Method for removing salts from papermaking waste water by using modified double ion exchange resin

Abstract

The application discloses a method for removing salt in papermaking wastewater by using modified double-ion exchange resin. The method comprises the following steps: taking 201x7 hydroxyl type anion exchange resin as raw material, mixing the raw material with a mixed solution of ferric citrate, ethanol and water, and fully reacting under acidic conditions; and loading hydroxyl iron oxide onto the surface of the resin by using a strong alkali solution to obtain modified 201x7 hydroxyl type ion exchange resin. The modified resin has the advantages of increased exchange capacity for sulfate, no introduction of other ions, excellent regeneration effect and no iron ion dissolution. The modified resin and 732 hydrogen type cation exchange resin are combined to effectively remove anions and cations in papermaking wastewater, control the dosage and proportion of the modified resin and the 732 hydrogen type cation exchange resin, control the salt content and pH of the effluent, and the method for combining the modified resin and the 732 hydrogen type cation exchange resin is a new method suitable for desalination of papermaking wastewater, plays an important role in recycling of wastewater, and has great application potential in the field of industrial wastewater desalination.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a method for removing salt in papermaking wastewater by using modified double ion exchange resin. BACKGROUND

[0002] The papermaking industry is an important industry in the national economy, but a large amount of wastewater with high salt and many organic pollutants is generated in the pulping and papermaking process, which causes harm to environmental protection. In order to solve the pollution problem of papermaking wastewater, so far a large number of studies have been carried out to remove organic pollutants, reduce COD, remove suspended substances and the like in papermaking wastewater, and the removal methods include physical method, chemical method and biological method. After technical treatment (catalytic oxidation, Fenton oxidation and the like), the wastewater is discharged after reaching the discharge standard, but at present, the desalination technology for papermaking wastewater is less concerned in China. The existing enterprises mostly adopt a combined desalination method of multiple processes, that is, a combined process flow of pretreatment + multi-stage membrane concentration + evaporation crystallization + membrane electrolysis. However, this process has problems such as high operation cost and membrane pollution in the actual process, and cannot be popularized.

[0003] Ion exchange resin is a kind of high molecular compound with active functional groups and network structure, and is widely used in water treatment due to its characteristics such as high mechanical strength, non-toxicity, good stability and reusability. According to the structural characteristics of the resin, ion exchange resin is divided into two categories of gel type and macroporous type. The gel type resin has a uniform cross-linked structure, and thus has high physical stability and chemical stability, can effectively exchange and release ions, and is suitable for exchanging inorganic ions. According to its function, it can be divided into anion exchange resin and cation exchange resin; according to its exchangeable ions, the cation exchange resin can be divided into sodium type and hydrogen type, and the anion exchange resin can be divided into chlorine type and hydroxyl type. For different wastewater characteristics and target removal substances, the suitable resin types are different, and the selection of appropriate resin can greatly improve the exchange efficiency and save economic cost. The existing resin exchange of salt in papermaking wastewater has problems such as low exchange capacity and high investment cost, which restricts its industrial application. It is necessary to develop a new type of high-efficiency ion exchange resin suitable for papermaking wastewater treatment and application technology. SUMMARY

[0004] In order to overcome the deficiencies in the prior art, the purpose of the present application is to provide a method for removing salt in papermaking wastewater by using modified double ion exchange resin.

