A method for recovering diamond powder from oily grinding waste liquid

Abstract

The present disclosure relates to a method for recovering diamond powder from oily grinding waste liquid, the method comprising: (1) subjecting the oily grinding waste liquid containing diamond powder to a first centrifugal process to collect a first centrifugal bottom material; (2) mixing the first centrifugal bottom material with water and subjecting the mixture to a second centrifugal process to a second centrifugal process to collect a second centrifugal bottom material; (3) mixing an oil remover with the second centrifugal bottom material and subjecting the resulting mixture to ultrasonic treatment, then subjecting the resulting mixed liquid to gravity sedimentation and collecting the sedimented material; (4) heat-treating the sedimented material to obtain a first powder; (5) mixing the first powder with an acid solution, washing and drying the resulting mixture to obtain a second powder; (6) contacting the second powder with an alkaline solution to perform a first reaction, or contacting the second powder with a molten alkali to perform a second reaction; the oil remover comprises an alkaline inorganic substance, a chelating agent and a surfactant. The method has high efficiency in removing oil and aluminum oxide, and recovers high-purity diamond powder.

Description

Technical Field

[0001] The present disclosure relates to the technical field of mineral processing, and in particular to a method for recovering diamond powder from oily grinding waste liquid. Background Art

[0002] Sapphire is a commonly used optical and semiconductor material. Due to its excellent light transmittance, high hardness, and resistance to damage, it is often used in high-end optical lenses. In recent years, with the popularity of smartphones, sapphire has gradually been used in phone screens, touch buttons, back cover glass, camera windows, etc. With the significant increase in the use of sapphire sheets, sapphire thinning has become a key factor.

[0003] The grinding and thinning process of sapphire substrate sheets mainly uses diamond as an abrasive, which is then mixed with an aqueous solvent (mainly ethylene glycol) or an oily solvent (mainly white oil) in a certain proportion, and an appropriate dispersant is added to prepare a suspension of a certain concentration, and the mechanical grinding action of the diamond is used to achieve the grinding and thinning effect. During the grinding process, the diamond powder will gradually become finer, and the particle size will gradually become smaller. These diamond powders and the grinding debris such as copper powder and aluminum oxide generated during the grinding process form grinding waste slurry with liquid substances such as grinding solvents, additives, and cleaning agents. In the subsequent treatment of the grinding waste slurry by the existing technology, only a part of the lower-value boron carbide particles in the front-end processing of sapphire can be recovered through a complex process, while the higher-value diamond powder in the back-end processing cannot be recovered and can only be wasted in the subsequent waste treatment process. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a method for recovering diamond powder from oily grinding waste liquid, which has high efficiency in removing oil and aluminum oxide and can obtain high-purity diamond powder.

[0005] In order to achieve the above object, the present disclosure provides a method for recovering diamond powder from oily grinding waste liquid, the method comprising the following steps:

[0006] (1) subjecting the oily grinding waste liquid containing diamond powder to a first centrifugation to collect the first centrifugal bottom material;

[0007] (2) mixing the first centrifugal bottom material with water and performing a second centrifugation to collect the second centrifugal bottom material;

[0008] (3) mixing the degreasing agent with the second centrifugal bottom material and subjecting the resulting mixture to ultrasonic treatment, then subjecting the resulting mixed solution to gravity sedimentation and collecting the sedimented material;

[0009] (4) heat-treating the sedimentation material to obtain a first powder;

[0010] (5) mixing the first powder with an acid solution, washing and drying the resulting mixture to obtain a second powder;

[0011] (6) contacting the second powder with an alkaline solution to perform a first reaction, or contacting the second powder with a molten alkali to perform a second reaction;

[0012] The degreasing agent comprises an alkaline inorganic substance, a chelating agent and a surfactant.

[0013] Optionally, the method further comprises, before step (1), filtering the oily grinding waste liquid using a sieve with a mesh size of 80 to 300.

[0014] Optionally, in step (3), the weight ratio of the deoiling agent to the second centrifugal bottom material is (0.1-0.5):1, preferably (0.1-0.3):1; based on the total weight of the mixture, the content of the deoiling agent is 10-30% by weight, preferably 10-20% by weight;

[0015] The alkaline inorganic substance includes one or more of sodium carbonate, sodium hydroxide, potassium hydroxide, sodium amide and sodium bicarbonate; the chelating agent includes one or more of sodium gluconate, sodium metaphosphate, sodium acid pyrophosphate, sorbitol and ethylenediaminetetraacetic acid; the surfactant includes a nonionic surfactant and / or an anionic surfactant; the nonionic surfactant includes one or more of isomeric fatty alcohol polyoxyethylene ether, polyethylene glycol, nonylphenol polyoxyethylene ether and polyvinyl pyrrolidone; the anionic surfactant includes one or more of sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium linear alkyl sulfonate and fatty alcohol polyoxyethylene ether sodium sulfate.

[0016] Optionally, in step (3), the degreasing agent includes sodium carbonate, sodium hydroxide, sodium gluconate, isomeric fatty alcohol polyoxyethylene ether and sodium dodecylbenzene sulfonate;

[0017] Based on the total weight of the degreasing agent, the content of the sodium carbonate is 60 to 70 weight percent, the content of the sodium hydroxide is 2 to 14 weight percent, the content of the sodium gluconate is 6 to 20 weight percent, the content of the isomerized fatty alcohol polyoxyethylene ether is 6 to 15 weight percent, and the content of the sodium dodecylbenzene sulfonate is 2 to 12 weight percent.

