Nanometer lignin-based multifunctional collecting agent and preparation method and application thereof

Abstract

The invention relates to a nano lignin-based multifunctional collecting agent and a preparation method and application thereof, and belongs to the technical field of mineral flotation. The embodiment of the invention provides a nano-lignin-based multifunctional collecting agent. The multifunctional collecting agent is prepared by carrying out graft copolymerization reaction on a nano-lignin carrier with the average particle size of 50-200 nm and loading a sulfydryl collecting agent component and an amine collecting agent component at the same time, wherein the sulfydryl collecting agent component and the amine collecting agent component are loaded on the nano-lignin carrier at the same time; wherein the mass ratio of the sulfydryl collecting agent component to the amine collecting agent component is (1.5: 1)-(4: 1). The high specific surface area and rich reaction sites of the nano lignin carrier are utilized, and two types of collecting agent components with different functions are fixed to the surface of the same nano lignin carrier through graft copolymerization, so that the nano lignin-based multifunctional collecting agent has the specific collecting capacity on pyrite and silicate minerals at the same time; the pyrite and silicate minerals are synchronously and efficiently removed, and the aluminum-silicon ratio and quality of the bauxite concentrate are remarkably improved.

Description

Technical Field

[0001] This application relates to the field of mineral flotation technology, and in particular to a nano-lignin-based multifunctional collector, its preparation method, and its application. Background Technology

[0002] In the field of mineral processing, flotation collectors are crucial in determining separation efficiency. Bauxite is an important aluminum resource in my country, but the development and utilization of high-sulfur, high-silica bauxite faces the technical challenge of simultaneously removing pyrite and silicate minerals. Pyrite mainly exists in the form of iron sulfide, while silicate minerals primarily include kaolinite and quartz.

[0003] Currently, flotation is commonly used for desulfurization and desilication of high-sulfur, high-silica bauxite. However, due to the significant differences in surface properties between pyrite and silicate minerals—the former possessing a certain degree of natural floatability while the latter is highly hydrophilic—commonly used collector systems struggle to simultaneously achieve efficient collection of both. Therefore, actual flotation operations often require the staged addition of different types of collectors or the use of combinations of various reagents, resulting in complex processes, difficulty in controlling the reagent formulation, and potential antagonistic effects between different reagents, thus impacting separation efficiency. Summary of the Invention

[0004] This application provides a nano-lignin-based multifunctional collector, its preparation method, and its application to solve the following technical problem: how to solve the technical problem that existing collectors are difficult to remove pyrite and silicate minerals simultaneously in bauxite reverse flotation.

[0005] In a first aspect, embodiments of this application provide a nano-lignin-based multifunctional collector, wherein the multifunctional collector is prepared by graft copolymerization of a nano-lignin carrier with an average particle size of 50nm~200nm, simultaneously loading a thiol-based collector component and an amine-based collector component; wherein the mass ratio of the thiol-based collector component to the amine-based collector component is (1.5:1)~(4:1).

[0006] Optionally, the mercapto-based collector component is at least one of butyl xanthate, isobutyl xanthate, pentyl xanthate, isopentyl xanthate, and ethyl thiocyanate; the amine collector component is at least one of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine.

[0007] Optionally, the zeta potential of the multifunctional collector is +20 mV to +50 mV.

[0008] Secondly, embodiments of this application provide a method for preparing the multifunctional collector described in the first aspect, the method comprising: Under an inert atmosphere, a nano-sized lignin dispersion, a quaternary ammonium salt surfactant, and a mixture of thiol-based and amine-based collectors are subjected to a graft copolymerization reaction in the presence of a free radical initiator; wherein the temperature of the graft copolymerization reaction is 60℃~90℃ and the time of the graft copolymerization reaction is 12 hours~36 hours.

[0009] Optionally, the solid content of the nano-sized lignin dispersion is 0.1 wt% to 1 wt%; the mass of the quaternary ammonium salt surfactant is 0.5% to 5% of the mass of the nano-sized lignin dispersion.

[0010] Optionally, the ratio of the total mass of the mercapto collector and the amine collector to the mass of the nano-sized lignin solid in the nano-sized lignin dispersion is (5~15):1.