[0005] The application is directed to the physicochemical properties of papermaking wastewater, and uses 732 hydrogen type cation exchange resin and 201x7 hydrogen-oxygen type anion exchange resin to treat salt in papermaking wastewater. The 732 hydrogen type cation exchange resin is a strong acid gel resin, with a full exchange capacity of 4.5 mmol / g, a volume exchange capacity of 1.9 mmol / mL, a particle size of 0.4-0.6 mm, a water content of 45-55%, and a transformation expansion rate of 8-10%. The 732 hydrogen type cation exchange resin can efficiently and quickly exchange out cations in papermaking wastewater, including calcium, sodium, magnesium and other ions, and has good stability and good regeneration performance. The 201x7 hydrogen-oxygen type anion exchange resin has a strong group exchange capacity of 3.6 mmol / g, a volume exchange capacity of 1.4 mmol / mL, a particle size of 0.4-0.7 mm, a water content of 42-48%, and a transformation expansion rate of 18-22%. The 201x7 hydrogen-oxygen type anion exchange resin can quickly and efficiently exchange out anions in papermaking wastewater, including sulfate and sodium ions, and has good stability and high removal efficiency. In view of the problems of high price, low exchange capacity and weak regeneration performance of the 201x7 hydrogen-oxygen type anion exchange resin, the application provides a modification method for the 201x7 hydrogen-oxygen type anion exchange resin. The modified resin and the 732 hydrogen type cation exchange resin are applied to papermaking wastewater desalination, and have the advantages of high exchange capacity and good regeneration performance.

[0006] To achieve the above object, the application provides the following technical scheme.

[0007] A method for removing salt in papermaking wastewater by using cation and anion exchange resins in combination, comprising the following steps.

[0008] (1) Preparation of modified anion exchange resin: a certain amount of pretreated strong alkaline resin is added to an ethanol-water mixed solution containing a certain concentration of ferric ions and acid, and then filtered into a strong alkali solution after constant temperature oscillation in a water bath for a certain time. The filtered, water-washed, anhydrous ethanol-rinsed and dried modified anion exchange resin is obtained.

[0009] (2) Wastewater desalination treatment: a certain amount of strong acid hydrogen type cation exchange resin is added to a certain amount of wastewater, and then filtered under normal pressure after stirring at a certain speed for a certain time by using a magnetic stirrer. A certain amount of modified anion exchange resin is added to the filtered water, and then filtered under normal pressure after stirring at a certain speed for a certain time by using a magnetic stirrer. The target ion concentration, conductivity and pH of the treated water sample are detected, the removal rate of the resin to different ions is calculated, and the exchange capacity of the resin is calculated.

[0010] The above method has good practical application effect, can remove most of the salt in papermaking wastewater in an environment with other pollutants, is a new way suitable for papermaking wastewater desalination, plays an important role in wastewater recycling, and has great application potential in the field of industrial wastewater desalination.

[0011] Preferably, the ferric compound in the preparation of the modified resin is ferric citrate.

[0012] Preferably, the concentration of the ferric compound in the preparation of the modified resin is 0.1-0.3 mol / L.

[0013] Preferably, the acid in the preparation of the modified resin is a mixture of citric acid and a small amount of concentrated hydrochloric acid.

[0014] Preferably, the concentration of the acid in the preparation of the modified resin is 0.5-2 mol / L.

[0015] Preferably, the ratio of the ethanol-water mixture in the preparation of the modified resin is 3:7-3:2.

[0016] Preferably, the temperature of the water bath constant temperature oscillation reaction in the preparation of the modified resin is 30-60°C.

[0017] Preferably, the time of the water bath constant temperature oscillation reaction in the preparation of the modified resin is 18-26 h.

[0018] Preferably, the temperature of the drying in the preparation of the modified resin is 30-60°C.

[0019] Preferably, the time of the drying in the preparation of the modified resin is 8-24 h.

[0020] Preferably, the optimal dosing ratio of the resin in the desalination treatment of wastewater is 732 hydrogen type cation exchange resin: modified 201x7 hydrogen-oxygen type anion exchange resin is 1:1.

[0021] Preferably, the speed of the magnetic stirrer in the desalination treatment of wastewater is 300-1500 rpm.

[0022] Preferably, the exchange time in the desalination treatment of wastewater is 20-60 min.

[0023] The modified 201x7 hydrogen-oxygen type anion exchange resin prepared by the above method is a spherical particle with hydroxyl iron oxide loaded on the surface, and the iron loading is not less than 4%.

