A method for removing sodium ions from electroplating wastewater based on ion exchange resin

Abstract

The application relates to the technical field of wastewater treatment, and discloses a method for removing sodium ions in electroplating wastewater based on ion exchange resin, which comprises the following steps: step 1, pretreating the electroplating wastewater; step 2, flocculating and precipitating; step 3, adopting plate-frame pressure filtration treatment; and step 4, ion exchange treatment; in step 4, a resin with sulfonic acid groups treated by polyethylene glycol grafting is used as a sodium ion selective ion exchange resin. The method for removing sodium ions in electroplating wastewater based on ion exchange resin can more effectively remove sodium ions in the wastewater, improve the removal efficiency of the sodium ions and prolong the service life of the ion exchange resin by treating the electroplating wastewater by using the resin with sulfonic acid groups treated by PEG grafting. In addition, the method adopts a combination of modified zeolite and PAM flocculants, so that a complexing agent with a higher price does not need to be used, and the cost of the reagents can be greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, and particularly relates to a method for removing sodium ions in electroplating wastewater based on ion exchange resin. BACKGROUND

[0002] The electroplating industry brings economic benefits, but also produces a large amount of wastewater. Electroplating wastewater contains various pollutants, such as heavy metal ions (e.g., copper, nickel, chromium, etc.), complexing agents (e.g., EDTA, citric acid, etc.), and a large amount of sodium ions. Sodium ions mainly come from various sodium salts used in the electroplating process, such as sodium hydroxide, sodium chloride, sodium sulfate, etc. If the electroplating wastewater is discharged without treatment or substandard treatment, it will cause serious pollution to the environment.

[0003] Traditional electroplating wastewater treatment methods include chemical precipitation, electrolysis, adsorption, membrane separation, and ion exchange. Among them, ion exchange technology is widely used due to its high treatment efficiency and wide application range. However, in practical application, traditional ion exchange technology faces many challenges in treating electroplating wastewater.

[0004] Firstly, in addition to sodium ions, electroplating wastewater also contains a large amount of other metal ions, such as copper, nickel, chromium, etc. These metal ions will compete with sodium ions for exchange sites of ion exchange resin, resulting in reduced selectivity of the resin to sodium ions and decreased adsorption capacity, thereby affecting the removal effect of sodium ions. Studies have shown that when there are multiple metal ions in wastewater, the adsorption capacity of ion exchange resin to sodium ions will be significantly reduced.

[0005] Secondly, electroplating wastewater usually contains various organic complexing agents, which are one of the core pollutants in electroplating wastewater, such as EDTA, citric acid, etc. These complexing agents will form stable complexes with metal ions, thereby reducing the binding ability of metal ions to ion exchange resin. In addition, organic complexing agents themselves may also occupy exchange sites of ion exchange resin, leading to resin poisoning and failure. Studies have found that complexing agents such as EDTA can significantly reduce the adsorption capacity of ion exchange resin to heavy metal ions, and even cause resin failure.

[0006] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0007] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a method for removing sodium ions in electroplating wastewater based on ion exchange resin, aiming to develop a more efficient and economical method for removing sodium ions in electroplating wastewater, so as to improve the removal efficiency of sodium ions and prolong the service life of ion exchange resin.

[0008] The technical solution of the present application is as follows:

[0009] A method for removing sodium ions from electroplating wastewater based on ion exchange resin, comprising the following steps:

[0010] Step 1: pretreating electroplating wastewater;

[0011] Step 2: flocculating and precipitating the electroplating wastewater treated in step 1;

[0012] Step 3: treating the electroplating wastewater treated in step 2 by plate and frame filter pressing to separate solid and liquid;

[0013] Step 4: ion exchanging the electroplating wastewater treated in step 3 by an ion exchange column filled with sodium ion selective ion exchange resin;

[0014] In step 4, the sodium ion selective ion exchange resin is a resin with sulfonic acid groups treated by polyethylene glycol grafting, and the polyethylene glycol grafting treatment process comprises the following steps:

[0015] Step a: soaking the resin with sulfonic acid groups in a hydrochloric acid solution with a concentration of 0.8-1.2 mol / L for 4-6 hours;

[0016] Step b: uniformly mixing the polyethylene glycol and crosslinking agent diglycidyl ether with a mixed solvent to obtain a mixed solution;

[0017] Step c: immersing the resin with sulfonic acid groups treated in step a in the mixed solution prepared in step b, adding a catalyst p-toluenesulfonic acid, and reacting at 55-65°C for 18-24 hours;

[0018] Step d: washing the resin with sulfonic acid groups treated in step c with deionized water until neutral.

[0019] The method for removing sodium ions from electroplating wastewater based on ion exchange resin, wherein the specific process of step 1 is adding zeolite to the electroplating wastewater, stirring for 20-40 minutes under the condition of pH=5.5-6.5, and standing for 0.5-1.5 hours for precipitation;

[0020] The zeolite is one of natural zeolite, synthetic zeolite and modified zeolite.

