Fatty acids and soaps are an important class of collectors in the flotation process, its most important use is as flotation on a mineral oxide (e.g. hematite, fluorite ore, etc.). Collector. Since fatty acids have very active carboxyl functional groups, almost all minerals can be floated. In general that form a cationic state in the solution having an ionic bond minerals, including all oxide ore, e.g. hematite, titanium ore, sulfate ore, mineral carbonates, phosphates and other mineral and fluorite; It was a cationic state in the solution minerals having a metal bond, including all the sulfide ore and gold, copper and other natural metal; a molecule having a covalent bond of the mineral or organic material, including graphite, coal, sulfur, molybdenite, talc Fumigation can be carried out using fatty acids or their soaps as collectors. For macromolecular covalently bonded compounds, minerals such as quartz , feldspar , garnet, clay , kaolin , mica, etc., which are anionic in solution, are not as effective as amine collectors.
The use of fatty acids and their soaps as oxidizing ore collectors is one of the major achievements of the mineral processing industry. Its wide range of applications is not comparable to general flotation reagents, but the biggest weakness of such agents is poor selectivity. It is also higher in dosage than xanthate.
I. Physicochemical properties of fatty acids and their soaps One of the important sources of fatty acids is natural animal and vegetable oils. After hydrolysis, one molecule of oil produces one molecule of glycerol and three molecules of fatty acids. Naturally occurring fatty acids contain an even number of carbon atoms, and most of the alkyl groups contained are linear. Fatty acids are divided into two major categories of saturated fatty acids and unsaturated fatty acids according to the saturation degree of their carbon chains. In the application of flotation industry, the latter is far more important than the former.
The most common saturated fatty acids in animal and vegetable oils are hexanoic acid (C 6 ), octanoic acid (C 8 ), citric acid (C 10 ), lauric acid (C 12 ), myristic acid (C 14 ), palmitic acid (C). 18 ) and stearic acid (C 18 ) and the like. Below the tannic acid, it is also known as low-grade fatty acids, and lauric acid is more commonly known as higher fatty acids. The physical properties of various saturated fatty acids such as freezing point, melting point, boiling point, refractive index, etc., increase according to the principle of organic compounds, and increase with molecular weight, but their solubility in solvents such as water, methanol, ethanol, acetone or benzene It decreases as the molecular weight increases. The physicochemical constants of some saturated fatty acids can be referred to Table 1.
Table 1   Physicochemical constants of some saturated fatty acids ( R-COOH )

Fatty acid name
Already
bitter
Tannic acid
Lauric acid
Myristic acid
Palmitic acid
Bentonic acid
Alkyl®
C 5 H 11 —
C 7 H 151 —
C 9 H 19 —
C 11 H 23 —
C 13 H 27 —
C 15 H 31 —
C 17 H 35 —
Molecular weight
116.09
144.12
172.16
200.09
228.22
256.25
284.28
Freezing point, °C
-3.2
16.3
31.2
43.9
54.1
62.8
69.3
Melting point, °C
-3.4
16.7
31.6
44.2
53.9
63.1
69.6
Density, g/cm 3
(80 ° C)
0.8751
0.8615
0.8531
0.8477
0.8439
0.8414
0.8390
Refractive index n D 8 0 °
1.3931
1.4049
1.4130
1.4191
1.4236
1.4272
1.4299
Boiling point, °C266.6Pa
(2mmHg)
71.9
97.6
121.1
141.8
161.1
179.0
195.9
1066.4Pa
(8mmHg)
94.6
121.3
145.5
167.4
187.6
206.1
224.1
101308Pa
(760mmHg)
205.8
239.7
270.0
298.9
Water solubility, mol/L
8.3×10 -2
4.7×10 -3
8.7×10 -4
2.7×10 -4
8.8×10 -5
2.8×10 -5
1.0×10 -5
Critical micelle concentration, mol/L
1.0×10-1
1.4×10 -1
(27 ° C)
2.4×10 -2
(27 ° C)
5.7×10 -2
(27 ° C)
1.3×10- 2
(27 ° C)
2.8×10 -3
(27 ° C)
4.5×10 -4
(27 ° C)
Same as above (sodium salt)
7.3×10 -1
(20 ° C)
3.5×10 -1
(25 ° C)
9.4×10 -2
(25 ° C)
2.6×10 -2
(250 ° C)
6.9×10 -3
(25 ° C)
2.1×10 -3
(50 ° C)
1.8×10 -3
(50 ° C)
Same as above ( potassium salt )
1.49×10 -3
0.4×10 -3
0.97×10 -4
0.24×10 -4
0.6×10 -5
HLB value (hydrophilic-lipophilic balance)
6.7
5.8
4.8
3.8
2.9
2.0
1.0
Solubility product of calcium salt (Ksp)
2.7×10 -7
3.8×10 -10
8.0×10 -13
1.0×10 -15
1.6×10 -6
1.4×10 -18
[next]
Commonly used unsaturated fatty acids in animal and vegetable oils include oleic acid, isooleic acid, linoleic acid, linolenic acid, and ricinoleic acid. Its molecular structure is
The oleic acid molecule contains an unsaturated double bond, the isooleic acid is a geometric isomer of oleic acid; linoleic acid contains two double bonds, and linolenic acid contains three double bonds. Ricinic acid is a characteristic fatty acid in castor oil. In addition to a double bond, the molecule also has a hydroxyl group. The physicochemical constants of some unsaturated fatty acids and their soluble salts are shown in Table 2.