[0018] Optionally, in step (5), the weight ratio of the first powder to the acid solution is (0.095-0.16):1, preferably (0.1-0.13):1; based on the total weight of the acid solution, the content of the acid is 15-40% by weight, preferably 20-30% by weight; the acid solution is selected from one or more of nitric acid solution, acetic acid solution and hydrochloric acid solution.

[0019] Optionally, in step (6), the weight ratio of the second powder to the alkaline solution is (0.08-0.25):1, preferably (0.09-0.2):1; the content of alkali in the alkaline solution is 20-45% by weight, preferably 25-38% by weight, based on the total weight of the alkaline solution; wherein the alkaline solution is selected from an alkaline inorganic solution, and the alkaline inorganic solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide solution, barium hydroxide solution and cesium hydroxide solution; or,

[0020] The weight ratio of the second powder to the molten alkali is (1-5):1, preferably (1-3):1; wherein the molten alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, lithium hydroxide and barium hydroxide.

[0021] Optionally, in step (6), the conditions for the first reaction include: a temperature of 180 to 400°C, preferably 200 to 300°C, and a time of 1 to 8 hours, preferably 1 to 5 hours; the conditions for the second reaction include: a temperature of 200 to 600°C, preferably 300 to 500°C, and a time of 1 to 10 hours, preferably 1 to 6 hours.

[0022] Optionally, in step (1), the first centrifugation is carried out in a flat scraper suction sedimentation centrifuge, and the conditions of the first centrifugation include: the centrifuge power is 30 to 50 Hz, the rotation speed is 1140 to 1900 r / min, and the centrifugation time is 5 to 60 min; preferably, the first centrifuged bottom material is collected by siphoning.

[0023] Optionally, in step (2), the conditions for mixing the first centrifugal bottom material with water include: a weight ratio of the first centrifugal bottom material to water of 1:(0.8-2.5); preferably, stirring is further performed during the mixing process, and the stirring speed is 50-100 r / min and the time is 5-60 min;

[0024] In step (3), the ultrasonic conditions include: ultrasonic frequency of 20 to 60 kHz, temperature of 60 to 70° C., and time of 1 to 3 hours.

[0025] In step (4), the heat treatment conditions include: a temperature of 300 to 500° C. and a time of 5 to 10 hours; preferably, before the heat treatment, the sedimentation material is washed with water once or multiple times until the pH of the washing liquid is 6.5 to 7.5, and the obtained solid material is dried;

[0026] The reaction slurry obtained in step (6) is washed and dried.

[0027] Optionally, the oily grinding waste liquid includes a liquid component and a solid component, the liquid component includes soybean oil, white oil and lubricating oil, and the solid component includes micron-sized diamond powder, copper, micron-sized aluminum oxide, nano-sized aluminum oxide, cupric oxide, cuprous oxide and epoxy resin;

[0028] Based on the total weight of the solid component, the content of the micron-sized diamond powder is 10 to 60% by weight, preferably 25 to 30% by weight, and the average particle size of the micron-sized diamond powder is 3 to 20 μm, preferably 3 to 5 μm; the average particle size of the micron-sized alumina is 1 to 50 μm, preferably 1 to 20 μm, and the average particle size of the nano-sized alumina is 100 to 1500 nm, preferably 100 to 800 nm.

[0029] Through the above technical solution, the method for recovering diamond powder from oily grinding waste liquid provided by the present invention adopts degreasing agent for chemical degreasing, which can effectively remove residual oil in the second centrifugal bottom material with high degreasing efficiency. The alkaline inorganic substance has a saponification effect and can clean the oil stains. The chelating agent has the functions of buffering, dispersing and promoting emulsification, which can significantly improve the wetting performance of the degreasing agent, which is conducive to the suspension of the detached oil to the surface of the solution for easy separation. The surfactant has a solubilizing effect and can enhance the degreasing agent's infiltration, dispersion and degreasing effect on the surface of the diamond powder, which is conducive to separating the diamond powder from the oil and achieving the purpose of removing the oil stains. Centrifugation is used to remove nano-sized aluminum oxide, and an alkaline solution or molten alkali is used to chemically etch and remove micron-sized aluminum oxide, so that the aluminum oxide removal rate is as high as 95% or more. The method disclosed in the present invention has simple procedures, can effectively remove oil and aluminum oxide, can obtain high-purity, reusable diamond powder, and effectively reduce the cost of diamond recovery.

[0030] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure.

[0032] Figure 1 This is a scanning electron microscope image of powder 1 prepared in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0033] The following describes the specific embodiments of the present disclosure in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0034] The present disclosure provides a method for recovering diamond powder from oily grinding waste liquid, the method comprising the following steps:

[0035] (1) subjecting the oily grinding waste liquid containing diamond powder to a first centrifugation to collect the first centrifugal bottom material;

[0036] (2) mixing the first centrifugal bottom material with water and performing a second centrifugation to collect the second centrifugal bottom material;

[0037] (3) mixing the degreasing agent with the second centrifugal bottom material and subjecting the resulting mixture to ultrasonic treatment, then subjecting the resulting mixed solution to gravity sedimentation and collecting the sedimented material;

[0038] (4) heat-treating the sedimentation material to obtain a first powder;

[0039] (5) mixing the first powder with an acid solution, washing and drying the resulting mixture to obtain a second powder;

[0040] (6) contacting the second powder with an alkaline solution to perform a first reaction, or contacting the second powder with a molten alkali to perform a second reaction;

[0041] The degreasing agent comprises an alkaline inorganic substance, a chelating agent and a surfactant.

