A method for resource utilization of cyanide wastewater

Abstract

The present application provides a method for resource utilization of cyanidation wastewater, which relates to the field of chemical technology. The method comprises: using a hydrophobic inert solvent containing a bromine dye filter cake in the presence of a small amount of phase transfer catalyst, directly adding the water-containing filter cake into the solvent, heating it to reflux conditions to dissolve the bromine dye filter cake; slowly adding a cyanidation reagent to the system in batches, cooling it to room temperature after the reaction of the raw materials is completed; slowly adding clean water to the reaction solution, adjusting the solvent concentration, further cooling it, filtering and separating the cyanidation filter cake and the mother liquor, and then performing post-processing steps to improve the atomic utilization rate of the process links and reduce costs.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a method for resource utilization of cyanide wastewater. Background Art

[0002] As for the resource utilization method of cyanide wastewater, this technology mainly involves subjecting industrial wastewater containing cyanide to a series of physical, chemical and biological treatment processes to achieve effective recovery and utilization of cyanide and at the same time purify the water quality. This method aims to solve the problem of safe, efficient and environmentally friendly resource utilization of cyanide in cyanide wastewater, that is, how to improve the recovery rate of cyanide and reduce the secondary pollution that may be generated during the treatment process under the premise of ensuring environmental safety, so as to achieve the dual goals of economic benefits and environmental protection.

[0003] Conventional cyanidation processes generally use DMF, DMAC, etc. as solvents. The dried bromine-containing dye filter cake is put into the above solvents, and then the cyanidation reagent is added for cyanidation. After the cyanidation reaction is completed, a solvent close to an equal amount of methanol is added, and then the temperature is lowered to below 10°C to filter and separate the mother liquor. The obtained filter cake is then pulped, detoxified, filtered, and washed with water to remove the metal salts, DMF, and methanol; the obtained solvent needs to be separated into methanol, DMF / DMAC by a distillation tower. Conventional cyanidation processes require a distillation device, which has high energy consumption. DMF and other solvents are prone to decomposition at high temperatures during distillation. The filter cake obtained by the traditional process contains bromine salts, residual cyanide salts, and a mixture of DMF and methanol. Bromine salts, cyanide salts, DMF, and methanol need to be further dissolved in water, and then filtered and washed to obtain a qualified dye filter cake. The mother liquor after separation is a mixture of the above components, which is difficult to recycle and costly.

[0004] Therefore, developing an environmentally friendly, low-cost method for resource utilization of cyanide wastewater is of great significance for achieving resource recycling. Summary of the invention

[0005] The invention provides a method for resource utilization of cyanide wastewater, which includes a dissolution step, a cyanidation step, a material separation step and a post-treatment step, thereby improving the atomic utilization rate of the process links and reducing the cost.

[0006] The present invention provides a method for resource utilization of cyanide wastewater, comprising the following steps:

[0007] Step 1: Cyanide using a hydrophobic inert solvent containing a bromine dye filter cake in the presence of a small amount of phase transfer catalyst, directly adding the water-containing filter cake into the above solvent, then adding an appropriate amount of process water to adjust the solvent concentration, and heating to reflux conditions to dissolve the bromine dye filter cake;

[0008] Step 2: Slowly add the cyaniding reagent to the above system in portions, wait for the reaction of the raw materials to be completed, and cool down to room temperature;

[0009] Step 3: Slowly add clean water to the above reaction solution to adjust the solvent concentration, further cool it down, and filter and separate the cyanide filter cake and mother liquor;

[0010] Step 4: Wash the solid filter cake obtained in step 3 with hot water to remove the residual solvent, collect the washing liquid and recover the solvent through layer separation, and use the recovered water layer in step 1 and step 3; recover the oil layer solvent through layer separation from the mother liquor obtained in step 3, and use the oil layer solvent in step 1 after simple distillation, reflux a small amount of kettle residue with 1.5 to 2 times of the kettle residue with methanol, and further filter and recover the solid after low-temperature recrystallization. This part of the solid material is a small amount of unreacted bromine-containing dye matrix raw material and a small amount of cyanide product dissolved in the solvent, which is collected and used for color matching; after the methanol filtrate is distilled and recovered, this step is repeated The mother liquor obtained in step 3 is separated and the water layer is collected. The water layer obtained is mainly a bromine-containing inorganic salt and a cyanide solution remaining from the reaction. The solution is acidified with hydrobromic acid and then hydrogen peroxide is added to oxidize and break the cyanide group. The small amount of organic matter carried is then removed by activated carbon adsorption. The solution is then adsorbed by a preferred cation exchange resin to recover the metal ions therein. The metal ions are recovered by more than 99%, and the metal cation concentration in the aqueous phase is less than 5PPM. At this time, the solution is evaporated and concentrated to obtain a by-product HBr solution with a content of 45-50%, which is circulated for the bromination synthesis of the previous bromine-containing filter cake.