[0024] The modified 201x7 hydrogen-oxygen type anion exchange resin prepared by the above method has a significantly increased removal rate of sulfate ions and basically unchanged removal rate of chloride ions compared to the original ion exchange resin, and no iron is dissolved out during the exchange process, and the regeneration efficiency is improved. Compared with the combination of the modified and unmodified anion exchange resins, the total salt removal rate of the modified resin is significantly improved under the same resin dosage, and the improvement effect increases with the increase of the concentration of sulfate ions in the solution.

[0025] The application includes but is not limited to using the modified anion exchange resin to remove salt from papermaking wastewater.

[0026] Compared with the prior art, the application has the following advantages and beneficial effects:

[0027] (1) The method for removing salt in papermaking wastewater by using the double ion exchange resin can efficiently, stably and quickly exchange cations and anions in the papermaking wastewater, and has important significance for wastewater recycling and reducing environmental burden under the background of the national sustainable development.

[0028] (2) The method for removing salt in papermaking wastewater by using the double ion exchange resin has wide applicability in wastewater desalination, is suitable for desalination and reuse of most papermaking industrial wastewater, has simple equipment, easy operation and practical application value.

[0029] (3) The modified 201x7 hydrogen type anion exchange resin has higher sulfate exchange effect, no iron ion leaching, no increase of external ions, and remarkable improvement of removal effect of sulfate ions and anions with similar structures in wastewater, which is beneficial to saving investment cost and improving economic benefits in practical application.

[0030] (4) The modified 201x7 hydrogen type material has excellent regeneration effect, can be used repeatedly, and is simple to regenerate, and has great application prospect in the field of wastewater desalination. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Effect diagram of exchange of sulfate ions by the 201x7 hydrogen type anion exchange resin before and after modification in Example 3.

[0032] Figure 2 Effect diagram of exchange of chloride ions by the 201x7 hydrogen type anion exchange resin before and after modification in Example 4.

[0033] Figure 3 Effect diagram of exchange of sulfate ions by the 201x7 hydrogen type anion exchange resin before and after modification in Example 5.

[0034] Figure 4 Effect diagram of exchange of chloride ions by the 201x7 hydrogen type anion exchange resin before and after modification in Example 5.

[0035] Figure 5 Effect diagram of TDS of effluent water treated by the 201x7 hydrogen type anion exchange resin before and after modification in Example 5.

[0036] Figure 6 Effect diagram of regeneration rate of the 201x7 hydrogen type anion exchange resin before and after modification in Example 6. DETAILED DESCRIPTION

[0037] The specific embodiments of the present application are further described below. It is to be understood that the embodiments described are illustrative of the principles of the present application and are not intended to limit the scope thereof. Furthermore, the various embodiments of the present application described below are not intended to be mutually exclusive, unless otherwise specifically noted.

[0038] Example 1

[0039] The present application provides a preparation method of modified 201x7 hydroxyl type anion exchange resin, comprising the following steps:

[0040] (1) 20g of wet 201x7 hydroxyl type ion exchange resin is weighed and soaked in 50mL of 1.5M HCl solution for 8h, then the resin is filtered and washed with deionized water until it is close to neutral, and then soaked in 50mL of 1M NaOH for 8h, and then the resin is filtered and washed with deionized water until it is close to neutral to remove the impurities and acid residues on the resin, and then the resin is dehydrated by centrifugation and dried at 45℃ for standby.

[0041] (2) 4g of the pretreated resin in step (1), 4.4g of iron citrate, 9g of citric acid, 1mL of concentrated hydrochloric acid, 30mL of ethanol, and 70mL of deionized water are mixed uniformly, and then reacted in a 45℃ 60rpm water bath constant temperature oscillator for 24h, and then filtered to obtain Fe 3+ impregnated 201x7 resin;

[0042] (3) The Fe 3+ impregnated 201x7 resin in step (2) is added to 100mL of 2M sodium hydroxide, and then reacted in a 45℃ 60rpm water bath constant temperature oscillator for 24h, and then the reacted resin is filtered, washed with water until it is close to neutral, rinsed with 20mL of ethanol, and then dried in an electric heating air drying oven at 45℃ for 12h to obtain modified 201x7 hydroxyl type anion exchange resin.

