Process method for recovering precious metal from POSM device waste liquid

Abstract

The invention relates to a process method for recovering precious metal from waste liquid of a POSM device. The process method comprises the following steps: (1) pretreating the waste liquid; (2) adsorption: enabling the waste liquid pretreated in the step (1) to flow through ion exchange resin for ion exchange, enabling the ion exchange resin to have CO3 < 2->, returning the liquid flowing out of the ion exchange resin to the step (1) until the molybdenum content reaches a set value, and then discharging the liquid, or directly discharging the liquid flowing out of the ion exchange resin; (3) desorption and regeneration: a desorption agent is made to flow through the ion exchange resin subjected to ion exchange in the step (2), the desorption agent is a sodium carbonate solution, and liquid flowing out of the ion exchange resin is called desorption liquid; (4) concentrating and crystallizing; and (5) filtering. The purity of the molybdenum product recovered by the process method is high, and the process is simple.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment in the petrochemical industry, and in particular to a process for recovering precious metals from waste liquid in a POSM device. Background Art

[0002] Molybdenum metal is a refractory rare metal, which is in great demand in steel smelting, nonferrous metallurgy, petroleum and chemical industries. The consumption of molybdenum products in the petrochemical industry accounts for about 14-15% of the total consumption, and the annual consumption is on the rise. It is mainly used in the preparation of catalysts, corrosion inhibitors, pigments, etc. However, as a limited resource, molybdenum is an important raw material and irreplaceable strategic material in the national economy.

[0003] The process of producing propylene oxide and styrene by co-oxidation using ethylbenzene, air and propylene as raw materials (POSM process) is a relatively mature process method in the world. This process requires the use of molybdenum-containing catalysts. There are two types of molybdenum catalysts currently used: fixed column and mobile column: fixed bed molybdenum catalysts are treated as solid waste after use; after the mobile bed is used, the molybdenum-containing catalyst is directly discharged after organic matter is incinerated. The latter method will cause serious waste of molybdenum resources and cause molybdenum metal pollution in water bodies. The recovery of molybdenum metal has great economic and environmental value.

[0004] At present, the technology for recovering molybdenum from wastewater, such as the "Resource Treatment Method for Molybdenum-Containing Wastewater" disclosed in the Chinese invention patent application with patent application number CN202311581623.8 (publication number CN117534238A), includes the following steps: (1) adjusting the pH value of the molybdenum-containing wastewater to 7-10, converting the molybdenum in the wastewater into molybdate ions, and precipitating the iron ions and aluminum ions, and filtering to remove the insoluble matter; (2) adjusting the pH value of the filtrate obtained in step (1) to 2.5-5, converting the molybdenum in the wastewater into a variety of polymolybdate ions, and adsorbing the various polymolybdate ions in the wastewater by adsorption resin; (3) after the adsorption resin is saturated, desorbing the resin with 8-15% ammonia solution, and the desorption liquid is ammonium molybdate solution; (4) after the resin is desorbed, draining the residual ammonia water in the resin, and then modifying the resin with 3-5% dilute nitric acid, draining the residual dilute nitric acid in the resin after the modification is completed, and washing the resin with washing water to complete the resin regeneration.

[0005] However, in this patent, after the resin is desorbed by ammonia water, it needs to be regenerated by dilute nitric acid, that is, desorption and regeneration need to be performed separately, and the process is complicated.

[0006] In addition, if the molybdenum recovery method of the above patent is used to treat the waste liquid generated by the POSM device, there will be many problems, because the volume of waste liquid generated by the POSM device is large, usually more than 1500m3 / d, the Mo concentration in the wastewater is low, about 0.5-2.5 g / l, CO3 2- The concentration is about 5 to 15 g / l. When the Mo concentration is so low, the adsorption effect of ordinary ion exchange resins may be poor, which will cause the loss of Mo. In addition, the waste liquid mainly contains Mo and carbonate ions. If the analytical agent and regeneration agent are not selected appropriately, new ions may be introduced into the waste liquid, further increasing the difficulty of Mo recovery. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a process for recovering precious metals from waste liquid of a POSM device in view of the current status of the prior art. The process is simple and convenient for recovering molybdenum from waste liquid of a POSM device.

