Synthesis and Application of α-Chloro fatty Acid Citric Acid Monoester Collector

Phosphorus ore mineral resources is of advantage, but more than 90% of the reserves of low-grade hard mineral, ore and most Mg0, A1 ₂ 0 ₃ and Fe ₂ O ₃ content is high, phosphate material and gangue minerals symbiotic Tight, the size of the inlay is fine, generally only through flotation can obtain better enrichment effect. The fatty acid collector is widely used in flotation, its water solubility and dispersibility at room temperature is poor, and heating flotation leads to energy consumption. A significant increase, therefore, the development of a new type of collector with relatively good flotation performance is of great significance. Theoretically, after introducing a chlorine atom into the alpha position of a fatty acid, its electron-withdrawing effect can increase the stability of the carboxylic acid anion, enhance the action of the hydrophilic group of the collector and the mineral, and improve the flotation activity of the collector; further pass through the capture The introduction of polycarboxyl groups at the hydrophilic end of the agent increases its HLB value, improves its water solubility at room temperature, dissociation degree and salt tolerance, so as to improve the efficiency of flotation at room temperature. In this paper, a new type of α-chloro fatty acid citric acid monoester flotation collector was prepared by means of rapeseed oil waste as the basic raw material by chemical modification and modification, and a medium-low grade refractory phosphate rock in Yunnan was prepared. The flotation test shows that the collector still has good flotation performance at 15~25 °C, and its synthesis and application development are of great significance to reduce the cost of heating flotation.

First, the collector synthesis

(1) Experimental instruments and reagents

Main instruments: collector type constant temperature heating magnetic stirrer (DF-101S, CL-200); stepless speed regulator (D-971); rotary evaporator (RE 52-98); rotary vane vacuum pump (2ZX- 4).

Main raw materials: rapeseed oil scraps (industrial products); liquid chlorine (industrial products, supplied by Gedian Chemical Group); caustic soda (CP); sodium chloride (CP); concentrated sulfuric acid (CP); dichlorosulfoxide (CP) ); citric acid (CP).

(2) Collecting agent synthesis step

1. Saponification. Add a certain amount of rapeseed oil scrap to the beaker, slowly add 40% sodium hydroxide solution slowly under heating and mechanical stirring, continue heating and stirring and keep the reaction temperature in the range of 90-95 °C for about 2 h. The mixture gradually changes during the reaction. For the emulsion, a small amount of the saponified mixture was taken with a glass rod, and all of the saponification was obtained by dropping the oil-free flower in the cold water. A small amount of sodium chloride was added in portions to the saponified product and stirred uniformly, and then an appropriate amount of 30% sodium hydroxide solution was added thereto, and the mixture was heated to 70 to 80 ° C and kept for 1 hour, cooled, and allowed to stand overnight to separate the layers. The lower yellow clear liquid is an aqueous glycerin solution, the upper saponified material is transferred into a large beaker, and the solidified saponified product is crushed, washed with a small amount of water, and suction filtered to remove the inclusion of sodium chloride, sodium hydroxide and glycerin to obtain sodium fatty acid. A. Using chlorinated fatty acids as raw materials, a similar process can be used to obtain sodium chlorinated fatty acid B.

2. Acidification. Appropriately weigh the above-mentioned fatty acid sodium in a beaker, slowly add a certain concentration of sulfuric acid solution to acidify under mechanical stirring, control the dropping rate so that the temperature does not exceed 90 ° C, continue heating and stirring and maintain 80-90 ° C for about 2 h to make the soap base fully acid. Solution, cooling and standing layering, the lower layer of acid can be recycled. 60~70 °C hot water to wash the crude fatty acid several times to the aqueous phase pH value of 6 ~ 6.5 is appropriate, otherwise oleic acid is easy to solidify and form a paste with water, difficult to stratify. The organic phase is distilled under reduced pressure to remove a small amount of water to obtain a higher fatty acid.