[0042] The method for recovering diamond powder from oily grinding waste liquid provided by the present invention adopts degreasing agent for chemical degreasing, which can effectively remove residual oil in the second centrifugal bottom material with high degreasing efficiency. The alkaline inorganic substance has a saponification effect and can clean the oil stains. The chelating agent has the functions of buffering, dispersing and promoting emulsification, which can significantly improve the wetting performance of the degreasing agent, which is conducive to the suspension of the detached oil to the surface of the solution for easy separation. The surfactant has a solubilizing effect and can enhance the degreasing agent's infiltration, dispersion and degreasing effect on the surface of the diamond powder, which is conducive to separating the diamond powder from the oil and achieving the purpose of removing the oil stains. The nano-alumina is removed by centrifugation, and the micro-alumina is removed by chemical etching with an alkaline solution or molten alkali, so that the alumina removal rate is as high as 95% or more. The method disclosed in the present invention has simple procedures, can effectively remove oil and alumina, can obtain high-purity, reusable diamond powder, and effectively reduce the cost of diamond recovery.

[0043] In one embodiment of the present disclosure, the method further comprises, before step (1), filtering the oily grinding waste liquid using a sieve with a mesh size of 80 to 300. In the above embodiment, by selecting the preferred filtration operation, large-sized solid impurities in the oily grinding waste liquid can be removed, thereby reducing the impact of the solid impurities on subsequent processing.

[0044] In one embodiment of the present disclosure, in step (1), the first centrifugation is carried out in a flat scraper suction sedimentation centrifuge, and the conditions of the first centrifugation include: the centrifuge power is 30 to 50 Hz, the rotation speed is 1140 to 1900 r / min, and the centrifugation time is 5 to 60 min; preferably, the first centrifugal bottom material is collected by siphoning. In the above embodiment, by selecting the preferred first centrifugation, it is beneficial to grade and separate the micron-sized diamond powder and nano-sized alumina in the oily grinding waste liquid, wherein the micron-sized diamond powder is settled in the first centrifugal bottom material and the nano-sized alumina floats in the upper solution; in a preferred embodiment, the upper solution is drained by siphoning to remove the nano-sized alumina, and the first centrifugal bottom material containing the micron-sized diamond powder is collected at the bottom.

[0045] In one embodiment of the present disclosure, in step (2), the conditions for mixing the first centrifugal bottom material with water include: a weight ratio of the first centrifugal bottom material to water of 1:(0.8-2.5); preferably, stirring is also performed during the mixing process, and the stirring speed is 50-100 r / min and the time is 5-60 min. In the above embodiment, by selecting the preferred second centrifugation, physical separation of oil and water can be achieved, and 80-95% of the oil in the first centrifugal bottom material can be removed.

[0046] In one embodiment of the present disclosure, in step (3), the weight ratio of the deoiling agent to the second centrifugal bottom material is (0.1-0.5):1, preferably (0.1-0.3):1; based on the total weight of the mixture, the content of the deoiling agent is 10-30% by weight, preferably 10-20% by weight; the alkaline inorganic substance includes one or more of sodium carbonate, sodium hydroxide, potassium hydroxide, sodium amide and sodium bicarbonate, the chelating agent includes one or more of sodium gluconate, sodium metaphosphate, sodium acid pyrophosphate, sorbitol and ethylenediaminetetraacetic acid, the surfactant includes a nonionic surfactant and / or an anionic surfactant, the nonionic surfactant includes one or more of isomeric fatty alcohol polyoxyethylene ether, polyethylene glycol, nonylphenol polyoxyethylene ether and polyvinyl pyrrolidone, and the anionic surfactant includes one or more of sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium linear alkyl sulfonate and fatty alcohol polyoxyethylene ether sodium sulfate. In the above embodiment, by selecting preferred alkaline inorganic substances, chelating agents and surfactants, grease can be effectively cleaned. Among them, the compound use of chelating agents, non-ionic surfactants and anionic surfactants has a significant synergistic effect, which effectively promotes the infiltration, dispersion, cleaning and emulsification of the degreasing agent on the diamond powder, so that the diamond powder can be stripped from the grease for easy recovery.

[0047] In one embodiment of the present disclosure, in step (3), the degreasing agent comprises sodium carbonate, sodium hydroxide, sodium gluconate, isomeric fatty alcohol polyoxyethylene ether, and sodium dodecylbenzene sulfonate; based on the total weight of the degreasing agent, the content of sodium carbonate is 60-70 weight%, the content of sodium hydroxide is 2-14 weight%, the content of sodium gluconate is 6-20 weight%, the content of isomeric fatty alcohol polyoxyethylene ether is 6-15 weight%, and the content of sodium dodecylbenzene sulfonate is 2-12 weight%. In the above embodiment, by selecting a degreasing agent with a preferred ratio, the cleaning, emulsification, and degreasing capabilities of the degreasing agent are improved.

[0048] In one embodiment of the present disclosure, in step (3), the ultrasonic conditions include: an ultrasonic frequency of 20 to 80 kHz, preferably 20 to 60 kHz, a temperature of 50 to 100° C., preferably 60 to 70° C., and a time of 0.5 to 5 hours, preferably 1 to 3 hours. In the above embodiment, the preferred ultrasonic treatment is used to facilitate the full reaction of the degreasing agent with the grease in the second centrifugal bottom material, thereby improving the degreasing efficiency.