[0011] Optionally, the mass of the free radical initiator is 10% to 20% of the total mass of the thiol collector and the amine collector.

[0012] Optionally, the quaternary ammonium salt surfactant is at least one of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide; and the free radical initiator is one of ammonium persulfate, potassium persulfate, and azobisisobutyramidine hydrochloride.

[0013] Thirdly, embodiments of this application provide an application of the multifunctional collector described in the first aspect in mineral flotation, wherein the multifunctional collector simultaneously removes pyrite and silicate minerals in a bauxite reverse flotation process.

[0014] Optionally, in the bauxite reverse flotation process, the dosage of the multifunctional collector is 200g / t raw ore to 400g / t raw ore.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a nano-lignin-based multifunctional collector, which is prepared by grafting and copolymerizing nano-lignin carriers with an average particle size of 50nm to 200nm simultaneously with a thiol-based collector component and an amine-based collector component; wherein the mass ratio of the thiol-based collector component to the amine-based collector component is (1.5:1) to (4:1). This application utilizes the high specific surface area and abundant reaction sites of the nano-lignin carrier to fix two different types of collector components with different functions onto the same nano-lignin carrier surface through graft copolymerization. This allows the nano-lignin-based multifunctional collector to simultaneously possess specific collecting capabilities for pyrite (provided by the mercapto-based collector component) and specific collecting capabilities for silicate minerals (provided by the amine-based collector component). By controlling the mass ratio of the mercapto-based collector component to the amine-based collector component to be 1.5:1 to 4:1, a balanced match of the two collecting functions on the nano-lignin carrier surface is achieved. This enables the nano-lignin-based multifunctional collector to act on the surfaces of both pyrite and silicate minerals simultaneously in the bauxite reverse flotation process through the synergistic effect of electrostatic adsorption and specific chemisorption, achieving synchronous and efficient removal of pyrite and silicate minerals, and significantly improving the aluminum-silicon ratio and quality of the bauxite concentrate. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart illustrating a method for preparing a nano-lignin-based multifunctional collector, as provided in an embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0021] In a first aspect, embodiments of this application provide a nano-lignin-based multifunctional collector, wherein the multifunctional collector is prepared by graft copolymerization of a nano-lignin carrier with an average particle size of 50nm~200nm, simultaneously loading a thiol-based collector component and an amine-based collector component; wherein the mass ratio of the thiol-based collector component to the amine-based collector component is (1.5:1)~(4:1).

[0022] The nano-lignin carrier acts as a framework and anchoring platform in nano-lignin-based multifunctional collectors, responsible for simultaneously loading thiol-based and amine-based collector components through graft copolymerization. When the average particle size of the nano-lignin carrier is in the range of 50 nm to 200 nm, it possesses a high specific surface area, providing sufficient grafting reaction sites to ensure that adequate amounts of thiol-based and amine-based collector components are simultaneously loaded onto the surface of the nano-lignin carrier through graft copolymerization. Simultaneously, nano-lignin carriers within this particle size range exhibit good dispersion stability in aqueous phase, which is beneficial for the uniformity of the graft copolymerization reaction and the stable preservation of the final nano-lignin-based multifunctional collector product.

[0023] If the average particle size of the nano-lignin carrier is less than 50 nm, although the specific surface area is higher, the surface energy of the nano-lignin carrier is too high, and the particles are prone to agglomeration. This results in poor dispersibility of the nano-lignin carrier during the graft copolymerization reaction, uneven loading of the thiol-based and amine-based collector components, and even irreversible agglomeration and precipitation, making it impossible to obtain a stable nano-lignin-based multifunctional collector. If the average particle size of the nano-lignin carrier is greater than 200 nm, the specific surface area of ​​the nano-lignin carrier decreases significantly, and the number of active sites available for grafting reactions on the surface decreases. This leads to insufficient loading of the thiol-based and amine-based collector components, resulting in a decrease in the collecting ability of the prepared nano-lignin-based multifunctional collector for pyrite and silicate minerals.

