Preparation method and application of pickling corrosion inhibitor based on bamboo pulp papermaking black liquor

Abstract

The application discloses an acid pickling corrosion inhibitor prepared based on bamboo pulp papermaking black liquor, and a preparation method and application thereof, and relates to the technical field of acid pickling corrosion inhibitors. The method comprises the following steps: (1) adding concentrated sulfuric acid into the bamboo pulp papermaking black liquor, adjusting the pH value of the solution to 1-3, and then fully reacting, standing and settling, and separating to obtain a precipitate A and a filtrate A; the precipitate A is washed and dried to obtain lignin; (2) the filtrate A is concentrated through multi-effect vacuum reduced pressure evaporation to obtain a precipitate B; (3) the precipitate B is extracted through sewage ethanol extraction, suction filtration and washing to obtain an ethanol extraction liquid and a precipitate C; the ethanol extraction liquid is distilled through reduced pressure distillation to obtain an ethanol extraction liquid; the precipitate C is recrystallized, and after removing solid inorganic salts, the precipitate C is distilled through reduced pressure distillation to obtain a distillation liquid; the ethanol extraction liquid and the distillation liquid are mixed, and then evaporated through reduced pressure evaporation and dried to obtain the acid pickling corrosion inhibitor.

Description

Technical Field

[0001] This invention belongs to the field of resource utilization technology, and specifically relates to an acid pickling corrosion inhibitor prepared from bamboo pulp papermaking black liquor, its preparation method and application. Background Technology

[0002] Wastewater from the alkaline pulping process (caustic soda process and sulfate process) in the papermaking industry contains a large amount of lignin, giving it a dark brown color, hence the name black liquor. Black liquor contains a large amount of suspended solids, organic pollutants, and toxic substances, and direct discharge into water bodies will cause serious pollution. Its main hazards include: papermaking wastewater containing large amounts of fiber, pigments, and inorganic salts will turn water bodies black and give them a distinctive foul odor; the biochemical oxygen demand (BOD) of papermaking black liquor containing high concentrations of organic pollutants can reach 5000-40000 g / L, which will consume a large amount of dissolved oxygen in the water and affect water quality; the large amount of alkaline substances in black liquor will cause the pH value of water bodies to rise sharply, disrupting the balance of the aquatic environment. Wastewater from the papermaking industry accounts for approximately 10% of the total industrial wastewater in China, and its pollution of my country's water resources is becoming increasingly serious.

[0003] Improving the resource utilization of papermaking black liquor has been a research hotspot in recent years. For example, invention patent CN1203297A discloses a process for recovering alkali from papermaking black liquor. First, the black liquor is concentrated. Then, white mud and lime are mixed with the solid black liquor. The mixture is sprayed into a spray dryer for drying. The dried powder is then granulated in a disc granulator using the black liquor as a binder. The granulated mixture is then fed into a fluidized bed combustion furnace for combustion and reaction. The reaction products are discharged into a dissolving tank for causticization. Although this process recovers alkali from the black liquor, its operating conditions are harsh, and its cost is high, making large-scale promotion difficult. Invention patent CN1068867A discloses a method for treating papermaking black liquor. This method recovers lignin through acidification, obtains barium sulfate through sulfate conversion, and recovers alkali through causticization treatment with sodium carbonate and lime milk. Although this process recovers lignin and utilizes its sulfate ions, it does not consider the low molecular weight organic matter in the black liquor. If recycled, this will inevitably affect subsequent processes. Meanwhile, this process uses sodium carbonate and lime slurry for causticization, which is costly and generates a large amount of waste calcium carbonate containing organic matter, including the aforementioned barium sulfate, all of which require further purification or treatment. Practical applications will face numerous challenges. Therefore, the pollution-free resource utilization of papermaking black liquor has always been a difficult problem hindering the development of the papermaking industry.