[0049] In one embodiment of the present disclosure, in step (4), the heat treatment conditions include: a temperature of 300 to 500°C and a time of 5 to 10 hours; in a preferred embodiment, the sedimentation material is washed with water once or multiple times before the heat treatment until the pH of the washing liquid is 6.5 to 7.5, and the obtained solid material is dried; wherein the washing liquid refers to a mixture of sedimentation material and water. In the above embodiment, washing and drying the sedimentation material is conducive to cleaning away the residual alkaline degreasing agent in the sedimentation material, thereby avoiding the neutralization reaction of the alkaline degreasing agent with the subsequently added acid solution; the preferred heat treatment can carbonize organic matter such as grease and epoxy resin in the sedimentation material to achieve the degreasing effect, and the heat treatment can oxidize copper and cuprous oxide into cupric oxide, which is convenient for subsequent processing. The solid components in the first powder obtained after the heat treatment are diamond, cupric oxide, silicon impurities remaining in the epoxy resin, and a small amount of residual micron-sized aluminum oxide.

[0050] In one embodiment of the present disclosure, in step (5), the weight ratio of the first powder to the acid solution is (0.095-0.16):1, preferably (0.1-0.13):1; the content of the acid is 15-40% by weight, preferably 20-30% by weight, based on the total weight of the acid solution; and the acid solution is selected from one or more of a nitric acid solution, an acetic acid solution, and a hydrochloric acid solution. In the above embodiment, by selecting a preferred acid solution, it is beneficial to remove substances that are easily soluble in the acid solution, such as copper oxide, from the first powder. At this time, the solid components of the second powder obtained are diamond, silicon impurities, and micron-sized aluminum oxide.

[0051] In one embodiment of the present disclosure, in step (6), the weight ratio of the second powder to the alkaline solution is (0.08-0.25):1, preferably (0.09-0.2):1; based on the total weight of the alkaline solution, the alkali content in the alkaline solution is 20-45% by weight, preferably 25-38% by weight; wherein the alkaline solution is selected from an alkaline inorganic solution, and the alkaline inorganic solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide solution, barium hydroxide solution and cesium hydroxide solution; or, the weight ratio of the second powder to the molten alkali is (1-5):1, preferably (1-3):1; wherein the molten alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, lithium hydroxide and barium hydroxide. In the above embodiment, by selecting a preferred alkaline solution or molten alkali for chemical etching, it is beneficial to remove silicon impurities and micron-sized aluminum oxide in the second powder, and the solid component in the reaction slurry obtained at this time is high-purity diamond powder.

[0052] In one embodiment of the present disclosure, in step (6), the conditions for the first reaction include: a temperature of 180-400°C, preferably 200-300°C, and a time of 1-8 hours, preferably 1-5 hours; and the conditions for the second reaction include: a temperature of 200-600°C, preferably 300-500°C, and a time of 1-10 hours, preferably 1-6 hours. In the above embodiment, by selecting the preferred first and second reaction conditions, silicon impurities and micron-sized aluminum oxide mixed in the diamond powder can be fully etched away to obtain high-purity diamond powder.

[0053] In one embodiment of the present disclosure, the reaction slurry obtained in step (6) is washed and dried. In the above embodiment, washing and drying the reaction slurry is beneficial for cleaning away the alkaline substances on the surface of the diamond powder.

[0054] In one embodiment of the present disclosure, the oily grinding waste liquid includes a liquid component and a solid component, the liquid component includes soybean oil, white oil and lubricating oil, and the solid component includes micron-sized diamond powder, copper, micron-sized aluminum oxide, nano-sized aluminum oxide, cupric oxide, cuprous oxide and epoxy resin, wherein the epoxy resin is a silicon-containing epoxy resin; based on the total weight of the solid component, the content of the micron-sized diamond powder is 10 to 60% by weight, preferably 25 to 30% by weight, and the average particle size of the micron-sized diamond powder is 3 to 20 μm, preferably 3 to 5 μm; the average particle size of the micron-sized aluminum oxide is 1 to 50 μm, preferably 1 to 20 μm, and the average particle size of the nano-sized aluminum oxide is 100 to 1500 nm, preferably 100 to 800 nm. In the above embodiment, the oily grinding waste liquid includes a variety of solid impurity particles, wherein copper, cupric oxide and cuprous oxide are all micron-sized, with an average particle size of 0.5 to 4 μm.

[0055] The method for recovering diamond powder from oily grinding waste liquid provided by the present invention adopts degreasing agent for chemical degreasing, which can effectively remove residual oil in the second centrifugal bottom material with high degreasing efficiency. The alkaline inorganic substance has a saponification effect and can clean the oil stains; the chelating agent has the functions of buffering, dispersing and promoting emulsification, which can significantly improve the wetting performance of the degreasing agent, and is conducive to the suspension of the detached oil to the surface of the solution for easy separation; the surfactant has a solubilizing effect, which can enhance the infiltration, dispersion and degreasing effect of the degreasing agent on the surface of the diamond powder, which is conducive to separating the diamond powder from the oil and achieving the purpose of removing the oil stains; centrifugation is used to remove nano-alumina, and alkaline solution or molten alkali is used to remove micron-alumina by chemical etching, so that the alumina removal rate is as high as 95% or more. The method disclosed in the present invention has simple procedures, can effectively remove oil and alumina, can obtain high-purity, reusable diamond powder, and effectively reduce the cost of diamond recovery.

