Synthesis method and application of carboxymethyl-phosphorylated bifunctional chitosan inhibitor

Abstract

The present invention belongs to the technical field of mineral processing, and specifically relates to a synthesis method and application of a carboxymethyl-phosphorylated bifunctional chitosan inhibitor. The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention consists of the following steps: (1) acid activation pretreatment; (2) phosphorylation reaction; (3) carboxymethylation modification; (4) solid-liquid separation and drying. The present invention also provides the application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor. The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention realizes the "one agent, two states" function switching of the synthesized carboxymethyl-phosphorylated chitosan inhibitor, avoids the cumbersome operation of frequently replacing agents in the traditional process, and simultaneously eliminates the interference of agent residues.

Description

Technical Field

[0001] The present invention belongs to the technical field of mineral processing, and specifically relates to a synthesis method and application of a carboxymethyl-phosphorylated bifunctional chitosan inhibitor. Background Art

[0002] The flotation separation of scheelite, fluorite, and calcite is difficult due to the similarity of their surface chemical properties. All three have calcium ions as the main surface active sites, and the charge distribution and coordination ability of the anionic groups are similar. In a conventional flotation system, an anionic collector synchronously adsorbs on the surfaces of the three minerals through the non-specific chelation of carboxyl groups with Ca 2+ , resulting in extremely small differences in their floatabilities. In addition, the synchronous effect of pulp pH regulation on the surface potentials of the three further weakens the selective separation potential based on electrostatic repulsion.

[0003] Although traditional inhibitors can inhibit non-target minerals through physical coverage or weak chemical adsorption, they have significant defects: inhibitors represented by water glass cover the mineral surface by generating silicic acid colloids, but have poor selectivity and will also affect the floatability of scheelite while inhibiting calcite and fluorite. Starch-based inhibitors are environmentally friendly, but rely on hydrogen bond adsorption and lack differential affinity for calcium-containing minerals. Lead salts are often introduced to activate scheelite, bringing the risk of heavy metal pollution.

[0004] In addition, the existing process adopts a multi-stage process of "inhibition-activation" (such as first inhibiting fluorite / calcite and floating scheelite, and then activating fluorite and inhibiting calcite), but faces double contradictions: the residue of the inhibitor hinders the selective activation of fluorite by the subsequent activator; high-dose activators are required for the reactivation of fluorite after inhibition, and calcite is easily co-activated, resulting in serious mutual inclusion in the concentrate. However, this "strong pressure and strong pull" type of flotation not only requires many types of reagents and large dosages, but also has extremely low reactivation efficiency after the inhibition of fluorite. When the dosage of the activator is large, calcite is also easily activated, resulting in poor separation efficiency of the three. Therefore, developing new and efficient inhibitors, reducing the types of reagents, and improving the targeted inhibition of reagents are important research directions at present.

[0005] Chitosan, as a natural polysaccharide, has potential selective adsorption ability on the amino (-NH2) and hydroxyl (-OH) groups on its molecular chain. However, unmodified chitosan has inherent defects: (1) poor solubility, especially prone to flocculation and sedimentation in alkaline pulp, resulting in the failure of inhibition; (2) adsorption depends on weak hydrogen bond / electrostatic interaction, with low binding force and easy desorption in high-shear pulp; (3) narrow pH response range, and the inhibition ability decreases rapidly after the deprotonation of amino groups; (4) although functional groups (such as phosphate groups) can be introduced into modified chitosan, the problem of "synchronous inhibition of double minerals" still generally exists, resulting in the loss of high-value fluorite.

[0006] Therefore, it is necessary to explore a new type of chitosan inhibitor for the selective separation of scheelite, fluorite and calcite. Summary of the Invention

[0007] The object of the present invention is to provide a synthesis method of a carboxymethyl-phosphorylated bifunctional chitosan inhibitor, which solves a series of problems such as poor selectivity of traditional inhibitors, poor solubility and dispersibility of single chitosan, unstable adsorption, limited pH adaptability, susceptibility to pulp environment, and a large variety and dosage of "strong pressure and strong pull" type flotation agents; the present invention also provides its application at the same time.

[0008] The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention comprises the following steps:

[0009] (1) Acid activation pretreatment

[0010] Mix chitosan powder with citric acid aqueous solution evenly and stir to react to prepare an activated chitosan dispersion;

[0011] (2) Phosphorylation reaction

[0012] Add phosphate and magnesium sulfate to the activated chitosan dispersion prepared in step (1), and react at 80-90 °C for 2-4 h to prepare phosphorylated chitosan;

[0013] (3) Carboxymethylation modification

[0014] Add sodium chloroacetate to the phosphorylated chitosan prepared in step (2), and then add sodium hydroxide to adjust the pH value of the reaction system to 7-8, and stir to react to generate carboxymethyl-phosphorylated bifunctional chitosan;

[0015] (4) Solid-liquid separation and drying

[0016] Precipitate the carboxymethyl-phosphorylated bifunctional chitosan prepared in step (3) with ethanol, and then wash it successively with ethanol-water mixture and NaOH solution, and dry it to obtain the carboxymethyl-phosphorylated bifunctional chitosan inhibitor.

[0017] Wherein:

[0018] In step (1), the deacetylation degree of the chitosan powder is 85%-95%, and the molecular weight is 50-200 kDa.

[0019] In step (1), the mass concentration of the citric acid aqueous solution is 1-3 wt%, and the mass ratio of the chitosan powder to the citric acid aqueous solution is 1:10-1:15.

[0020] In step (1), the stirring and mixing temperature is 40-60 °C, and the stirring and mixing time is 30-60 min.

[0021] The phosphate described in step (2) is one of disodium hydrogen phosphate, sodium dihydrogen phosphate or trisodium phosphate.

[0022] In step (2), the mass ratio of the phosphate to the activated chitosan dispersion is 0.5:1 - 3:1, and the mass of magnesium sulfate accounts for 0.5 - 2 wt% of the mass of the phosphate. Magnesium sulfate serves as a catalyst for the phosphorylation reaction.

[0023] In step (3), the mass ratio of phosphorylated chitosan, sodium chloroacetate and sodium hydroxide is 1:0.5 - 3:0.3 - 1.5.

[0024] In step (3), the temperature of the stirring reaction is 50 - 80 °C, and the time of the stirring reaction is 2 - 6 h.

[0025] In step (4), the mass ratio of ethanol to carboxymethyl-phosphorylated bifunctional chitosan is 4:1.

[0026] In the ethanol-water mixture described in step (4), the volume ratio of ethanol to water is 4:1 - 2:1, and the washing time is 5 - 20 min.

[0027] In the NaOH solution described in step (4), the concentration is 0.2 - 0.4 mol / L, and the washing time is 10 - 30 min.

[0028] In step (4), vacuum drying is used, the drying temperature is 40 - 60 °C, and the drying time is 12 - 24 h.

[0029] The application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention is used for the flotation separation of scheelite, fluorite and calcite, and consists of the following steps:

[0030] ① Grind the ore containing scheelite, fluorite and calcite to -0.074 mm accounting for 50% - 95%, then adjust the pulp pH value to 8 - 10, and successively add the carboxymethyl-phosphorylated bifunctional chitosan inhibitor and an anionic collector. After one rough selection, multiple scavenging selections and multiple cleaning selections, a scheelite rough concentrate and a mixed tailing containing fluorite and calcite are obtained;

[0031] ② Adjust the pH value of the scheelite rough concentrate pulp prepared in step ① to 8 - 10, add the carboxymethyl-phosphorylated bifunctional chitosan inhibitor and an anionic collector, and after one rough selection, multiple scavenging selections and multiple cleaning selections at room temperature, a scheelite concentrate and a scavenging selection tailing are obtained;

[0032] ③ Adjust the pH value of the mixed tailing pulp containing fluorite and calcite prepared in step ① to 4 - 6, add the carboxymethyl-phosphorylated bifunctional chitosan inhibitor and a cationic collector, and after one rough selection, multiple scavenging selections and multiple cleaning selections, a fluorite concentrate and a calcite-containing tailing are obtained.