[0021] The method for removing sodium ions from electroplating wastewater based on ion exchange resin, wherein the zeolite is modified zeolite;

[0022] The preparation method of the modified zeolite comprises the following steps:

[0023] Crushing natural clinoptilolite to 200 mesh;

[0024] Mix the natural clinoptilolite with a mixed solution containing ferric chloride and sodium dodecyl sulfate, solid-liquid ratio of 1g:10mL, under the condition of pH=6.0, stirring reaction for 1.5-2.5 hours;

[0025] Drying at 100-110℃ for 22-26 hours to obtain the modified zeolite;

[0026] The concentration of ferric chloride in the mixed solution containing ferric chloride and sodium dodecyl sulfate is 0.08-0.12mol / L, and the addition amount of sodium dodecyl sulfate accounts for 0.04-0.06% of the mass of the mixed solution.

[0027] The sodium ion removal method for electroplating wastewater based on ion exchange resin, wherein the dosage of the zeolite is 5-20g per 1 liter of the electroplating wastewater.

[0028] The sodium ion removal method for electroplating wastewater based on ion exchange resin, wherein in the step a, the volume ratio of the resin with sulfonic acid group to the hydrochloric acid solution is 3-5:1;

[0029] In the step b, the molecular weight of the polyethylene glycol is 2000-6000;

[0030] The mixed solvent is a mixed solution of DMSO and ethanol, and the volume ratio of DMSO to ethanol is 7:3;

[0031] The mass concentration of the polyethylene glycol in the mixed solvent is 5-15%, and the mass concentration of the crosslinking agent in the mixed solvent is 2-3%;

[0032] In the step c, the amount of the catalyst is 1-3% of the weight of the polyethylene glycol.

[0033] The sodium ion removal method for electroplating wastewater based on ion exchange resin, wherein the specific process of step 2 is to add polyacrylamide to the electroplating wastewater treated in step 1, the addition amount is 0.1-15mg / L, stir uniformly, and stand for 1-2 hours.

[0034] The sodium ion removal method for electroplating wastewater based on ion exchange resin, wherein the polyacrylamide is anionic polyacrylamide with a molecular weight of 8-10 million;

[0035] The stirring process is 100-200rpm stirring for 5-10 minutes and 30-50rpm stirring for 15-30 minutes.

[0036] The ion exchange resin-based electroplating wastewater sodium ion removal method, wherein, in the step 4, the flow rate is controlled to be 5-10 BV / h.

[0037] The ion exchange resin-based electroplating wastewater sodium ion removal method, wherein, the ion exchange resin-based electroplating wastewater sodium ion removal method further comprises the following steps:

[0038] Step 5: when the ion exchange column reaches saturation, the resin is regenerated by adopting the method of alternating elution of weak acid and weak base.

[0039] The ion exchange resin-based electroplating wastewater sodium ion removal method, wherein, the process of alternating elution comprises the following steps:

[0040] Firstly, reverse elution is carried out by using 0.3-0.7 mol / L hydrochloric acid solution at a flow rate of 2 BV / h, and the elution time is 1.5-2.5 hours; then, reverse elution is carried out by using 0.3-0.7 mol / L sodium hydroxide solution at a flow rate of 2 BV / h, and the elution time is 1.5-2.5 hours; finally, deionized water is used for washing until neutral.

[0041] Beneficial effects: the ion exchange resin-based electroplating wastewater sodium ion removal method of the present application can more effectively remove sodium ions in the wastewater, improve the removal efficiency of sodium ions, and prolong the service life of the ion exchange resin by using PEG grafted resin with sulfonic acid groups to treat electroplating wastewater. In addition, the combination of modified zeolite and PAM flocculant can greatly reduce the cost of reagents without using high-priced complexing agents. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present application, the present application is illustrated as follows. It should be understood by those skilled in the art that the examples are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0043] The ion exchange resin-based electroplating wastewater sodium ion removal method of the present application specifically comprises the following steps:

[0044] Step 1: pretreatment of electroplating wastewater.

[0045] Step 1 is pretreatment, which removes suspended solids and part of heavy metal ions in the electroplating wastewater, protects the ion exchange resin in the subsequent steps, and prolongs the service life of the ion exchange resin.

[0046] Specifically, the pretreatment process of step 1 comprises the following steps:

[0047] The zeolite is added to the electroplating wastewater, stirred for 20-40 minutes under the condition of pH=5.5-6.5, and left to settle for 0.5-1.5 hours.

[0048] In the pretreatment process of step 1, the dosage of zeolite is 5-20 g per 1 liter of electroplating wastewater. The pH is controlled at 5.5-6.5, which is conducive to the adsorption of heavy metal ions by the zeolite. Through stirring and static precipitation, it can be ensured that the adsorption reaction is fully carried out, and the precipitation effect is good.

[0049] In step 1, the zeolite can be one of natural zeolite, synthetic zeolite, modified zeolite, etc. Preferably, the zeolite is a modified zeolite. The modified zeolite used in the embodiment scheme of the present application is obtained by modifying natural clinoptilolite.