[0056] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0057] In the following examples and comparative examples, unless otherwise specified, the raw materials used are commercially available products.

[0058] The particle size was measured using a laser particle size analyzer, using the LT3600S laser particle size analyzer from Zhuhai Zhenli Optical Instrument Co., Ltd.

[0059] Example 1

[0060] (1) 100 g of oily grinding waste liquid was filtered through an 80-mesh screen, and the filtered filtrate was introduced into a flat scraper suction sedimentation centrifuge for a first centrifugation. The centrifuge power was 30 Hz, the speed was 1140 r / min, and the centrifugation time was 10 min, so that particles of different particle sizes in the filtrate were graded and separated, wherein micron-sized diamonds were centrifugally settled in the first centrifugal bottom material, and nano-sized alumina was located in the supernatant; the supernatant was discharged by siphoning, and then the first centrifugal bottom material at the bottom was discharged; wherein the composition and weight percentage of the oily grinding waste liquid were as follows: liquid component: accounting for 88%, the main component of which was soybean oil; Solid content: 12%, mainly composed of: micron-sized copper (average particle size 2.5μm, content 8%), micron-sized diamond (average particle size 3μm, content 43%), nano-sized aluminum oxide (average particle size 500nm, content 16%), micron-sized aluminum oxide (average particle size 25μm, content 4%), micron-sized cupric oxide (average particle size 2.5μm, content 11%), micron-sized cuprous oxide (average particle size 3μm, content 6%), and organic substances such as silicon-containing epoxy resin (content 12%, based on the total weight of the epoxy resin, the silicon content is 15% by weight);

[0061] (2) adding 80% of the weight of pure water to the first centrifugal bottom material, stirring the mixture with a high-speed stirrer for 5 minutes, and then introducing the stirred mixture into a centrifuge for a second centrifugation to achieve physical separation of oil and water, remove 80-95% of the soybean oil in the mixture, and obtain a second centrifugal bottom material;

[0062] (3) The degreasing agent and the second centrifugal bottom material are mixed in a weight ratio of 0.2:1 to obtain a mixture, wherein the degreasing agent content is 10% by weight based on the total weight of the mixture, and the mixture is placed in a single-tank ultrasonic cleaning machine for ultrasonication at an ultrasonic frequency of 40 kHz and a temperature of 60°C. After heating and ultrasonication for 2 hours, the obtained mixed solution is subjected to gravity sedimentation, and the grease on the upper layer is removed, and the sedimentation material on the lower layer is collected. At this time, the solid components in the sedimentation material are organic matter such as diamond powder, copper, copper oxide, cuprous oxide, epoxy resin, and a small amount of residual micron-sized aluminum oxide;

[0063] (4) washing the sediment material with water once or multiple times until the pH of the washing liquid is 6.5 to 7.5, drying the sediment material, and baking the dried material at 300° C. for 2 hours to perform heat treatment to remove organic impurities and oxidize copper and cuprous oxide to cupric oxide to obtain a first powder. At this time, the solid components of the first powder are diamond powder, cupric oxide, silicon impurities remaining in the epoxy resin, and micron-sized aluminum oxide;

[0064] (5) adding the first powder to a 20% by mass nitric acid solution for reaction at room temperature to remove copper oxide, washing the resulting mixture to a pH of 6.5 to 7.5, and then drying to obtain a second powder, wherein the mass ratio of the first powder to the nitric acid solution is 1:10, and the solid components in the second powder are diamond, silicon impurities, and micron-sized aluminum oxide;

[0065] (6) The second powder was mixed with sodium hydroxide solution at a weight ratio of 0.125:1 and subjected to a first reaction. The temperature of the first reaction was 200°C and the time was 2 hours. The mass fraction of the sodium hydroxide solution was 20%, and a reaction slurry was obtained. At this time, the solid component in the reaction slurry was high-purity diamond powder. The obtained reaction slurry was repeatedly washed with pure water until the pH of the supernatant was 6.5-7.5 and dried to obtain powder 1. The results were obtained from a scanning electron microscope. Figure 1 It can be seen that the recovered diamond powder has complete crystal form, particle size of 3-5μm, less surface impurities, high purity, and can be reused;

[0066] The degreasing agent comprises sodium carbonate, sodium hydroxide, sodium gluconate, isomeric fatty alcohol polyoxyethylene ether and sodium dodecylbenzene sulfonate; based on the total weight of the degreasing agent, the content of sodium carbonate is 65 weight%, the content of sodium hydroxide is 10 weight%, the content of sodium gluconate is 12 weight%, the content of isomeric fatty alcohol polyoxyethylene ether (isomeric tridecyl alcohol polyoxyethylene ether, CAS No. 9043-30-5) is 8 weight%, and the content of sodium dodecylbenzene sulfonate is 5 weight%.