[0004] Corrosion inhibitors are agents (chemical substances or compounds) that can effectively mitigate metal corrosion. They are generally added to the environment in which the metal is located to protect it. Corrosion inhibitors used in industrial circulating cooling systems for carbon steel are complex and can be classified into inorganic, organic, and composite corrosion inhibitors based on their chemical composition. Single inorganic salt corrosion inhibitors are used in large quantities in seawater. Although some inhibitors are effective, they cause varying degrees of environmental damage, such as chromates. Single organic compounds have low corrosion inhibition efficiency in seawater, and their high cost limits their further promotion and large-scale use. Natural corrosion inhibitors, while easily biodegradable and non-toxic, generally have low corrosion inhibition efficiency, require large quantities, and have complex compositions. Studies have found that papermaking black liquor contains a large amount of suspended solids and organic pollutants. Approximately 30-35% is inorganic, mainly composed of sodium hydroxide, sodium carbonate, sodium sulfide, sodium sulfate, and other sodium salts combined with organic matter. It also contains 65-70% organic matter, primarily lignin, resin, starch, and low-molecular-weight compounds. Recycling and utilizing the substances in papermaking black liquor not only reduces resource waste but also mitigates environmental pollution during emissions, which is of significant practical importance for maintaining sustainable industrial and agricultural development. For example, invention patent CN86104445A discloses a corrosion inhibitor for preventing steel corrosion, containing 0.4-6% (by weight) of plant extracts. These plant extracts are acid precipitates, essentially non-water-soluble macromolecular compounds of lignin, requiring neutralization with alkali. The resulting corrosion inhibitor is suitable for use under neutral, weakly acidic (pH 1-5), and weakly alkaline conditions. It will redeprecipitate in strongly acidic solutions, thus limiting its application range. Corrosion inhibitors are highly selective; different corrosion inhibitors are often used for different solution systems. Currently, there are no reports on the preparation of corrosion inhibitors suitable for strong acid environments using papermaking black liquor. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide an acid pickling corrosion inhibitor prepared from bamboo pulp papermaking black liquor, its preparation method and application. This invention can extract the acid pickling corrosion inhibitor from bamboo pulp papermaking black liquor, realizing the resource utilization and near-zero emission of bamboo pulp papermaking black liquor.

[0006] The technical solution of this invention is implemented as follows:

[0007] A method for preparing an acid pickling corrosion inhibitor based on bamboo pulp papermaking black liquor specifically includes the following steps:

[0008] (1) Add concentrated sulfuric acid to the black liquor of bamboo pulp papermaking, adjust the pH value of the solution to 1-3, and after the reaction is complete, let it stand to settle and separate to obtain precipitate A and filtrate A. The precipitate A is washed and dried to obtain lignin.

[0009] (2) The filtrate A was concentrated by multi-effect vacuum evaporation to obtain precipitate B;

[0010] (3) The precipitate B is extracted with ethanol from sewage, filtered and washed to obtain ethanol extract and precipitate C. The ethanol extract is distilled under reduced pressure to obtain ethanol extract. The precipitate C is recrystallized to remove solid inorganic salts and then distilled under reduced pressure to obtain distillate. The ethanol extract and distillate are mixed, evaporated under reduced pressure and dried to obtain the pickling corrosion inhibitor.

[0011] The aforementioned pickling corrosion inhibitor, prepared from bamboo pulp black liquor, is applied in acidic solution environments during steel pickling and oil and gas acidizing.

[0012] Furthermore, the acidic solution is an aqueous solution of sulfuric acid, hydrochloric acid, or nitric acid, and the concentration of the acidic solution is 0.1–6 mol / L.

[0013] Furthermore, the amount of pickling corrosion inhibitor added is 0.25–1.5 g / L.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. This invention uses bamboo pulp black liquor as raw material and obtains an acid-washing corrosion inhibitor through steps such as acid precipitation, anhydrous ethanol extraction, and vacuum distillation. This corrosion inhibitor requires a low dosage, exhibits excellent corrosion inhibition effect (up to 87%), and produces carbon steel samples with a smooth surface free of black spots and darkening defects after strong acid washing. The raw materials are widely available, the preparation process is environmentally friendly, and the preparation method is simple, facilitating industrial production and demonstrating promising application prospects.