[0024] When the mass ratio of the mercapto-based collector component to the amine collector component is within the range of 1.5:1 to 4:1, the mass proportion of the mercapto-based collector component is consistently higher than that of the amine collector component. This ratio ensures that the multifunctional collector has a strong collecting ability for pyrite, while the amine collector component provides collecting ability for silicate minerals. When the mass ratio of the mercapto-based collector component to the amine collector component is lower than 1.5:1, the mercapto-based collector component is relatively insufficient, leading to a decrease in the multifunctional collector's collecting ability for pyrite and a reduction in desulfurization efficiency. When the mass ratio of the mercapto-based collector component to the amine collector component is higher than 4:1, the amine collector component is relatively insufficient, leading to a decrease in the multifunctional collector's collecting ability for silicate minerals and a reduction in desilication efficiency. By controlling the mass ratio of mercapto-based collector components to amine-based collector components within the range of 1.5:1 to 4:1, multifunctional collectors can simultaneously and efficiently remove pyrite and silicate minerals in the bauxite reverse flotation process.

[0025] In some embodiments, the mercapto collector component is at least one selected from butyl xanthate, isobutyl xanthate, pentyl xanthate, isopentyl xanthate, and ethyl thiocyanate; the amine collector component is at least one selected from dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine.

[0026] Butyl xanthate, isobutyl xanthate, pentyl xanthate, and isopentyl xanthate belong to the xanthate collector class, and their molecular structures contain thiol and hydrocarbon groups. Ethyl thiocyanate (chemical name: sodium diethyldithiocarbamate) belongs to the thiocarbamate collector class, and its molecular structure also contains sulfur atoms that strongly coordinate with metal ions. These compounds have a strong coordination effect on iron ions on the surface of pyrite, forming a hydrophobic adsorption layer on the pyrite surface, changing the pyrite from hydrophilic to hydrophobic, thereby allowing it to float and be removed by the action of bubbles.

[0027] Dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine belong to the aliphatic primary amine collectors, containing an amino group and a long-chain alkyl group in their molecular structure. Under the pH conditions of the slurry, the amino group undergoes protonation and becomes positively charged, adsorbing onto the negatively charged surface of silicate minerals through electrostatic interactions. After adsorption, the long-chain alkyl group faces the water, hydrophobizing the silicate mineral surface, causing it to float and be removed by the action of bubbles. Aliphatic amines with different carbon chain lengths (dodecylamine to octadecylamine) vary slightly in collecting ability and selectivity, but all belong to the amine collector components effective against silicate minerals. Therefore, limiting the collection to at least one of the above compounds ensures the achievement of desilication while providing flexibility.

[0028] In some embodiments, the zeta potential of the multifunctional collector is +20 mV to +50 mV.

[0029] In this embodiment, the Zeta potential refers to the net charge potential value carried by the surface of the multifunctional collector particles in the aqueous dispersion system. This potential value is positive, with a lower limit of +20 mV and an upper limit of +50 mV, including the endpoint value. The amine collector component loaded on the nano-lignin carrier through graft copolymerization carries a positive charge after protonation in the solution; simultaneously, the quaternary ammonium salt surfactant used in the preparation process imparts a positive charge to the surface of the multifunctional collector through grafting or adsorption. The combined effect of the above two positively charged components maintains the Zeta potential of the multifunctional collector within the range of +20 mV to +50 mV. The Zeta potential of +20 mV to +50 mV ensures the selective electrostatic adsorption of the multifunctional collector on the target gangue minerals. Pyrite and silicate minerals (including kaolinite and quartz) in bauxite are usually negatively charged on the surface under the pH conditions of the slurry. For the multifunctional collector to effectively collect these two minerals, it first needs to overcome the energy barrier through electrostatic interaction and adsorb onto the mineral surface. The higher the positive value of the Zeta potential of the multifunctional collector, the stronger the electrostatic attraction between it and the negatively charged mineral surface, which is more conducive to the spread of the multifunctional collector on the mineral surface and the subsequent collection effect. When the Zeta potential of the multifunctional collector is below +20 mV, the electrostatic attraction weakens, resulting in a decrease in the collection ability of the multifunctional collector for silicate minerals and a reduction in desilication efficiency; at the same time, insufficient interparticle repulsion makes it easy to agglomerate, affecting the dispersion performance of the multifunctional collector. When the Zeta potential of the multifunctional collector is above +50 mV, the excessive positive charge may cause the multifunctional collector to undergo non-selective adsorption with non-target minerals, reducing flotation selectivity. At the same time, excessively high surface charge density may affect the chemical adsorption of mercapto-based collector components on the pyrite surface.