[0050] Further, the preparation method of the modified zeolite comprises the following steps:

[0051] The natural clinoptilolite is crushed to 200 mesh;

[0052] The natural clinoptilolite is mixed with a mixed solution containing ferric chloride and sodium dodecyl sulfate (SDS), the solid-liquid ratio is 1 g:10 mL, and the stirring reaction is carried out at pH=6.0 for 1.5-2.5 hours;

[0053] Drying at 100-110℃ for 22-26 hours to obtain the modified zeolite.

[0054] In the mixed solution containing ferric chloride and sodium dodecyl sulfate, the concentration of ferric chloride is 0.08-0.12 mol / L, and the addition amount of sodium dodecyl sulfate accounts for 0.04-0.06% of the mass of the mixed solution.

[0055] In the scheme of the present application, the modified zeolite is prepared by one-step in-situ modification technology, which simplifies the preparation process and reduces the preparation cost. After the natural clinoptilolite is crushed, it is directly mixed with a mixed solution containing ferric chloride and SDS, without the need for steps such as acid leaching, washing, and drying, and the preparation is simple. SDS is an anionic surfactant that can reduce the surface tension of the solution, improve the dispersibility of the iron salt on the surface of the natural clinoptilolite, increase the loading amount of the iron salt, and thus improve the adsorption performance of the modified zeolite.

[0056] The natural clinoptilolite is impregnated with a mixed solution containing ferric chloride to load iron ions on the surface of the natural clinoptilolite, form amorphous Fe(OH)3, improve the adsorption capacity of the natural clinoptilolite for heavy metal ions, and meanwhile, retain the natural porous structure of the natural clinoptilolite. The amorphous Fe(OH)3 has a positive charge on the surface at pH = 6, and can also adsorb anionic heavy metals or complex heavy metals, thereby reducing the load of the subsequent ion exchange resin. The modified zeolite adsorbs the suspended solids, heavy metal ions and complex heavy metals in the wastewater through the van der Waals force, electrostatic force and the like, thereby reducing the load of the subsequent ion exchange resin. The modified zeolite used as the adsorbent for pretreatment has higher adsorption capacity and selectivity, and can more effectively remove the suspended solids and heavy metals in the electroplating wastewater. In the pretreatment process in step 1, the pH is controlled at 5.5-6.5, which is beneficial to the existence of heavy metal ions in the form of ions, and also beneficial to the positive charge on the surface of the amorphous Fe(OH)3, so that the anionic heavy metals or complex heavy metals are more easily adsorbed, thereby reducing the load of the subsequent ion exchange resin.

[0057] Step 2: The electroplating wastewater is subjected to flocculation and sedimentation.

[0058] In the pretreated electroplating wastewater, polyacrylamide (PAM) is added, the addition amount is 0.1-15 mg / L, rapid stirring is performed for 5-10 minutes (100-200 rpm), then slow stirring is performed for 15-30 minutes (30-50 rpm), so that the flocculation body is formed, and the flocculation body is allowed to stand and settle for 1-2 hours.

[0059] In this step, the PAM is a flocculant, which is used to aggregate the fine particles in the electroplating wastewater to form flocculation body, so as to be easily removed subsequently. The PAM is a high molecular polymer, and the amide group on the molecular chain can adsorb and bridge the suspended solids and colloidal particles in the wastewater to form flocculation body. The flocculation body is removed through gravity sedimentation or plate and frame filter pressing. The rapid stirring is performed to uniformly disperse the flocculant, and the slow stirring is performed to promote the formation of the flocculation body. The standing and settling is performed to allow the flocculation body to settle, so as to be easily separated.

[0060] Moreover, in the scheme of the present application, the PAM flocculant is used, a new complexing agent is avoided to be introduced, the interference on the subsequent ion exchange is reduced, and the load of the subsequent ion exchange resin is reduced. In addition, the combination of the modified zeolite and the PAM flocculant is used, and a complexing agent with a high price is not needed, so that the cost of the reagents can be greatly reduced.

[0061] In this step, the PAM can be anionic PAM with a molecular weight of 8-10 million.

[0062] Step 3: The plate and frame filter pressing is used to treat the electroplating wastewater, and solid-liquid separation is performed.

[0063] The electroplating wastewater is treated by a plate-and-frame filter press, mainly to remove the suspended solids and flocculation bodies in the electroplating wastewater.

[0064] In step 4, the electroplating wastewater treated in step 3 is subjected to ion exchange treatment by an ion exchange column filled with sodium ion selective ion exchange resin, and the flow rate is controlled to be 5-10 BV / h.

[0065] Step 4 is ion exchange, which removes sodium ions in the electroplating wastewater.

[0066] In this step, by controlling the water inflow rate to be 5-10 BV / h, it is ensured that the ion exchange reaction is fully carried out, and the sodium ion removal efficiency is improved.

[0067] In this step, the sodium ion selective ion exchange resin is preferably a resin with sulfonic acid groups, which can increase the selectivity for sodium ions, reduce the interference of other ions and complexing agents, thereby improving the removal effect of sodium ions and prolonging the service life of the resin. There are many types of resins with sulfonic acid groups on the market, which can be selected according to the actual situation. In the embodiment of the present application, the sodium ion selective ion exchange resin is Amberlite IR120 of Rohm & Haas Company.

