A process for separating and purifying a mixture of hcl and nacl using chromatographic techniques

Abstract

The application discloses a process for separating and purifying a mixed solution of HCl and NaCl by using a chromatographic technique. Liquid containing HCl and NaCl is loaded into a chromatographic column containing an anion exchange resin, adsorbed, washed, desorbed, and the effluent is collected. The application uses acid retardation and ion exchange mechanism, adopts fixed bed technology, and realizes the purpose of removing NaCl and separating and purifying high-concentration HCl in one step. The whole process does not use acid and alkali, the Na content in the product liquid is lower than the ion chromatography detection limit, the yield of HCl reaches more than 95%, and the average concentration reaches more than 50%. + The application also uses ultrapure water as a desorbent, so that the product elution and resin regeneration are completed at the same time, and the process is simplified.

Description

Technical Field

[0001] This invention belongs to the field of bioseparation technology, specifically relating to a process for separating and purifying a mixed solution of HCl and NaCl using chromatographic techniques. Background Technology

[0002] The rapid development of factories has led to the generation of large amounts of wastewater. Wastewater treatment has become an urgent problem to be solved. Currently, methods for treating wastewater include acid-base neutralization, spray roasting, evaporation crystallization, ion exchange resin methods, extraction, and precipitation. Among these, resin exchange has gradually become a hot topic in recent years. In 1963, Hatch, while conducting ion retardation experiments using zwitterionic ion exchange resins, used Dowex 1×8 resin as a control. He unexpectedly discovered that Dowex 1×8, a Cl-type strongly basic anion exchange resin, could also separate HCl and its corresponding salts, and named this phenomenon "acid retardation" based on the concept of "ion retardation." [1] Liu Fuqiang et al. [2] Significant progress has been made in treating wastewater containing organic acids using macroporous adsorption resins, and the effects of temperature and initial concentration on equilibrium time and adsorption rate have been explored in depth. Acid-blocking technology for adsorbing strong acids primarily relies on the non-ion exchange of strongly basic anion exchange resins. These resins only adsorb the corresponding strong acids and do not adsorb the corresponding metal salts. Separation is achieved because of the different adsorption capacities for acids and salts. The advantage of acid-blocking is its ability to effectively separate ions, thereby achieving high-concentration recovery standards. This technology significantly improves resource utilization and reduces the amount of eluent used. Currently, the main research direction worldwide is based on the separation of high-valence ions, while research on monovalent sodium ions is limited. This patent primarily addresses some of its shortcomings, mainly studying the separation of monovalent ions using acid-blocking technology.

[0003] References:

[0004] [1]Hatch MJ, Dillon J A.Acid Retardation-Simple physical Method for Separation of Strong Acids from Their Salts[J].Ind.Eng.Chem.ProcessDes.Dev.1963,2(4):253-263.

[0005] [2] Liu Fuqiang, Chen Jinlong, Ge Junjie, et al. Adsorption kinetics of benzoic acid on adsorption resin [J]. Environmental Science and Technology, 2004, 27(6). Summary of the Invention

[0006] Purpose of the Invention: Currently, treating large quantities of high-concentration industrial waste acid containing heavy metals as industrial wastewater after neutralization is not only a waste of valuable resources but also requires large amounts of neutralizing agents such as lime, generates significant amounts of solid pollutants, and incurs high operating costs, posing a significant threat to the ecological environment. The technical problem this invention aims to solve is to address the shortcomings of existing technologies, such as cumbersome experimental processes and high energy consumption, by providing a process for separating and purifying a mixed solution of HCl and NaCl using chromatographic techniques, thereby recovering waste acid from the wastewater.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A process for separating and purifying HCl and NaCl using chromatographic technology involves loading liquids containing HCl and NaCl onto a chromatographic column containing anion exchange resin for ion exchange. Through adsorption, washing, and desorption, the eluent is collected to obtain a high concentration of HCl.

[0009] The fixed-bed column separation device used in this invention consists of a resin column packed with resin, a peristaltic pump, and an automatic collector. The entire system is divided into three steps—adsorption, washing, and desorption—by switching the mobile phase, which are switched sequentially. First, a liquid containing HCl and NaCl is loaded onto the chromatographic column containing anion exchange resin. After the resin column becomes saturated with HCl, ultrapure water is switched to wash away impurities, removing material from the interstitial spaces between the resin particles. This interstitial material mainly contains NaCl. + Cl - (a small amount of HCl and a large amount of Na) + ); wait for Na + After reduction, desorb the HCl using an ultrapure aqueous solution until the collected solution is neutral, and collect the higher concentration of HCl. When desorption is complete, the resin is completely converted to the chloride form and no regeneration operation is required. Before reuse, it can be rinsed with pure water. At this time, there are no special restrictions on the amount and flow rate of pure water. The preferred amount of pure water is 0.5 to 3 BV, and the preferred flow rate is 0.3 to 1.5 BV / h.