Table 2   Physicochemical constants of some unsaturated fatty acids ( R- COOH)
Unsaturated fat
Fatty acid name
Oleic acid
Isoic acid
Linoleic acid
Linolenic acid
Ricinic acid
In the molecule
Number of carbon atoms
C18
C18
C18
C18
C18
Olefin based®
C 17 H 3 3 —
C 17 H 3 3 —
C 17 H 31 —
C 17 H 29 —
C 17 H 32 (OH)—
Molecular weight
282.44
282.44
280.44
287.42
298.45
Fusion, °C
13.4(a)16.3(a)
40.7
-5~ -5.2
-11~ -11.3
5
Acid value
198.63
198.63
200.06
201.51
187.98
Iodine value theory
89.87
89.87
181.03
273.51
85.04
Refractive index n D 2 0 °
1.45823
1.4699
1.4780
1.4716
Brush point (℃) Hg
Pressure, mm
166/0.25mm
234~235/15mm
266/60mm
229/16mm
157~158/0.001mm
230~2/17mm
Ice solubility, mol/L
Critical micelle
Degree, mol/L
1.2×10 -3
1.5×10 -3
Same as above (sodium salt)
2.1×10 -3
2.7×10 -3
(25 ° C)
1.4×10 -3
2.5×10 -3
(40 ° C)
0.15g/L
0.20g/L
0.45g/L
Same as above (potassium salt)
8.0×10 -4
(25 ° C)
HLB value (hydrophilic
- lipophilic balance)
19 4.5 (sodium salt)
PLCaA 2 (20°C)
12.4
14.3
12.4
12.2
Second, the fatty acid collector commonly used in flotation practice In the flotation process, the amount of fatty acid collector is much larger than that of xanthate, and generally no pure product is used, so as to reduce the cost of the medicament. Their most obvious shortcomings are poor selectivity to minerals, resistance to hard water, and sensitivity to temperature. [next]
1. Oleic acid The purification of oleic acid is difficult. The industrial oleic acid used in the flotation plant generally has an oleic acid content of no more than 75%. Since it contains almost the same amount of linoleic acid and saturated acid, if the iodine value is determined, the theoretical iodine value of almost pure oleic acid is determined. very close. In 1961, nine industrial oleic acid samples were sampled by gas chromatography. The analysis results are very useful. See Table 3.  