[0008] The technical solution adopted by the present invention to solve the above technical problems is: a process for recovering precious metals from waste liquid of a POSM device, characterized in that it comprises the following steps:

[0009] (1) Pre-treating the waste liquid: adding a pH regulator to the waste liquid so that the pH value of the waste liquid is between 2 and 6, and removing impurities from the waste liquid;

[0010] (2) Adsorption: The waste liquid pretreated in step (1) is passed through an ion exchange resin for ion exchange. The ion exchange resin has CO3 2- , the liquid flowing out of the ion exchange resin is returned to step (1) until the molybdenum content reaches a set value and then discharged, or the liquid flowing out of the ion exchange resin is directly discharged;

[0011] (3) Desorption and regeneration: a desorbent is passed through the ion exchange resin after ion exchange in step (2), wherein the desorbent is a sodium carbonate solution, and the liquid flowing out of the ion exchange resin is called a desorbent;

[0012] (4) Concentration and crystallization: the desorption liquid of step (3) is concentrated and crystallized to form a slurry;

[0013] (5) Filtration: The slurry of step (4) is filtered, and the solid matter is dried to obtain sodium molybdate. The crystallization mother liquor after filtration is returned to step (4) until the molybdenum content reaches the set value and then discharged, or the crystallization mother liquor is directly discharged.

[0014] In the above scheme, in step (1), the pH regulator is an inorganic acid.

[0015] Preferably, in step (2), the linear velocity of the pretreated waste liquid passing through the ion exchange resin is 1 to 15 m / h. Within this range, the adsorption effect on molybdenum is good.

[0016] Preferably, in step (2), the liquid is neutralized with an alkaline substance before being discharged so that the liquid is neutral and meets the requirements for wastewater discharge, and the molybdenum content in the discharged liquid is less than 0.5 mg / l.

[0017] In order to improve the adsorption performance of ion exchange resin for molybdenum, the ion exchange resin has a polystyrene-divinylbenzene cross-linked skeleton structure, and sulfur- and / or nitrogen-containing functional groups are grafted on the skeleton. The sulfur atoms of this special ion exchange resin can form a stable coordination bond with the molybdenum ions, and the nitrogen-containing functional groups can enhance the affinity of the resin for the molybdenum ions, so that the molybdenum ions can be preferentially adsorbed on the resin, while most of the other impurity ions in the wastewater are separated, so as to adapt to the recovery of molybdenum in wastewater with low molybdenum content.

[0018] In the above scheme, in step (1), the waste liquid of the POSM device is incinerated to remove organic matter, the pH value of the molybdenum-containing waste liquid after incineration is adjusted to between 2 and 6, and then filtered to remove solid insoluble matter.

[0019] Preferably, in step (2), the concentration of the sodium carbonate solution is 100-300 g / L, and the desorption effect is good.

[0020] The slurry can be evaporated and concentrated by various heat sources such as electricity. Preferably, in step (4), the desorption liquid is evaporated and crystallized by steam, the steam pressure is 0.1 to 1.0 MPa, the vacuum degree is -0.02 to -0.06 MPa, and the temperature of the desorption liquid is controlled between 85 and 100° C. By adjusting different evaporation parameters, the evaporation efficiency and crystallization speed can be adjusted to improve the purity of the sodium molybdate product.

[0021] Preferably, in step (4), the desorption liquid is placed in an evaporator for concentration and crystallization, and the side wall of the evaporator has an interlayer, through which steam or cooling water can be passed. While steam is passed through the interlayer, the desorption liquid is continuously injected into the evaporator until the concentration of the slurry in the evaporator reaches a set value, after which the injection of the desorption liquid is stopped, and cooling water is passed through the interlayer. After the temperature of the slurry in the evaporator drops to room temperature, the next step is performed.

[0022] Compared with the prior art, the present invention has the following advantages: the present invention selects an ion exchange resin having carbonate, and a sodium carbonate solution is selected as a desorbent; the sodium ions of the sodium carbonate can react with the molybdate ions to generate sodium molybdate; the carbonate ions of the sodium carbonate can be replaced with the molybdate ions to simultaneously realize the desorption and regeneration of the ion exchange resin.

[0023] As can be seen from the above, the desorbent of the present invention does not introduce additional ions, which does not increase the difficulty of molybdenum recovery, facilitates molybdenum recovery, and the recovered molybdenum product has high purity; and sodium carbonate can simultaneously realize the desorption and regeneration of ion exchange resin, that is, the desorption and regeneration of ion exchange resin can be realized simultaneously through one process, which simplifies the operation process, reduces the processing cost, and improves the stability and reliability of the overall process, so that the recovery of molybdenum from complex petrochemical catalytic waste liquid can be realized more economically and efficiently on an industrial scale.

[0024] The present invention not only realizes the effective recovery of molybdenum resources and reduces the dependence on primary molybdenum ore resources, but also significantly reduces the molybdenum content of petroleum catalytic wastewater, thereby greatly reducing the difficulty of subsequent treatment and potential harm to the environment, and has good environmental benefits and comprehensive benefits of resource recovery.

