PHOSPHATES Sympo~iumpraented before the joint maetina of the Division8 of 1nduatri.l and Ensineeriog Chamistry and of Fertiiina Chemistry at the 102od Meetina of the Awllrcm Carurcn. Bonmn. Atlentio City. N. J.
PHOSPHATE DEPOSITS OF THE FIEILD With Special Reference
to Those of the United States GEORGE R. MANSFIELD
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U. S. Geological Snrvey,Washington, D. C.
The phosphate deposita of the word weam estimated by the Fomta.uth htfxnational Geologianl Con09%)at 7,1?2,429,78!4 metrio toms (known re-m of phosphate mcL) and 467,585,916,000 to^ (prohble -m), with Lge additional possible -m not mtimated. The h e r limit of p b phate wntant C a M i d d by the mugrew w u 5 per cemt PA. &timat.cn by MannMd 0%) and Jacob (1938) placed world rmezvm at 16,86'7,000,000 and 17,464,351,000 metric tons, reapantivdy. In thae edmat.cn Msmiidd d o w e d 6,431,000,000 metric tons for the United Stata, and Jamb 7,370,950,000 UWta'iC t0M.
COngrmsional committee netidtien in 1938 called fm a review in the field by M a d e d of the eddenw
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most comprehensive and probably the most authoritative ~onrceof infomytion about phosphate depceib inithe diaerent countries of the world is the series of ppem published by the Fourteenth International Geological Congress (14)which met in Madrid in 1926. Each country wan represented by one or more speoialists. Raporta were presented in German, French, Spanish,and English for 42 countries as follows: Europe 13, Asia 5, Africa 8, America (North and h u t h ) 10, and O&ca 6. For some unexplained reason no accounta were given of Algeria, Ocean and Nauru Islands, and a number of other leawr sonrcea. However the total makes an impressive showing. In the circular announcing the plana of the congress it wan brought out that new methods of treatmeut permit the we of low-grade phosphate@. Hence the minimum phosphate content to be coneiderad in estimating rasem WBB plaoed at 6 par cent of phosphoric anhydride ( P a ) . M e s were to be clsssi6ed in three categories: (a) known, those for which estimates were based on specific data derived from a c t a investigations; (b) probable, those for which only approximate figure% could be wed; and (c) possible, those for which no figure% were available. The low figure set for minimum
for FLmidn and the weatem stam and by Whltlatah of that for Tsnneaaea. A.a result, Mendmeld n&ed the &te for the United States m 13,503,514,000 metric tans. Tbme iigwes, topthex with these for -tiy exploited apatite deposits in the U. 9. S. R. and new 6gurea for some other coulleiss, 6the total to a6,m,s4,000 metric tom, of which the United .3tat.cn h a n about 5lper-t. Tbe t h e n great phosphmte-benring wiom of the world the United Scatas the U. 9. S. R., end North Ma. k v e a in dIfFcrmt countrim M &en. The princlpd phosphate deposits of the united stat- a m b r a y dbousd and slltimatea of reserves M included.
phosphate content makes the estimate@ of the congreea, espeaislly those for probable and possible m e a , higher than the figures given by writers in this country. The first volume of the work begins with an introduction by C. Rubio and J. De Gorostbaga, which includes a list (Table I) sUmmSri5hg world phosphate reserves.
Later Estimates In 1926 the writer (If) presented estimates of world resources in phosphate More the Institute of Politics at Williamstown, Maas. The Sgures then given are reproduced in Table 11. The latest estimates of world reserves of phoephates that have come to the writer's attention were compiled by the Phcaphate Rock Institute and published by Jamb (S, S). Table I11 gives his figures. Since the publication of Table 111, Jacob, who seems to have covered the literature thoronghly, hae reported additional resem for certain countries an shown in Table IV. Of the figure% in thie table, those for China, Italy, India, and Russia are undoubtedly new, whareas thoee for the other
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Total
Gnnd tow
16,887
three countries may be covered in part by the older figures. The most ~ p e o h ~development, ls~ both in knowledge of reserves and in exploitation of phosphate, has been made in connection with the apatites in the Kola PBninsula, Ruesis, within the Arctic Circle. These received only brief mention in the International Geological Congrwa volumes (14). Now, however, it is Btated (4) that a r m e of 2 billion tons is available in this area. Production is mid to be prooeeding at the ~ t ofe2 million tons of ore per year: "The ore body
Vol. 34, No. 1
is divided into an upper zone consisting of aa much ea 80 per cent apatite and 20 per cent nepheline, averaging 30.8 per cent of P&,, and a lower Bone consistiing of 40 to 70 per cent nepheline and contSining 7 to 22 per cent Pa'. The southern face of Kuki~~umchorr Mountain has been blasted into fipe bmsd ldgea to a height of 1wO feet, and 20 miles of galleries, 7 feet high and electrically equipped, have been driven into the mountain. The town of Kirovsk, which now has 40,000 inhabitants, did not exist 9 yesrs ago." This great new Rusaisn development, which employs American prooessas for beneficiation and concentration and state controlled labor, may become a threat to our pbosphate industry, although thua far only minor amounts of Russian phosphate have been imported into this country. In the United States, too, recent studies have shown that are far greater t b waa previously supposad; they are now conesrvatively estiited at 13,290,860,000 long tons, quivalent to 13,503,514,000 metric tons of phosphate rock containing 40 per cent or more of tricalcium phosphate (bone phosphate of lime). In Table 111the North African countries Algeria, Egypt, Morocco, and Tunis are reported to have reaervea of 3,695,wO,OOO metric tons, Rue& 5,568,000,000, and the United States 7,370,950,000. Thus these three great regions are credited with 16,634,450,000 metric tons or 95 per cent of the total world reserves, aa of the date of these e s t i i t e s . The new discoverieslisted in Table IV (amount-