[0011] In some specific embodiments, the cyanation uses a hydrophobic inert solvent containing a bromine dye filter cake in the presence of a small amount of phase transfer catalyst, directly adding the water-containing filter cake to the above solvent, adding an appropriate amount of process water to adjust the solvent concentration, and heating to reflux conditions to dissolve the bromine dye filter cake, comprising:

[0012] According to the amount of bromine-containing dye filter cake, calculate the amount of hydrophobic inert solvent required, and the amount of solvent used is 3 to 5 times the amount of bromine-containing dye filter cake;

[0013] Adding the calculated hydrophobic inert solvent into the reaction vessel, and then adding a small amount of phase transfer catalyst;

[0014] The water-containing filter cake is directly added to a reaction vessel containing a hydrophobic inert solvent and a phase transfer catalyst, and a certain amount of process water is added to adjust the solvent concentration, and the solvent: water ratio is 1 to 1.5:1;

[0015] Heating the reaction vessel to raise the temperature to reflux conditions;

[0016] The reaction vessel was continuously stirred under reflux conditions until the bromine dye filter cake was completely dissolved;

[0017] Determine whether the bromine-containing dye filter cake is completely dissolved. If not, continue to stir the reaction container until it is completely dissolved;

[0018] If the bromine-containing dye filter cake has completely dissolved, stop heating and cool the reaction vessel to 70-90°C.

[0019] In some specific embodiments, the step of slowly adding the cyaniding reagent to the above system in portions, and cooling the raw materials to room temperature after the reaction is complete, comprises:

[0020] According to the raw material content of HPLC, the amount of cyaniding reagent added is determined, and the amount of cyaniding reagent added is 1:1 to 1:1.1 equivalents of the raw material content;

[0021] The cyaniding agent is added to the reaction system by slowly adding in portions, and the amount of the cyaniding agent added each time is 1 / 5 to 1 / 3 of the total amount;

[0022] By monitoring the temperature change of the reaction system, it is judged whether the addition speed of the cyaniding reagent is appropriate. If the temperature rises too fast, the addition speed of the cyaniding reagent is slowed down;

[0023] If the temperature rises too slowly, speed up the addition of the cyaniding reagent;

[0024] Obtaining the pH value of the reaction system, the pH value is controlled between 8 and 10, if the pH value is lower than 8, adding sodium hydroxide solution to adjust;

[0025] If the pH value is higher than 10, add dilute hydrochloric acid solution to adjust;

[0026] Judging whether the raw materials have reacted completely is based on the color change of the reaction system. If the color becomes clear, it indicates that the raw materials have reacted completely.

[0027] If the color is still turbid, continue the reaction;

[0028] By detecting the residual amount of the raw material in the reaction system, it is determined whether the raw material has been completely reacted. If the residual amount is less than 1%, it indicates that the raw material has been completely reacted;

[0029] If the residual amount is higher than 1%, continue the reaction;

[0030] When it is determined that the raw materials have reacted completely, stop heating;

[0031] Use a cooling water bath to speed up the cooling of the reaction system so that it reaches room temperature as quickly as possible;

[0032] Obtain the temperature of the reaction system. When the temperature drops to 25-30°C, subsequent separation and purification operations can be performed.

[0033] In some specific embodiments, the step of slowly adding clean water to the reaction solution, adjusting the solvent concentration, further cooling the reaction solution, and filtering and separating the cyanide filter cake and the mother liquor comprises:

[0034] According to the composition and properties of the reaction solution, determine the amount and rate of adding clean water so that the solvent concentration reaches a preset range;

[0035] The temperature sensor is used to monitor the temperature of the reaction liquid in real time, and the temperature is slowly reduced to the specified value by controlling the cooling system;

[0036] Obtain the turbidity data of the reaction solution to determine the degree of solid particle precipitation. When the turbidity reaches the set threshold, stop cooling;

[0037] According to the volume and viscosity of the reaction liquid, select the appropriate filtration device and filtration medium, and control the filtration pressure and flow rate;

[0038] The filter cake mass is measured by a weighing sensor, the moisture content of the filter cake is calculated, and the washing conditions are adjusted to reach the target value;

[0039] An infrared spectrometer was used to detect the type and concentration of residual solvents in the filtrate and optimize the stratified recovery process parameters;

[0040] Obtain the pH value and conductivity data of the mother liquor, determine the acidity and salt concentration, and calculate the required acid, alkali and flocculant dosage accordingly;

[0041] The metal ion content in the water phase is measured by atomic absorption spectrometry to determine whether the discharge standards are met and to further optimize the adsorption conditions if necessary;

[0042] According to the concentration and purity of the by-product hydrobromic acid solution, the feed ratio in the bromination synthesis is determined to realize the closed-loop circulation of the materials.