[0033] Among them:

[0034] In step ①, the mass concentration of the flotation pulp is 25%-45%.

[0035] In step ①, sodium hydroxide or sodium carbonate is added to adjust the pH value of the pulp to 8-10.

[0036] In step ①, the dosage of carboxymethyl-phosphorylated bifunctional chitosan inhibitor is 100-500 g / t, and the anionic collector is at least one of sodium oleate, oleic acid, sodium dodecyl sulfate or sodium dodecyl sulfonate, and the dosage is 300-1000 g / t.

[0037] In step ①, the number of cleaning times is 2-3 times, and carboxymethyl-phosphorylated bifunctional chitosan inhibitor is added to the scheelite flotation cleaning operation, and the dosage is 1 / 4-1 / 2 of the previous operation.

[0038] In step ①, the number of scavenging times is 3 times, and anionic collector is added to the scheelite flotation scavenging operation, and the dosage is 1 / 4-1 / 2 of the previous operation.

[0039] In step ②, the mass concentration of the scheelite rough concentrate pulp is 10%-20%.

[0040] In step ②, the dosage of carboxymethyl-phosphorylated bifunctional chitosan inhibitor is 100 g / t -500 g / t, and the anionic collector is at least one of sodium oleate, oleic acid, sodium dodecyl sulfate or sodium dodecyl sulfonate, and the dosage is 100 g / t -200 g / t.

[0041] In step ②, the number of cleaning times is 3-4 times, and the number of scavenging times is 2-3 times.

[0042] In step ③, the mass concentration of the flotation pulp is 20%-40%.

[0043] In step ③, one of sulfuric acid, hydrochloric acid or oxalic acid is added to adjust the pH value of the pulp to 4-6.

[0044] In step ③, the dosage of carboxymethyl-phosphorylated bifunctional chitosan inhibitor is 200-500 g / t, and the cationic collector is at least one of dodecylamine, octadecylamine or ether amine collector, and the dosage is 100-500 g / t.

[0045] In step ③, the number of cleaning times is 6-7 times, and the number of scavenging times is 2 times.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention realizes the "one agent, two states" function switching of the synthesized carboxymethyl-phosphorylated chitosan inhibitor, avoiding the cumbersome operation of frequently replacing agents in the traditional process, and at the same time eliminating the interference of agent residues; the introduction of carboxymethyl is beneficial to improving the high stability and selectivity of the inhibitor in the pH range of 4-10: the buffering capacity of carboxymethyl (pKa≈4.3) can neutralize the local pH fluctuation of the pulp to ensure stable inhibition effect; in addition, carboxymethyl chelates Ca 2+ / Mg 2+ in the pulp, reducing the competitive consumption of hardness ions on the phosphate group.

[0048] (2) The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention uses citric acid to replace traditional concentrated hydrochloric acid or sulfuric acid for the pretreatment of chitosan. Citric acid gently hydrolyzes the β-1,4 glycosidic bond of chitosan through its carboxylic acid group (-COOH), partially opening the crystalline region and exposing more hydroxyl (-OH) and amino (-NH2) active sites, while avoiding excessive degradation of the molecular chain caused by strong acids. At the same time, citric acid molecules can bind to chitosan through hydrogen bonds, and some carboxylic acid groups remain on the surface of chitosan, providing pre-activated sites for subsequent phosphorylation reactions and enhancing the uniformity of phosphate group substitution. The introduction of carboxylic acid groups on the surface of chitosan after pretreatment endows it with preliminary pH sensitivity (carboxylic acid group pKa≈3.1), laying the foundation for subsequent bifunctionalization.

[0049] (3) The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention adds magnesium sulfate as a catalyst in the phosphorylation reaction. Mg 2+ forms a soluble complex with phosphate, promoting the directional attack of phosphate ions on the hydroxyl groups of chitosan and avoiding the generation of by-products by traditional urea catalysis. At the same time, constant temperature control is adopted, and the reaction is carried out in a water bath at 80-90 °C to ensure that the phosphate group (-PO3H2) preferentially substitutes the C6 hydroxyl group and avoids random modification of the C3 hydroxyl group, improving the controllability of the molecular structure. The stepwise ionization of the phosphate group (pK a1 ≈2.1, pK a2 ≈7.2, pK a3 ≈12.3) endows the agent with a wide range of pH response capabilities, especially chelating calcium-containing minerals preferentially in the form of -PO3 2- under alkaline conditions.

[0050] (4) The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention phosphorylates first and then carboxymethylates during the synthesis process, avoiding the competitive reaction between sodium chloroacetate (a strong nucleophile) and the phosphate group, ensuring the precise introduction of carboxymethyl to the remaining sites of the C6 hydroxyl group, and realizing the bifunctional group (-PO3H2 and -CH2COO -Spatial separation reduces steric hindrance effects. In addition, the reaction system is adjusted to weak alkalinity with sodium hydroxide to promote the Williamson etherification reaction between sodium chloroacetate and chitosan hydroxyl groups preferentially rather than the N-carboxymethylation of amino groups, retaining the pH-responsive activity of amino groups. The introduction of carboxymethyl expands the pH-responsive range of the agent. Under acidic conditions, in the form of -CH2COOH, it reduces the electrostatic repulsion with scheelite, synergistically with -PO3H of phosphate groups - Achieve targeted inhibition of calcite.

[0051] (5)For the synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention, carboxymethyl and phosphate groups are introduced into chitosan. Among them, carboxymethyl endows the agent with strong hydrophilicity, enabling it to dissolve rapidly and disperse uniformly in the pulp at room temperature, avoiding the drawback of traditional inhibitors (such as starch and water glass) that need to be heated due to insufficient solubility at low temperatures; while phosphate groups directly anchor to the Ca 2+ active sites of fluorite and calcite through chemical chelation, forming stable five-membered ring chelates at room temperature without relying on thermal energy to enhance adsorption kinetics. At the same time, its pH-responsive property dynamically regulates the inhibition behavior, repelling scheelite under alkaline conditions and targeting the inhibition of calcite under acidic conditions. Compared with the traditional scheelite beneficiation process that needs to heat above 70 °C to activate the agent or break the hydration layer on the mineral surface, this inhibitor has high solubility, strong adsorption efficiency and precise selectivity at room temperature.

[0052] (6)For the application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention, phosphate groups and carboxymethyl groups are inserted into chitosan through phosphorylation reaction and carboxymethylation modification to form carboxymethyl-phosphorylated bifunctional chitosan. Among them, carboxymethyl exists in the form of -CH2COO - under alkaline conditions (pH 8 - 10), which will repel scheelite, while phosphate groups are ionized into -PO3 2- , forming five-membered ring chelates with Ca 2+ of fluorite and calcite, and thus can target the inhibition of fluorite and calcite; under acidic conditions (pH 4 - 6), carboxymethyl exists in the form of -CH2COOH, which will reduce the hydrogen bond interaction with fluorite, while phosphate groups in the form of -PO3H - strengthen the inhibition of calcite, and thus form a bifunctional pH-responsive inhibitor based on chitosan, and the effective separation of scheelite, fluorite and calcite can be achieved only by regulating the pulp pH.