[0067] Example 2

[0068] The same degreasing agent and oily grinding waste liquid as in Example 1 were used;

[0069] (1) 100 g of oily grinding waste liquid was filtered through a 100-mesh screen, and the filtered filtrate was introduced into a flat scraper suction sedimentation centrifuge for a first centrifugation. The centrifuge power was 50 Hz, the speed was 1900 r / min, and the centrifugation time was 10 min, so that particles of different particle sizes in the filtrate were graded and separated, wherein micron-sized diamonds were centrifugally settled in the first centrifugal bottom material, and nano-sized alumina was located in the supernatant; the supernatant was discharged by siphoning, and then the first centrifugal bottom material at the bottom was discharged;

[0070] (2) adding 100% of the weight of pure water to the first centrifugal bottom material, stirring the mixture with a high-speed stirrer for 5 minutes, and then introducing the stirred mixture into a centrifuge for a second centrifugation to achieve physical separation of oil and water, remove 80-95% of the soybean oil in the mixture, and obtain a second centrifugal bottom material;

[0071] (3) The degreasing agent and the second centrifugal bottom material are mixed in a weight ratio of 0.3:1 to obtain a mixture, wherein the degreasing agent content is 10% by weight based on the total weight of the mixture, and the mixture is placed in a single-tank ultrasonic cleaning machine for ultrasonication at an ultrasonic frequency of 40 kHz and a temperature of 60°C. After heating and ultrasonication for 2 hours, the obtained mixed solution is subjected to gravity sedimentation, and the grease on the upper layer is removed, and the sedimentation material on the lower layer is collected. At this time, the solid components in the sedimentation material are organic matter such as diamond powder, copper, copper oxide, cuprous oxide, epoxy resin, and a small amount of residual micron-sized aluminum oxide;

[0072] (4) washing the sediment material with water once or multiple times until the pH of the washing liquid is 6.5 to 7.5, drying the sediment material, and baking the dried material at 500° C. for 2 hours to perform heat treatment to remove organic impurities and oxidize copper and cuprous oxide to cupric oxide to obtain a first powder. At this time, the solid components of the first powder are diamond powder, cupric oxide, silicon impurities remaining in the epoxy resin, and micron-sized aluminum oxide;

[0073] (5) adding the first powder to a 20% by mass nitric acid solution for reaction at room temperature to remove copper oxide, washing the resulting mixture to a pH of 6.5 to 7.5, and then drying to obtain a second powder, wherein the mass ratio of the first powder to the nitric acid solution is 1:10, and the solid components in the second powder are diamond, silicon impurities, and micron-sized aluminum oxide;

[0074] (6) The second powder and sodium hydroxide powder are mixed in a graphite crucible at a weight ratio of 2:1, placed in a muffle furnace and heated at 300°C for a second reaction for 3 hours to obtain a reaction slurry. At this time, the solid component in the reaction slurry is high-purity diamond powder; the obtained reaction slurry is added with pure water and repeatedly washed until the pH of the supernatant is 6.5-7.5 and dried to obtain powder 2.

[0075] Example 3

[0076] The same degreasing agent and oily grinding waste liquid as in Example 1 were used;

[0077] (1) filtering the oily grinding waste liquid with a 300-mesh screen, and introducing the filtered filtrate into a flat scraper suction sedimentation centrifuge for a first centrifugation at a power of 40 Hz, a rotation speed of 1520 r / min, and a centrifugation time of 10 min, so that particles of different particle sizes in the filtrate are graded and separated, wherein micron-sized diamonds are centrifugally settled in the first centrifugal bottom material, and nano-sized alumina is located in the supernatant; the supernatant is discharged by siphoning, and then the first centrifugal bottom material is discharged;

[0078] (2) adding 200% of the weight of pure water to the first centrifugal bottom material, stirring the mixture with a high-speed stirrer for 5 minutes, and then introducing the stirred mixture into a centrifuge for a second centrifugation to achieve physical separation of oil and water, remove 80-95% of the soybean oil in the mixture, and obtain a second centrifugal bottom material;

[0079] (3) The degreasing agent and the second centrifugal bottom material are mixed in a weight ratio of 0.2:1 to obtain a mixture, wherein the degreasing agent content is 10% by weight based on the total weight of the mixture, and the mixture is placed in a single-tank ultrasonic cleaning machine for ultrasonication at an ultrasonic frequency of 40 kHz and a temperature of 60°C. After heating and ultrasonication for 2 hours, the obtained mixed solution is subjected to gravity sedimentation, and the grease on the upper layer is removed, and the sedimentation material on the lower layer is collected. At this time, the solid components in the sedimentation material are organic matter such as diamond powder, copper, copper oxide, cuprous oxide, epoxy resin, and a small amount of residual micron-sized aluminum oxide;

[0080] (4) washing the sediment material with water once or multiple times until the pH of the washing liquid is 6.5 to 7.5, drying the sediment material, and baking the dried material at 400° C. for 2 hours for heat treatment to remove organic impurities and oxidize copper and cuprous oxide to cupric oxide to obtain a first powder. At this time, the solid components of the first powder are diamond powder, cupric oxide, silicon impurities remaining in the epoxy resin, and micron-sized aluminum oxide;

[0081] (5) adding the first powder to a 33% by mass nitric acid solution for reaction at room temperature to remove copper oxide, washing the resulting mixture to a pH of 6.5 to 7.5, and then drying to obtain a second powder, wherein the mass ratio of the first powder to the nitric acid solution is 1:10, and the solid components in the second powder are diamond, silicon impurities, and micron-sized aluminum oxide;

[0082] (6) The second powder was mixed with a sodium hydroxide solution at a weight ratio of 0.1:1 and subjected to a first reaction. The temperature of the first reaction was 250°C and the time was 3 hours. The mass fraction of the sodium hydroxide solution was 25%, and a reaction slurry was obtained. At this time, the solid component in the reaction slurry was high-purity diamond powder. The obtained reaction slurry was added with pure water and repeatedly washed until the pH of the supernatant was 6.5-7.5 and dried to obtain powder 3.