3. Chlorine. The obtained higher fatty acid is placed in a three-necked flask, and a catalyst of phosphorus pentoxide (or thionyl chloride) is added thereto. Chlorine gas is introduced into the chlorine gas under mechanical stirring at 120 ° C, and the chlorine gas flow rate is controlled by a pressure reducing valve and a rotameter. When the tail gas is light yellow chlorine gas, the reaction is completed, and a black viscous paste is obtained, which is distilled under reduced pressure to remove a small amount of HCl gas and excess chlorine gas, and the product is a chlorinated fatty acid.

4. Acid chloride and esterification. The chlorinated fatty acid was slowly stirred and added with SOCl _{2 to} carry out acylation. After the dropwise addition, the mixture was heated and refluxed for 1 hour, depressurized with a water pump until no acid gas escaped, and then decompressed with an oil pump for 0.5 h to obtain an acylated product; dissolved with chloroform. Anhydrous citric acid is added to the acylated product under stirring, and the mixture is heated to reflux until the reaction is completed. A small amount of water is added to dissolve the remaining citric acid, and the aqueous layer is separated by liquid separation. The chloroform was distilled off to obtain a brown viscous paste, that is, a chloro fatty acid citric acid monoester C.

The structural formulas of sodium chloro fatty acid and chloro fatty acid citric acid monoester are:

5. Compounding. The chlorinated fatty acid citric acid monoester C and the chlorinated fatty acid sodium B are mixed in a certain ratio to obtain a novel composite flotation collector HND.

The block diagram of the collector synthesis is shown in Figure 1.

Second, the test

(1) Test equipment and test

Main equipment: rod mill (XMB-70); single tank flotation machine (XFD-3-63); wet type sampler (XSHF-3); circulating pump suction filter (RK/ZL-Φ260/Φ200).

Test reagents: sodium carbonate (CP), sodium silicate (CP), sodium hexametaphosphate (CP), fatty acid soap collector A, sodium chlorate fatty acid collector B. New composite flotation collector HND, cosolvent. self made.

(2) Ore characteristics and chemical composition

The ore is collected from a phosphate mine in Yunnan. The ore is a type of siliceous phosphate rock. The majority of phosphate minerals are amorphous colloidal phosphate, crypto-apatite, fluoroapatite and secondary silver star. less. Gangue minerals are quartz, chalcedony, dolomite, organic, clay, clay minerals, biotite, creep chlorite, sericite, yellow (brown) iron ore, iron oxide quality, muscovite. The chemical composition of the ore is shown in Table 1. It is a medium-low grade refractory colloidal phosphate rock.

Table 1 Multi-element analysis results of ore chemistry (mass fraction) /%

(3) Flotation test

1. Comparison of collector types

The flotation test is carried out in the XFD-3-63 single-tank flotation machine. The dosage of the inhibitor is suitable for the optimum conditions of the above-mentioned ore samples. The traditional fatty acid collector (A) and two new types of harvesting are used respectively. The agent (B, HND) was subjected to an open-circuit rough selection comparison experiment. The normal roughing process is shown in Figure 2, and the flotation comparison test results are shown in Table 2.

Table 2 Comparison results of different collectors at room temperature

It can be seen from Table 2 that when traditional fatty acid A is used as the collector, the dosage of the agent needs to be 5.0 kg/t, the recovery rate can reach the industrial requirement, and the selectivity to the low-grade phosphate rock is low, which indicates that the traditional collector and The useful component of the mine is weak; when sodium chlorinated fatty acid B is used as the collector, higher grade and recovery rate can be obtained with less dosage (1.8kg/t); use HND instead For the collector, the grade and recovery rate are further improved. Comparative experiments showed that after the modification of the fatty acid α-chloro modification, the activity of the reagent ions increased, and the binding ability of the agent to the collophosphate increased. This indicates that the electron-withdrawing effect of the α-chloride atom does increase the stability of the fatty acid carboxyl group. The action of the hydrophilic group of the collector and the mineral is enhanced, and the flotation activity of the collector is increased.