[0068] Even after the previous pretreatment steps, most of the suspended solids, complexes and heavy metal ions are removed, but there are still residues in the electroplating wastewater. Therefore, by modifying the resin, the selectivity for sodium ions is further improved, the competitive adsorption of other cations is reduced, and the service life of the resin is prolonged.

[0069] Further, the sodium ion selective ion exchange resin is preferably a resin with sulfonic acid groups subjected to polyethylene glycol (PEG) grafting treatment to further improve the selectivity for sodium ions and reduce the competitive adsorption of other cations.

[0070] Specifically, the polyethylene glycol (PEG) grafting treatment of the resin with sulfonic acid groups includes the following steps:

[0071] Step a: Soak the resin with sulfonic acid groups (Amberlite IR120 of Rohm & Haas Company) in a hydrochloric acid solution with a concentration of 0.8-1.2 mol / L for 4-6 hours.

[0072] Step b: Mix polyethylene glycol (PEG) and crosslinking agent diglycidyl ether with a mixed solvent uniformly to obtain a mixed solution.

[0073] Step c: Soak the resin with sulfonic acid groups treated in step a in the mixed solution prepared in step b, add a catalyst p-toluenesulfonic acid, and react at 55-65°C for 18-24 hours.

[0074] Step d: the resin with sulfonic acid groups after reaction is washed with deionized water until neutral.

[0075] In step a, the volume ratio of the resin with sulfonic acid groups to hydrochloric acid solution can be 3-5:1, ensuring that the reaction can proceed smoothly.

[0076] In step b, the molecular weight of polyethylene glycol can be 2000-6000. In the embodiment of the present application, polyethylene glycol is PEG4000 from Shanghai Aladdin Biochem Technology Co., Ltd. The crosslinking agent can be diglycidyl ether, which can crosslink the PEG molecules, improve the fixation and stability of PEG on the resin surface, and prevent PEG from falling off. The mixed solvent is a mixed solution of DMSO and ethanol, and the volume ratio of DMSO to ethanol is 7:3. The mass concentration of polyethylene glycol in the mixed solvent can be 5-15%, and the mass concentration of the crosslinking agent in the mixed solvent can be 2-3%, ensuring that the reaction can proceed smoothly and PEG can be grafted on the resin.

[0077] In step c, the catalyst can be p-toluenesulfonic acid, and the amount of catalyst can be 1-3% of the weight of PEG, ensuring that the reaction can proceed smoothly, and too much can easily lead to hydrolysis and breakage of PEG chains. In step c, the water of the resin with sulfonic acid groups can be slightly drained before being put into the mixed solution, which can avoid diluting the concentration of PEG-crosslinking agent too much by the water brought by the resin itself. During the reaction process, it is necessary to ensure that the resin with sulfonic acid groups is soaked in the mixed solution.

[0078] Step 5: when the ion exchange column reaches saturation, the resin is regenerated by alternating elution of weak acid and weak base.

[0079] Step 5 is resin regeneration, which restores the adsorption performance of sodium ion selective ion exchange resin. By alternating elution of weak acid and weak base, the damage to the sodium ion selective ion exchange resin can be reduced, and the service life of the resin can be prolonged.

[0080] In this step, the hydrochloric acid solution can exchange with the sodium ions on the resin, so that the resin returns to the hydrogen type, and the sodium hydroxide solution can neutralize the acidic groups on the resin and remove impurity ions on the resin. By alternating elution, the purpose of resin regeneration can be achieved.

[0081] Specifically, the elution process of step 5 can be: first, 0.3-0.7 mol / L hydrochloric acid solution is used for reverse elution at a flow rate of 2 BV / h, and the elution time is 1.5-2.5 hours; then, 0.3-0.7 mol / L sodium hydroxide solution is used for reverse elution at a flow rate of 2 BV / h, and the elution time is 1.5-2.5 hours; finally, deionized water is used for washing until neutral.

[0082] Compared with the prior art, the ion exchange resin-based electroplating wastewater sodium ion removal method has the following advantages:

[0083] 1. Better pretreatment effect: using modified zeolite as a pretreatment adsorbent, compared with traditional coagulation sedimentation, the modified zeolite has higher adsorption capacity and selectivity, can more effectively remove suspended solids and part of heavy metal ions in electroplating wastewater, and can better protect the subsequent ion exchange resin.

[0084] 2. Higher selectivity: using PAM flocculant instead of traditional EDTA analogs, avoiding the introduction of new complexing agents, reducing interference with subsequent ion exchange, and improving the selectivity of the resin for sodium ions.

[0085] 3. Better ion exchange effect: using sodium ion selective ion exchange resin, the resin is specially modified to improve the selectivity for sodium ions and reduce the interference of other ions, thereby improving the removal effect of sodium ions and reducing.

[0086] 4. Longer resin life: using weak acid and weak base alternating elution for resin regeneration can reduce damage to the resin and prolong its service life.