[0030] Figure 1 This is a schematic flowchart illustrating a method for preparing a nano-lignin-based multifunctional collector, as provided in an embodiment of this application.

[0031] Please see Figure 1 Secondly, embodiments of this application provide a method for preparing the multifunctional collector described in the first aspect, the method comprising: Under an inert atmosphere, a nano-sized lignin dispersion, a quaternary ammonium salt surfactant, and a mixture of thiol-based and amine-based collectors are subjected to a graft copolymerization reaction in the presence of a free radical initiator; wherein the temperature of the graft copolymerization reaction is 60℃~90℃ and the time of the graft copolymerization reaction is 12 hours~36 hours.

[0032] In the preparation method of the nano-lignin-based multifunctional collector in this application, the graft copolymerization reaction is limited to an inert atmosphere to eliminate oxygen in the reaction system. Oxygen consumes the active free radicals generated by the decomposition of the free radical initiator, inhibiting the initiation process of the graft copolymerization reaction.

[0033] This preparation method involves graft copolymerization of a nano-sized lignin dispersion, a quaternary ammonium salt surfactant, and a mixture of thiol and amine collectors in the presence of a free radical initiator. The nano-sized lignin dispersion provides a nano-lignin carrier with an average particle size of 50 to 200 nanometers, serving as the framework for the graft copolymerization reaction. The quaternary ammonium salt surfactant improves the dispersibility of the nano-lignin carrier in the reaction system and provides a source of positive charge. The mixture of thiol and amine collectors is the active component of the target loading, respectively endowing the nano-lignin-based multifunctional collector with the ability to collect pyrite and silicate minerals. The free radical initiator decomposes under heating conditions to generate free radicals, initiating the graft copolymerization reaction.

[0034] The graft copolymerization reaction temperature is 60℃ to 90℃, a range that matches the thermal decomposition characteristics of the free radical initiator. Within this temperature range, the free radical initiator can continuously decompose at a suitable rate to generate free radicals, driving the grafting reaction of thiol and amine collectors on the surface of the nano-lignin support. The graft copolymerization reaction time is 12 hours to 36 hours, ensuring sufficient conversion. Within this time range, the thiol and amine collector components can complete grafting on the surface of the nano-lignin support, forming stable chemical bonds.

[0035] In some embodiments, the solid content of the nano-sized lignin dispersion is 0.1 wt% to 1 wt%; the mass of the quaternary ammonium salt surfactant is 0.5% to 5% of the mass of the nano-sized lignin dispersion.

[0036] The solid content of a nano-sized lignin dispersion refers to the percentage of the mass of solid nano-lignin in the dispersion relative to the total mass of the dispersion. This range has a lower limit of 0.1 wt% and an upper limit of 1 wt%, including the endpoints. Controlling the solid content of the nano-sized lignin dispersion within the range of 0.1 wt% to 1 wt% ensures a suitable amount of nano-lignin carrier in the reaction system: when the solid content is below 0.1 wt%, the concentration of nano-lignin carrier is too low, leading to a decrease in graft copolymerization efficiency and insufficient loading of the collector component per unit time; when the solid content is above 1 wt%, the concentration of nano-lignin carrier is too high, increasing the probability of particle collisions and making aggregation more likely, affecting the uniformity of the graft copolymerization reaction and the dispersion stability of the multifunctional collector.

[0037] The mass of the quaternary ammonium salt surfactant is 0.5% to 5% of the mass of the nano-sized lignin dispersion. This ratio refers to the percentage of the mass of the quaternary ammonium salt surfactant to the total mass of the nano-sized lignin dispersion, with a lower limit of 0.5% and an upper limit of 5%, including the endpoints. Controlling the mass of the quaternary ammonium salt surfactant within the range of 0.5% to 5% of the mass of the nano-sized lignin dispersion ensures that the quaternary ammonium salt surfactant can exert its emulsifying and charge-modifying functions: when the ratio is below 0.5%, the amount of quaternary ammonium salt surfactant is insufficient, failing to effectively emulsify hydrophobic thiol and amine collectors, and the introduction of insufficient positive charge on the surface of the nano-lignin carrier affects the Zeta potential of the multifunctional collector; when the ratio is above 5%, excess quaternary ammonium salt surfactant forms a large number of micelles in the reaction system, interfering with the normal progress of the graft copolymerization reaction, and the residual free quaternary ammonium salt surfactant may affect the flotation selectivity of the multifunctional collector.