[0010] The pH of the liquid containing HCl and NaCl is ≤7, such as pH 1 to 6.

[0011] The liquid containing HCl and NaCl has the following characteristics: the concentration of HCl is 0.3–40 g / L, such as 0.4 g / L, 0.5 g / L, 1 g / L, 2 g / L, 5 g / L, 10 g / L, 15 g / L, 25 g / L, 30 g / L, or 35 g / L; the concentration of Na+ in the liquid containing HCl and NaCl is 0.2–90 g / L, such as 15 g / L, 20 g / L, 50 g / L, 55 g / L, 60 g / L, 70 g / L, or 85 g / L; in some embodiments, the concentration of HCl is 0.01 mol / L, and the concentration of NaCl is 0.4 mol / L, 1 mol / L, 1.5 mol / L, or 0.5 mol / L. mol / L; in some embodiments, the NaCl concentration is 0.01 mol / L, and the HCl concentrations are 0.4 mol / L, 1 mol / L, and 1.5 mol / L, respectively; in some embodiments, the concentrations of HCl and NaCl in the liquid containing HCl and NaCl are 36.5 g / L and 87.75 g / L, 36.5 g / L and 58.5 g / L, 0.365 g / L and 23.4 g / L, 0.365 g / L and 58.5 g / L, 0.365 g / L and 87.75 g / L, 0.585 g / L and 14.6 g / L, 0.585 g / L and 36.5 g / L, and 0.585 g / L and 54.75 g / L, respectively.

[0012] The anion exchange resin is a strong basic quaternary ammonium type I anion exchange resin B-6, whose main structure is a polystyrene copolymer.

[0013] The anion exchange resin B-6 has a quaternary ammonium group as its functional group, and the content of the quaternary ammonium group is 1.0-2.5 mmol / g of the anion exchange resin; the exchangeable ion of the anion exchange resin is chloride ion, the content of chloride ion is 1.0-2.5 mmol / g, and the total volume exchange capacity is ≥1.35 mmol / mL; the degree of crosslinking of the anion exchange resin is 3%-10%.

[0014] The anion exchange resin B-6 has a particle size of 0.1–0.4 mm, a water content of 45%–55%, and a wet true density of 1.03–1.18 g / cm³. 3 Specific surface area is 100-2000 m² 2 / g, pore volume is 0.51~1.33cm 3 / g, pore size is 1~200nm, mesh size is 50~150 mesh.

[0015] The loading rate is 0.3–1.5 BV / h, preferably 0.55–1.1 BV / h, and more preferably 0.8 BV / h. Preferably, the loading amount is sufficient to bring the resin to near saturation; further increasing the loading amount may cause the resin to adsorb to saturation, resulting in excessive loss of HCl and NaCl liquids in the washing solution. The saturation point (C / C0 = 1) of the breakthrough curve in the fixed-bed breakthrough experiment can be used to determine whether the resin is adsorbed to saturation. For example, the loading amount is 1.4–4.2 BV, preferably 1.6–3 BV, and more preferably 2.8 BV.

[0016] Wherein, the washing agent is water; preferably, the washing rate is 0.3 to 1.3 BV / h, such as 1.1 BV / h or 0.8 BV / h; preferably, the washing volume is 0.6 to 2 BV, such as 1.1 BV.

[0017] Wherein, the desorbent is water; preferably, the desorption rate is 0.3 to 1.3 BV / h, such as 1 BV / h or 0.8 BV / h; preferably, the amount of desorbent is 0.6 to 2 BV, such as 1 BV.

[0018] The adsorption, washing, and desorption processes described in this invention are all carried out at room temperature.

[0019] The process described in this invention achieves a HCl recovery rate of over 90%, preferably over 95%, and more preferably over 96%; the recovered HCl concentration reaches over 50% of the original concentration, such as 54% and 56%.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0021] (1) In this invention, the chromatographic separation operations are all carried out at room temperature, which greatly reduces energy consumption.

[0022] (2) The resin in this invention is easy to regenerate, can be reused, has low operating costs, and can be directly scaled up.

[0023] (3) This invention uses only a single resin column, which is simple to operate, has low equipment requirements, low energy consumption, and low environmental pollution.

[0024] (4) This invention utilizes acid retardation and ion exchange mechanisms to achieve the purpose of recovering HCl from HCl / NaCl mixture through a single chromatographic column. The NaCl content in the separated HCl is lower than the ultraviolet detection limit, that is, the purity of HCl is very high, and the recovery rate of HCl in the collected solution reaches about 95%. Attached Figure Description

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0026] Figure 1 This is a diagram of the experimental setup for the present invention.