[0053] (7)For the application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention, the dynamic ionization behavior of carboxymethyl (-CH2COOH) and phosphate groups (-PO3H2) in the carboxymethyl-phosphorylated chitosan inhibitor molecule under different pH conditions is utilized. Under alkaline conditions, carboxymethyl is ionized into -CH2COO-, which reacts with WO4 on the surface of scheelite 2-Generate electrostatic repulsion to reduce its adsorption. At the same time, the phosphate group chelates Ca in fluorite and calcite selectively in the form of -PO3 2- and inhibits their flotation; under acidic conditions, the phosphate group is partially protonated to -PO3H 2+ , preferentially binds to the active Ca in calcite - , while the amino group (-NH2) is protonated to -NH3 2+ . The adsorption of calcite is enhanced through electrostatic interaction. At the same time, the carboxymethyl group returns to neutral (-CH2COOH), weakening the inhibition of fluorite, thus achieving stepwise selective inhibition. This pH-responsive mechanism of multi-functional group cooperation enables a single reagent to dynamically adapt to the requirements of different flotation stages and achieve precise separation of calcium-containing minerals with similar surface properties. +

[0054] (8) The application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention utilizes the activity differences of Ca on the surfaces of scheelite, fluorite, and calcite. By adjusting the pH, the action mode of the inhibitor is precisely matched. First, under alkaline conditions, the ionization of CO3 on the calcite surface is enhanced, the dissolution amount of Ca is high, and it is preferentially chelated by -PO3 2+ . The ionization of F on the fluorite surface is limited, the activity of Ca is the second, and WO4 on the scheelite surface is strongly negatively charged, electrostatically repelling -CH2COO 2- , ensuring its floatability; while under acidic conditions: CO3 on the calcite surface is converted to HCO3 2+ / CO2, the dissolution amount of Ca further increases, and its binding ability with -PO3H 2- is enhanced. At the same time, the ionization of F⁻ on the fluorite surface increases, the surface negative charge increases, and the inhibitory adsorption weakens. By synergistically "amplifying" the mineral property differences through pH and the reagent, the separation of scheelite, fluorite, and calcite by a single inhibitor in flotation is achieved. - 2+ 2- - 2- - 2+ - BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a schematic flow chart of the synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention;

[0056] Figure 2 is a schematic diagram of the flotation application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in the present invention for separating scheelite, fluorite, and calcite. DETAILED DESCRIPTION OF THE INVENTION

[0057] The present invention will be further described below with reference to the embodiments.

[0058] ​​​​​​​​​Example 1

[0059] The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in this Example 1 consists of the following steps:

[0060] (1) Acid activation pretreatment: Mix chitosan powder (chitosan with a deacetylation degree of 92% and a molecular weight of 100 kDa) with a 2 wt% aqueous citric acid solution at a mass ratio of 1:13, and stir at 50 °C for 40 minutes to obtain an activated chitosan dispersion;

[0061] (2) Phosphorylation reaction: Add disodium hydrogen phosphate to the activated chitosan dispersion. The mass ratio of disodium hydrogen phosphate to the chitosan dispersion is 1:1. At the same time, add 1 wt% of magnesium sulfate as a catalyst and react in a water bath at 80 °C for 4 hours to obtain phosphorylated chitosan;

[0062] (3) Carboxymethylation modification: Add sodium chloroacetate to the phosphorylated chitosan, and then add sodium hydroxide to adjust the pH of the reaction system to 7. The mass ratio of phosphorylated chitosan, sodium chloroacetate to sodium hydroxide is 1:2:1, and stir and react at 80 °C for 2 hours to generate carboxymethyl-phosphorylated bifunctional chitosan;

[0063] (4) Solid-liquid separation and drying: Precipitate the carboxymethyl-phosphorylated bifunctional chitosan obtained above with ethanol. The mass ratio of ethanol to carboxymethyl-phosphorylated bifunctional chitosan is 4:1. Wash it successively with an ethanol-water mixture with a volume ratio of 3:1 for 13 min and a 0.3 mol / L NaOH solution for 20 min, and dry (vacuum drying is used, the drying temperature is 50 °C, and the drying time is 18 h) to obtain the carboxymethyl-phosphorylated chitosan inhibitor.

[0064] The application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in this Example 1 is used for the flotation separation of scheelite, fluorite and calcite, and consists of the following steps:

[0065] ① Use a tungsten ore in Hunan. The grade of WO3 in this ore is 0.353%, the grade of CaF2 is 25.73%, and the grade of CaCO3 is 25.17%. Grind the ore to 75% passing -0.074 mm, then add sodium hydroxide to adjust the pH of the pulp (the mass concentration of the flotation pulp is 35%) to 8, and successively add 500 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 1 and 1000 g / t of sodium oleate. After one rough selection, two cleanings and three scavengings to recover scheelite. Among them, 500 g / t, 250 g / t and 100 g / t of sodium oleate are added for scavenging I, scavenging II and scavenging III respectively, and 200 g / t and 100 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 1 are added for cleaning I and cleaning II respectively to obtain a rough concentrate of scheelite and a mixed tailing containing fluorite and calcite;

[0066] ②Adjust the pH of the scheelite rough concentrate pulp (the mass concentration of the scheelite rough concentrate pulp is 15%) to 8 with sodium hydroxide, and successively add 500 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 1 and 200 g / t of sodium oleate. After one rough selection, four fine selections and three scavenging selections at room temperature, scheelite is recovered. Among them, 100 g / t, 50 g / t and 20 g / t of sodium oleate are added for Scavenging I, Scavenging II and Scavenging III respectively, and 200 g / t and 100 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 1 are added for Fine I and Fine II respectively. No drugs are added for Fine III and Fine IV, and scheelite concentrate and selected tailings are obtained;

[0067] ③Adjust the pH of the mixed tailings pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 30%) to 4 with sulfuric acid, and add 200 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 1 and 300 g / t of octadecylamine again. After one rough selection, six fine selections and two scavenging selections, fluorite concentrate is obtained. Among them, 100 g / t and 50 g / t of octadecylamine are added for Scavenging I and Scavenging II respectively, and 100 g / t and 50 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 1 are added for Fine I and Fine II respectively. No drugs are added for Fine III, Fine IV, Fine V and Fine VI, and fluorite concentrate and calcite-containing tailings are obtained.

[0068] Comparative Example 1

[0069] The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in this Comparative Example 1 consists of the following steps:

[0070] (1) Dispersion: Mix chitosan powder (chitosan with a deacetylation degree of 92% and a molecular weight of 100 kDa) with water at a mass ratio of 1:15, and stir at 50 °C for 40 minutes to obtain a chitosan dispersion;

[0071] (2) Phosphorylation reaction: Add disodium hydrogen phosphate to the chitosan dispersion. The mass ratio of disodium hydrogen phosphate to the chitosan dispersion is 1:1, and 1 wt% of magnesium sulfate is added as a catalyst at the same time. React in a water bath at 80 °C for 4 hours to obtain phosphorylated chitosan;

[0072] (3) Carboxymethylation modification: Add sodium chloroacetate to the phosphorylated chitosan, and then add sodium hydroxide to adjust the pH of the reaction system to 7. The mass ratio of phosphorylated chitosan, sodium chloroacetate to sodium hydroxide is 1:2:1. Stir and react at 80 °C for 2 hours to generate carboxymethyl-phosphorylated bifunctional chitosan;

[0073] (4) Solid-liquid separation and drying: The carboxymethyl-phosphorylated bifunctional chitosan obtained above was precipitated with ethanol, and the mass ratio of ethanol to carboxymethyl-phosphorylated bifunctional chitosan was 4:1. It was washed successively with an ethanol-water mixture with a volume ratio of 3:1 for 13 min and a 0.3 mol / L NaOH solution for 20 min, and dried (vacuum drying was used, the drying temperature was 50 °C, and the drying time was 18 h) to obtain a carboxymethyl-phosphorylated chitosan inhibitor.