[0043] In some specific embodiments, the solid filter cake obtained in step 3 is washed with hot water to remove residual solvent, the washing liquid is collected and the solvent is recovered by layering, and the water layer is recovered and used in step 3; the mother liquor obtained in step 3 is layered to recover the oil layer solvent, the oil layer solvent is simply distilled and applied to step 1, a small amount of kettle residue is refluxed with methanol 1.5 to 2 times the amount of kettle residue, and then further filtered and recovered after low-temperature recrystallization. This part of the solid material is a small amount of unreacted bromine-containing dye matrix raw material and a small amount of cyanide product dissolved in the solvent, which is collected and used for color matching; the methanol filtrate is distilled and recovered in this step Cyclic application; the mother liquor obtained in step 3 is separated and the water layer is collected. The obtained water layer is mainly a bromine-containing inorganic salt and a cyanide solution remaining from the reaction. The solution is acidified with hydrobromic acid and then hydrogen peroxide is added to oxidize and break the cyanide group. A small amount of organic matter is removed by adsorption on activated carbon. The solution is then adsorbed on a preferred cation exchange resin to recover metal ions. The metal ions are recovered by more than 99%, and the metal cation concentration in the aqueous phase is less than 5 PPM. At this time, the solution is evaporated and concentrated to obtain a byproduct HBr solution with a content of 45-50%, which is circulated for the bromination synthesis of the previous bromine-containing filter cake, comprising:

[0044] The solid filter cake obtained in step 3 is washed with hot water, and the washing liquid is separated from the filter cake to obtain a washing liquid containing a solvent and a washed solid filter cake;

[0045] The washing liquid containing the solvent is layered to separate an organic phase and an aqueous phase, wherein the organic phase contains the solvent and the aqueous phase is used as the recovered water layer in step 3;

[0046] The mother liquor obtained in step 3 is layered to separate an organic phase and an aqueous phase, wherein the organic phase mainly contains the solvent;

[0047] The organic phase is distilled to distill out the solvent, and the solvent is returned to step 1 for recycling, and the distillation residue is the kettle residue;

[0048] Add 5 to 2 times the amount of methanol to the still residue, heat to reflux to dissolve the dye in the still residue, then cool to a low temperature to allow the dye to recrystallize and precipitate;

[0049] Filter the precipitated dye crystals to obtain dye solids, which are unreacted bromine-containing dye matrix and a small amount of cyanide product, and are collected for dye color matching;

[0050] The methanol filtrate is distilled to distill out methanol, and the methanol is returned to step 5 for recycling;

[0051] Acidifying the aqueous phase obtained by separation in step 3, adding hydrobromic acid to adjust the pH, then adding hydrogen peroxide to oxidize and break the cyanide, and then using activated carbon to adsorb and remove a small amount of organic matter in the aqueous phase to obtain an aqueous phase containing metal ions;

[0052] The aqueous phase containing metal ions is separated by adsorption through a cation exchange resin to recover the metal ions, so that the concentration of metal cations in the aqueous phase is reduced to below 5 ppm. Finally, the aqueous phase is evaporated and concentrated to obtain a hydrobromic acid solution with a content of 45-50%, which is returned to the bromine-containing filter cake bromination synthesis process for recycling.

[0053] In some specific embodiments, the chemical formula of step 1 is expressed as follows:

[0054]

[0055] X=H, CH3, NHCOCH3, NHCOC2H5

[0056] Y=H、NO2、halogen

[0057] R1=C2H5, C2H4CN, CH2COOCH3, C2H4OCOCH3

[0058] R2=C2H4CN, CH2COOCH3, C2H4OCOCH3, C2H4OC2H4CN

[0059] Z=Zn2+ , Cu + 、Na + Or CH2OH, etc.

[0060] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0061] The present invention provides a method for resource utilization of cyanide wastewater, comprising a dissolution step, a cyanidation step, a material separation step, and a post-treatment step. Compared with the traditional process, the method for resource utilization of cyanide wastewater has the following technical advantages:

[0062] 1. The use of hydrophobic inert solvents facilitates solvent recovery and can be recycled after simple distillation. There is no risk of high temperature decomposition during distillation of solvents such as DMF.

[0063] 2. The bromide matrix does not need to be dried, which saves energy and reduces the hidden dangers of dust pollution and flammability of dry dust.

[0064] 3. Due to the high solubility of DMF, the traditional process requires the use of methanol for separation. The separation of DMF-methanol mixed liquid requires a distillation device, which consumes a lot of energy.