[0027] Figure 2 This is a process flow diagram of the present invention.

[0028] Figure 3 This is the hydrochloric acid adsorption isotherm diagram of the present invention.

[0029] Figure 4 The adsorption-elution curves are for 36.5 g / L hydrochloric acid and 87.75 g / L sodium chloride.

[0030] Figure 5 The adsorption-elution curves are for 36.5 g / L hydrochloric acid and 58.5 g / L sodium chloride.

[0031] Figure 6 The adsorption-elution curves are for 98 g / L sulfuric acid and 152 g / L ferrous sulfate. Detailed Implementation

[0032] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0033] The resin B-6 described in the following examples is a strongly basic quaternary ammonium type I anion exchange resin (Cl type resin). It can be converted before use by using a mixed solution of high concentration HCl and NaCl or by directly passing it through a high concentration NaCl solution.

[0034] The detection methods and steps in the following embodiments are as follows:

[0035] (1) Hydrochloric acid in the feed solution and the recovery solution was determined by acid-base titration. The titration conditions were phenolphthalein reagent with pH = 7.2 and standard NaOH solution with a concentration of 4.108 g / L.

[0036] Detection methods and procedures at room temperature:

[0037] 1) Take 1 mL of the sample to be tested into a measuring cup and titrate it with 4.108 g / L sodium hydroxide solution.

[0038] 2) Titration endpoint: The titration endpoint is when phenolphthalein just turns red. At this point, read the volume of sodium hydroxide standard solution consumed.

[0039] Calculate the hydrochloric acid content using the following method: C H + =C NaOH ×VNaOH / V H +

[0040] (2) In the following examples, an 848 potentiometric titrator was used to measure the Cl in the stock solution. - Perform potentiometric titration.

[0041] Sodium ion detection methods and procedures:

[0042] 1) Add 28.9 g / L of standard AgNO3 solution to the measuring cup of the 848 potentiometric titrator.

[0043] 2) Take 1 mL of the sample solution to be tested into the measuring cup, add ultrapure water, insert the electrode of the 848 potentiometric titrator below the liquid surface, and read the value after the value stabilizes. The data at this time is the volume of AgNO3 consumed.

[0044] 3)C Na+ =C AgNO3 ×V AgNO3 -C H+

[0045] (3) Calculate the adsorption capacity in the static experiment using the following method:

[0046]

[0047] C0: Blank control H + concentration;

[0048] Ce: Test group H + concentration;

[0049] V: Volume added to HCl;

[0050] m: Weigh the resin.

[0051] (4) The recovery rate and average concentration of hydrochloric acid in the dynamic adsorption test were calculated using the following method.

[0052]

[0053]

[0054] Example 1: Static shake-flask test of resin's effect on H + Adsorption isotherm diagram.

[0055] Weigh 4g of B-6 resin into a conical flask, making a total of 10 flasks and dividing them into 5 groups. Each group has 2 parallel experiments plus a control group. Add 15ml of HCl solutions with concentrations of 7.3, 14.6, 21.9, 29.2, and 36.5 g / L to each group respectively. A blank control sample is retained for each group. After preparing the reagents, place the flask on a shaker at 120 rpm and 25℃. After 12 hours, remove the flask and take the supernatant to measure the H2O. + The concentration was calculated and plotted. Figure 3 This indicates that the resin has the ability to adsorb HCl.

[0056] Example 2: Preparation of NaCl / HCl mixed solution

[0057] The NaCl / HCl mixed solution was prepared in the laboratory, and two batches of NaCl / HCl mixed solutions with different concentrations were prepared.

[0058] The first batch of mixed solution had a concentration of 36.5 g / L HCl + 87.75 g / L NaCl, and was prepared in 200 mL.

[0059] The concentration of the second batch of mixed solution was 36.5 g / L HCl + 58.5 g / L NaCl, and 200 mL was prepared.

[0060] Example 3: Dynamic adsorption test.

[0061] Adopting such Figure 1 The separation system shown (fixed bed column separation device) includes a feed tank 1, a constant flow pump 2, an iron stand 3, a glass-jacketed resin column 4, an automatic collector 5, and a constant temperature water bath (room temperature) 6 for separation. The resin column is filled with 80g of resin (B-6), with a diameter of 3.2cm and a height of 28cm.

[0062] like Figure 2 As shown, the entire system is divided into three steps—adsorption, washing, and desorption—by switching the mobile phase. One tube of recovered liquid is collected every ten minutes at the outlet of the automatic distribution collector.