[0038] In some embodiments, the ratio of the total mass of the mercapto collector and the amine collector to the mass of the nano-sized lignin solid in the nano-sized lignin dispersion is (5~15):1.

[0039] The ratio of the total mass of thiol-based and amine-based collectors to the mass of nano-sized lignin solids in the nano-sized lignin dispersion is 5:1 to 15:1. This ratio refers to the ratio of the sum of the masses of the thiol-based and amine-based collectors participating in the graft copolymerization reaction to the mass of nano-sized lignin solids contained in the nano-sized lignin dispersion. The lower limit of the ratio range is 5:1, and the upper limit is 15:1, including the endpoints. Controlling the ratio of the total mass of thiol-based and amine-based collectors to the mass of nano-sized lignin solids within the range of 5:1 to 15:1 ensures that the surface of the nano-lignin carrier has sufficient grafting reaction sites to load the collector components.

[0040] In some embodiments, the mass of the free radical initiator is 10% to 20% of the total mass of the thiol collector and the amine collector.

[0041] In graft copolymerization, the free radical initiator is responsible for decomposing to generate primary free radicals, initiating the copolymerization reaction between the nano-lignin carrier and the mercapto and amine collectors. If the mass of the free radical initiator is less than 10% of the total mass of the mercapto and amine collectors, the concentration of free radicals generated is too low, failing to effectively initiate all reactive components, leading to incomplete graft copolymerization, low grafting rates of the mercapto and amine collector components, insufficient number of functional groups on the surface of the resulting nano-lignin-based multifunctional collector, and decreased collection ability for pyrite and silicate minerals. If the mass of the free radical initiator is more than 20% of the total mass of the mercapto and amine collectors, the concentration of free radicals generated is too high, which may lead to mutual quenching of free radicals and an increase in side reactions, such as self-polymerization of the mercapto collector component and excessive cross-linking of the amine collector component, affecting the selectivity of the graft copolymerization reaction and the structural uniformity of the product.

[0042] In some embodiments, the quaternary ammonium salt surfactant is at least one of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide; and the free radical initiator is one of ammonium persulfate, potassium persulfate, and azobisisobutyramidine hydrochloride.

[0043] Dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide are all long-chain alkyltrimethylammonium bromide cationic surfactants, with molecular structures composed of hydrophobic long-chain alkyl groups and hydrophilic quaternary ammonium salt head groups. In graft copolymerization, these quaternary ammonium salt surfactants are adsorbed onto the surface of nano-lignin carriers through electrostatic and hydrophobic interactions. On the one hand, this improves the compatibility of the nano-lignin carriers with the reaction medium and hydrophobic reaction components; on the other hand, it introduces a positive charge into the surface of the nano-lignin carriers, providing a basis for the final product's Zeta potential to reach +20mV to +50mV.

[0044] Ammonium persulfate, potassium persulfate, and azobisisobutyramidine hydrochloride are all water-soluble free radical initiators. These free radical initiators have suitable decomposition rates in the reaction temperature range of 60℃ to 90℃, and can continuously generate sufficient concentrations of free radicals to drive the graft copolymerization reaction between thiol collectors and amine collectors and the active sites on the surface of nano-lignin carriers.

[0045] Thirdly, embodiments of this application provide an application of the multifunctional collector described in the first aspect in mineral flotation, wherein the multifunctional collector simultaneously removes pyrite and silicate minerals in a bauxite reverse flotation process.

[0046] The bauxite reverse flotation process is a mineral separation technology that separates pyrite and silicate minerals from aluminum-bearing minerals by causing the target desiccant minerals (pyrite and silicate minerals) to float to the surface and enter the froth product, while leaving the target recoverable minerals (aluminate-bearing minerals in bauxite) at the bottom of the tank as concentrate. In this application's embodiments, the multifunctional collector selectively adsorbs onto the surfaces of pyrite and silicate minerals, changing them from hydrophilic to hydrophobic, thus allowing them to float and be removed by the action of bubbles.