[0065] 4. The filter cake obtained by the traditional process contains bromine salt, residual cyanide salt, DMF, and methanol mixture. It is necessary to further dissolve the bromine salt, cyanide salt, DMF, and methanol in water, and then filter and wash to obtain a qualified dye filter cake. The mother liquor after separation is a mixture of the above components, which is difficult to recycle and has high cost.

[0066] 5. This process further recovers the residual material after solvent recovery and recrystallizes it through methanol. Due to the low solubility of the dye structure in methanol, the dye can be almost completely recovered after methanol recrystallization. The commercial performance of the obtained dye is slightly worse than that of the pure cyanide product, but it can be used for the matching and color matching of dark dyes, further improving the atomic utilization rate of the process link and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 The present invention is a flow chart of a method for resource utilization of cyanide wastewater. DETAILED DESCRIPTION

[0068] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0069] like Figure 1 In this embodiment, a method for resource utilization of cyanide wastewater may specifically include:

[0070] S101. Cyanide using a hydrophobic inert solvent containing bromine dye filter cake in the presence of a small amount of phase transfer catalyst, directly adding the water-containing filter cake into the above solvent, adding process water to adjust the solvent concentration, and heating to reflux conditions to dissolve the bromine dye filter cake.

[0071] According to the amount of the bromine-containing dye filter cake, the amount of the required hydrophobic inert solvent is calculated, and the amount of the solvent is 3 to 5 times the amount of the bromine-containing dye filter cake; the calculated hydrophobic inert solvent is added to the reaction container, and then a small amount of phase transfer catalyst is added; the water-containing filter cake is directly added to the reaction container containing the hydrophobic inert solvent and the phase transfer catalyst, and an appropriate amount of process water is added to adjust the solvent concentration; the reaction container is heated to raise the temperature to the reflux condition; under the reflux condition, the reaction container is continuously stirred until the bromine-containing dye filter cake is completely dissolved; it is determined whether the bromine-containing dye filter cake is completely dissolved, and if not, the reaction container is continuously stirred until it is completely dissolved; if the bromine-containing dye filter cake is completely dissolved, the heating is stopped, and the reaction container is cooled to 70 to 90° C.; the dissolution of the bromine-containing dye filter cake is determined by sampling and analysis, and relevant data is recorded; according to the analysis results, the optimal dissolution process parameters of the bromine-containing dye filter cake in the hydrophobic inert solvent are obtained to prepare for the subsequent cyanidation reaction.

[0072] S102, slowly adding cyaniding reagent into the above system in batches, and cooling to room temperature after the raw materials react.

[0073] According to the raw material content of HPLC, the amount of cyaniding reagent added is determined, and the amount of cyaniding reagent added is 1:1 to 1.1 equivalents of the raw material content. The cyaniding reagent is added to the reaction system by slow addition in batches, and the amount of cyaniding reagent added each time is 1 / 5 to 1 / 3 of the total amount. By monitoring the temperature change of the reaction system, it is judged whether the addition speed of the cyaniding reagent is appropriate. If the temperature rises too fast, the addition speed of the cyaniding reagent is slowed down; if the temperature rises too slowly, the addition speed of the cyaniding reagent is accelerated. The pH value of the reaction system is obtained, and the pH value is controlled between 8 and 10. If the pH value is lower than 8, sodium carbonate or sodium hydroxide solution is added to adjust; if the pH value is higher than 10, dilute hydrobromic acid solution is added to adjust. According to the color change of the reaction system, it is judged whether the raw material has been completely reacted. If the color becomes clear, it indicates that the raw material has been completely reacted; if the color is still turbid, the reaction is continued. By detecting the residual amount of the raw material in the reaction system, it is determined whether the raw material has been completely reacted. If the residual amount is less than 1%, it indicates that the raw material has been completely reacted; if the residual amount is higher than 1%, the reaction is continued. When it is determined that the raw materials have reacted completely, stop heating. Use a cooling water bath to speed up the cooling of the reaction system so that it reaches room temperature as soon as possible. Obtain the temperature of the reaction system. When the temperature drops to 25-30°C, subsequent separation and purification operations can be carried out.

[0074] S103, slowly adding clean water to the above reaction solution to adjust the solvent concentration, further cooling the solution, and filtering to separate the cyanide filter cake and the mother liquor.