[0025] The process of the present invention can effectively recover molybdenum from petrochemical catalytic waste liquid, has good application prospects and economic benefits, and reduces the impact of waste liquid discharge on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0027] like Figure 1 As shown, the present invention is aimed at the recovery of molybdenum metal in the wastewater of POSM device. The main components of Mo-containing wastewater are: Mo concentration: 0.5-2.5g / l, CO3 2- : 5~15g / l, pH: 8~9.

[0028] The process for recovering precious metals from waste liquid of POSM device comprises the following steps:

[0029] (1) Pre-treating the waste liquid: adding a pH regulator to the waste liquid so that the pH value of the waste liquid is between 2 and 6, and removing impurities from the waste liquid; specifically, the pH regulator is an inorganic acid, such as sulfuric acid or hydrochloric acid.

[0030] The present invention pre-treats wastewater by the following method: removing organic matter from waste liquid of the POSM device by high-temperature incineration, adjusting the pH value of the molybdenum-containing waste liquid after incineration to between 2 and 6, and then filtering through a filter press or other filtering devices to remove solid insoluble matter.

[0031] (2) Adsorption: The waste liquid pretreated in step (1) is passed through an ion exchange resin at a linear velocity of 1 to 15 m / h for ion exchange. MoO4 2- With CO3 on ion exchange resin 2- Exchange, during this process, MoO4 2-are adsorbed on the resin and enriched, while cations such as K, Na, Ca, Mg, and Fe are not adsorbed and all flow out of the ion exchange resin. The liquid flowing out of the ion exchange resin ( Figure 1 The post-exchange liquid in the reaction mixture is returned to step (1) until the molybdenum content reaches the set value and is then discharged. Alternatively, the liquid flowing out of the ion exchange resin is directly discharged. In this case, the liquid must be neutralized with an alkaline substance (such as sodium hydroxide or sodium carbonate) before being discharged, and the molybdenum content in the discharged liquid is less than 0.5 mg / l.

[0032] The ion exchange resin of the present invention has a polystyrene-divinylbenzene cross-linked skeleton structure and also has CO3 2- , sulfur-containing and / or nitrogen-containing functional groups are grafted onto the skeleton of the ion exchange resin, the sulfur-containing functional groups may be, for example, thiol groups, and the nitrogen-containing functional groups may be, for example, amine groups. Preferably, the ion exchange resin has both thiol groups and amine groups. This special ion exchange resin forms a stable coordination bond with the molybdenum ion through the sulfur atom, and the presence of the amine group enhances the affinity of the resin for the molybdenum ion, so that the molybdenum ion can be preferentially adsorbed on the resin, while most of the other impurity ions in the wastewater are separated, effectively improving the recovery efficiency and purity of molybdenum.

[0033] (3) Desorption and regeneration: The desorbent is passed through the ion exchange resin after ion exchange in step (2). The desorbent is a sodium carbonate solution with a concentration of 100 to 300 g / L. The liquid flowing out of the ion exchange resin is called the desorption liquid. Under alkaline conditions, CO3 in the desorbent is 2- MoO4 on exchange resin 2- Desorb into the solution, and stop desorbing when the Mo concentration in the desorbed liquid is less than 5 mg / L. After the desorbent is added, continue to add industrial water to the ion exchange resin. Stop adding water when the pH of the solution flowing out of the ion exchange resin is between 7 and 8.

[0034] The ion exchange reaction process is as follows:

[0035] R2CO3(S)+MoO4 2- ——R2MoO4(S)+CO3 2- Adsorption process

[0036] R2MoO4(S)+CO3 2- ——R2CO3(S)+MoO4 2- Desorption process

[0037] In the reaction formula, R represents the skeleton of the ion exchange resin, and (S) represents the solid phase.

[0038] Sodium carbonate can simultaneously realize the desorption and regeneration of ion exchange resin, that is, the desorption and regeneration of ion exchange resin can be realized simultaneously through one process, which simplifies the operation process. In addition, sodium carbonate realizes the desorption and regeneration of ion exchange resin at the same concentration. In this process, there is no need to adjust the concentration of sodium carbonate, and the operation is simple and convenient.

[0039] As can be seen from the above, the ion exchange resin of the present invention is specially designed for the characteristics of molybdenum ions in the waste liquid of the POSM device, has high selectivity and strong adsorption capacity for molybdenum ions, effectively improves the recovery efficiency and purity of molybdenum, and has obvious advantages over traditional general ion exchange resins. The ion exchange resin of this application is an existing product purchased from Zhejiang Zhengguang Industrial Co., Ltd.