[0087] The application is further illustrated by the following examples.

[0088] In the following examples, the detection of sodium, copper, nickel, chromium and other ion concentrations uses HJ776-2015 Determination of Water Quality 32 Elements by Inductively Coupled Plasma Optical Emission Spectrometry.

[0089] The test method for suspended solids uses GB / T11901-1989 (gravimetric method).

[0090] The resin adsorption capacity test uses GB / T8144-2008 Determination of Cation Exchange Resin Exchange Capacity. The calculation method of resin regeneration efficiency is: regenerated resin exchange capacity / new resin exchange capacity * 100%.

[0091] Example 1

[0092] Take 10L of electroplating wastewater discharged by a certain electroplating enterprise, and determine that the wastewater contains 500mg / L of sodium ions, 15mg / L of copper ions, 10mg / L of nickel ions, 5mg / L of EDTA, pH 8.5, and 100mg / L of suspended solids.

[0093] The process flow is as follows:

[0094] Step 1: Pretreatment

[0095] The natural clinoptilolite (from Gongyi Jindi water treatment material Co. Ltd.) was added to the electroplating wastewater, the dosage was 7g / L, under the condition of pH=5.5, stirring for 30 minutes, and standing for 1 hour.

[0096] Step 2: flocculation and precipitation.

[0097] The polyacrylamide (anionic PAM, molecular weight 8 million, North China Fine Chemical Industry) was added to the pretreated electroplating wastewater, the dosage was 1.5mg / L, fast stirring for 5 minutes (150rpm), then slow stirring for 20 minutes (40rpm), to form flocculation, and standing for 1 hour.

[0098] Step 3: plate and frame filter press was used to treat the electroplating wastewater, and solid-liquid separation was carried out.

[0099] Step 4: ion exchange

[0100] The electroplating wastewater was passed through the ion exchange column filled with sodium ion selective ion exchange resin (Amberlite IR120 of Rohm & Haas Company), the column height was 1 meter, and the inner diameter was 5 centimeters. The water inflow rate was controlled at 5 BV / h.

[0101] Step 5: resin regeneration

[0102] When the ion exchange column reached saturation, first, reverse elution was carried out with 0.5mol / L hydrochloric acid solution at a flow rate of 2BV / h, and the elution time was 2 hours; then, reverse elution was carried out with 0.5mol / L sodium hydroxide solution at a flow rate of 2BV / h, and the elution time was 2 hours; finally, deionized water was used for washing until neutral.

[0103] The concentrations of sodium ions, copper ions, nickel ions and suspended solids in the treated electroplating wastewater were determined to calculate the removal rate, and the regeneration efficiency of the resin was calculated, and the results were as follows:

[0104] Sodium ion: removal rate 80.3%;

[0105] Copper ion: removal rate 85%;

[0106] Nickel ion: removal rate 81.3%;

[0107] Suspended solids removal rate: removal rate 93%;

[0108] Resin regeneration efficiency: 73.5%.

[0109] Example 2

[0110] The source of the electroplating wastewater 10L was the same as that of example 1.

[0111] The process flow was as follows:

[0112] Step 1: Pretreatment

[0113] The natural clinoptilolite (from Gongyi Jindi Water Treatment Material Co., Ltd.) was added to the electroplating wastewater at a dosage of 6 g / L. After stirring for 30 minutes at pH = 6.0, the wastewater was allowed to stand for 1 hour for sedimentation.

[0114] Step 2: Flocculation and sedimentation.

[0115] Polyacrylamide (anionic PAM, molecular weight 8 million, North China Fine Chemical Industry) was added to the pretreated electroplating wastewater at a dosage of 1.5 mg / L. After rapid stirring for 5 minutes (150 rpm) and slow stirring for 20 minutes (40 rpm), the flocculation was formed, and the wastewater was allowed to stand for 1 hour for sedimentation.

[0116] Step 3: Plate and frame filter press was used to treat the electroplating wastewater for solid-liquid separation.

[0117] Step 4: Ion exchange

[0118] The electroplating wastewater was passed through an ion exchange column filled with polyethylene glycol grafted sodium ion selective ion exchange resin (Amberlite IR120, Rohm & Haas) with a column height of 1 meter and an inner diameter of 5 centimeters. The water flow rate was controlled at 5 BV / h.

[0119] In which, the process of grafting polyethylene glycol to the resin with sulfonic acid group is as follows:

[0120] Step a: The resin with sulfonic acid group (Amberlite IR120, Rohm & Haas) was soaked in a 1.0 mol / L hydrochloric acid solution for 5 hours, with a resin to hydrochloric acid solution volume ratio of 4:1.

[0121] Step b: PEG4000 and crosslinking agent diglycidyl ether were mixed uniformly with a mixed solvent (DMSO: ethanol = 7:3 (volume ratio)) to obtain a mixed solution, wherein the mass concentration of PEG4000 in the mixed solvent was 10%, and the mass concentration of the crosslinking agent in the mixed solvent was 2%.