[0043] Example 2

[0044] The present application provides a preparation method of modified 201x7 hydroxyl type anion exchange resin, comprising the following steps:

[0045] (1) 20g of wet 201x7 hydroxyl type ion exchange resin is weighed and soaked in 50mL of 1.5M HCl solution for 8h, then the resin is filtered and washed with deionized water until it is close to neutral, and then soaked in 50mL of 1M NaOH for 8h, and then the resin is filtered and washed with deionized water until it is close to neutral to remove the impurities and acid residues on the resin, and then the resin is dehydrated by centrifugation and dried at 45℃ for standby.

[0046] (2) Take 4 g of the resin pretreated in step (1), 4.4 g of ferric citrate, 10 g of citric acid, 1 mL of concentrated hydrochloric acid, 50 mL of ethanol, and 50 mL of deionized water, mix them uniformly, and react in a 30°C 120 rpm water bath constant temperature oscillator for 24 h, filter, and obtain Fe 3+ impregnated 201 x 7 resin;

[0047] (3) The Fe 3+ impregnated 201 x 7 resin in step (2) is added to 100 mL of 2M sodium hydroxide, reacted in a 30°C 120 rpm water bath constant temperature oscillator for 24 h, the resin after reaction is filtered, washed with water until nearly neutral, rinsed with 20 mL of ethanol, and dried in an electric heating air drying oven at 45°C for 12 h to obtain modified 201 x 7 hydrogen type anion exchange resin.

[0048] Example 3

[0049] To further analyze the modification effect of the modified 201 x 7 hydrogen type anion exchange resin in Example 1, sodium sulfate and deionized water are used to configure sulfate ion standard gradient solutions of 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L, and 5000 mg / L, 100 mL of the prepared solution is added to 1 g of unmodified 201 x 7 hydrogen type ion exchange resin and modified 201 x 7 hydrogen type ion exchange resin respectively, stirred by a magnetic stirrer at 500 rpm for 20 min, filtered, and the sulfate content of the obtained solution is measured by EDTA indirect titration method, the results are shown in Table 1. Figure 1 As shown in Table 1, the exchange capacity of the modified resin for sulfate ions is enhanced, the higher the concentration of sulfate ions, the more obvious the effect, and the maximum exchange capacity is increased by 16% compared with the original resin.

[0050] Example 4

[0051] To further analyze the modification effect of the modified 201 x 7 hydrogen type anion exchange resin in Example 1, sodium chloride and deionized water are used to configure chloride ion standard gradient solutions of 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L, and 5000 mg / L, 100 mL of the prepared solution is added to 1 g of unmodified 201 x 7 hydrogen type ion exchange resin and modified 201 x 7 hydrogen type ion exchange resin respectively, stirred by a magnetic stirrer at 500 rpm for 20 min, filtered, and the chloride content of the obtained solution is measured by silver nitrate titration method, the results are shown in Table 2. Figure 2 As shown in Table 2, the exchange capacity of the modified resin for chloride ions is basically unchanged, and under the condition of increasing chloride ion concentration, the exchange capacity for chloride ions is slightly improved.