[0075] According to the composition and properties of the reaction liquid, the amount and rate of adding clean water are determined so that the solvent concentration reaches a preset range; the temperature of the reaction liquid is monitored in real time by a temperature sensor, and the temperature is slowly reduced to a specified value by controlling the cooling system; the turbidity data of the reaction liquid is obtained to determine the degree of precipitation of solid particles, and when the turbidity reaches the set threshold, the cooling is stopped; according to the volume and viscosity of the reaction liquid, a suitable filtering device and filtering medium are selected to control the filtering pressure and flow rate; the mass of the filter cake is measured by a weighing sensor, the water content of the filter cake is calculated, and the washing conditions are adjusted to achieve the target value; the type and concentration of the residual solvent in the filtrate are detected by an infrared spectrometer, and the stratified recovery process parameters are optimized; the pH value and conductivity data of the mother liquor are obtained to determine the acidity and alkalinity and salt concentration, and the required acid, alkali and flocculant dosage are calculated accordingly; the metal ion content in the water phase is measured by an atomic absorption spectrometer to determine whether the emission standards are met, and the adsorption conditions are further optimized if necessary; according to the concentration and purity of the by-product hydrobromic acid solution, its feed ratio in the bromination synthesis is determined to realize the closed-loop circulation of the material.

[0076] Specifically, according to the type and concentration of the solvent in the reaction solution, the solubility curve is used to calculate that the amount of clean water to be added is 5 times the volume of the reaction solution, and it is added uniformly at a rate of 20mL / min through a flow control valve. The temperature of the reaction solution is monitored in real time using a Pt100 thermal resistor, and the cooling water flow is adjusted by a PID controller to reduce the temperature from 80°C to 5°C at a rate of 5°C / min. The transmittance of the reaction solution is detected by an online turbidity meter, and cooling is stopped when the transmittance drops to 60%. According to the viscosity of the reaction solution of 500mPa·s, a solvent-resistant polypropylene hollow fiber membrane is selected, the operating pressure is controlled to be 1MPa, and the filtration flux is 50L / (m2·h). The mass of the filter cake is measured by an electronic balance, and the water content is calculated by the weight gain rate of the filter cake. When the water content drops to 20%, washing is stopped. The residual concentrations of ethanol and ethyl acetate in the filtrate are detected by a Fourier transform infrared spectrometer, and the concentrations are reduced to below 100ppm by optimizing the reflux ratio of the distillation tower. The pH value of the mother liquor measured by the pH meter and conductivity meter was 5, and the conductivity was 15mS / cm. Based on this, the amount of NaOH and polyacrylamide added was calculated to be 2kg and 8kg respectively. The inductively coupled plasma emission spectrometer measured the Cu 2+ The concentration is 5 mg / L, which is removed to below 1 mg / L through two-stage activated carbon adsorption. The mass fraction of hydrobromic acid solution is 48% and the purity is 95%, which can be directly used for the next batch of bromination reactions to achieve full recycling of materials.

[0077] S104, washing the solid filter cake obtained in step S103 with hot water to remove residual solvent, collecting the washing liquid and recovering the solvent through layer separation, and the water layer is recovered and used in step S103; recovering the oil layer solvent from the mother liquor obtained in step S103 through layer separation, and applying the oil layer solvent to step S101 after simple distillation, refluxing a small amount of kettle residue with 1.5 to 2 times of the kettle residue with methanol, and further filtering and recovering the solid after low-temperature recrystallization, the solid material is a small amount of unreacted bromine-containing dye matrix raw material and a small amount of cyanide product dissolved in the solvent, which is collected and used for color matching; the methanol filtrate is distilled and recovered The steps are cyclically applied; the mother liquor obtained in step S103 is separated and the water layer is collected. The obtained water layer mainly contains bromine-containing inorganic salts and cyanide solution remaining from the reaction. The solution is acidified with hydrobromic acid and then hydrogen peroxide is added to oxidize and break the cyanide group. The small amount of organic matter carried is then removed by activated carbon adsorption. The solution is then adsorbed by a preferred cation exchange resin to recover metal ions therein. The metal ions are recovered by more than 99%, and the metal cation concentration in the aqueous phase is less than 5PPM. At this time, the solution is evaporated and concentrated to obtain a by-product HBr solution with a content of 45-50%, which is cyclically used for the bromination synthesis of the previous bromine-containing filter cake.