[0016] 2. This invention focuses on bamboo pulp papermaking black liquor. Lignin is recovered from the black liquor through acid precipitation, followed by water recovery using multi-effect vacuum evaporation. The resulting solid is extracted with anhydrous ethanol to remove organic matter. The ethanol is then reused after vacuum distillation. The solid after ethanol extraction is recrystallized to obtain inorganic salts. The recrystallization waste liquid and the ethanol-free extract are then vacuum distilled and dried to obtain the solid extract, which is the acid etching corrosion inhibitor. The entire process generates no waste liquid, achieving resource utilization and near-zero emissions of bamboo pulp papermaking black liquor. This invention effectively improves the resource utilization of papermaking black liquor to achieve high added value, while avoiding environmental pollution and resource waste, realizing a process that turns waste into treasure. Furthermore, it is the first to propose the preparation of an acid etching corrosion inhibitor based on papermaking black liquor, providing a new approach and option for corrosion inhibitor preparation. Attached Figure Description

[0017] Figure 1 - This invention is based on a flowchart of the preparation of corrosion inhibitors using black liquor from bamboo pulp papermaking;

[0018] Figure 2- Infrared spectrum of the ethanol extract.

[0019] Figure 3 - XRD patterns of recovered inorganic salts.

[0020] Figure 4 - Polarization curves of carbon steel electrodes in 0.5 mol / L H2SO4 containing different concentrations of corrosion inhibitor at different temperatures.

[0021] Figure 5 - Electrochemical impedance spectroscopy of carbon steel electrodes in 0.5 mol / L H2SO4 containing different concentrations of corrosion inhibitor at different temperatures.

[0022] Figure 6 - Equivalent circuit diagram for fitting electrochemical impedance spectroscopy.

[0023] Figure 7-3 SEM images of carbon steel at 0℃ in 0.5mol / L H2SO4 with and without corrosion inhibitor (1.5g / L corrosion inhibitor).

[0024] Figure 8-3 Polarization curves of carbon steel electrodes at 0℃ in 2 mol / L H2SO4 and 1 mol / L HCl containing different concentrations of corrosion inhibitor. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] I. A method for preparing pickling corrosion inhibitors based on bamboo pulp papermaking black liquor, the flowchart of which is as follows: Figure 1 As shown, it specifically includes:

[0027] 1) Take 7.3L of bamboo pulp papermaking black liquor (density 1.084g / mL) and 7.92kg of wastewater. Add concentrated sulfuric acid to adjust the pH of the resulting mixed solution to 1. After the reaction is complete, allow it to stand and settle, and separate the solid and liquid to obtain precipitate and filtrate 1. Then, microfilter filtrate 1 to further remove solid suspended matter (no aggregated or low molecular weight lignin). Wash and dry the obtained precipitate and solid suspended matter to recover lignin. The obtained lignin can be used as a papermaking raw material or modified for use. At the same time, filtrate 2 is concentrated by multi-effect vacuum depressurization evaporation to recover water and obtain solid 1.

[0028] 2) The solid 1 obtained in step 1) is extracted with anhydrous ethanol, filtered and washed to obtain ethanol extract and solid 2. The ethanol extract is distilled under reduced pressure to obtain ethanol extract. The solid 2 is recrystallized to remove solid inorganic salts, and then water is recovered by reduced pressure distillation to obtain organic matter (solid 3). The ethanol extract and solid 3 are then mixed to obtain the corrosion inhibitor.

[0029] Calculations showed that 385g of lignin was obtained, with a yield of 4.86%; 22.5g of the corrosion inhibitor (a mixture of ethanol extract and solid 3) was obtained, with a yield of 0.28%; and 460g of salt was obtained by recrystallization of precipitate 2, with a yield of 5.81%. Throughout the process, water was recovered and reused, ethanol was reused, and no new waste liquid was generated, achieving resource utilization and zero-emission treatment of bamboo pulp papermaking black liquor.

[0030] 1. The ethanol extract obtained in this embodiment was subjected to infrared spectroscopy detection, and the results are as follows: Figure 2 As shown.