[0052] Example 5

[0053] To further analyze the modification effect of the modified 201 x 7 hydroxide type anion exchange resin in Example 1, standard gradient solutions with chloride ion concentration:sulfate ion concentration of 1:4, 1:2, 1:1, 2:1, and 4:1 were prepared using sodium chloride, sodium sulfate, and deionized water. 100 mL of each prepared solution was added to 1 g of unmodified 201 x 7 hydroxide type ion exchange resin and modified 201 x 7 hydroxide type ion exchange resin, respectively. The mixture was stirred at 500 rpm for 20 min using a magnetic stirrer, filtered, and the sulfate ion and chloride ion contents of the obtained solution were measured by silver nitrate titration. The results are shown in Table 1. Figure 3 、 Figure 4 、 Figure 5 As shown in Table 1, under the coexistence of sulfate ions and chloride ions, both the modified and unmodified resins first exchanged sulfate ions. Compared to the original resin, the modified resin had an increased exchange capacity for sulfate ions and an unchanged exchange capacity for chloride ions. In combination, the TDS of the solution decreased. The higher the ratio of sulfate ions to chloride ions, the more obvious the decrease in TDS. When the chloride ion concentration:sulfate ion concentration was 1:4, the ability of the modified resin to reduce the TDS of the solution increased by 15%.

[0054] Example 6

[0055] To further analyze the regeneration effect of the modified 201 x 7 hydroxide type anion exchange resin material in Example 1, 10 g of saturated exchanged original 201 x 7 hydroxide type anion exchange resin and modified 201 x 7 hydroxide type anion exchange resin were placed in 50 mL of 0.1 M acetic acid solution in a 30°C water bath for 12 h. The filtered resin was then placed in 50 mL of 1 M sodium hydroxide solution in a 30°C water bath for 12 h. The filtered resin was washed until it was nearly neutral, dried at 45°C for 12 h, and obtained as regenerated resin. The regenerated resin was used to treat the solution with a chloride ion:sulfate ion ratio of 1:4 in the static exchange treatment experiment. The ion removal rates before and after regeneration were compared, the regeneration rate was calculated, and the regeneration effect of the resin before and after modification was evaluated by repeating the cycle five times. The results are shown in Table 2. Figure 6 As shown in Table 2, the five-time regeneration rate of the modified 201 x 7 hydroxide type anion exchange resin remained above 90%, which was 3% to 5% higher than that of the original resin.

[0056] Example 7

[0057] To further analyze the desalination effect of the modified 201x7 hydroxyl type anion exchange resin material combined with the cation resin in Example 1, a mixed solution containing 324 mg / L of calcium ions, 20 mg / L of magnesium ions, 972 mg / L of sodium ions, 2108 mg / L of sulfate ions, and 576 mg / L of chloride ions was prepared by dissolving 0.9 g of calcium chloride, 3 g of sodium sulfate, and 0.1 g of magnesium sulfate in 1 L of deionized water. 200 mL of the solution was added to 2.4 g of 732 hydroxyl type cation resin, and stirred at 500 rpm for 20 min using a magnetic stirrer. The filtered solution was divided into two equal parts, one of which was added with 1.4 g of 201x7 hydroxyl type anion exchange resin, and the other was added with 1.4 g of modified 201x7 hydroxyl type anion exchange resin. The solutions were stirred at 500 rpm for 20 min using a magnetic stirrer, and the ion content of the filtered solutions was measured to calculate the total salt content (TDS). The results are shown in Table 1. After the combined treatment of the ion exchange resins, the content of each ion in the solution was significantly reduced. The cation exchange resin removed the calcium and magnesium ions and most of the sodium ions in the solution, and the exchange order was Mg 2+ , Ca 2+ , Na + The removal rate of sulfate ions by the modified 201x7 resin was 13.4% higher than that of the original resin, and the removal rate of chloride ions remained basically unchanged. The TDS of the solution decreased by 9%.