[0122] Step c: The resin with sulfonic acid group treated in step a was immersed in the mixed solution prepared in step b, and a catalyst p-toluenesulfonic acid was added. The reaction was carried out at 60°C for 24 hours, wherein the amount of catalyst was 2% of the weight of PEG4000.

[0123] Step d: The resin with sulfonic acid group treated in step c was washed with deionized water until it was neutral.

[0124] Step 5: Resin regeneration

[0125] When the ion exchange column reaches saturation, first, reverse elution is carried out with 0.5 mol / L hydrochloric acid solution at a flow rate of 2 BV / h, and the elution time is 2 hours; then, reverse elution is carried out with 0.5 mol / L sodium hydroxide solution at a flow rate of 2 BV / h, and the elution time is 2 hours; finally, deionized water is used for washing until neutral.

[0126] The concentrations of sodium ions, copper ions, nickel ions and suspended solids in the treated electroplating wastewater are determined to calculate the removal rates, and the regeneration efficiency of the resin is calculated, and the results are as follows:

[0127] Sodium ions: removal rate 95.6%;

[0128] Copper ions: removal rate 86.7%;

[0129] Nickel ions: removal rate 80.5%;

[0130] Suspended solids removal rate: removal rate 95%;

[0131] Resin regeneration efficiency: 75.8%.

[0132] Example 3:

[0133] The source of 10 L of electroplating wastewater is the same as that of Example 1.

[0134] The process flow is as follows:

[0135] Step 1: pretreatment

[0136] The natural clinoptilolite (from Gongyi Jindi Water Treatment Material Co., Ltd.) is crushed to 200 mesh, then mixed with a mixed solution containing 0.1 mol / L ferric chloride and 0.05 wt% sodium dodecyl sulfate, the solid-liquid ratio is 1:10 (g / mL), under the condition of pH=6.0, stirring for 2 hours, then drying at 105℃ for 24 hours, to obtain modified zeolite.

[0137] The modified zeolite is added to the electroplating wastewater, the addition amount is 7 g / L, under the condition of pH=5.5, stirring for 30 minutes, and standing for 1 hour.

[0138] Step 2: flocculation and sedimentation.

[0139] Polyacrylamide (anionic PAM, molecular weight 8 million, Zhongbei Fine Chemical Industry) is added to the pretreated electroplating wastewater, the addition amount is 1 mg / L, rapid stirring for 5 minutes (150 rpm), then slow stirring for 20 minutes (40 rpm), to form flocculation, and standing for 1 hour.

[0140] Step 3: plate and frame filter press is used to treat electroplating wastewater, and solid-liquid separation is carried out.

[0141] Step 4: Ion exchange

[0142] The electroplating wastewater was passed through an ion exchange column filled with sodium ion selective ion exchange resin treated by polyethylene glycol grafting, with a column height of 1 meter and an inner diameter of 5 centimeters. The water inflow rate was controlled at 5 BV / h.

[0143] In the process of treating the resin with sulfonic acid groups by polyethylene glycol grafting, the following steps were taken:

[0144] Step a: The resin with sulfonic acid groups (Amberlite IR120 from Rohm & Haas) was soaked in a hydrochloric acid solution with a concentration of 1.0 mol / L for 5 hours, with a volume ratio of resin to hydrochloric acid solution of 4:1.

[0145] Step b: PEG4000 and crosslinking agent diglycidyl ether were mixed uniformly with a mixed solvent (DMSO: ethanol = 7:3 (volume ratio)) to obtain a mixed solution, wherein the mass concentration of PEG4000 in the mixed solvent was 10%, and the mass concentration of the crosslinking agent in the mixed solvent was 2%.

[0146] Step c: The resin with sulfonic acid groups treated in step a was immersed in the mixed solution prepared in step b, and a catalyst p-toluenesulfonic acid was added, and the reaction was carried out at 60°C for 24 hours, wherein the amount of catalyst was 2% of the weight of PEG4000.

[0147] Step d: The resin with sulfonic acid groups after reaction was washed with deionized water until neutral.

[0148] Step 5: Resin regeneration

[0149] When the ion exchange column reached saturation, first, reverse elution was carried out with 0.5 mol / L hydrochloric acid solution at a flow rate of 2 BV / h, and the elution time was 2 hours; then, reverse elution was carried out with 0.5 mol / L sodium hydroxide solution at a flow rate of 2 BV / h, and the elution time was 2 hours; finally, deionized water was used for washing until neutral.

[0150] The concentrations of sodium ions, copper ions, nickel ions, and suspended solids in the treated electroplating wastewater were determined to calculate the removal rates, and the regeneration efficiency of the resin was calculated, with the following results:

[0151] Sodium ions: removal rate 98.9%;

[0152] Copper ions: removal rate 97.6%;

[0153] Nickel ions: removal rate 99.1%;

[0154] Suspended solids removal rate: removal rate 98.3%;

[0155] Resin regeneration efficiency: 86.5%.