[0031] Depend on Figure 2 It can be seen that the ethanol extract at 1590 cm⁻¹ -1 There is a very strong absorption peak at 3390 cm⁻¹, corresponding to the bending vibration of NH in amines. -1 The absorption peak at 1410 cm⁻¹ originates from the stretching vibrations of OH and NH. -1 1356cm -1 and 1120cm -1 The absorption peaks at certain locations may be generated by CN, CO, CH, and phenyl groups. Infrared spectroscopy results of the ethanol extract of bamboo pulp papermaking black liquor indicate that the extract is an organic compound rich in N and O heteroatoms, thus possessing potential as a corrosion inhibitor.

[0032] 2. The inorganic salts recovered in this embodiment were analyzed by XRD to detect their phase composition. The results are as follows: Figure 3 As shown.

[0033] XRD patterns of the recovered inorganic salts were analyzed using standard cards, revealing that the recovered salts mainly consisted of sodium sulfate and potassium sulfate. Simultaneously, XRD analysis revealed the presence of triethylenediamine sulfate in the recovered salts. Triethylenediamine may originate from additives used in the papermaking process and is a major component of paper lubricants. Ion chromatography was used to determine the sulfate ion content in the recovered salts; after conversion to sodium sulfate, the content was 86.35%, indicating the presence of a considerable amount of potassium sulfate and triethylenediamine sulfate, or other components, in the recovered salts. Further in-depth research is needed to determine the composition and content of each component.

[0034] II. Performance study of corrosion inhibitors.

[0035] 1. At different temperatures, carbon steel electrodes were placed in 0.5 mol / L H₂SO₄ solution, and different concentrations of the corrosion inhibitor prepared in Example 1 were added. Potentiodynamic polarization curves were obtained, as shown below. Figure 4 As shown.

[0036] from Figure 4It can be seen that the addition of the corrosion inhibitor had no significant effect on the shape of the cathode and anodic branches in the polarization curves. The cathodic polarization curves were nearly parallel in the strong polarization region, indicating that the addition of the corrosion inhibitor did not change the reaction mechanism of carbon steel in 0.5 mol / L H2SO4 solution. With the increase of the corrosion inhibitor concentration, both the cathodic and anodic polarization curves shifted towards lower current densities, indicating that the addition of the corrosion inhibitor simultaneously inhibited the anodic and cathodic reactions of carbon steel in 0.5 mol / L H2SO4 solution.

[0037] right Figure 4 The polarization curves in the figure, and the corrosion electrochemical parameters obtained by extrapolation using the Tafel linear segment are shown in Table 1. The calculation formulas for the corrosion inhibition efficiency (η) are shown in Equations (1-1) and (1-2).

[0038] η icorr = (1-i corr,inh / i corr,0 )×100% (1-1)

[0039] η Rp =(1-R) p,0 / R p,inh )×100% (1-2)

[0040] In the formula: i corr,inh and i corr,0 These represent the corrosion current densities of carbon steel electrodes in solutions with added corrosion inhibitors and in blank solutions, respectively, while R... p,inh and R p,0 This is the corresponding polarization resistance.

[0041] Table 1 Electrochemical parameters of carbon steel electrodes in 0.5 mol / L H2SO4 containing different concentrations of corrosion inhibitor

[0042]

[0043] Table 1 shows that the corrosion potential of the carbon steel electrode generally shifts positively with increasing corrosion inhibitor concentration, but the shift is less than 45 mV compared to the blank solution without corrosion inhibitor. Simultaneously, it can be observed that the Tafel slope β changes before and after the addition of the corrosion inhibitor. a and β c The value did not change significantly. Therefore, the corrosion inhibitor extracted in this invention is a mixed-inhibition type corrosion inhibitor for carbon steel in 0.5 mol / L H2SO4 solution. Table 1 also shows that at the same temperature, with the increase of the corrosion inhibitor concentration, the corrosion current density (i)... corr The polarization resistance R decreases. pAs the value of increases, the corrosion inhibition efficiency increases. At the same concentration, with increasing temperature, the corrosion current density increases, the polarization resistance decreases, and the corrosion inhibition efficiency decreases. However, the corrosion inhibition efficiency of the corrosion inhibitor for carbon steel does not change significantly with temperature, indicating that the corrosion inhibitor has a good corrosion inhibition effect on carbon steel in 0.5 mol / L H2SO4 solution, and at the maximum concentration, the corrosion inhibition efficiency can reach over 87%.