[0074] The application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in this Comparative Example 1 was the same as that in Example 1. The only difference was that the carboxymethyl-phosphorylated bifunctional chitosan inhibitor was prepared by Comparative Example 1.

[0075] Comparative Example 2

[0076] The synthesis method of the phosphorylated bifunctional chitosan inhibitor described in Comparative Example 2 consisted of the following steps:

[0077] (1) Acid activation pretreatment: Chitosan powder (chitosan with a deacetylation degree of 92% and a molecular weight of 100 kDa) was mixed with a 2 wt% citric acid aqueous solution at a mass ratio of 1:13, and stirred at 50 °C for 40 minutes to obtain an activated chitosan dispersion;

[0078] (2) Phosphorylation reaction: Disodium hydrogen phosphate was added to the activated chitosan dispersion, and the mass ratio of disodium hydrogen phosphate to the chitosan dispersion was 1:1. At the same time, 1 wt% of magnesium sulfate was added as a catalyst, and the reaction was carried out in a water bath at 80 °C for 4 hours to obtain phosphorylated chitosan;

[0079] (3) Solid-liquid separation and drying: The phosphorylated chitosan obtained above was precipitated with ethanol, and the mass ratio of ethanol to phosphorylated chitosan was 4:1. It was washed successively with an ethanol-water mixture with a volume ratio of 3:1 for 13 min and a 0.3 mol / L NaOH solution for 20 min, and dried (vacuum drying was used, the drying temperature was 50 °C, and the drying time was 18 h) to obtain a pH-responsive phosphorylated chitosan inhibitor.

[0080] The application of the phosphorylated chitosan inhibitor described in this Comparative Example 2 was the same as that in Example 1. The only difference was that the phosphorylated chitosan inhibitor was prepared by Comparative Example 2.

[0081] Comparative Example 3

[0082] The synthesis method of the carboxymethyl chitosan inhibitor described in this Comparative Example 3 consisted of the following steps:

[0083] (1) Acid activation pretreatment: Chitosan powder (chitosan with a deacetylation degree of 92% and a molecular weight of 100 kDa) was mixed with a 2 wt% aqueous citric acid solution at a mass ratio of 1:13, and stirred at 50 °C for 40 minutes to obtain an activated chitosan dispersion;

[0084] (2) Carboxymethylation modification: Sodium chloroacetate was added to the activated chitosan dispersion, and then sodium hydroxide was added to adjust the pH of the reaction system to 7. The mass ratio of the activated chitosan dispersion, sodium chloroacetate, and sodium hydroxide was 1:2:1, and the reaction was stirred thoroughly at 80 °C for 2 hours to produce carboxymethyl chitosan;

[0085] (3) Solid-liquid separation and drying: The carboxymethyl chitosan obtained above was precipitated with ethanol. The mass ratio of ethanol to carboxymethyl chitosan was 4:1, and it was washed successively with an ethanol-water mixture with a volume ratio of 3:1 for 13 min and a 0.3 mol / L NaOH solution for 20 min. After drying (vacuum drying was used, the drying temperature was 50 °C, and the drying time was 18 h), a carboxymethyl chitosan inhibitor was obtained.

[0086] The application of the carboxymethyl chitosan inhibitor described in Comparative Example 3 was the same as that in Example 1. The only difference was that the carboxymethyl chitosan inhibitor was prepared by Comparative Example 3.

[0087] Comparative Example 4

[0088] The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in this Comparative Example 4 consists of the following steps:

[0089] (1) Acid activation pretreatment: Chitosan powder (chitosan with a deacetylation degree of 92% and a molecular weight of 100 kDa) was mixed with a 2 wt% aqueous citric acid solution at a mass ratio of 1:13, and stirred at 50 °C for 40 minutes to obtain an activated chitosan dispersion;

[0090] (2) Carboxymethylation modification: Sodium chloroacetate was added to the activated chitosan dispersion, and then sodium hydroxide was added to adjust the pH of the reaction system to 7. The mass ratio of the activated chitosan dispersion, sodium chloroacetate, and sodium hydroxide was 1:2:1, and the reaction was stirred thoroughly at 80 °C for 2 hours to produce carboxymethyl chitosan;

[0091] (3) Phosphorylation reaction: Disodium hydrogen phosphate was added to the carboxymethyl chitosan dispersion. The mass ratio of disodium hydrogen phosphate to carboxymethyl chitosan was 1:1, and 1 wt% of magnesium sulfate was added as a catalyst at the same time. The reaction was carried out in a water bath at 80 °C for 4 hours to obtain carboxymethyl-phosphorylated bifunctional chitosan;

[0092] (4) Solid-liquid separation and drying: The carboxymethyl-phosphorylated bifunctional chitosan obtained above was precipitated with ethanol, and the mass ratio of ethanol to carboxymethyl-phosphorylated bifunctional chitosan was 4:1. It was washed successively with an ethanol-water mixture with a volume ratio of 3:1 for 13 min and a 0.3 mol / L NaOH solution for 20 min, and dried (vacuum drying was used, the drying temperature was 50 °C, and the drying time was 18 h) to obtain a carboxymethyl-phosphorylated chitosan inhibitor.

[0093] The application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in Comparative Example 4 was the same as that in Example 1, and the only difference was that the carboxymethyl-phosphorylated bifunctional chitosan inhibitor was prepared by Comparative Example 4.

[0094] Comparative Example 5

[0095] The flotation separation method of scheelite, fluorite and calcite described in this Comparative Example 5 consists of the following steps:

[0096] ① A tungsten ore in Hunan was used. The grade of WO3 in the ore was 0.353%, the grade of CaF2 was 25.73%, and the grade of CaCO3 was 25.17%. The ore was ground to 75% passing -0.074 mm, and then sodium hydroxide was added to adjust the pH of the pulp (the mass concentration of the flotation pulp was 35%) to 8. 500 g / t of water glass and 1000 g / t of sodium oleate were added successively. After one rough selection, two cleanings and three scavengings, scheelite was recovered. Among them, 500 g / t, 250 g / t and 100 g / t of sodium oleate were added for Scavenging I, Scavenging II and Scavenging III respectively, and 200 g / t and 100 g / t of water glass were added for Cleaning I and Cleaning II respectively, to obtain a rough concentrate of scheelite and a mixed tailing containing fluorite and calcite;

[0097] ② Sodium hydroxide was used to adjust the pH of the scheelite rough concentrate pulp (the mass concentration of the scheelite rough concentrate pulp was 15%) to 8. 500 g / t of water glass and 200 g / t of sodium oleate were added successively. After one rough selection, four cleanings and three scavengings in a 90 °C pulp, scheelite was recovered. Among them, 100 g / t, 50 g / t and 20 g / t of sodium oleate were added for Scavenging I, Scavenging II and Scavenging III respectively, and 200 g / t and 100 g / t of water glass were added for Cleaning I and Cleaning II respectively. No medicine was added for Cleaning III and Cleaning IV, to obtain a scheelite concentrate and a selected tailing;

[0098] ③Adjust the pH of the mixed tailings pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 30%) to 4 with sulfuric acid, add 200 g / t of acidified water glass and 300 g / t of octadecylamine again. After one rough selection, six fine selections and two scavenging selections, fluorite concentrate is obtained. Among them, 100 g / t and 50 g / t of octadecylamine are added to scavenging I and scavenging II respectively, 100 g / t and 50 g / t of acidified water glass are added to fine selection I and fine selection II respectively, and no drugs are added to fine selection III, fine selection IV, fine selection V and fine selection VI, obtaining fluorite concentrate and tailings containing calcite.