[0078] Specifically, the solid filter cake obtained in step S103 is washed with hot water, the washing temperature is controlled at 80-90°C, the washing time is 30 minutes, and the mass ratio of the washing liquid to the filter cake is 3:1. The washing liquid and the filter cake are separated by a centrifuge at a speed of 1500r / min, and separated for 10 minutes to obtain a washing liquid containing a solvent and a solid filter cake after washing. The washing liquid containing a solvent is allowed to stand for 30 minutes for stratification, and the solvent content in the organic phase can reach more than 90%, and the aqueous phase is returned as the recovered water layer of step S103. The mother liquor obtained in step S103 is allowed to stand for stratification for 1 hour, and the solvent content in the organic phase reaches more than 95%, and the aqueous phase is subsequently treated. The organic phase is distilled by a rectification tower, the tower bottom temperature is 120°C, the reflux ratio is 8:1, the distilled solvent purity is greater than 95%, and it is returned to step 1 for recycling, and the distillation residue is the kettle residue. Methanol is added to the kettle residue, and the amount of methanol is 3 times the mass of the kettle residue, and heated to reflux, and maintained for 2 hours to fully dissolve the dye in the kettle residue. Then the temperature is lowered to 5°C and maintained for 4 hours to allow the dye crystals to precipitate. The precipitated dye crystals are filtered out, and the filter cake is washed twice with cold methanol, each time with a methanol dosage of 5 times the mass of the filter cake to obtain a dye solid. The methanol filtrate is distilled in a rectification tower, the tower bottom temperature is 65°C, the reflux ratio is 5:1, and the purity of the distilled methanol is greater than 99%, which is returned for recycling. The aqueous phase obtained by stratification in step S103 is adjusted to pH 2-3 with hydrobromic acid, and then hydrogen peroxide is added, the amount of hydrogen peroxide is 1% of the volume of the aqueous phase, and the reaction is carried out at 50°C for 1 hour to break the cyanide. Then 1% of activated carbon is added, stirred and adsorbed for 30 minutes, trace organic matter in the aqueous phase is removed, and the aqueous phase containing metal ions is filtered. The aqueous phase containing metal ions passes through a macroporous adsorption resin exchange column, the amount of resin is 1 / 10 of the mass of the aqueous phase, and the flow rate is 10BV / h, so that the concentration of metal cations in the aqueous phase is reduced to below 5ppm. Finally, the aqueous phase is evaporated and concentrated under reduced pressure at 50°C to obtain a hydrobromic acid solution with a content of 45-50%, which is returned to the bromine-containing filter cake bromination synthesis step for recycling. Through the above method, the material recycling process of the bromine-containing dye synthesis process is realized, the discharge of three wastes is reduced, and the entire production process is green and environmentally friendly.

[0079] Comparison between this process and conventional cyanidation process:

[0080] Conventional cyanidation processes generally use DMF, DMAC, etc. as solvents. The dried bromine-containing dye filter cake is put into the above solvents, and then a cyanidation reagent is added for cyanidation. After the cyanidation reaction is completed, a solvent close to an equal amount of methanol is added, and then the temperature is lowered to below 10°C to filter and separate the mother liquor. The obtained filter cake is then pulped, detoxified, filtered, and washed to remove the metal salts, DMF, and methanol; the obtained solvent needs to be separated into methanol and DMF / DMAC by a distillation tower. Compared with the traditional process, this process has the following technical advantages:

[0081] a. The use of hydrophobic inert solvents facilitates solvent recovery and can be recycled after simple distillation. There is no risk of high-temperature decomposition during distillation of solvents such as DMF.

[0082] b. The bromide matrix does not need to be dried, which saves energy and reduces the hidden dangers of dust pollution and flammability of dry dust.

[0083] c. Due to the high solubility of DMF, the traditional process requires the use of methanol as the material, and the separation of DMF-methanol mixed liquid requires a distillation device, which consumes a lot of energy.

[0084] d. The filter cake obtained by the traditional process contains bromine salt, residual cyanide salt, DMF, and methanol mixture. It is necessary to further dissolve the bromine salt, cyanide salt, DMF, and methanol in water, and then filter and wash to obtain a qualified dye filter cake. The mother liquor after separation is a mixture of the above components, which is difficult to recycle and has high costs.

[0085] e. This process further uses methanol recrystallization to recover the residual material after solvent recovery. Due to the low solubility of the dye structure in methanol, the dye can be almost completely recovered after methanol recrystallization. The commercial performance of the obtained dye is slightly worse than that of the pure cyanide product, but it can be used for the matching and color matching of dark dyes, further improving the atomic utilization rate of the process and reducing costs.