[0044] 2. At different temperatures, carbon steel electrodes were placed in 0.5 mol / L H₂SO₄ solution, and different concentrations of the corrosion inhibitor prepared in Example 1 were added. Electrochemical impedance spectroscopy tests were then performed, and the results are as follows: Figure 5 As shown.

[0045] As shown in the figure, the addition of the corrosion inhibitor did not alter the shape of the impedance spectrum of carbon steel in 0.5 mol / L H2SO4 solution. It consisted of one capacitive arc and one inductive arc, indicating that the addition of the corrosion inhibitor did not change the electrochemical corrosion reaction mechanism of carbon steel in 0.5 mol / L H2SO4, which is consistent with the results of the polarization curve. The capacitive arc in the high-frequency region of the electrochemical impedance spectrum corresponds to the charge transfer process of the electric double layer and appears as an imperfect semicircle, caused by the inhomogeneity of the carbon steel electrode surface. The inductive arc in the low-frequency region is generally related to the relaxation process of the material on the electrode surface, caused by the adsorption-desorption process of the material on the electrode surface. However, after adding the corrosion inhibitor, the diameter of the capacitive arc increased, indicating that the effective components of the corrosion inhibitor inhibited the corrosion of carbon steel in H2SO4 solution. The diameter of the capacitive arc increased with increasing ethanol extract concentration, indicating that its inhibitory effect was enhanced.

[0046] right Figure 5 The electrochemical impedance spectroscopy shown utilizes... Figure 6 The equivalent circuit in the figure was fitted, and the results are given in Table 2. Where Y0 is the fitted value of the constant phase angle element (CPE), and the corrosion inhibition efficiency (η) is... Rct ) by charge transfer resistor R ct The calculation yields the following formula:

[0047] Z CPE =Y0 -1 (jω) -n (1-3)

[0048] η Rct =(1-R) ct,inh / R ct,0 )×100% (1-4)

[0049] In the formula, Y0 and n are the CPE constant and exponent, respectively, and j is the imaginary unit. 2 =1, ω is the angular frequency, R ct,inh and R ct,0These are the charge transfer resistances of the carbon steel sample in the solution with added corrosion inhibitor and in the blank solution, respectively.

[0050] Table 2 Electrochemical impedance parameters of carbon steel electrodes in 0.5 mol / L H2SO4 containing different concentrations of corrosion inhibitor

[0051]

[0052] As shown in Table 2, at the same temperature, the value of Y0 generally decreases with increasing corrosion inhibitor concentration. This indicates that the effective components in the corrosion inhibitor are adsorbed on the carbon steel surface, and the adsorption amount of the effective corrosion inhibitor increases, increasing the resistance to the reaction and thus slowing down the corrosion of carbon steel in sulfuric acid solution. The values ​​of n are all greater than 0.88 and close to 1, reflecting the capacitance characteristics of the carbon steel electrode-solution interface. Correspondingly, as shown in Table 2, with increasing corrosion inhibitor concentration, R... ct and η Rct The increase in the value indicates that the effective components in the corrosion inhibitor suppress the corrosion of carbon steel in H2SO4 solution through adsorption. Table 2 also shows that, at the same concentration, R increases with increasing temperature. ct and η Rct The decrease in the value is consistent with the results of the polarization curve. At the highest concentration, the corrosion inhibition efficiency of the inhibitor reached 92.7%, 91.4%, and 91.4% at the tested temperatures of 30℃, 40℃, and 50℃, respectively, demonstrating good corrosion inhibition performance.