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ImnaIY, 1942
I N D U S T R I A L A N D E N.G I N EE RIN G C H E id I S T R Y
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limiting thickness, but with improved techniques and krger soale operations this limiting depth has i n d to 50 feet or more. The controlling factor is not so much the thickneea of the overburden aa the quantity of it that must be moved in
an opportunity to check the figures for Florida and to prepara new estimates for that state. Similarly Q. I. Whit latch of the Term- DivSon of Geology was enabled to ratudx the reserves for Tennessee. Meanwhile J. Stewart Willisms made an independent study of the reserves for Utah. These different &orb led to the preparation or publication of several articles (S,9,10,14 is,CO, #I) which now constitute the most recent sources of information.
Florida The phosphate deposita of Florida are ckdied aa river v e r pebble, pebble, land pebble, bard rock, and soft rock. a an the name impliea, o m m in hand flabin or adjacent to ambin rivers. A total of 1,306,007 tom wae produced during the %year period IS88-lsoS, but it waa gradually forced off the market by land pebble and bard rock p h w phate, which are of bigher grade. A considerable wmve tonnage remaina for future w if and when needed (Table V). Ita grade would probably be less than 66 per cent trid c i n m phosphate (bone phosphate of lime) and much of it less than 55 per Cent. LANDPEBBLE F’HOBPEATE. The land pebble phosphate is cbiefly associsted with the formation hown 88 the Bone Valley gravel of Pliocene age, found chiefly in Polk County and parts of adjacent counties, but land pebble pbosphate is slso found in a nnmber of s c s t k d meas in more distant counties. It consists lsraelv of material reworked from the Hawthorn formation (Mi&ne) under estuarine and marine conditiona but includes additional material contempormy with the Pliocene. It in a bedded depoait hid down upon a relatively even surface of limestone or day, and consiata of day and sand along with pebblm of phosphate and some M y divided phosphstic material (mft phosphate). The deposit 88 a whole in called the “matrix”. In the pebble field the matrix generally contains 15 to 40 per cent B. P. L. (bone phosphate of h e \ snd has to be mncenhtad bv -i&(some mpanim ~ISO emp10j. Botation) to obtain marketable products. The writer wae told that material with a phasphate aonteat of about a5 per cent is best for this p r o w . When the matrix contains 40 per ce?t or mow B. P. L., so much phosphatic material will go into slime that much of the higher grade portion may be lost. The phosphate beds are generally not mtnrally eJrposed but lie benath an overburden of ssnds and days ranging in thiokness from a few featto more than 100 feet. The thickness of the overbunlen is more or leee a controlling factor in phaephate mining. I n the Tdd early days 12 feat waa conaided the
proportion to the quantity of recoverable phosphate. Thus one of the compdes reporta that 10 yard8 of overburden to 1 yard of recoverable rock hen the lower limit of depth of overburden in a workable property. The methods of pmepecting and of recovery of the phmphate rock are an interestiig and important part of the story of Florida phosphate, but they are not within the smpe of paper. Eetimates of res8r-m of pebble phosphate have changed from time to time 88 more data became available. F i e praented by the industry before the Joint Congressional Committee showed that the available quantity of pebble phosphate is far greater than bad previously been supposed. Through the m u r k y of the industry and of ita representative who teatilied before the oammittee, the writer has had opportunity to study much prospecting data, to make independent estimates, to OlaaSifJr the remvm accordingto grade, and to divide them into categories an known, probable, and poesible reeervgl (Table V). HABIIROCK F’H~SPEATE.. The hard rock phosphates are contained in the Alaohua formation of Pliocene age. They cohsist of residual material derived from the Hawthorn formationby solution, leaching, and redeposition. They r e p resent former I i l h g a of caverna and underground channels, now jumbled together aa a result of the s l ~ m p h and g solution of the rock that once enclosed them. The material consists of fragments and boulders ranging in mm from less than an s m a l tom, together inch in diameter to m & ~ ~ eweighing with soft phosphates, enclosed in a matrix of clay and d. The solution proceea which plays so important a pert in the aooumulation of the phosphate has also affected the lime atone floor on whicb the deposita rat, making it highly irregular. Thus the deposita vary greatly in the thickness and c h a r a h withi short diatanca. The local and irmguhr c h a r a h of the deposita makes them more d y to prospeat and mine. On this account only high-grade rock can be mined under present conditions, and both pmpecting and mining must be bigbly selective. Rmslpavrs. On the bssia of the study mentioned, eatimatea of reeervglfor river pebble, land pebble, and hard rock phosphates are included in Table V. Other souma of lower grade phosphate are present in Florida and the total quantity
676
666
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lad,wO 1.870,WO 11961
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............ 816.7W SlS.7W 141,sW W0.108
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4W070
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of phosphate represented by them may be large,but at present data couc~mingthem m W c i e n t to justify their consideration.