[0086] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the principle of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for resource utilization of cyanide wastewater, characterized in that: The method comprises: Step 1: Cyanide using a hydrophobic inert solvent containing a bromine dye filter cake in the presence of a small amount of phase transfer catalyst, directly adding the water-containing filter cake into the above solvent, adding process water to adjust the solvent concentration, and heating to reflux conditions to dissolve the bromine dye filter cake; Step 2: Slowly add the cyaniding reagent to the above system in portions, wait for the reaction of the raw materials to be completed, and cool down to room temperature; Step 3: Slowly adding clean water to the above reaction solution to adjust the solvent concentration, further cooling the reaction solution to room temperature, and filtering to separate the cyanide filter cake and the mother liquor; Step 4: Wash the solid filter cake obtained in step 3 with hot water to remove the residual solvent, collect the washing liquid and recover the solvent through layer separation, and use the water layer recovery set for step 3; recover the oil layer solvent from the mother liquor obtained in step 3 through layer separation, and use the oil layer solvent in step 1 after simple distillation, reflux a small amount of kettle residue with 1.5 to 2 times of the kettle residue with methanol, and further filter and recover the solid after low-temperature recrystallization. This part of the solid material is a small amount of unreacted bromine-containing dye matrix raw material and a small amount of cyanide product dissolved in the solvent, which is collected and used for color matching; after the methanol filtrate is distilled and recovered, this step is circulated and used The mother liquor obtained in step 3 is separated and the water layer is collected. The water layer obtained mainly contains bromine-containing inorganic salts and cyanide solution remaining from the reaction. The solution is acidified with hydrobromic acid and then hydrogen peroxide is added for oxidation to break the cyanide group. The small amount of organic matter carried is then removed by adsorption on activated carbon. The solution is then adsorbed on a preferred cation exchange resin to recover metal ions. The metal ions are recovered by more than 99%, and the metal cation concentration in the aqueous phase is less than 5 PPM. At this time, the solution is evaporated and concentrated to obtain a by-product HBr solution with a content of 45-50%, which is recycled for the bromination synthesis of the previous bromine-containing filter cake.

2. The method for resource utilization of cyanide wastewater according to claim 1, characterized in that: The cyanation process uses a hydrophobic inert solvent containing a bromine dye filter cake in the presence of a small amount of phase transfer catalyst, directly adding the water-containing filter cake into the solvent, adding process water to adjust the dissolved concentration, and heating to reflux conditions to dissolve the bromine dye filter cake, comprising: According to the amount of bromine-containing dye filter cake, calculate the amount of hydrophobic inert solvent required, and the amount of solvent used is 3 to 5 times the amount of bromine-containing dye filter cake; Adding the calculated hydrophobic inert solvent into the reaction vessel, and then adding a small amount of phase transfer catalyst; The water-containing filter cake is directly added to a reaction vessel containing a hydrophobic inert solvent and a phase transfer catalyst, and process water is added to adjust the solvent ratio; Heating the reaction vessel to raise the temperature to reflux conditions; The reaction vessel was continuously stirred under reflux conditions until the bromine dye filter cake was completely dissolved; Determine whether the bromine-containing dye filter cake is completely dissolved. If not, continue to stir the reaction container until it is completely dissolved; If the bromine-containing dye filter cake has completely dissolved, stop heating and cool the reaction vessel to 70-90°C.

3. The method for resource utilization of cyanide wastewater according to claim 1, characterized in that: The cyaniding reagent is slowly added to the above system in portions, and after the raw materials have reacted, the temperature is cooled to room temperature, comprising: According to the raw material content of HPLC, the amount of cyaniding reagent added is determined, and the amount of cyaniding reagent added is 1:1 to 1:1.1 equivalents of the raw material content; The cyaniding agent is added to the reaction system by slowly adding in portions, and the amount of the cyaniding agent added each time is 1 / 5 to 1 / 3 of the total amount; By monitoring the temperature change of the reaction system, it is judged whether the addition speed of the cyaniding reagent is appropriate. If the temperature rises too fast, the addition speed of the cyaniding reagent is slowed down; If the temperature rises too slowly, speed up the addition of the cyaniding reagent; Obtaining the pH value of the reaction system, the pH value is controlled between 8 and 10, if the pH value is lower than 8, sodium carbonate or sodium hydroxide solution is added to adjust; If the pH value is higher than 10, add dilute hydrobromic acid solution to adjust; Judging whether the raw materials have reacted completely is based on the color change of the reaction system. If the color becomes clear, it indicates that the raw materials have reacted completely. If the color is still turbid, continue the reaction; By detecting the residual amount of the raw material in the reaction system, it is determined whether the raw material has been completely reacted. If the residual amount is less than 1%, it indicates that the raw material has been completely reacted; If the residual amount is higher than 1%, continue the reaction; When it is determined that the raw materials have reacted completely, stop heating and allow the reaction system to cool naturally to room temperature; Use a cooling water bath to speed up the cooling of the reaction system so that it reaches room temperature as quickly as possible; Obtain the temperature of the reaction system. When the temperature drops to 25-30°C, subsequent separation and purification operations can be performed.