Table 3 Industrial oleic acid sample composition analysis (gas chromatography)
Sample serial number
I
II
III
IV
V
VI
VII
VIII
IX
ingredient
Percentage %
Dodecanoic acid (lauric acid)
Fourteen carbonic acid (myristate)
Tetradecenoic acid (containing a double bond)
Hexaenoic acid (palmitate)
Hexaenoic acid (containing a double bond)
Heptadecenoic acid (containing a double bond)
Octadecyl carbonate (stearic acid)
Oleic acid (with one double bond)
Octadecenoic acid (linoleic acid)
Octadecatrienoic acid (linolenic acid)
0.1
2.8
2.7
4.8
12.5
1.7
0.4
70.5
2.2
1.2
0.4
3.0
3.0
4.8
12.9
1.9
0.4
71.0
2.6
0
0.2
4.0
3.0
2.8
12.6
1.4
0.8
73.2
1.9
0
0
1.0
0.8
3.3
6.8
1.4
1.0
73.8
8.2
3.4
0.2
3.1
2.8
4.0
12.3
1.8
0
68.6
4.6
1.8
0
0.6
0.1
4.5
5.9
0.2
0.3
75.8
12.6
0
0
0.7
0.4
1.6
5.7
0.7
0
77.8
6.5
0
0.2
3.7
3.2
3.3
13.0
1.8
0
70.9
3.6
0.3
0
3.2
2.1
2.7
11.3
0.8
0
74.7
5.2
0
Peroxide value
Oxygen in the structure of ethylene oxide, %
Iodine value (Wei's method)
Unsaponifiable, %
2
0.01
91.3
0.44
0
0.01
87.6
0.22
8
0.00
87.6
0.29
11
0.01
92.2
0.33
4
0.02
94.0
0.30
6
0.06
91.6
0.35
2
0.14
94.0
0.25
3
0.00
92.6
0.41
3
0.01
93.2
0.28
Note: The theoretical iodine value of oleic acid is 89.8.
The molecular weight of oleic acid is 282.44, the dissociation constant is 1 x 10 -6 , and the hydrophilic lipophilic balance is 45. Due to the variety of methods for measuring critical micelle concentration, the data obtained by different testers often differ greatly. The critical micelle concentration (CMC mole/liter) of sodium oleate is: 2.7×10 -3 (20 ° C) , 2.1 × 10 -3 (25 ° C); the critical micelle concentration of potassium oleate (CMC mole / liter) values ​​are: 8.0 × 10 -4 (25 ° C), 7.12 × 10 -4 (25.8 ° C); The sodium salt was: 2.5 × 10 -3 , 1.4 × 10 -3 (40 ° C); potassium isooleate was 1.5 × 10 -3 .
The main uses of oleic acid in the flotation industry are flotation of alkaline earth metal carbonates, metal oxide minerals, carbonate minerals and barites . When flotation of the poor iron ore in Donganshan, the best condition for sorting with quartz is pH 8-9. Flotation of cassiterite with oleic acid or sodium oleate has done a lot of work in this area and achieved good production results.
2. Tal oil Tal oil is a mixture of fatty acid and rosin acid, which is the acidified product of the by-product pulp waste liquid (also known as black liquor soap) obtained by the sulfuric acid paper mill. It contains about 40% fatty acid, about 40% rosin acid, and about 5-20% unsaponifiable matter. The fatty acids in Tal oil are mainly composed of oleic acid (~45%) and linoleic acid (~48%). In the rosin acid part, the main component is rosin acid (30~40%) and neostearic acid. (10~20%). The general properties of crude tar oil are listed in Table 4.
Table 4   General properties of crude tar oil

name
Lowest value
Highest value
name
Lowest value
Highest value
Density, g/cm 3
Acid value
Saponification value
Iodine value
Ash, %
0.95
107
142
135
0.39
1.024
179
185
216
7.2
Insoluble in petroleum ether, %
Fatty acid content, %
Ruthenic acid content, %
Non-acidic, %
Viscosity (18 ° C), Pa·S
0.1
18
28
5
0.760
8.5
60
65
twenty four
15×10 3
As a flotation reagent, the application range of Tal oil is basically the same as that of fatty acid agents, but the price of Tal oil is much cheaper than oleic acid. At present, at home or abroad, Tal oil is an important oxidizing mineral collector, especially for flotation iron oxide ore and phosphate rock. [next]
The experience of flotation confirmed that the use of Tal oil as a collector can float hematite, limonite, magnetite, magnetic separation tailings, iron ore containing ilmenite, iron gangue, fine-grained, manganese ore and manganese ore mud. Flotation of apatite, iron ore dephosphorization. White lead flotation ore, chrome ore oxide. Flotation barite, fluorite, limestone , spodumene and uranium .
In short, Tal oil is the best and cheapest substitute for animal and vegetable oil fatty acids. The shortcoming is still that the selectivity is not strong. The current research work on Tal oil focuses on how to mix and mix with other types of chemicals. Collectors, especially in combination with petroleum sulfonates, are used to increase the selectivity of the oil.