[0156] Example 4:

[0157] Take 10 L of mixed electroplating wastewater actually produced by a certain electroplating plant, wherein the main pollutant concentrations are: sodium ion 800 mg / L, copper ion 10 mg / L, nickel ion 12.5 mg / L, EDTA 8 mg / L, pH 9.0, and suspended solids 150 mg / L.

[0158] The process flow is as follows:

[0159] Step 1: Pretreatment

[0160] The natural clinoptilolite (from Gongyi Jindi Water Treatment Material Co., Ltd.) is crushed to 200 mesh, then mixed with a mixed solution containing 0.1 mol / L ferric chloride and 0.05 wt% sodium dodecyl sulfate, the solid-liquid ratio is 1:10 (g / mL), under the condition of pH=6.0, stirring for 2 hours, then drying at 105°C for 24 hours, to obtain modified zeolite.

[0161] Add the modified zeolite to the electroplating wastewater, the dosage is 8 g / L, under the condition of pH=6.0, stirring for 30 minutes, and standing for 1 hour.

[0162] Step 2: Flocculation and sedimentation.

[0163] Add polyacrylamide (anionic PAM, molecular weight 8 million, North China Fine Chemical Industry) to the pretreated electroplating wastewater, the dosage is 2 mg / L, fast stirring for 5 minutes (150 rpm), then slow stirring for 20 minutes (40 rpm), to form flocculation, and standing for 1 hour.

[0164] Step 3: Plate and frame filter press is used to treat electroplating wastewater for solid-liquid separation.

[0165] Step 4: Ion exchange

[0166] The electroplating wastewater is passed through an ion exchange column filled with sodium ion selective ion exchange resin treated by polyethylene glycol grafting, the column height is 1 meter, and the inner diameter is 5 centimeters. The water inlet flow rate is controlled at 5 BV / h.

[0167] Among them, the process of polyethylene glycol grafting treatment of the resin with sulfonic acid groups is as follows:

[0168] Step a: Soak the resin with sulfonic acid groups (Amberlite IR120, Rohm & Haas) in a 1.0 mol / L hydrochloric acid solution for 5 hours, the volume ratio of resin to hydrochloric acid solution is 4:1.

[0169] Step b: PEG4000 and crosslinking agent diglycidyl ether were mixed with mixed solvent (DMSO: ethanol = 7:3 (volume ratio)) to obtain a mixed solution, wherein the mass concentration of PEG4000 in the mixed solvent was 10%, and the mass concentration of the crosslinking agent in the mixed solvent was 2%.

[0170] Step c: the resin with sulfonic acid group treated in step a was immersed in the mixed solution prepared in step b, a catalyst p-toluenesulfonic acid was added, and the reaction was carried out at 60°C for 24 hours, wherein the amount of catalyst was 2% of the weight of PEG4000.

[0171] Step d: the resin with sulfonic acid group after reaction was washed with deionized water until neutral.

[0172] Step 5: resin regeneration

[0173] When the ion exchange column reached saturation, first, reverse elution was carried out with 0.5 mol / L hydrochloric acid solution at a flow rate of 2 BV / h, and the elution time was 2 hours; then, reverse elution was carried out with 0.5 mol / L sodium hydroxide solution at a flow rate of 2 BV / h, and the elution time was 2 hours; finally, deionized water was used to wash until neutral.

[0174] The concentrations of sodium ions, copper ions, nickel ions and suspended solids in the treated electroplating wastewater were determined to calculate the removal rate, and the regeneration efficiency of the resin was calculated, and the results were as follows:

[0175] Sodium ions: removal rate 98.2%;

[0176] Copper ions: removal rate 98.5%;

[0177] Nickel ions: removal rate 99.2%;

[0178] Suspended solids removal rate: removal rate 98.5%;

[0179] Resin regeneration efficiency: 89.3%.

[0180] Comparative example 1:

[0181] The coagulation sedimentation-ion exchange process was used to treat 10 L of electroplating wastewater from the same source as in example 1.

[0182] Step 1: coagulation sedimentation: polyaluminum chloride (PAC, National Pharmaceutical Group Chemical Reagent Co., Ltd.) was added to the wastewater, the dosage was 10 g / L, under the condition of pH = 7.0, stirring for 30 minutes, and standing for 1 hour. Then, the suspended solids and part of the heavy metal ions in the wastewater were removed by plate and frame filter press.

[0183] Step 2: Ion exchange: The precipitated wastewater is passed through an ion exchange column filled with sodium ion selective ion exchange resin (Rohm & Haas, Amberlite IR120), the column is 1 meter high and 5 centimeters in diameter. The water flow rate is controlled at 5 BV / h.

[0184] Step 3: Resin regeneration: When the ion exchange column is saturated, reverse elution is performed using 0.5 mol / L hydrochloric acid solution at a flow rate of 2 BV / h, and the elution time is 2 hours. Then, reverse elution is performed using 0.5 mol / L sodium hydroxide solution at a flow rate of 2 BV / h, and the elution time is 2 hours. Finally, deionized water is used for washing until neutral.