[0099] Comparative Example 6

[0100] The flotation separation method of scheelite, fluorite and calcite described in this Comparative Example 6 consists of the following steps:

[0101] ①Use a tungsten ore in Hunan. The grade of WO3 in the ore is 0.353%, the grade of CaF2 is 25.73%, and the grade of CaCO3 is 25.17%. Grind the ore to 75% passing -0.074 mm, then add sodium hydroxide to adjust the pH of the pulp (the mass concentration of the flotation pulp is 35%) to 8, and add 500 g / t of water glass and 1000 g / t of sodium oleate successively. After one rough selection, two fine selections and three scavenging selections, scheelite is recovered. Among them, 500 g / t, 250 g / t and 100 g / t of sodium oleate are added to scavenging I, scavenging II and scavenging III respectively, and 200 g / t and 100 g / t of water glass are added to fine selection I and fine selection II respectively, obtaining a rough scheelite concentrate and a mixed tailings containing fluorite and calcite;

[0102] ②Adjust the pH of the rough scheelite concentrate pulp (the mass concentration of the rough scheelite concentrate pulp is 15%) to 8 with sodium hydroxide, add 500 g / t of water glass and 200 g / t of sodium oleate successively. At room temperature, after one rough selection, four fine selections and three scavenging selections, scheelite is recovered. Among them, 100 g / t, 50 g / t and 20 g / t of sodium oleate are added to scavenging I, scavenging II and scavenging III respectively, 200 g / t and 100 g / t of water glass are added to fine selection I and fine selection II respectively, and no drugs are added to fine selection III and fine selection IV, obtaining scheelite concentrate and selected tailings;

[0103] ③Adjust the pH of the mixed tailings pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 30%) to 4 with sulfuric acid, add 200 g / t of acidified water glass and 300 g / t of octadecylamine again. After one rough selection, six fine selections and two scavenging selections, fluorite concentrate is obtained. Among them, 100 g / t and 50 g / t of octadecylamine are added to scavenging I and scavenging II respectively, 100 g / t and 50 g / t of acidified water glass are added to fine selection I and fine selection II respectively, and no drugs are added to fine selection III, fine selection IV, fine selection V and fine selection VI, obtaining fluorite concentrate and tailings containing calcite.

[0104] Example 2

[0105] The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in Example 2 consists of the following steps:

[0106] (1) Acid activation pretreatment: Mix chitosan powder (chitosan with a deacetylation degree of 95% and a molecular weight of 50 kDa) with 1 wt% citric acid aqueous solution at a mass ratio of 1:15, and stir at 60 °C for 60 minutes to obtain an activated chitosan dispersion;

[0107] (2) Phosphorylation reaction: Add sodium dihydrogen phosphate to the activated chitosan dispersion. The mass ratio of sodium dihydrogen phosphate to the chitosan dispersion is 0.5:1. At the same time, add 0.5 wt% magnesium sulfate as a catalyst and react in a 90 °C water bath for 2 hours to obtain phosphorylated chitosan;

[0108] (3) Carboxymethylation modification: Add sodium chloroacetate to the phosphorylated chitosan, and then add sodium hydroxide to adjust the pH of the reaction system to 8. The mass ratio of phosphorylated chitosan, sodium chloroacetate to sodium hydroxide is 1:0.5:1.5, and stir thoroughly at 65 °C for 4 hours to generate carboxymethyl-phosphorylated bifunctional chitosan;

[0109] (4) Solid-liquid separation and drying: Precipitate the obtained carboxymethyl-phosphorylated bifunctional chitosan with ethanol. The mass ratio of ethanol to carboxymethyl-phosphorylated bifunctional chitosan is 4:1. Wash it successively with an ethanol-water mixture with a volume ratio of 4:1 for 20 min and 0.2 mol / L NaOH solution for 10 min, and dry (vacuum drying is used, the drying temperature is 60 °C, and the drying time is 12 h) to obtain the carboxymethyl-phosphorylated chitosan inhibitor.

[0110] The application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in Example 2 is used for the flotation separation of scheelite, fluorite and calcite, and consists of the following steps:

[0111] ① Use a tungsten ore in Jiangxi. The WO3 grade in this ore is 0.546%, the CaF2 grade is 32.17%, and the CaCO3 grade is 18.97%. Grind this ore to -0.074 mm accounting for 50%. Then, add sodium carbonate to adjust the pH of the pulp (the mass concentration of the flotation pulp is 45%) to 9. First, add 300 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 2 and 600 g / t of oleic acid, and recover scheelite through one rough selection, two fine selections and three scavenger selections. Among them, 300 g / t, 150 g / t and 60 g / t of oleic acid are added to scavenger I, scavenger II and scavenger III respectively, and 100 g / t and 50 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 2 are added to fine I and fine II respectively to obtain a scheelite concentrate and a mixed tailing containing fluorite and calcite.

[0112] ②Adjust the pH of the scheelite rough concentrate pulp (the mass concentration of the scheelite rough concentrate pulp is 20%) to 9 with sodium carbonate, and successively add 300 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 2 and 200 g / t of oleic acid. After one rough selection, three cleanings and two scavengings at room temperature, recover scheelite. Among them, 100 g / t and 50 g / t of oleic acid are added for scavenging I and scavenging II respectively, and 150 g / t, 50 g / t and 20 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 2 are added for cleaning I, cleaning II and cleaning III respectively, to obtain scheelite concentrate and selected tailings.

[0113] ③Adjust the pH of the mixed tailings pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 40%) to 5 with hydrochloric acid, and add 300 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 2 and 500 g / t of dodecylamine again. After one rough selection, seven cleanings and two scavengings, obtain fluorite concentrate. Among them, 200 g / t and 10 g / t of dodecylamine are added for scavenging I and scavenging II respectively, and 100 g / t and 50 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 2 are added for cleaning I and cleaning II respectively. No medicine is added for cleaning III, cleaning IV, cleaning V, cleaning VI and cleaning VII, to obtain fluorite concentrate and tailings containing calcite.

[0114] Comparative Example 7

[0115] The flotation separation method of scheelite, fluorite and calcite described in this Comparative Example 7 consists of the following steps:

[0116] ①Use a tungsten ore in Jiangxi. The grade of WO3 in the ore is 0.546%, the grade of CaF2 is 32.17%, and the grade of CaCO3 is 18.97%. Grind the ore to 50% passing -0.074 mm. Then, add sodium carbonate to adjust the pH of the pulp (the mass concentration of the flotation pulp is 45%) to 9, and successively add 300 g / t of water glass and 600 g / t of oleic acid. After one rough selection, two cleanings and three scavengings, recover scheelite. Among them, 300 g / t, 150 g / t and 60 g / t of oleic acid are added for scavenging I, scavenging II and scavenging III respectively, and 100 g / t and 50 g / t of water glass are added for cleaning I and cleaning II respectively, to obtain scheelite concentrate and a mixed tailings containing fluorite and calcite.

[0117] ②Adjust the pH of the scheelite rough concentrate pulp (the mass concentration of the scheelite rough concentrate pulp is 20%) to 9 with sodium carbonate, and successively add 300 g / t of water glass and 200 g / t of oleic acid. After one rough selection, three fine selections and two scavenging selections in the 90 °C pulp, recover scheelite. Among them, 100 g / t and 50 g / t of oleic acid are added for scavenging I and scavenging II respectively, and 150 g / t, 50 g / t and 20 g / t of water glass are added for fine selection I, fine selection II and fine selection III respectively to obtain scheelite concentrate and selected tailings.