[0047] In some embodiments, the dosage of the multifunctional collector in the bauxite reverse flotation process is 200 g / t raw ore to 400 g / t raw ore.

[0048] The dosage of the multifunctional collector refers to the mass of multifunctional collector added per ton of bauxite ore processed. In this embodiment, the dosage of the multifunctional collector is controlled within the range of 200 g / ton to 400 g / ton of ore. This ensures a sufficient concentration of the multifunctional collector in the slurry, forming an effective adsorption layer on the surfaces of pyrite and silicate minerals, achieving thorough flotation and removal of pyrite and silicate minerals, while avoiding non-selective adsorption and foaming problems caused by excessive multifunctional collector dosage. Within this dosage range, combined with the conventional process parameters of the bauxite reverse flotation process, the multifunctional collector can fully utilize its structural characteristics to reduce the sulfur content of the bauxite concentrate, increase the aluminum-silicon ratio, and achieve simultaneous and efficient removal of pyrite and silicate minerals.

[0049] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0050] Example 1 Take 200 g of a nano-sized lignin dispersion with a solid content of 0.5 wt%, the average particle size of the nano-sized lignin in the dispersion being 100 nm. Add 1 g of hexadecyltrimethylammonium bromide (quaternary ammonium salt surfactant) to the nano-sized lignin dispersion and stir to fully dissolve and disperse it.

[0051] Weigh out 9 grams of butyl xanthate (thiol-based collector component) and 3 grams of dodecylamine (amine-based collector component), and mix them evenly to obtain a mixture of thiol-based collector and amine-based collector.

[0052] The mixture of the above-mentioned thiol-based and amine-based collectors was added to the nano-sized lignin dispersion and stirred until homogeneous. Then, 1.8 g of ammonium persulfate (a free radical initiator) was added.

[0053] The mixture was heated to 75°C under nitrogen protection for a graft copolymerization reaction for 24 hours. After the reaction, it was cooled to room temperature to obtain a nano-lignin-based multifunctional collector. The zeta potential of the nano-lignin-based multifunctional collector was measured to be +35 mV.

[0054] Example 2 Take 500 g of a nano-sized lignin dispersion with a solid content of 0.2 wt% and an average particle size of 180 nm in the dispersion. Add 2.5 g of dodecyltrimethylammonium bromide (quaternary ammonium salt surfactant) to the nano-sized lignin dispersion and stir to fully dissolve and disperse it.

[0055] Weigh 8 grams of isobutyl xanthate (thiol-based collector component) and 2.5 grams of tetradecylamine (amine-based collector component), and mix them evenly to obtain a mixture of thiol-based collector and amine-based collector.

[0056] The mixture of the above-mentioned thiol-based and amine-based collectors was added to the nano-sized lignin dispersion and stirred until homogeneous. Then, 2.5 g of azobisisobutyramidine hydrochloride was added.

[0057] The mixture was heated to 65°C under nitrogen protection for a graft copolymerization reaction for 30 hours. After the reaction, it was cooled to room temperature to obtain a nano-lignin-based multifunctional collector. The Zeta potential of the nano-lignin-based multifunctional collector was measured to be +42 mV.

[0058] Example 3 Take 125 g of a nano-sized lignin dispersion with a solid content of 0.8 wt% and an average particle size of 60 nm in the dispersion. Add 6.25 g of octadecyltrimethylammonium bromide (quaternary ammonium salt surfactant) to the nano-sized lignin dispersion and stir to fully dissolve and disperse it.

[0059] Weigh 6 grams of pentyl xanthate (thiol-based collector component) and 4 grams of hexadecylamine (amine-based collector component), and mix them evenly to obtain a mixture of thiol-based collector and amine-based collector.

[0060] The mixture of the above-mentioned thiol-based and amine-based collectors was added to the nano-sized lignin dispersion and stirred until homogeneous. Then, 1 gram of potassium persulfate (free radical initiator) was added.