[0058] Table 1 Ion concentration of simulated wastewater effluent

[0059]

[0060] Application Example 1

[0061] To further analyze the desalination effect of the modified 201x7 hydrogen-oxygen type anion exchange resin material combined with 732 hydrogen type cation resin in Example 1, the advanced oxidation effluent of a papermaking enterprise was desalinated, and its physicochemical properties are shown in Table 2. The enterprise added various papermaking additives during production and the wastewater was recycled after treatment, so there were more calcium ions, sodium ions, a small amount of magnesium ions and iron ions in the wastewater, and the anions were mainly sulfate ions and chloride ions. 200 mL of the wastewater was added to 2.4 g of 732 hydrogen type cation resin, and the mixture was stirred at 500 rpm for 20 min by a magnetic stirrer. The filtered solution was divided into two equal parts, one was added with 1.4 g of 201x7 hydrogen-oxygen type anion exchange resin, and the other was added with 1.4 g of modified 201x7 hydrogen-oxygen type anion exchange resin. The mixture was stirred at 500 rpm for 20 min by a magnetic stirrer, and the ion content, electric, and total salt content (TDS) of the filtered solution were measured. The results are shown in Table 3. After the ion exchange resin treatment, the main ion content in the papermaking industrial wastewater was greatly reduced, and the desalination effect was obvious. Compared with the original resin, the removal rate of sulfate in the wastewater increased by 12.3% after the modification of the resin, and the desalination effect was 7% higher than that of the original resin, which had practical application value.

[0062] Table 2 Ion content in advanced oxidation effluent

[0063]

[0064] Table 3 Ion concentration of actual wastewater effluent

[0065]

Claims

1. A method for removing salts from papermaking wastewater by using a modified dual ion exchange resin, characterized in that, It comprises the following steps: (1) ethanol impregnation of Fe 3+ : The pretreated 201x7 hydroxyl type anion exchange resin is weighed and added to a mixed solution of ethanol and water containing 0.1-0.3 M ferric citrate, 1-3 M citric acid, and 0-0.5 M concentrated hydrochloric acid, and reacted in a water bath constant temperature oscillator, and filtered; the addition amount of the pretreated 201x7 hydroxyl type anion exchange resin is 2-4 g; the volume of the mixed solution is 100-200 mL; the volume ratio of the ethanol and water is 3:7-3:2; the water bath temperature in the water bath constant temperature oscillator is 30-60°C, and the rotation speed is 60-150 rpm; the reaction time is 18-24 h; (2) loading hydroxyl iron oxide: the resin obtained in step (1) is added to a 1-2 M strong alkali solution, and the reaction is carried out in a water bath constant temperature oscillator, the resin after the reaction is filtered, washed with water until it is close to neutral, rinsed with anhydrous ethanol, and then dried to obtain modified 201x7 hydrogen oxygen type anion exchange resin; the water bath temperature of the water bath constant temperature oscillator is 30-60℃, and the rotation speed is 60-150 rpm; the reaction time is 18-24 h; the drying is carried out in an electric heating air drying oven at 30-60℃ for 8-24 h; (3) desalination by combination of cation and anion resins: 732 hydrogen type cation exchange resin is added to wastewater, stirred, and then filtered at normal pressure; the filtered water is added with modified 201x7 hydrogen oxygen type anion exchange resin, stirred, and then filtered at normal pressure; the treated water sample is detected for target ion concentration, conductivity, and pH, the removal rate of the resin for different ions is calculated, and the exchange capacity of the resin is calculated; In step (2), the strong alkali solution is one of sodium hydroxide and potassium hydroxide; In step (3), the wastewater is simulated wastewater or actual papermaking wastewater.

2. The method of claim 1, wherein the modified dual ion exchange resin is used to remove salt from papermaking wastewater. In step (3), the stirring is carried out by using a magnetic stirrer at a rotation speed of 300-1500 rpm for 20-60 min.

3. The method of claim 1, wherein the modified dual ion exchange resin is used to remove salt from papermaking wastewater. The optimal reaction time of the desalination by combination of cation and anion resins is 20 min, and the optimal mass ratio of 732 hydrogen type cation exchange resin to 201x7 hydrogen oxygen type anion exchange resin is 1:1.

Images