[0118] ③Adjust the pH of the mixed tailings pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 40%) to 5 with hydrochloric acid, and add 300 g / t of acidified water glass and 500 g / t of dodecylamine again. After one rough selection, seven fine selections and two scavenging selections, obtain fluorite concentrate. Among them, 200 g / t and 10 g / t of dodecylamine are added for scavenging I and scavenging II respectively, 100 g / t and 50 g / t of acidified water glass are added for fine selection I and fine selection II respectively, and no drugs are added for fine selection III, fine selection IV, fine selection V, fine selection VI and fine selection VII to obtain fluorite concentrate and tailings containing calcite.

[0119] Comparative Example 8

[0120] The flotation separation method of scheelite, fluorite and calcite described in this Comparative Example 8 consists of the following steps:

[0121] ①Use a tungsten ore in Jiangxi. The grade of WO3 in this ore is 0.546%, the grade of CaF2 is 32.17%, and the grade of CaCO3 is 18.97%. Grind the ore to -0.074 mm accounting for 50%. Then, adjust the pH of the pulp (the mass concentration of the flotation pulp is 45%) to 9 with sodium carbonate, and successively add 300 g / t of water glass and 600 g / t of oleic acid. After one rough selection, two fine selections and three scavenging selections, recover scheelite. Among them, 300 g / t, 150 g / t and 60 g / t of oleic acid are added for scavenging I, scavenging II and scavenging III respectively, and 100 g / t and 50 g / t of water glass are added for fine selection I and fine selection II respectively to obtain scheelite concentrate and mixed tailings containing fluorite and calcite.

[0122] ②Adjust the pH of the scheelite rough concentrate pulp (the mass concentration of the scheelite rough concentrate pulp is 20%) to 9 with sodium carbonate, and successively add 300 g / t of water glass and 200 g / t of oleic acid. After one rough selection, three fine selections and two scavenging selections at room temperature, recover scheelite. Among them, 100 g / t and 50 g / t of oleic acid are added for scavenging I and scavenging II respectively, and 150 g / t, 50 g / t and 20 g / t of water glass are added for fine selection I, fine selection II and fine selection III respectively to obtain scheelite concentrate and selected tailings.

[0123] ③Adjust the pH of the mixed tailings pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 40%) to 5 with hydrochloric acid, and add 300 g / t of acidified water glass and 500 g / t of dodecylamine again. After one rough selection, seven fine selections and two scavenging selections, fluorite concentrate is obtained. Among them, 200 g / t and 10 g / t of dodecylamine are added for Scavenging I and Scavenging II respectively, 100 g / t and 50 g / t of acidified water glass are added for Fine Selection I and Fine Selection II respectively, and no drugs are added for Fine Selection III, Fine Selection IV, Fine Selection V, Fine Selection VI and Fine Selection VII, obtaining fluorite concentrate and tailings containing calcite.

[0124] Example 3

[0125] The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in this Example 3 consists of the following steps:

[0126] (1) Acid activation pretreatment: Mix chitosan powder (chitosan with a deacetylation degree of 85% and a molecular weight of 200 kDa) with 3 wt% citric acid aqueous solution at a mass ratio of 1:10, and stir at 40 °C for 30 minutes to obtain an activated chitosan dispersion;

[0127] (2) Phosphorylation reaction: Add trisodium phosphate to the activated chitosan dispersion. The mass ratio of trisodium phosphate to the chitosan dispersion is 3:1. At the same time, add 2 wt% of magnesium sulfate as a catalyst and react in a water bath at 85 °C for 3 hours to obtain phosphorylated chitosan;

[0128] (3) Carboxymethylation modification: Add sodium chloroacetate to the phosphorylated chitosan, and then add sodium hydroxide to adjust the pH of the reaction system to 7.5. The mass ratio of phosphorylated chitosan, sodium chloroacetate and sodium hydroxide is 1:3:0.3, and stir and react fully at 50 °C for 6 hours to generate carboxymethyl-phosphorylated bifunctional chitosan;

[0129] (4) Solid-liquid separation and drying: Precipitate the obtained carboxymethyl-phosphorylated bifunctional chitosan with ethanol. The mass ratio of ethanol to carboxymethyl-phosphorylated bifunctional chitosan is 4:1. Wash it successively with an ethanol-water mixture with a volume ratio of 2:1 for 5 minutes and 0.4 mol / L NaOH solution for 30 minutes, and dry (the drying is carried out by vacuum drying, the drying temperature is 40 °C, and the drying time is 24 h) to obtain the carboxymethyl-phosphorylated chitosan inhibitor.

[0130] The application of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor described in this Example 3 is used for the flotation separation of scheelite, fluorite and calcite, and consists of the following steps:

[0131] ① Use a tungsten ore from Henan. The grade of WO3 in this ore is 0.428%, the grade of CaF2 is 28.17%, and the grade of CaCO3 is 22.92%. Grind the ore to -0.074 mm with 95% passing through. Then, add sodium hydroxide to adjust the pH of the pulp (the mass concentration of the flotation pulp is 25%) to 10. First, add 100 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 3, 200 g / t of sodium dodecyl sulfate, and 100 g / t of sodium dodecyl sulfonate. After one rough selection, three cleanings, and three scavengings to recover scheelite. Among them, for scavenging I, II, and III, add 100 g / t, 50 g / t, and 20 g / t of sodium dodecyl sulfate, and 50 g / t, 20 g / t, and 10 g / t of sodium dodecyl sulfonate respectively. For cleaning I and II, add 50 g / t and 20 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 3 respectively, to obtain scheelite concentrate and a mixed tailing containing fluorite and calcite. No medicine is added in cleaning III.

[0132] ② Use sodium hydroxide to adjust the pH of the scheelite rough concentrate pulp (the mass concentration of the scheelite rough concentrate pulp is 10%) to 10. First, add 100 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 3 and 100 g / t of sodium dodecyl sulfate. After one rough selection, three cleanings, and two scavengings at room temperature to recover scheelite. Among them, for scavenging I and II, add 50 g / t and 20 g / t of sodium dodecyl sulfate respectively. For cleaning I, II, and III, add 50 g / t, 20 g / t, and 10 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 3 respectively, to obtain scheelite concentrate and selected tailings.

[0133] ③ Use oxalic acid to adjust the pH of the mixed tailing pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 20%) to 6. Add 500 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 3 and 100 g / t of ether amine again. After one rough selection, six cleanings, and two scavengings, fluorite concentrate is obtained. Among them, for scavenging I and II, add 50 g / t and 20 g / t of ether amine respectively. For cleaning I and II, add 200 g / t and 100 g / t of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor prepared in Example 3 respectively. No medicine is added in cleaning III, IV, V, and VI, to obtain fluorite concentrate and tailings containing calcite.

[0134] Comparative Example 9

[0135] The flotation separation method of scheelite, fluorite, and calcite described in this Comparative Example 9 consists of the following steps:

[0136] ① Using a tungsten ore from Henan. The grade of WO3 in this ore is 0.428%, the grade of CaF2 is 28.17%, and the grade of CaCO3 is 22.92%. Grind the ore to 95% passing -0.074 mm. Then, add sodium hydroxide to adjust the pH of the pulp (the mass concentration of the flotation pulp is 25%) to 10. Successively add 100 g / t of water glass, 200 g / t of sodium dodecyl sulfate, and 100 g / t of sodium dodecyl sulfonate. Recover scheelite through one roughing, three cleanings, and three scavengings. Among them, 100 g / t, 50 g / t, and 20 g / t of sodium dodecyl sulfate and 50 g / t, 20 g / t, and 10 g / t of sodium dodecyl sulfonate are added in scavenging I, scavenging II, and scavenging III respectively, and 50 g / t and 20 g / t of water glass are added in cleaning I and cleaning II respectively, obtaining scheelite concentrate and a mixed tailing containing fluorite and calcite. No reagent is added in cleaning III.

