.
Dreschsel explains that in the process a ball mill step may be used, but alternatively, the device used can be an attrition scrubber (col. 13, lines 51-52).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to employ an attrition scrubber at the ball mill step, as taught by Dreschel for use with the process of Nie, Gradl and Rissanen because Dreschel shows that this stream can be later ball-milled after processing through an attrition scrubbing device (see Fig. 5).
Claim(s) 5, 7, 8, 12 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie, Gradl and Rissanen as applied to claims 1 or 4 above, and further in view of El-Shall “Comparative analysis of dolomite/francolite flotation techniques”.
The references do not teach adjusting the pH of the process to 2-4.5.
El-Shall describes a method of processing phosphate rock (Introduction, line 1). In their process, El-Shall describes a first step that includes a first step of milling, followed by screening (see Fig. 1, steps 1 and 2), followed by desliming (Fig. 1) (this is another sieving step). El-Shall describes multiple process steps used to isolate, separate and purifying various factions from the ore (see Fig. 1, 2 and 3). In Fig. 3, El-Shall explains that in the faction separated from Fig. 2, this faction is treated with sulfuric acid (it contains apatite, dolomite and fine quartz, see Fig. 3). This stream is treated so adjust the pH to 3-5 (fig. 3) in order to yield a final phosphate concentration and to a separated amine tailing (pg 138, left col. para. 1).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the pH of the slurry to 3-5, as taught by El-Shall for use with the process of Nie, Gradl and Rissanen because this facilitates separation of phosphate from the other components of a dolomite, quartz and apatite-containing solution.
As to Claim 7, the references do not describe a second screening and separating the ore that passes through the second screening.
El-Shall describes a method of processing phosphate rock (Introduction, line 1). In their process, El-Shall describes a first step that includes a first step of milling, followed by screening (see Fig. 1, steps 1 and 2), followed by desliming (Fig. 1) (this is another sieving step). The desliming step removes dolomite from the phosphate and a silica removal step (pg 137, left col, lines 4-9). The desliming step separates the feed between a 28 x 150 mesh from the 35 x150 mesh feed (pg 137, left col, lines 31) takes the particles separated in the desliming step that has a size of 28 x 150 mesh is then processed by attrition scrubbing and then further deslimed (screened) again using another screen (pg 137, left col, lines 33-35). After this step, the mixture is then treated with sulfuric acid (see Fig. 4, “conditioning”).
The other fraction, the 35 x 150 mesh separated in the sieve on pg. 137, lines 5-7 is described in Fig. 3. This second fraction, is treated under acid “see Fig. 3, “recondition”, followed by froth flotation (Fig. 3, “frother”). This separates fine silica from dolomite to yield phosphate concentrate and a siliceous amine tailing (pg 138, left col, lines 7, 9-11).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to include a second screening step and then separate the coarser material from the finer particles and process them, as taught by El-Shall for use with the phosphate ore of Nie, Gradl and Rissanen because these steps are known to facilitate purification of compounds from the others in the ore mixture.
As to Claim 12, El-Shall teaches that the flotation cell (which is previously screened again, see the rejection to claim 7 incorporated here by reference) yields a final phosphate concentrate (pg 138, left col, para. 1). This phosphate concentration is analyzed to be about 28.2% (pg. 138, left col, para. 2). This can be considered a high-grade size fraction.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to screen the separated faction, as taught by El-Shall for use in the ore purification of Nie, Gradl and Rissanen because this process further purifies the ore to produce a high phosphate-containing product.
Claim(s) 6 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie, Gradl and Rissanen and El-Shall as applied to claim 5 above, and further in view of Cao (CN 105562213).
The references do not teach that mixing is performed until one of the stop conditions of Claim 6 is reached.
Cao describes a method of treating phosphorus ore (abstract). The process first crushes the ore (abstract) and then treats the ore with sulfuric acid (abstract). Cao explains that the mixture can be stirred for 5 to 40 minutes (see pg 2, step. 4, para. 2) as a method of separating the phosphorite (pg. 2, para. 1, 2).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to mix the slurry for a certain preset amount of time, as taught by Cao for use with the process of Nie, Gradl and Rissanen and El-Shall because this amount of time is taught in the prior art to be effective for blending a phosphate-ore with sulfuric acid.
Claim(s) 9, 10 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie, Gradl and Rissanen as applied to claim 4 above, and in view of El-Shall and further in view of Phillips (US Pat.: 4238459).