[0083] Example 4

[0084] The same as Example 1, the only difference is that in step (3), the sodium carbonate in the degreasing agent is replaced with the same weight of sodium hydroxide to obtain powder 4.

[0085] Example 5

[0086] The same as Example 1, the only difference is that in step (3), the isomeric fatty alcohol polyoxyethylene ether and sodium dodecylbenzene sulfonate in the degreasing agent are replaced with the same weight of sodium dodecyl sulfate to obtain powder 5.

[0087] Example 6

[0088] The same as Example 1, the only difference is that in step (6), the weight ratio of the second powder to the sodium hydroxide solution is 0.4:1, and powder 6 is obtained.

[0089] Example 7

[0090] The same as Example 2, the only difference is that in step (6), the weight ratio of the second powder to the sodium hydroxide powder is 8:1, and powder 7 is obtained.

[0091] Comparative Example 1

[0092] The same as Example 1, except that the degreasing agent in step (3) is replaced by the same weight of sodium hydroxide solution to obtain comparative powder 1.

[0093] Comparative Example 2

[0094] The same as Example 1, except that step (6) is not adopted, the second powder obtained in step (5) is added with pure water and repeatedly washed until the pH of the supernatant is 6.5-7.5 and then dried to obtain comparative powder 2.

[0095] Comparative Example 3

[0096] The same as Example 1, except that the chelating agent sodium gluconate in the degreasing agent is replaced with the same weight of sodium hydroxide to obtain comparative powder 3.

[0097] Test Case

[0098] The powders obtained in the Examples and Comparative Examples were subjected to scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis. The powders were gold-sprayed and placed in a vacuum chamber. The powders were then scanned and imaged using a LYRA 3XMH instrument manufactured by Tescan. The powders were then analyzed for composition, measuring the C content (i.e., diamond content), Al and O content (i.e., aluminum oxide content), Cu content (i.e., copper and oxide content), and Si content. The testing was conducted in accordance with GB / T 17359-2012, Microbeam Analysis-Energy Dispersive Spectroscopy Quantitative Analysis. The elemental contents of Powder 1 are shown in Table 1.

[0099] The oil content was measured using a synchronous thermal analyzer (TG-DSC). The specific method was as follows: STA449C produced by NETZSCH, Germany was used for testing. The mass of the material to be tested was 3-10 mg. The weighed material to be tested was placed in an aluminum oxide crucible and tested in an oxygen environment. The oxygen air flow rate was fixed at 50 cm 3 / min, the heating rate is set to 10K / min, and the test temperature range is 25~500℃. Test basis: GB / T 13464-2008 Thermal analysis test method for thermal stability of materials;

[0100] Confirm the removal rate of each impurity: Scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) characterizes the content of each element before impurity removal, thereby calculating its mass. After the impurity removal process, Scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) characterizes the content of each element after impurity removal, and calculates the mass after impurity removal.

[0101] Wherein, diamond recovery rate % = (mass of diamonds in powder after recovery / mass of diamonds in oily grinding waste liquid before recovery) × 100%;

[0102] Grease removal rate (%) = (1-mass of grease in powder after recovery / mass of grease in oily grinding waste liquid before recovery) × 100%;

[0103] Alumina removal rate (%) = (1-mass of alumina in the powder after recovery / mass of alumina in the oily grinding waste liquid before recovery) × 100%;

[0104] Copper and oxide removal rate (%) = (1-mass of copper and oxide in powder after recovery / mass of copper and oxide in oily grinding waste liquid before recovery) × 100%.

[0105] Table 1

[0106]

[0107] Table 2

[0108]

[0109] The above data show that Examples 1-7, using the method disclosed herein, achieve high grease and aluminum oxide removal rates, high diamond recovery rates, and a high proportion of the recovered powder being diamond powder, effectively recovering high-purity diamond powder. Comparative Examples 1-3, which do not employ the method disclosed herein, produce powders containing a high level of impurities, resulting in lower diamond recovery rates and purity. Therefore, the methods provided by Examples 1-7 of the present disclosure are superior to those of Comparative Examples 1-3.

[0110] The preferred embodiments of the present disclosure are described in detail above. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0111] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0112] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure. In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for recovering diamond powder from oily grinding waste liquid, characterized in that: The method comprises the following steps: (1) subjecting the oily grinding waste liquid containing diamond powder to a first centrifugation to collect the first centrifugal bottom material; (2) mixing the first centrifugal bottom material with water and performing a second centrifugation to collect the second centrifugal bottom material; (3) mixing the degreasing agent with the second centrifugal bottom material and subjecting the resulting mixture to ultrasonic treatment, then subjecting the resulting mixed solution to gravity sedimentation and collecting the sedimented material; (4) heat-treating the sedimentation material to obtain a first powder; (5) mixing the first powder with an acid solution, washing and drying the resulting mixture to obtain a second powder; (6) contacting the second powder with an alkaline solution to perform a first reaction, or contacting the second powder with a molten alkali to perform a second reaction; The degreasing agent includes an alkaline inorganic substance, a chelating agent and a surfactant; the alkaline inorganic substance includes one or more of sodium carbonate, sodium hydroxide, potassium hydroxide, sodium amide and sodium bicarbonate; the chelating agent includes one or more of sodium gluconate, sodium metaphosphate, sodium acid pyrophosphate, sorbitol and ethylenediaminetetraacetic acid; the surfactant includes a nonionic surfactant and / or an anionic surfactant; the nonionic surfactant includes one or more of isomeric fatty alcohol polyoxyethylene ether, polyethylene glycol, nonylphenol polyoxyethylene ether and polyvinyl pyrrolidone; the anionic surfactant includes one or more of sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium linear alkyl sulfonate and fatty alcohol polyoxyethylene ether sodium sulfate.