[0137] ② Use sodium hydroxide to adjust the pH of the scheelite rough concentrate pulp (the mass concentration of the scheelite rough concentrate pulp is 10%) to 10. Successively add 100 g / t of water glass and 100 g / t of sodium dodecyl sulfate. Recover scheelite through one roughing, three cleanings, and two scavengings in a 90°C pulp. Among them, 50 g / t and 20 g / t of sodium dodecyl sulfate are added in scavenging I and scavenging II respectively, and 50 g / t, 20 g / t, and 10 g / t of water glass are added in cleaning I, cleaning II, and cleaning III respectively, obtaining scheelite concentrate and selected tailings.

[0138] ③ Use oxalic acid to adjust the pH of the mixed tailing pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 20%) to 6. Add 500 g / t of acidified water glass and 100 g / t of ether amine again. After one roughing, six cleanings, and two scavengings, fluorite concentrate is obtained. Among them, 50 g / t and 20 g / t of ether amine are added in scavenging I and scavenging II respectively, and 200 g / t and 100 g / t of acidified water glass are added in cleaning I and cleaning II respectively. No reagent is added in cleaning III, cleaning IV, cleaning V, and cleaning VI, obtaining fluorite concentrate and tailings containing calcite.

[0139] Comparative Example 10

[0140] The flotation separation method of scheelite, fluorite, and calcite described in this Comparative Example 10 consists of the following steps:

[0141] ① Use a tungsten ore from Henan. The grade of WO3 in this ore is 0.428%, the grade of CaF2 is 28.17%, and the grade of CaCO3 is 22.92%. Grind the ore to 95% passing -0.074 mm. Then, add sodium hydroxide to adjust the pH of the pulp (the mass concentration of the flotation pulp is 25%) to 10. Successively add 100 g / t of water glass, 200 g / t of sodium dodecyl sulfate, and 100 g / t of sodium dodecyl sulfonate. Recover scheelite through one roughing, three cleanings, and three scavengings. Among them, 100 g / t, 50 g / t, and 20 g / t of sodium dodecyl sulfate and 50 g / t, 20 g / t, and 10 g / t of sodium dodecyl sulfonate are added in Scavenging I, Scavenging II, and Scavenging III respectively. 50 g / t and 20 g / t of water glass are added in Cleaning I and Cleaning II respectively, obtaining scheelite concentrate and a mixed tailing containing fluorite and calcite. No reagent is added in Cleaning III.

[0142] ② Use sodium hydroxide to adjust the pH of the scheelite rougher concentrate pulp (the mass concentration of the scheelite rougher concentrate pulp is 10%) to 10. Successively add 100 g / t of water glass and 100 g / t of sodium dodecyl sulfate. Recover scheelite through one roughing, three cleanings, and two scavengings at room temperature. Among them, 50 g / t and 20 g / t of sodium dodecyl sulfate are added in Scavenging I and Scavenging II respectively. 50 g / t, 20 g / t, and 10 g / t of water glass are added in Cleaning I, Cleaning II, and Cleaning III respectively, obtaining scheelite concentrate and the selected tailings.

[0143] ③ Use oxalic acid to adjust the pH of the mixed tailing pulp containing fluorite and calcite (the mass concentration of the flotation pulp is 20%) to 6. Add 500 g / t of acidified water glass and 100 g / t of ether amine again. After one roughing, six cleanings, and two scavengings, obtain fluorite concentrate. Among them, 50 g / t and 20 g / t of ether amine are added in Scavenging I and Scavenging II respectively. 200 g / t and 100 g / t of acidified water glass are added in Cleaning I and Cleaning II respectively. No reagent is added in Cleaning III, Cleaning IV, Cleaning V, and Cleaning VI, obtaining fluorite concentrate and calcite-containing tailings.

[0144] Summarize the comparison of the flotation effects of Example 1 and Comparative Examples 1 - 5. The main flotation indexes are listed in Table 1 as follows.

[0145] Table 1 Flotation test results of Example 1 and Comparative Examples 1 - 6

[0146]

[0147] Table 2 Flotation test results of Example 2 and Comparative Examples 7 - 8

[0148]

[0149] Table 3 Flotation test results of Example 3 and Comparative Examples 9 - 10

[0150]

[0151] From the data obtained from the flotation tests in Table 1-3, it can be seen that:

[0152] (1) The chitosan used in Comparative Example 1 was not pretreated with citric acid and was directly diluted for phosphorylation reaction and carboxymethyl modification. The flotation test results showed that Comparative Example 1 could only obtain tungsten concentrate with a WO3 grade of 35.12% and a recovery rate of 67.56%, and fluorite concentrate with a CaF2 grade of 87.22% and a recovery rate of 64.27%. Both the concentrate grade and the recovery rate were lower than those of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor obtained in Example 1, where chitosan was activated with citric acid and then subjected to phosphorylation reaction and carboxymethyl modification. This indicates that citric acid washing can open the crystalline region, expose more hydroxyl and amino active sites, provide pre-activation sites for the subsequent phosphorylation reaction, enhance the uniformity of phosphate group substitution, and thus improve the selectivity of the inhibitor.

[0153] (2) The carboxymethyl modification of chitosan was omitted during the synthesis process in Comparative Example 2. The test results showed that Comparative Example 2 could only obtain tungsten concentrate with a WO3 grade of 37.28% and a recovery rate of 64.68%, and fluorite concentrate with a CaF2 grade of 85.37% and a recovery rate of 66.98%. Both the concentrate grade and the recovery rate were lower than those of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor obtained in Example 1 with carboxymethyl modification. Under alkaline conditions, carboxymethyl ionizes to -CH2COO ‒ , which can generate electrostatic repulsion with WO4 2‒ on the surface of scheelite, reducing non-target adsorption. At the same time, it competitively binds to CO3 2‒ of calcite, amplifying the charge difference on the mineral surface and enhancing the pH responsiveness.

[0154] (3) The phosphorylation reaction was omitted during the synthesis process in Comparative Example 3. The test results showed that Comparative Example 3 could only obtain tungsten concentrate with a WO3 grade of 41.05% and a recovery rate of 56.59%, and fluorite concentrate with a CaF2 grade of 85.69% and a recovery rate of 65.11%. Both the concentrate grade and the recovery rate were lower than those of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor obtained in Example 1 with phosphorylation reaction. The phosphate group ionizes to -PO3 2‒ under alkaline conditions and forms a five-membered ring chelate with Ca 2+ of fluorite and calcite. In addition, the stepwise ionization of the phosphate group (pKa1≈2.1, pKa2≈7.2, pKa3≈12.3) endows it with a wide range of pH adaptability: at pH 8-10: targeting the inhibition of fluorite / calcite with -PO3 2‒ ; at pH 4-6: preferentially binding to the active Ca ‒ of calcite with -PO3H 2+Therefore, phosphorylation will greatly enhance the selectivity and pH responsiveness of the inhibitor.

[0155] (4) In the synthesis process, the carboxymethylation reaction was first carried out in Comparative Example 4, and then the phosphorylation reaction was carried out. The flotation test results show that the comparative application example 3 can only obtain tungsten concentrate with a WO3 grade of 45.66% and a recovery rate of 66.39%, and a fluorite concentrate with a CaF2 grade of 88.67% and a recovery rate of 62.04%. The concentrate grade and recovery rate are lower than the carboxymethyl-phosphorylated bifunctional chitosan inhibitor obtained in Example 1, which is first phosphorylated and then carboxymethylated. Since sodium chloroacetate is added during the carboxymethylation reaction, it will compete with the phosphate group, resulting in the inability to introduce the carboxymethyl group into the remaining C6 hydroxyl site, resulting in a steric hindrance effect, which reduces the selectivity of the inhibitor.