[0061] The mixture was heated to 85°C under nitrogen protection for a graft copolymerization reaction for 15 hours. After the reaction, it was cooled to room temperature to obtain a nano-lignin-based multifunctional collector. The zeta potential of the nano-lignin-based multifunctional collector was measured to be +28 mV.

[0062] Comparative Example 1 This comparative example is basically the same as Example 1, except that the lignin carrier used is not nanoscale, but microscale.

[0063] The same preparation method as in Example 1 was used, but the nano-sized lignin dispersion was replaced with a micron-sized lignin dispersion with an average particle size of 5 μm. During the reaction, it was found that the micron-sized lignin had poor dispersibility and was prone to precipitation. The final product was measured to have a Zeta potential of +18 mV.

[0064] The collectors prepared in Examples 1-3 and Comparative Example 1 were applied to reverse flotation desulfurization and desilication tests of high-sulfur, high-silica bauxite ore in a certain area of ​​Guizhou Province. The main chemical composition of the raw ore was: Al2O3: 56.72%, S: 2.85%, and the aluminum-silica ratio (A / S) was 3.47. After a reverse flotation process consisting of one roughing and two cleaning stages, aluminum concentrate was obtained. The collector dosage was 300 g / t of raw ore in all cases. The experimental results are shown in Table 1.

[0065] Table 1

[0066] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: The nano-lignin-based multifunctional collector obtained in this invention has both strong collecting ability for pyrite and selective collecting ability for silicate minerals, realizing the simultaneous removal of two types of gangue minerals with different properties in the same flotation operation.

[0067] The preparation method of this invention adopts an aqueous reaction system, uses lignin, a renewable biomass resource, as raw material, does not use organic solvents in the synthesis process, has mild reaction conditions, is easy to operate, and meets the requirements of green chemistry and sustainable development.

[0068] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A nano-lignin-based multifunctional collector, characterized in that, The multifunctional collector is prepared by grafting copolymerization of lignin nanocarriers with an average particle size of 50nm to 200nm with both thiol-based and amine-based collector components; wherein the mass ratio of the thiol-based collector component to the amine-based collector component is (1.5:1) to (4:1).

2. The multifunctional collector according to claim 1, characterized in that, The mercapto-based collector component is at least one of butyl xanthate, isobutyl xanthate, pentyl xanthate, isopentyl xanthate, and ethyl thiocyanate; the amine collector component is at least one of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine.

3. The multifunctional collector according to claim 1 or 2, characterized in that, The zeta potential of the multifunctional collector is +20 mV to +50 mV.

4. A method for preparing the multifunctional collector according to any one of claims 1 to 3, characterized in that, The method includes: Under an inert atmosphere, a nano-sized lignin dispersion, a quaternary ammonium salt surfactant, and a mixture of thiol-based and amine-based collectors are subjected to a graft copolymerization reaction in the presence of a free radical initiator; wherein the temperature of the graft copolymerization reaction is 60℃~90℃ and the time of the graft copolymerization reaction is 12 hours~36 hours.

5. The method according to claim 4, characterized in that, The solid content of the nano-sized lignin dispersion is 0.1wt%~1wt%; the mass of the quaternary ammonium salt surfactant is 0.5%~5% of the mass of the nano-sized lignin dispersion.

6. The method according to claim 4, characterized in that, The ratio of the total mass of the mercapto collector and the amine collector to the mass of the nano-sized lignin solid in the nano-sized lignin dispersion is (5~15):

1.

7. The method according to claim 4, characterized in that, The mass of the free radical initiator is 10% to 20% of the total mass of the thiol collector and the amine collector.

8. The method according to claim 4, characterized in that, The quaternary ammonium salt surfactant is at least one of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide; the free radical initiator is one of ammonium persulfate, potassium persulfate, and azobisisobutyramidine hydrochloride.

9. The application of the multifunctional collector according to any one of claims 1 to 3 in mineral flotation, characterized in that, The multifunctional collector simultaneously removes pyrite and silicate minerals in the bauxite reverse flotation process.

10. The method according to claim 9, characterized in that, In the bauxite reverse flotation process, the dosage of the multifunctional collector is 200 g / t raw ore to 400 g / t raw ore.

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