[0185] The concentrations of sodium ions, copper ions, nickel ions, and suspended solids in the treated electroplating wastewater are determined to calculate the removal rates, and the regeneration efficiency of the resin is calculated, and the results are as follows:

[0186] The removal rate of sodium ions is 85.0%;

[0187] The removal rate of copper ions is 80.0%;

[0188] The removal rate of nickel ions is 70.0%;

[0189] The removal rate of suspended solids is 90%;

[0190] The regeneration efficiency of the resin is 65.0%.

[0191] As can be seen from the above examples, the application of the present application to treat electroplating wastewater can improve the removal rates of sodium ions, copper ions, nickel ions and suspended solids, and can improve the regeneration efficiency of sodium ion exchange resin and prolong the service life of sodium ion resin. Therefore, the present application has significant advantages in the removal of sodium ions in electroplating wastewater and has good application prospects.

[0192] It should be understood that the application of the present application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the present application.

Claims

1. A method for removing sodium ions from electroplating wastewater based on ion exchange resin, characterized by, It comprises the following steps: Step 1: pretreatment of electroplating wastewater; Step 2: flocculation and sedimentation of the electroplating wastewater treated in step 1; Step 3: plate and frame filter pressing treatment of the electroplating wastewater treated in step 2 for solid-liquid separation; Step 4: ion exchange treatment of the electroplating wastewater treated in step 3 by passing through an ion exchange column filled with sodium ion selective ion exchange resin; In step 4, the sodium ion selective ion exchange resin is a resin with sulfonic acid groups treated by polyethylene glycol grafting, and the polyethylene glycol grafting treatment process comprises the following steps: Step a: soaking the resin with sulfonic acid groups in a hydrochloric acid solution with a concentration of 0.8-1.2 mol / L for 4-6 hours; Step b: uniformly mixing the polyethylene glycol and crosslinking agent diglycidyl ether with a mixed solvent to obtain a mixed solution; Step c: immersing the resin with sulfonic acid groups treated in step a in the mixed solution prepared in step b, adding a catalyst p-toluenesulfonic acid, and reacting at 55-65°C for 18-24 hours; Step d: washing the resin with sulfonic acid groups treated in step c with deionized water until neutral.

2. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 1, characterized by, The specific process of step 1 is adding zeolite to the electroplating wastewater, stirring for 20-40 minutes under the condition of pH=5.5-6.5, and standing for 0.5-1.5 hours for sedimentation. The zeolite is one of natural zeolite, synthetic zeolite, and modified zeolite.

3. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 2, characterized by, The zeolite is modified zeolite; The preparation method of the modified zeolite comprises the following steps: Grinding the natural clinoptilolite to 200 mesh; Mixing the natural clinoptilolite with a mixed solution containing ferric chloride and sodium dodecyl sulfate, with a solid-liquid ratio of 1g:10mL, stirring and reacting for 1.5-2.5 hours under the condition of pH=6.0; Drying at 100-110°C for 22-26 hours to obtain the modified zeolite; In the mixed solution containing ferric chloride and sodium dodecyl sulfate, the concentration of ferric chloride is 0.08-0.12 mol / L, and the addition amount of sodium dodecyl sulfate accounts for 0.04-0.06% of the mass of the mixed solution.

4. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 3, characterized by, The addition amount of the zeolite is 5-20g per 1 liter of the electroplating wastewater.

5. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 1, characterized by, In step a, the volume ratio of the resin with sulfonic acid groups to the hydrochloric acid solution is 3-5:1; In step b, the molecular weight of the polyethylene glycol is 2000-6000; The mixed solvent is a mixed solution of DMSO and ethanol, and the volume ratio of DMSO to ethanol is 7:3; The mass concentration of the polyethylene glycol in the mixed solvent is 5-15%, and the mass concentration of the crosslinking agent in the mixed solvent is 2-3%; In step c, the amount of the catalyst is 1-3% of the weight of the polyethylene glycol.

6. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 1, characterized by, The specific process of step 2 is adding polyacrylamide to the electroplating wastewater treated in step 1, with an addition amount of 0.1-15mg / L, uniformly stirring, and standing for 1-2 hours for sedimentation.

7. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 6, characterized by, The polyacrylamide is an anionic polyacrylamide with a molecular weight of 8-10 million; The stirring process is first stirring at 100-200 rpm for 5-10 minutes, and then stirring at 30-50 rpm for 15-30 minutes.

8. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 1, characterized by, In the step 4, the flow rate is controlled to be 5-10 BV / h.

9. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 1, characterized by, Further comprising the following steps: Step 5: when the ion exchange column reaches saturation, the resin is regenerated by using acid-alkali alternating elution.

10. The ion exchange resin-based method for removing sodium ions from electroplating wastewater according to claim 9, characterized by, The alternating elution process comprises the following steps: First, reverse elution is performed with 0.3-0.7 mol / L hydrochloric acid solution at a flow rate of 2 BV / h, and the elution time is 1.5-2.5 hours; then, reverse elution is performed with 0.3-0.7 mol / L sodium hydroxide solution at a flow rate of 2 BV / h, and the elution time is 1.5-2.5 hours; finally, deionized water is used for washing until neutral.