The references do not describe the features of Claim 9.
El-Shall a method of processing phosphate rock (Introduction, line 1). In their process, El-Shall describes a first step that includes a first step of milling, followed by screening (see Fig. 1, steps 1 and 2), followed by desliming (Fig. 1) (this is another sieving step). The process describes in Fig. 3 shows that dolomite, apatite and quartz are mixed together (see Fig. 3).
The reference describes separating dolomite being separated from apatite (see Fig. 3, step “Dolo Flotation” that separates dolomite from apatite), but this reference does not teach adjusting the pH so that it does not cause apatite to dissolve.
Phillips describes a method of selectively extracting calcite and dolomite away from apatite in phosphate rock (abstract). The reference explains that selective extraction of dolomite from apatite is difficult (col. 11, lines 1-5). To do this, Phillips explains that the pH of the solution is controlled so that apatite is not dissolved (col. 8, lines 29-33, col. 9, lines 7-11), but other compounds, such as calcite, are removed (col. 9, line 30-32). Phillips proposes changing the acid in this step from sulfuric to another acid to facilitate adjusting the pH (col. 8, lines 17-32), such as SO2 (col. 8, lines 28-32).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the pH of the solution using a weaker acid, such as SO2, in place of sulfuric acid in this step, in order to avoid dissolution of apatite from dolomite, as taught by Phillips, for use with the process of isolating dolomite from phosphate ore, as taught by El-Shall for use with the process of Nie, Gradl and Rissanen because Phillips explains that phosphate-containing ores typically contain these mineral factions, whose separation is desirable.
As to Claim 10, Phillips explains that the pH of the solution is controlled by adjusting the rate at which SO2 is added to the system (col. 8, lines 28-24). In examples, Phillips teaches that SO2 added to the reaction mixture can be for 2.7 hrs (example 1), or for a set time.
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to mix the slurry in weak acid for 2.7 hrs, as taught by Phillips for use in the process of Nie, Gradl and Rissanen because this is a known and effective amount of time for separating phosphate from these slurries.
Claim(s) 27 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie, Gradl and Rissanen 20 as applied to claim above, and further in view of Snow (US Pat.: 3259242).
Nie describes a method of processing a phosphorous-containing ore (title). In one example, the raw calcium-phosphate ore is crushed and ball milled and ground to a size of 0.074mm (para. 8 of translation). To this slurry, sulfuric acid is added (para. 9), followed by use of a floatation step used to separate apatite and carbonate from phosphate (para. 12). Nie does not describe using a sieve to perform this step.
Snow teaches that froth floatation of apatite and calcite ores is known in the field (title and pg 1, left col, para. 1) and that separation of phosphate from these is highly beneficial (pg 1, left col, lines 37-43). To do this, Snow explains that micro-crystalline apatite values may be substantially liberated from calcite and silicate mineral gangues by use of a mesh amenable to froth floatation operations (pg 1, right col, lines 50-55). To do this, meshes with a sizes of about 325 mesh may be employed (pg 1, right col, lines 58-60).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to add a separating sieve, as taught by Snow to the froth flotation step of Nie because Snow explains that this effectively separates micro-crystalline apatite from the slurry mixture.
Since the pH is adjust to the desired level using acid, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that this can be considered “maintaining the pH level in the slurry to a pH range”, while mixing the slurry.
Example 1 of Snow describes milling, followed by screening, conditioning, followed by treating the ore in a froth floation (see example 1). Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to condition the slurry prior to floatation, as taught by Snow for use with Nie, Gradl and Rissanen because conditioning facilitates removal of unwanted byproduct in the slurry.
Claim(s) 21, 23, 24 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie, Gradl and Rissanen as applied to claim 20 above, and in view of Snow and further in view of El-Shall “Comparative analysis of dolomite/francolite flotation techniques”.
The references do not describe the features of Claims 21, 23 and 24.
Snow teaches that froth floatation of apatite and calcite ores is known in the field (title and pg 1, left col, para. 1) and that separation of phosphate from these is highly beneficial (pg 1, left col, lines 37-43). To do this, Snow explains that micro-crystalline apatite values may be substantially liberated from calcite and silicate mineral gangues by use of a mesh amenable to froth floatation operations (pg 1, right col, lines 50-55). To do this, meshes with a sizes of about 325 mesh may be employed (pg 1, right col, lines 58-60).