[0053] 3. Weightlessness experiment and surface morphology analysis

[0054] The corrosion rate of carbon steel at 30℃ in 0.5 mol / L H₂SO₄ without corrosion inhibitor (control group) and with 1.5 g / L corrosion inhibitor (experimental group) was determined by the weight loss method. The results were 15.23 g·m⁻¹, respectively. -2 ·h -1 and 1.17 g·m -2 ·h -1 The corrosion inhibition efficiency of the inhibitor was calculated to be 92.3%, consistent with the aforementioned electrochemical test results. After the experiment, the corrosion morphology of the sample surface was tested using scanning electron microscopy (SEM), and the results are as follows: Figure 7 As shown, where Figure 7 (a) is the control group. Figure 7 (b) is the experimental group. As can be seen from the figure, the carbon steel surface in the control group was severely corroded, while the carbon steel sample surface in the experimental group showed slight corrosion and obvious corrosion inhibitor adsorption.

[0055] 4. The carbon steel electrode was completely immersed in 2 mol / L H2SO4 solution and 1 mol / L HCl solution containing different concentrations of corrosion inhibitor. Polarization curve tests were performed at 30℃, and the corrosion inhibition efficiency (η) was calculated using the aforementioned method. The results are shown in [Figure number missing]. Figure 8 The test results are listed in Table 3.

[0056] Table 3 Electrochemical parameters of carbon steel at 30℃ in 2 mol / L H2SO4 and 1 mol / L HCl containing different concentrations of corrosion inhibitors.

[0057]

[0058] As can be seen from Table 3, the corrosion inhibitor prepared by this invention can be used in high-concentration H2SO4 solutions. Comparing the data with Table 1, it can be found that the corrosion inhibitor prepared by this invention is not significantly affected by the H2SO4 concentration. Meanwhile, Table 3 and... Figure 8 It can be observed that the corrosion inhibitor prepared by this invention can also effectively inhibit the corrosion of carbon steel in HCl solution.

[0059] Finally, it should be noted that the above embodiments of the present invention are merely illustrative examples and not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for preparing an acid etching corrosion inhibitor based on bamboo pulp papermaking black liquor, characterized in that, Specifically, the following steps are included: (1) Add concentrated sulfuric acid to the black liquor of bamboo pulp papermaking, adjust the pH value of the solution to 1~3, and after the reaction is complete, let it stand to settle, and separate the solid and liquid to obtain precipitate and filtrate 1. Then, remove the solid suspended matter from filtrate 1 by microfiltration. The solid suspended matter is lignin with no aggregation or low molecular weight. The precipitate and solid suspension obtained are washed and dried to recover lignin. The obtained lignin can be used as a papermaking raw material or modified for use. Filtrate 1 is microfiltered to obtain filtrate 2. At the same time, filtrate 2 is concentrated by multi-effect vacuum depressurization evaporation to recover water and obtain solid 1. (2) The solid 1 obtained in step (1) is extracted with anhydrous ethanol, filtered and washed to obtain ethanol extract and solid 2. The ethanol extract is distilled under reduced pressure to obtain ethanol extract. The solid 2 is recrystallized to remove solid inorganic salts and then water is recovered by reduced pressure distillation to obtain organic matter, which is solid 3. The ethanol extract and solid 3 are then mixed to obtain the corrosion inhibitor.

2. An acid etching inhibitor prepared from bamboo pulp black liquor, characterized in that, The acid pickling corrosion inhibitor was prepared using the method described in claim 1, which is based on bamboo pulp papermaking black liquor.

3. The application of the pickling corrosion inhibitor prepared from bamboo pulp black liquor as described in claim 2 in acidic solution environments of steel pickling and oil and gas acidizing mining.

4. The application of the pickling corrosion inhibitor prepared from bamboo pulp papermaking black liquor according to claim 3, characterized in that, The acidic solution is an aqueous solution of sulfuric acid, hydrochloric acid, or nitric acid, and the concentration of the acidic solution is 0.1~6 mol / L.

5. The application of the pickling corrosion inhibitor prepared from bamboo pulp papermaking black liquor according to claim 3, characterized in that, The amount of pickling corrosion inhibitor added is 0.25~1.5 g / L.

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