Tennessee The phosphate deposits of Tennessee have been claesified
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into three groups: brown rock, a residual type derived from phosphatic limestones of Ordovician age; blue rock, an original sedimeutmy deposit of m ~ p p age; h and white "
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V o l 34, No. L 4
TAB= VI. PHOSPHATE Resll~pas OF T B I ~UNITEDSTATES (Taouwim NO TONS) Eastern Stnta Florida6.081 838 T-neuee 194'tBS Bouth Csiolina 8:788 Kentu& 883
2o.ow
h!-.su,
6,305,868 s
AU g~ada diuerentiatad,
date.
W n t n n Stataa
Idaho Montana
Wyomiw
T.81y1.801 Grand total 13.a80,mo r a u i ~of gOTleTnment p r m m t i w to
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INDUSTRIAL AND ENGINEERING CHEMISTRY
from phmphate mek. Jamb and co-workern have demon-
&rated that the fluorine can be substantially completely r e
moved by calciniqg phosphate rooL in the presenceof and -tar vapor at about 1400° C. They found that the fluorine was m o v e d in two stages. The first half of the fluorine waa datively easily removed but did not greatly afiect the citrate a d b i i t y of the P&. However, when the calcination was &ed further and the second atom of fluorine e w l d , the
s~a6.886 881.3a8 1,741 480 116:7M
utab
Vol. 34, No. 1
the problem of m o v i n g or reducing the fluorine content of fluorhsoonbining mtem to a d e limit. Generally it ia b e l i d that the fluorinemust be reducedto less than 1 p. p. m. to render the water harmlese. Of the several methodn p m pOeea for m o v i n g the fluorine, the one which &em greatest pro& appesrs to be the use of tricalcium phosphate. The fluorine-Cantaininp water is paeaed through a bed of granular tricalcium ~hoa~hate. usuallv of the hvdroxv tvm. The fluorine is dso&d or taken" up hy ch&caI reaction with the tricalcium phosphate and gives an efEuent water which may be controll4 so 88 to contain lese than 1 p. p. m. of fluorine. The chief difliculty with the p r o w was the fact that the tricalcium phosphate would take up only a limited mount of fluorine before becoming eatumtd. To overcome this defect, Adler developd a regeneration prooess for removing the fluorine from the spent tricalcium phosphate. This regenerstion waa accomplished by mhing the 0uorinesaturated tricalcium phosphate with a dilute solution of caw tic scda to diasolve out the fluoride. The excess caustic scda remaining in the adsorbent mthen neutralized with a rrmall mount of dilute acid. In thia way the original tricalcium phosphate could he r e - d many times with only s small loss due to partial solution by the acid in each regeneration. Behrman improved on the regeneration hy the use of wbonic acid to neutralize the ace88 caustic, and thereby greatly increased the n u m h of possible mgenemtionn and made the p r o w more e d c a l . The tricalmum phosphate employed in the pmcw is made by neutrahing a dilute solution of phosphoric acid with a wesk slurry of milk of limeto a pH of approximately 7.0. The precipitated product is a hydmq type of tricalcium p h w phate having the composition 3CsJ'O4.Ca(OH)r. Smith developd a suitable bone phosphate for the purpose hy boiling bone in dilute caustic &a, neutralizing the excauatia, calcining the prcduct, and retreatingit with a dilute acid. Smith claims the resulting prcduct is e5cient 88 a 0110rine treating agent. Elvove of the National Institute of Health waa amom the early invmtigatom and waa probably the first to the we of tricalcium phouphate for removing fluorinefrom water.
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.AlkaliMetal Meta- and Pdyphoephatea In the last derade a great amount of re8esMh and cornmeroial development has taken plsce in the hrosd field of manufacture and use of the metsr and flyphosphate. Posaihly the prindpal development in thin field was the application of soluble alkali metal metaphosphate8 for water softening and other purposes. The Hall hbomtoriea, h., nsba pioneer in this development, particularly in the use of . ' t&e &di metal hexametaphosphatea for watar dtening purpa&u. Their research men have beem successful in d e '. vebpjng many new industrial applications involving the use of the hexametaphosphatm The hasic principle involved :---.A
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