Snow explains that in the ball milling, sieving and sulfuric acid treatment (see col. 5, left col, line 67) that apatite is separated from BPL (phosphate), calcite, dolomite, micro and other compounds (see example 1, list of percentages of organics and col. 8, lines 35-40).
The references do not teach adjusting the pH of the process to 2-4.5.
El-Shall describes a method of processing phosphate rock (Introduction, line 1). In their process, El-Shall describes a first step that includes a first step of milling, followed by screening (see Fig. 1, steps 1 and 2), followed by desliming (Fig. 1) (this is another sieving step). El-Shall describes multiple process steps used to isolate, separate and purifying various factions from the ore (see Fig. 1, 2 and 3). In Fig. 3, El-Shall explains that in the faction separated from Fig. 2, this faction is treated with sulfuric acid (it contains apatite, dolomite and fine quartz, see Fig. 3). This stream is treated so adjust the pH to 3-5 (fig. 3) in order to yield a final phosphate concentration and to a separated amine tailing (pg 138, left col. para. 1).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the pH of the slurry to 3-5, as taught by El-Shall for use with the process of Nie, Gradl and Rissanen and Snow because this facilitates separation of phosphate from the other components of a dolomite, quartz-containing solution.
As to Claims 23 and 24, Snow teaches the second screening (see the rejection to Claim 20 above). Snow applies another screen step to the floatation step (see above).
Claim(s) 22 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie, Snow and El-Shall as applied to claim 21 above, and further in view of Cao (CN 105562213).
The references do not teach that mixing is performed until one of the stop conditions of Claim 22 is reached.
Cao describes a method of treating phosphorus ore (abstract). The process first crushes the ore (abstract) and then treats the ore with sulfuric acid (abstract). Cao explains that the mixture can be stirred for 5 to 40 minutes (see pg 2, step. 4, para. 2) as a method of separating the phosphorite (pg. 2, para. 1, 2).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to mix the slurry for a certain preset amount of time, as taught by Cao for use with the process of Nie, Snow and El-Shall because this amount of time is taught in the prior art to be effective for blending a phosphate-ore with sulfuric acid.
Claim(s) 25, 22, 26 is/are rejected under 35 U.S.C. 103 as being unpatentable over Nie, Gradl, Rissanen, Snow and El-Shall as applied to claim 21 above, further in view of Phillips (US Pat.: 4238459).
The references do not describe the features of Claim 25.
El-Shall a method of processing phosphate rock (Introduction, line 1). In their process, El-Shall describes a first step that includes a first step of milling, followed by screening (see Fig. 1, steps 1 and 2), followed by desliming (Fig. 1) (this is another sieving step). The process describes in Fig. 3 shows that dolomite, apatite and quartz are mixed together (see Fig. 3).
The reference describes separating dolomite being separated from apatite (see Fig. 3, step “Dolo Floation” that separates dolomite from apatite), but this reference does not teach adjusting the pH so that it does not cause apatite to dissolve.
Phillips describes a method of selectively extracting calcite and dolomite away from apatite in phosphate rock (abstract). The reference explains that selective extraction of dolomite from apatite is difficult (col. 11, lines 1-5). To do this, Phillips explains that the pH of the solution is controlled so that apatite is not dissolved (col. 8, lines 29-33, col. 9, lines 7-11), but other compounds, such as calcite, are removed (col. 9, line 30-32). Phillips proposes changing the acid in this step from sulfuric to another acid to facilitate adjusting the pH (col. 8, lines 17-32), such as SO2 (col. 8, lines 28-32).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the pH of the solution using a weaker acid, such as SO2, in place of sulfuric acid in this step, in order to avoid dissolution of apatite from dolomite, as taught by Phillips, for use with the process of isolating dolomite from phosphate ore, as taught by El-Shall for use with the process of Nie, Gradl, Rissanen, Snow and El-Shall because Phillips explains that phosphate-containing ores typically contain these mineral factions, whose separation is desirable.
As to Claim 26, Phillips explains that the pH of the solution is controlled by adjusting the rate at which SO2 is added to the system (col. 8, lines 28-24). In examples, Phillips teaches that SO2 added to the reaction mixture can be for 2.7 hrs (example 1), or for a set time.
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to mix the slurry in weak acid for 2.7 hrs, as taught by Phillips for use in the process of Nie, Gradl, Rissanen, Snow and El-Shall because this is a known and effective amount of time for separating phosphate from these slurries.
Conclusion
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/SHENG H DAVIS/Primary Examiner, Art Unit 1732 January 22, 2026