2. The method according to claim 1, characterized in that The method further comprises, before step (1), filtering the oily grinding waste liquid using a sieve with a mesh size of 80 to 300.

3. The method according to claim 1, characterized in that In step (3), the weight ratio of the deoiling agent to the second centrifugal bottom material is (0.1-0.5):1, and the content of the deoiling agent is 10-30% by weight based on the total weight of the mixture.

4. The method according to claim 3, characterized in that In step (3), the weight ratio of the deoiling agent to the second centrifugal bottom material is (0.1-0.3):1, and the content of the deoiling agent is 10-20% by weight based on the total weight of the mixture.

5. The method according to claim 1, wherein In step (3), the degreasing agent includes sodium carbonate, sodium hydroxide, sodium gluconate, isomeric fatty alcohol polyoxyethylene ether and sodium dodecylbenzene sulfonate; Based on the total weight of the degreaser, the content of the sodium carbonate is 60-70 weight %, the content of the sodium hydroxide is 2-14 weight %, the content of the sodium gluconate is 6-20 weight %, the content of the isomerized fatty alcohol polyoxyethylene ether is 6-15 weight %, and the content of the sodium dodecylbenzene sulfonate is 2-12 weight %.

6. The method according to claim 1, characterized in that In step (5), the weight ratio of the first powder to the acid solution is (0.095-0.16):1; the content of the acid is 15-40% by weight based on the total weight of the acid solution; and the acid solution is selected from one or more of nitric acid solution, acetic acid solution and hydrochloric acid solution.

7. The method according to claim 6, characterized in that In step (5), the weight ratio of the first powder to the acid solution is (0.1-0.13):1; based on the total weight of the acid solution, the content of the acid is 20-30 weight %.

8. The method according to claim 1, characterized in that In step (6), the weight ratio of the second powder to the alkaline solution is (0.08-0.25):1; the content of alkali in the alkaline solution is 20-45% by weight based on the total weight of the alkaline solution; wherein the alkaline solution is selected from an alkaline inorganic solution, and the alkaline inorganic solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide solution, barium hydroxide solution and cesium hydroxide solution; or, The weight ratio of the second powder to the molten alkali is (1-5):1; wherein the molten alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, lithium hydroxide and barium hydroxide.

9. The method according to claim 8, characterized in that In step (6), the weight ratio of the second powder to the alkaline solution is (0.09-0.2):1; based on the total weight of the alkaline solution, the content of alkali in the alkaline solution is 25-38% by weight; or, The weight ratio of the second powder to the molten alkali is (1-3):

1.

10. The method according to claim 1, characterized in that In step (6), the conditions for the first reaction include: temperature of 180-400°C, and time of 1-8 hours; the conditions for the second reaction include: temperature of 200-600°C, and time of 1-10 hours.

11. The method according to claim 10, characterized in that In step (6), the conditions for the first reaction include: temperature of 200-300°C, time of 1-5 hours; the conditions for the second reaction include: temperature of 300-500°C, time of 1-6 hours.

12. The method according to claim 1, characterized in that In step (1), the first centrifugation is performed in a flat scraper suction sedimentation centrifuge, and the conditions of the first centrifugation include: the centrifuge power is 30~50Hz, the rotation speed is 1140~1900r / min, and the centrifugation time is 5~60min.

13. The method according to claim 12, characterized in that In step (1), the first centrifugal bottom material is collected by siphoning.

14. The method according to claim 1, wherein In step (2), the conditions for mixing the first centrifugal bottom material with water include: the weight ratio of the first centrifugal bottom material to water is 1: (0.8-2.5); In step (3), the ultrasonic conditions include: ultrasonic frequency of 20-60 kHz, temperature of 60-70°C, and time of 1-3 hours; In step (4), the heat treatment conditions include: temperature of 300-500°C and time of 5-10 hours; The reaction slurry obtained in step (6) is washed and dried.

15. The method according to claim 14, characterized in that In step (2), stirring is also performed during the mixing process, and the stirring speed is 50-100 r / min and the time is 5-60 min; In step (4), the sedimentation material is washed with water once or multiple times before the heat treatment until the pH of the washing liquid is 6.5-7.5, and the obtained solid material is dried.

16. The method according to claim 1, wherein The oily grinding waste liquid includes a liquid component and a solid component, wherein the liquid component includes soybean oil, white oil and lubricating oil, and the solid component includes micron-sized diamond powder, copper, micron-sized aluminum oxide, nano-sized aluminum oxide, cupric oxide, cuprous oxide and epoxy resin; Based on the total weight of the solid component, the content of the micron-sized diamond powder is 10-60% by weight, the average particle size of the micron-sized diamond powder is 3-20 μm; the average particle size of the micron-sized alumina is 1-50 μm, and the average particle size of the nano-sized alumina is 100-1500 nm.

17. The method according to claim 16, characterized in that Based on the total weight of the solid component, the content of the micron-sized diamond powder is 25-30% by weight, the average particle size of the micron-sized diamond powder is 3-5 μm; the average particle size of the micron-sized alumina is 1-20 μm, and the average particle size of the nano-sized alumina is 100-800 nm.

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