2. Flotation comparison test of HND at different temperatures

In order to detect the flotation efficiency of the new collector HND at different temperatures for the low-grade refractory colloidal phosphate rock, the flotation comparison experiment of the collector at different temperatures was designed. The test flow is shown in Figure 2. The test results are as follows. image 3.

The results in Figure 3 show that the concentrate grade increases slightly with increasing temperature. When the temperature reaches 29 °C, the recovery rate decreases. A low temperature and a rough selection can increase the grade of the medium and low grade refractory colloidal phosphate by about 5 percentage points, and the low-temperature flotation performance of the collector HND is better. It is indicated that the introduction of polycarboxyl groups is beneficial to improve the water solubility and flotation effect of the collector at room temperature.

3. Normal temperature closed-circuit flotation experiment

According to the flow shown in Figure 4, a closed-circuit test was conducted on the Yunnan refractory phosphate rock. The results are shown in Table 3.

Table 3 Closed circuit test results

The ore is subjected to normal method grinding and sample processing, and then subjected to normal temperature closed-circuit flotation. The amount of collector and inhibitor is the best condition for adapting to the above-mentioned ore samples. It can be seen from Table 3 that the collector HND is selected by a selection (and sweeping)-reverse selection (and re-election of the mine) and the simple normal temperature closed-circuit flotation can make the medium-low grade difficult-to-select colloidal phosphate grade. 29.01%, the recovery rate is 84.3%, and the normal temperature flotation effect is excellent. The normal temperature flotation effect of the collector is obviously superior to the traditional fatty acid collector under the same conditions, and the dosage of the agent is small, and the flotation process is simple. It shows that the collector HND has a good industrial application prospect.

Third, the results and discussion

(1) In the process of saponification-acid hydrolysis of rapeseed oil, slowly add alkali, add salt, add acid, and stir evenly, and be heated to ensure sufficient contact of oil/water phase and complete reaction; Avoiding the conversion of the water-oil emulsion into the oil-water emulsion results in the oil soap not being easily separated, resulting in a slow and incomplete reaction. The alkali waste liquid can recover and purify glycerin, and the acid waste liquid can be recycled, which can further reduce the cost and reduce the waste liquid discharge.

(2) Structural characterization of synthetic products and intermediates, and infrared detection of α-chloro fatty acids is shown in Fig. 5. As can be seen from Fig. 5, the strong absorption peak of the C=O double bond appears at 1737 cm ^-1 , and the C=0 double bond of the fatty acid absorbs 1680 to 1720 cm ^{-1 of} blue shift, which is a fatty acid. The obvious characteristic of α-halogenation is that the two absorption peaks at 724 cm ^-1 and 650 cm ^-1 are characteristic peaks of C-Cl bond; the infrared detection pattern of α-chloro fatty acid citric acid monoester is strong at 1249 cm ^-1 The absorption peak, which is the characteristic peak of the C-0-C bond of the ester. Chlorine by iodine value and the determination further validate compounds.

(III) Collector HND The main component of α-chloro fatty acid citrate is distinctly different from traditional higher fatty acid. HND is chlorinated at the alpha position of oleic acid and polycarboxylate is introduced at the hydrophilic end. . The purpose of the structural modification modification is to improve the binding ability of the collector to the ore, the amphiphilicity of the collector and the water solubility at room temperature, and optimize the flotation performance at room temperature. The flotation test results of a refractory colloidal phosphate mine in Yunnan show that HND has better normal temperature flotation performance and achieves the goal of improving the efficiency of normal temperature flotation.

Fourth, the conclusion

The new collector HND has good flotation performance at low temperature for difficult selection of low-grade phosphate rock, which is conducive to the development and utilization of low-grade phosphate rock. The normal temperature flotation saves the cost of heating flotation and reduces the phosphate rock. The cost of mineral processing has practical significance, and its research and development is in line with the sustainable development strategy and energy conservation and emission reduction policies. The synthetic raw material of the collector comes from the rapeseed oil scrap, which has a wide range of sources and low price, which is conducive to comprehensive utilization of resources. The collector has simple synthesis process, low cost, easy industrialization, and broad market development prospects.

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