[0040] (4) Concentration and crystallization: the desorption liquid of step (3) is concentrated and crystallized to form a slurry;

[0041] The present invention adopts a method of concentrating and crystallizing the desorbed liquid in an evaporating kettle by steam. The side wall of the evaporating kettle is provided with an interlayer, and steam or cooling water can be passed into the interlayer. When steam is passed into the interlayer, the desorbed liquid is continuously injected into the evaporating kettle until the concentration of the slurry in the evaporating kettle reaches a set value, and then the injection of the desorbed liquid is stopped, and cooling water is passed into the interlayer. After the temperature of the slurry in the evaporating kettle drops to room temperature, the next step of operation is performed;

[0042] In the process of evaporating and concentrating the desorption liquid by steam in the interlayer, the steam pressure is 0.1 to 1.0 MPa, the vacuum degree is -0.02 to -0.06 MPa, and the temperature of the desorption liquid is controlled between 85 and 100°C.

[0043] (5) Filtration: The slurry of step (4) is filtered through a centrifuge or other filtering device. The solid matter after filtration is dried to obtain sodium molybdate. The crystallization mother liquor after filtration is returned to step (4) until the molybdenum content reaches the set value and then discharged, or the crystallization mother liquor is directly discharged.

[0044] The present invention is further described in detail below in conjunction with specific embodiments.

[0045] Example 1

[0046] The process for recovering precious metals from waste liquid of POSM device comprises the following steps:

[0047] (1) Pretreatment of waste liquid: In this embodiment, waste water is pretreated by the following method: the waste liquid of the POSM device is incinerated at high temperature to remove organic matter, and a pH regulator is added to the molybdenum-containing waste liquid after incineration to adjust the pH value to 3.5-4, wherein sulfuric acid is selected as the pH regulator, and then the solid insoluble matter is removed by a filter press.

[0048] (2) Adsorption: The waste liquid pretreated in step (1) is passed through an ion exchange resin at a linear velocity of 1 m / h for ion exchange, and the liquid flowing out of the ion exchange resin is returned to step (1) until the molybdenum content reaches a set value and then discharged. Alternatively, the liquid flowing out of the ion exchange resin is directly discharged. Before being discharged, the liquid must first be neutralized with an alkaline substance (sodium hydroxide), and the molybdenum content in the discharged liquid is less than 0.5 mg / l.

[0049] (3) Desorption and regeneration: The desorbent is passed through the ion exchange resin after ion exchange in step (2). The desorbent is a sodium carbonate solution with a concentration of 150 g / l. The liquid flowing out of the ion exchange resin is called the desorbent. Under alkaline conditions, CO3 in the desorbent 2- MoO4 on exchange resin 2- Desorb into the solution, and stop desorbing until the Mo concentration in the desorbed liquid is less than 5 mg / L. After the desorbent is added, continue to add industrial water to the ion exchange resin. Stop adding water when the pH of the column solution is between 7 and 8.

[0050] (4) Concentration and crystallization: the desorption liquid of step (3) is concentrated and crystallized to form a slurry;

[0051] This embodiment adopts a method of concentrating and crystallizing the desorbed liquid in an evaporator. The side wall of the evaporator has an interlayer, and steam or cooling water can be passed into the interlayer. When steam is passed into the interlayer, the desorbed liquid is continuously injected into the evaporator until the slurry concentration in the evaporator reaches a set value, and cooling water is passed into the interlayer. After the slurry temperature in the evaporator drops to room temperature, the next step is performed;

[0052] In the process of steam evaporating and concentrating the desorption liquid in the interlayer, the steam pressure is 0.2MPa, the vacuum degree is -0.02~-0.03MPa, and the temperature of the desorption liquid is controlled between 85~90℃.

[0053] (5) Filtration: The slurry of step (4) is filtered by a centrifuge, and the solid matter is dried to obtain sodium molybdate. The crystallization mother liquor after filtration is returned to step (4) until the molybdenum content reaches the set value and then discharged, or the crystallization mother liquor is directly discharged. In this embodiment, the purity of sodium molybdate is 99.4%.

[0054] Example 2

[0055] The difference between Example 2 and Example 1 is that: in step (1) of this embodiment, a pH regulator is added to the molybdenum-containing waste liquid after incineration to adjust the pH value to 5.5-6, the linear speed in step (2) is 8 m / h, the concentration of the desorbent sodium carbonate solution is 100 g / l, the steam pressure in step (4) is 0.8 MPa, the vacuum degree is -0.07 to -0.08 MPa, the temperature of the desorbent is controlled at 95 to 100° C., and the concentrated crystallized product is centrifuged to obtain a sodium molybdate product with a purity of 99.1%. The other process methods are the same as those in Example 1.