3. Oxide paraffin A C10~C22 mixed fatty acid prepared by artificial catalytic oxidation of paraffin as a raw material is called "oxidized paraffin". Its sodium soap is oxidized paraffin soap. In the early 1960s, China had used oxidized paraffin soap as a poor hematite collector for the flotation of the Donganshan iron ore, replacing the shortage of soybean fatty acid supply and succeeded. It is an important oxidizing mineral collector in China.
China's Ministry of Petroleum Industry issued standards, oxidized paraffin must meet the requirements listed in Table 5:
Table 5   Oxidized paraffin quality index

project
Quality Index
experiment method
colour
Saponification value, mg·KOH/g
Acid value, mg·KOH/g
Ash, no more than %
The iron content in the ash is not more than %
Light yellow to light brown
140~160
75~90
0.25
trace
Visual inspection
Petroleum 2604-66
National Standard 264-64
Petroleum 2703-66
Note
Note: Refer to the national standard 534-65 "Industrial sulfuric acid", and measure the result as 0.01% or less as a trace.
At present, there are many chemical plants producing oxidized paraffin in China, including Yingkou Chemical Plant, Fushun Chemical Third Plant, Fuxin Chemical Plant, Shanxi Changzhi Chemical Plant, Wuhan Chemical Second Plant, and Shanghai Soap Factory.
The so-called "731" oxidized paraffin soap is an oxidized paraffin soap made from the atmospheric third line of the Petrochemical No. 7 Plant in Dalian. The distillation range of oxidized paraffin is 262-350 ° C (40% distillation), the melting point is 39.7 ° C, the hydrocarbon-containing oil content is 20.07%, the normal paraffin content is 84.10%, and the isoparaffin content is 14.8%. The oxidized paraffin soap processed from the oxidized paraffin contains 31.5% of carboxylic acid, 10.22% of hydroxy acid, 16.71% of unsaponifiable matter, 0.397% of free base, 22.0% of water, and iodine value of 3.46%.
Over the years, the experience of flotation has confirmed that oxidized paraffin soap can be used as a collector for flotation of lean hematite, fluorite ore, phosphate rock and some rare metal oxide ore; barite ore, zirconium ore of titanium oxide (titanium) Flotation of iron ore, rutile, zircon, molybdenum oxide, tungsten ore.
In summary, the advantages of oxidized paraffin and its sodium soap are that the source of the raw material is large, the price is cheap, and the selectivity is slightly stronger than that of the vegetable oil fatty acid; its disadvantage is that the flotation rate is not as fast as the vegetable oil fatty acid, and the dosage is high. To improve the performance of oxidized paraffin flotation, we should start with sulfonation in the future to improve its selection performance.
4. Naphthenic acid naphthenic acid is a by-product of the petroleum refining industry. When different fractions of petroleum are washed and refined with caustic soda, the petroleum acidic component contained in the alkali washing liquid (alkaline residue), so-called naphthenic acid, is generally The molecular structure is:
The naphthenic acid washed out from the petroleum light fraction is a colorless liquid, and the molecular weight is also low. The liquid obtained from the lubricating oil fraction is a micro-colored liquid, the molecular weight is higher, and the higher the fraction, the more easily the naphthenic acid is purified. The amount of naphthenic acid in petroleum produced in Xinjiang, China is relatively high.
The larger the molecular weight of the sodium naphthenate soap, the easier it is to form a micelle, as listed in Table 6.
Table 6   Critical micelle concentration of sodium naphthenate soap

Molecular weight of sodium naphthenate soap
216
222
244
270
312
334
Critical micelle concentration, g/L
14.5
9.8
4.5
2.1
0.7
0.36

The standard issued by the Ministry of Petroleum, naphthenic acid must meet the requirements listed in Table 7. [next]
Table 7 Naphthenic acid quality indicators

project
Quality Index
Test method
Level 1
level 2
Level 3
Exterior
colour
Petroleum acid, %
Unsaponifiable (calculated as organic matter), not more than %
Acid value, mg·KOH/g
Inorganic salt, no more than %
Where the chloride is not greater than
Paste substance
From grass yellow to light brown
43
9
220
1.0
2.0
Cit
Cit
43
13
210
4.0
2.0
Cit
Cit
43
15
190
6.0
2.0
Visual inspection
Visual inspection
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Oil 2912-59
Oil 2912-59
Oil 2912-59
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