4. The method for resource utilization of cyanide wastewater according to claim 1, characterized in that: The step of slowly adding clean water to the reaction solution to adjust the solvent concentration, further cooling the reaction solution, and filtering and separating the cyanide filter cake and the mother liquor comprises: According to the composition and properties of the reaction solution, determine the amount and rate of adding clean water so that the solvent concentration reaches a preset range; The temperature sensor is used to monitor the temperature of the reaction liquid in real time, and the temperature is slowly reduced to the specified value by controlling the cooling system; Obtain the turbidity data of the reaction solution to determine the degree of solid particle precipitation. When the turbidity reaches the set threshold, stop cooling; According to the volume and viscosity of the reaction liquid, select the appropriate filtration device and filtration medium, and control the filtration pressure and flow rate; The filter cake mass is measured by a weighing sensor, the moisture content of the filter cake is calculated, and the washing conditions are adjusted to reach the target value; An infrared spectrometer was used to detect the type and concentration of residual solvents in the filtrate and optimize the stratified recovery process parameters; Obtain the pH value and conductivity data of the mother liquor, determine the acidity and salt concentration, and calculate the required acid, alkali and flocculant dosage accordingly; The metal ion content in the water phase is measured by atomic absorption spectrometry to determine whether the discharge standards are met and to further optimize the adsorption conditions if necessary; According to the concentration and purity of the by-product hydrobromic acid solution, the feed ratio in the bromination synthesis is determined to realize the closed-loop circulation of the materials.

5. The method for resource utilization of cyanide wastewater according to claim 1, characterized in that: The solid filter cake obtained in step 3 is washed with hot water to remove the residual solvent, the washing liquid is collected and the solvent is recovered by layering, and the water layer is recovered and used in step 1 and step 3; the mother liquor obtained in step 3 is layered to recover the oil layer solvent, the oil layer solvent is simply distilled and applied to step 1, a small amount of kettle residue is refluxed with methanol 1.5 to 2 times the kettle residue, and then further filtered and recovered after low-temperature recrystallization. This part of the solid material is a small amount of unreacted bromine-containing dye matrix raw material and a small amount of cyanide product dissolved in the solvent, which is collected and used for color matching; the methanol filtrate is distilled and recovered and then recycled in this step The mother liquor obtained in step 3 is separated and the water layer is collected. The water layer mainly contains bromine-containing inorganic salts and cyanide solution remaining from the reaction. The solution is acidified with hydrobromic acid and then hydrogen peroxide is added to oxidize and break the cyanide group. The small amount of organic matter carried is removed by activated carbon adsorption. The solution is then adsorbed by a preferred cation exchange resin to recover metal ions. The metal ions are recovered by more than 99%, and the metal cation concentration in the aqueous phase is less than 5 PPM. At this time, the solution is evaporated and concentrated to obtain a byproduct HBr solution with a content of 45-50%, which is circulated for the bromination synthesis of the previous bromine-containing filter cake, comprising: The solid filter cake obtained in step 3 is washed with hot water, and the washing liquid is separated from the filter cake to obtain a washing liquid containing a solvent and a washed solid filter cake; The washing liquid containing the solvent is layered to separate an organic phase and an aqueous phase, wherein the organic phase contains the solvent and the aqueous phase is used as the recovered water layer in step 3; The mother liquor obtained in step 3 is layered to separate an organic phase and an aqueous phase, wherein the organic phase mainly contains the solvent; The organic phase is distilled to distill out the solvent, and the solvent is returned to step 1 for recycling, and the distillation residue is the kettle residue; Add 1 to 2 times the amount of methanol to the still residue, heat under reflux to dissolve the dye in the still residue, then cool to a low temperature to allow the dye to recrystallize and precipitate; Filter the precipitated dye crystals to obtain dye solids, which are unreacted bromine-containing dye matrix and a small amount of cyanide product, and are collected for dye color matching; The methanol filtrate is distilled to distill out methanol, and the methanol is returned to step 5 for recycling; Acidifying the aqueous phase obtained by separation in step 3, adding hydrobromic acid to adjust the pH, then adding hydrogen peroxide to oxidize and break the cyanide group, and then using activated carbon to adsorb and remove a small amount of organic matter in the aqueous phase to obtain an aqueous phase containing metal ions; The aqueous phase containing metal ions is separated by adsorption through a cation exchange resin to recover the metal ions, so that the concentration of metal cations in the aqueous phase is reduced to below 5 ppm. Finally, the aqueous phase is evaporated and concentrated to obtain a hydrobromic acid solution with a content of 45-50%, which is returned to the bromine-containing filter cake bromination synthesis process for recycling.

6. The method for resource utilization of cyanide wastewater according to claim 1, characterized in that: The chemical equation of step 1 is expressed as follows: X=H, CH3, NHCOCH3, NHCOC2H5 Y=H、NO2、halogen R1=C2H5, C2H4CN, CH2COOCH3, C2H4OCOCH3 R2=C2H4CN, CH2COOCH3, C2H4OCOCH3, C2H4OC2H4CN Z = Zn 2+ , Cu + , Na + or CH2OH.

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