[0056] Example 3

[0057] The difference between Example 3 and Example 1 is that: in step (1) of this embodiment, a pH regulator is added to the molybdenum-containing waste liquid after incineration to adjust the pH value to 2.0-2.5, the linear speed in step (2) of this embodiment is 15 m / h, the concentration of the desorbent sodium carbonate solution is 300 g / l, the obtained desorbent is crystallized by evaporation, the steam pressure is 0.5 MPa, the vacuum degree is -0.04 to -0.06 MPa, the temperature of the desorbent is controlled at 90 to 95° C., and the concentrated crystallized product is centrifuged to obtain a sodium molybdate product with a purity of 99.4%. The other process methods are the same as those in Example 1.

[0058] In the above embodiments, the Mo concentration in the wastewater discharged after ion exchange is lower than 0.5 mg / l, and the molybdenum metal is separated from most of the impurity ions, and finally a sodium molybdate product with a purity higher than 99% is formed, and the product has high economic value.

[0059] The process method of the present application enriches the molybdenum concentration to 80-120g / l through ion exchange. Compared with the method of directly concentrating and crystallizing to recover molybdenum, it greatly saves the energy consumption required for concentration and crystallization, and has low production costs. At the same time, the process is fully automated, safe and environmentally friendly.

Claims

1. A process for recovering precious metals from waste liquid of a POSM device, characterized in that: The steps include: (1) Pre-treating the waste liquid: adding a pH regulator to the waste liquid so that the pH value of the waste liquid is between 2 and 6, and removing impurities from the waste liquid; (2) Adsorption: The waste liquid pretreated in step (1) is passed through an ion exchange resin for ion exchange. The ion exchange resin has CO3 2- , the liquid flowing out of the ion exchange resin is returned to step (1) until the molybdenum content reaches a set value and then discharged, or the liquid flowing out of the ion exchange resin is directly discharged; (3) Desorption and regeneration: a desorbent is passed through the ion exchange resin after ion exchange in step (2), wherein the desorbent is a sodium carbonate solution, and the liquid flowing out of the ion exchange resin is called a desorbent; (4) Concentration and crystallization: the desorption liquid of step (3) is concentrated and crystallized to form a slurry; (5) Filtration: The slurry of step (4) is filtered, and the solid matter is dried to obtain sodium molybdate. The crystallization mother liquor after filtration is returned to step (4) until the molybdenum content reaches the set value and then discharged, or the crystallization mother liquor is directly discharged.

2. The process according to claim 1, characterized in that: In the step (1), the pH regulator is an inorganic acid.

3. The process according to claim 1, characterized in that: In the step (2), the linear velocity of the pretreated waste liquid passing through the ion exchange resin is 1 to 15 m / h.

4. The process according to claim 1, characterized in that: In step (2), the liquid is neutralized with an alkaline substance before being discharged, and the molybdenum content in the discharged liquid is less than 0.5 mg / l.

5. The process according to claim 1, characterized in that: The ion exchange resin has a polystyrene-divinylbenzene cross-linked skeleton structure, on which sulfur and / or nitrogen-containing functional groups are grafted.

6. The process according to claim 1, characterized in that: In the step (1), the waste liquid of the POSM device is incinerated to remove organic matter, the pH value of the molybdenum-containing waste liquid after incineration is adjusted to between 2 and 6, and then filtered to remove solid insoluble matter.

7. The process according to claim 1, characterized in that: In the step (2), the concentration of the sodium carbonate solution is 100 to 300 g / L.

8. The process according to any one of claims 1 to 7, characterized in that: In the step (4), the desorption liquid is evaporated and crystallized by steam, the steam pressure is 0.1 to 1.0 MPa, the vacuum degree is -0.02 to -0.06 MPa, and the temperature of the desorption liquid is controlled between 85 and 100°C.

9. The process according to claim 8, characterized in that: In the step (4), the desorption liquid is placed in an evaporator for concentration and crystallization. The side wall of the evaporator has an interlayer, and steam or cooling water can be passed into the interlayer. When steam is passed into the interlayer, the desorption liquid is continuously injected into the evaporator until the concentration of the slurry in the evaporator reaches a set value. Then, the injection of the desorption liquid is stopped, and cooling water is passed into the interlayer. After the temperature of the slurry in the evaporator drops to room temperature, the next step is performed.

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