[0063] The process was repeated sequentially. First, the NaCl / HCl mixed solution from Example 2 was loaded onto the column at a volume of 2.1 BV and a loading rate of 0.8 BV / h, and the solution was collected for 150 min. Then, pure water was used for washing, with a washing volume of 1.1 BV and a washing rate of 0.8 BV / h, and the solution was collected for another 80 min. Next, water was introduced for desorption, with a desorption volume of 1 BV and a desorption rate of 0.8 BV / h, and the desorbed HCl was collected.

[0064] After desorption is complete, the NaCl and HCl in the resin column gaps are washed away with 1 BV of pure water at a flow rate of 0.6 BV / h. Finally, the resin is completely converted to the chloride form.

[0065] The HCl concentration in the collected product effluent was determined by acid-base titration. The calculated hydrochloric acid yields for the first and second batches of the mixture were 97.8% and 96.9%, respectively, with average concentrations reaching 54% and 56% of the original concentrations. A graph was then plotted. Figure 4 and Figure 5 .

[0066] Example 4

[0067] Similar to Example 2, multiple different NaCl / HCl mixed solutions were prepared.

[0068] Low-concentration acid group: Three groups of solutions were prepared with HCl concentration fixed at 0.365 g / L and NaCl concentrations of 23.4 g / L, 58.5 g / L, and 87.75 g / L, respectively.

[0069] Low-concentration salt group: Three groups of solutions were prepared with NaCl concentration fixed at 0.585 g / L and HCl concentrations of 14.6 g / L, 36.5 g / L, and 54.75 g / L, respectively.

[0070] The above six groups of solutions were tested according to the method in Example 3. The calculated yields of HCl were all above 95%, and the Na+ content in the desorbate was low. + The results were below the testing standard, verifying that the resin can separate NaCl / HCl mixed solutions at different concentration ratios, indicating that the resin has a strong adsorption capacity for acids.

[0071] Comparative Example 1

[0072] Similar to Example 3, using a mixed solution of 36.5 g / L hydrochloric acid and 87.75 g / L sodium chloride, and under the same conditions of injection volume, flow rate, and time, the Cl-type strong basic anion exchange resin was replaced with the weak anion exchange resin Dow-TM WBA and the strong cation exchange resin POROS XS. The measured HCl concentration and recovery yield during the analysis stage were both low, indicating that the separation effect of these two resins was not good and could not obtain HCl with high purity.

[0073] Comparative Example 2

[0074] Inject the sample using a mixed solution of 98 g / L sulfuric acid and 152 g / L ferrous sulfate, such as... Figure 6 As shown, there is a tailing phenomenon, which means that subsequent acid washing is not clean. Severe acid tailing will cause serious waste of eluent, and a large amount of eluent will result in low recovered acid concentration.

[0075] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A process for separating and purifying HCl and NaCl using chromatographic techniques, characterized in that, The liquid containing HCl and NaCl was loaded onto a chromatographic column containing anion exchange resin for adsorption, washing, and desorption, and the eluent was collected. Wherein, the pH of the liquid containing HCl and NaCl is ≤7; the concentration of HCl in the liquid containing HCl and NaCl is 0.3~40g / L, and the concentration of NaCl is... + The concentration is 0.2~90g / L; The anion exchange resin is a strongly basic quaternary ammonium type I anion exchange resin, with a main structure of polystyrene copolymer and functional groups of quaternary ammonium groups, the content of which is 1.0~2.5 mmol / g anion exchange resin; the exchangeable ion of the anion exchange resin is chloride ion, the chloride ion content is 1.0~2.5 mmol / g, and the total volume exchange capacity is ≥1.35 mmol / mL; the degree of crosslinking of the anion exchange resin is 3%~10%; the particle size of the anion exchange resin is 0.1~0.4 mm, the water content is 45%~55%, and the wet true density is 1.03~1.18 g / cm³. 3 Specific surface area is 100~2000 m² 2 / g, pore volume 0.51~1.33cm 3 / g, pore size 1~200nm, mesh size 50~150 mesh; The sample loading rate is 0.3~1.5 BV / h; the sample loading amount is 1.4-4.2 BV; the washing agent is water; the washing rate is 0.3~1.3 BV / h; the washing volume is 0.6~2 BV; the desorption agent is water; the desorption rate is 0.3~1.3 BV / h; the amount of desorption agent is 0.6~2 BV. The recovery rate of HCl is over 90%.

2. The process according to claim 1, characterized in that, The loading rate is 0.55-1.1 BV / h.

3. The process according to claim 1, characterized in that, The loading rate was 0.8 BV / h.

4. The process according to claim 1, characterized in that, The sample loading amount is 2.6-3 BV.

5. The process according to claim 1, characterized in that, The sample loading volume was 2.8 BV.

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