[0156] (5) Comparative Examples 5, 7 and 9 used conventional fluorite and calcite flotation depressants, water glass and acidified water glass, and carried out scheelite concentration in a slurry environment heated to 90°C. The results showed that the grade and recovery rate of scheelite and fluorite concentrates obtained in Comparative Examples 5, 7 and 9 were lower than those of the carboxymethyl-phosphorylated bifunctional chitosan depressant obtained in Examples 1, 2 and 3. This indicates that the carboxymethyl-phosphorylated bifunctional chitosan depressant developed by the present invention can achieve efficient separation of scheelite, fluorite and calcite in the flotation process at room temperature.

[0157] (6) Comparative Examples 6, 8 and 10 used conventional fluorite and calcite flotation inhibitors, water glass and acidified water glass, and carried out scheelite concentration in a slurry environment at room temperature. The results showed that the grade and recovery rate of scheelite and fluorite concentrate obtained in Comparative Examples 6, 8 and 10 were lower than those of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor obtained in Examples 1, 2 and 3, as well as Comparative Examples 5, 7 and 9. This indicates that conventional flotation agents must be heated to ensure a certain flotation selectivity during scheelite concentration, further highlighting the advanced nature of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor obtained in the present invention.

Claims

1. A method for synthesizing a carboxymethyl-phosphorylated bifunctional chitosan inhibitor, characterized by: It consists of the following steps: (1) Acid activation pretreatment Mix chitosan powder evenly with an aqueous citric acid solution and stir to react to prepare an activated chitosan dispersion; (2) Phosphorylation reaction Add phosphate and magnesium sulfate to the activated chitosan dispersion prepared in step (1), react at 80 - 90 °C for 2 - 4 h to prepare phosphorylated chitosan; (3) Carboxymethylation modification Add sodium chloroacetate to the phosphorylated chitosan prepared in step (2), then add sodium hydroxide to adjust the pH value of the reaction system to 7 - 8, and stir to react to generate carboxymethyl-phosphorylated bifunctional chitosan; (4) Solid-liquid separation and drying Precipitate the carboxymethyl-phosphorylated bifunctional chitosan prepared in step (3) with ethanol, then wash it successively with an ethanol-water mixture and a NaOH solution, and dry to obtain a carboxymethyl-phosphorylated bifunctional chitosan inhibitor; Among them: The phosphate in step (2) is one of disodium hydrogen phosphate, sodium dihydrogen phosphate or trisodium phosphate; In step (2), the mass ratio of the phosphate to the activated chitosan dispersion is 0.5:1 - 3:1, and the mass of magnesium sulfate accounts for 0.5 - 2 wt% of the mass of the phosphate. Magnesium sulfate is used as a catalyst for the phosphorylation reaction; In step (3), the mass ratio of phosphorylated chitosan, sodium chloroacetate, and sodium hydroxide is 1:0.5 - 3:0.3 - 1.5; In step (3), the stirring reaction temperature is 50 - 80 °C, and the stirring reaction time is 2 - 6 h; In step (4), the mass ratio of ethanol to carboxymethyl-phosphorylated bifunctional chitosan is 4:1; In the ethanol-water mixture in step (4), the volume ratio of ethanol to water is 4:1 - 2:1, and the washing time is 5 - 20 min; In the NaOH solution in step (4), the concentration is 0.2 - 0.4 mol / L, and the washing time is 10 - 30 min; In step (4), drying is carried out by vacuum drying, the drying temperature is 40 - 60 °C, and the drying time is 12 - 24 h.

2. The synthesis method of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor according to claim 1, wherein: In step (1), the deacetylation degree of the chitosan powder is 85% - 95%, and the molecular weight is 50 - 200 kDa; In step (1), the mass concentration of the aqueous citric acid solution is 1 - 3 wt%, and the mass ratio of the chitosan powder to the aqueous citric acid solution is 1:10 - 1:15; In step (1), the stirring and mixing temperature is 40 - 60 °C, and the stirring and mixing time is 30 - 60 min.

3. Application of a carboxymethyl-phosphorylated bifunctional chitosan inhibitor, characterized in that: For the flotation separation of scheelite, fluorite and calcite, it consists of the following steps: ① Grind the ore containing scheelite, fluorite and calcite to -0.074 mm accounting for 50% - 95%, then adjust the pulp pH value to 8 - 10, successively add a carboxymethyl-phosphorylated bifunctional chitosan inhibitor and an anionic collector, and obtain a scheelite rough concentrate and a mixed tailings containing fluorite and calcite through one rough selection, multiple cleaning selections and multiple scavenging selections; ② Adjust the pH value of the scheelite rough concentrate pulp prepared in step ① to 8 - 10, add a carboxymethyl-phosphorylated bifunctional chitosan inhibitor and an anionic collector, and obtain a scheelite concentrate and a cleaned tailings through one rough selection, multiple cleaning selections and multiple scavenging selections at room temperature; ③Adjust the pH value of the mixed tailings pulp containing fluorite and calcite prepared in step ① to 4 - 6, add carboxymethyl-phosphorylated bifunctional chitosan inhibitor and cationic collector, and obtain fluorite concentrate and tailings containing calcite through one rough selection, multiple cleaning selections, and multiple scavenging selections.

4. Use of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor according to claim 3, characterized in that: In step ①, the mass concentration of the flotation pulp is 25% - 45%; In step ①, add sodium hydroxide or sodium carbonate to adjust the pH value of the pulp to 8 - 10; In step ①, the dosage of carboxymethyl-phosphorylated bifunctional chitosan inhibitor is 100 - 500 g / t, and the anionic collector is at least one of sodium oleate, oleic acid, sodium dodecyl sulfate, or sodium dodecyl sulfonate, with a dosage of 300 - 1000 g / t; In step ①, the number of cleaning selections is 2 - 3 times. During the cleaning selection operation of scheelite flotation, add carboxymethyl-phosphorylated bifunctional chitosan inhibitor, and the dosage is 1 / 4 - 1 / 2 of the previous operation; In step ①, the number of scavenging selections is 3 times. During the scavenging selection operation of scheelite flotation, add anionic collector, and the dosage is 1 / 4 - 1 / 2 of the previous operation.

5. Use of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor according to claim 3, characterized in that: In step ②, the mass concentration of the scheelite rough concentrate pulp is 10% - 20%; In step ②, the dosage of carboxymethyl-phosphorylated bifunctional chitosan inhibitor is 100 g / t - 500 g / t, and the anionic collector is at least one of sodium oleate, oleic acid, sodium dodecyl sulfate, or sodium dodecyl sulfonate, with a dosage of 100 g / t - 200 g / t; In step ②, the number of cleaning selections is 3 - 4 times, and the number of scavenging selections is 2 - 3 times.

6. Use of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor according to claim 3, characterized in that: In step ③, the mass concentration of the flotation pulp is 20% - 40%; In step ③, add one of sulfuric acid, hydrochloric acid, or oxalic acid to adjust the pH value of the pulp to 4 - 6.

7. Use of the carboxymethyl-phosphorylated bifunctional chitosan inhibitor according to claim 3, characterized in that: In step ③, the dosage of carboxymethyl-phosphorylated bifunctional chitosan inhibitor is 200 - 500 g / t, and the cationic collector is at least one of dodecylamine, octadecylamine, or ether amine collector, with a dosage of 100 - 500 g / t; In step ③, the number of cleaning selections is 6 - 7 times, and the number of scavenging selections is 2 times.

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