Improved synthesis method of insoluble humic acid and environmental application of insoluble humic acid
By using no-water calcination to produce insoluble humic acid, the method addresses inefficiencies and high solubility issues in existing methods, achieving low-cost, stable, and effective humic acid production for metal ion separation and carbon fixation.
Patent Information
- Application Number
- CN202510438780.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-09
- Publication Date
- 2025-07-15
AI Technical Summary
In the prior art, Huminic acid has high solubility in a natural environment, which makes it difficult to separate from the reaction system of key elements. The traditional synthesis method is costly and inefficient, making it difficult to achieve large-scale production and maintain low solubility in an alkaline environment.
The anhydrous firing process is used to replace the traditional CaCl2-assisted firing method, and insoluble huriac acid is prepared by multi-step centrifugation and pH adjustment, reducing its solubility and improving environmental stability, and is used for the adsorption and fixation of heavy metal Zn2+.
It significantly reduces the solubility of Huminic acid to below 0.2%, achieves stability within the entire environmental pH range, reduces preparation costs, and improves the adsorption and fixation effect of heavy metals, which is suitable for large-scale production and environmental restoration applications.
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Figure CN120305939A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of material adsorption, and particularly to an improved synthesis method of insoluble humic acid and its environmental application. Background Art
[0002] Humic acid is an important component of organic matter in the earth's surface system, controlling the epigeochemical cycle of trace key elements and their isotopes. The research on the interfacial reaction mechanism between humic acid and key elements is the scientific basis for understanding the global carbon cycle, the law of heavy metal migration and transformation, and the paleoenvironmental tracing of metal stable isotopes. At the same time, as a natural green negative carbon material, humic acid can effectively fix heavy metal ions through adsorption, thereby reducing their bioavailability and environmental risks. However, humic acid has high solubility in natural environments, resulting in difficulty in separating complexed metal ions and free ionic metal ions in the humic acid-key element reaction system, severely restricting the research of related theories and the development of negative carbon remediation technologies.
[0003] Converting dissolved humic acid into insoluble (particulate) form is an effective strategy for separating the reaction products of humic acid and key metal ions. The traditional methods recorded in the literature usually use rapid heating condensation for 1 h. Although it can reduce the solubility of humic acid to a certain extent and achieve a certain degree of granulation, there are defects such as vague technical details, low synthesis efficiency, unsatisfactory synthesis effect, and a product solubility as high as 22% under the condition of pH 10. The previous patent (application number 2024117995877) clarified the preparation details of particulate humic acid by heating condensation and made improvements. By extending the synthesis time, the product solubility was reduced to 2%. However, there are still two significant defects: (1) In the second step of this method, a large amount of CaCl2 is required (at least 22 g of solid CaCl2 is needed to prepare 10 g of particulate humic acid), resulting in high costs and difficulty in large-scale production; (2) The generated humic acid still has a solubility of 2% in an alkaline environment (such as pH = 10).
[0004] Therefore, the present invention proposes a preparation method of insoluble humic acid that has the advantages of low cost, is more suitable for mass production, and has lower solubility in an alkaline environment. Summary of the Invention
[0005] Aiming at the problems of high solubility of hydrothermally synthesized particulate humic acid and waste of CaCl2 usage in the prior art, the present invention proposes an improved synthesis method of insoluble humic acid. By adopting an anhydrous firing process instead of the traditional CaCl2-assisted firing method, while reducing the preparation cost, it significantly improves the insolubility and environmental stability of the product, and finally obtains a product with enhanced adsorption and fixation effect on heavy metal Zn 2+ The method can serve both the research on interfacial adsorption theory and the development of negative carbon remediation technologies for heavy metal pollution.
[0006] To achieve the above object, the present invention provides the following technical solutions:
[0007] An improved synthesis method of insoluble humic acid, comprising the following steps:
[0008] S1. Place natural humic acid in 0.1M NaOH solution, stir well for 15 min to dissolve it, put the reacted suspension into a centrifuge, use the centrifuge to centrifuge, and collect the supernatant;
[0009] S2. Adjust the collected supernatant to pH = 1 with 6M hydrochloric acid. At this time, black humic acid solid precipitates from the solution. Transfer the suspension with pH = 1 to a centrifuge tube, use the centrifuge to centrifuge, collect the centrifuged solid, disperse the collected solid in ultrapure water, use the centrifuge to centrifuge again, pour off the supernatant, repeat this step 5 times to wash away residual impurity ions, and finally collect the solid and put it into an oven, dry it at 75 °C to obtain pure humic acid powder;
[0010] S3. Directly put the pure humic acid powder obtained in step S2 into a muffle furnace, calcine it anhydrously at 330 °C for 6 h to promote its condensation and fixation. After the calcination is completed, collect the solid substance, disperse the solid substance in ultrapure water, adjust the suspension to pH = 8, stir at room temperature for 48 h and stand for 12 h, remove the overlying solution to remove slightly soluble humic acid; disperse the obtained humic acid solid in ultrapure water, use the centrifuge to centrifuge, separate and collect the solid, repeat this step 3 times to remove residual slightly soluble humic acid, and finally freeze-dry to obtain a solid, thus obtaining the product.
[0011] The insoluble humic acid synthesized by the above anhydrous calcination is applied to adsorb and fix heavy metal Zn 2+ .
[0012] Further, after collecting the supernatant in step S1, centrifuge again and collect the supernatant to ensure sufficient separation of humic acid and impurities.
[0013] Further, in steps S1 and S4, the centrifuge centrifuges at 10740×g for 10 min, and in step S2, the centrifuge centrifuges at 4650×g for 10 min.
[0014] Compared with the prior art (application number 2024117995877), the present invention has the following advantages:
[0015] (1) Adopting the anhydrous calcination technology, the solubility of humic acid is significantly reduced from 2% to below 0.2%, realizing stability under the full environmental pH conditions (pH = 5 - 10).
[0016] (2) Abandon the operation of using CaCl2 solution as the firing medium in the patent (application number 2024117995877). By heating pure humic acid powder without water, the preparation cost is reduced, the process flow is simplified, and large-scale preparation is facilitated.
[0017] (3) Avoid high-temperature and high-pressure operations and the use of toxic and harmful reagents throughout the process, which is an environmentally friendly technology. Description of the Drawings
[0018] Figure 1 It is the flow chart of the preparation process of the present invention;
[0019] Figure 2 It is the dissolution effect diagram of humic acid before and after the preparation of the present invention;
[0020] Figure 3 Solubility diagram of the insoluble humic acid prepared by the present invention and the humic acid prepared by the comparative example;
[0021] Figure 4 Fourier transform infrared (FTIR) diagram of different humic acids prepared by the present invention and the humic acid prepared by the comparative example;
[0022] Figure 5 Adsorption and fixation effect of the insoluble humic acid prepared by the present invention and the dissolved humic acid prepared by the comparative example on Zn 2+ under different concentration conditions of Zn 2+ Detailed Embodiments
[0023] The present invention will be further described in detail below with reference to the drawings and embodiments:
[0024] As Figure 1 shown is the flow chart of the preparation process of the present invention. An improved synthesis method of insoluble humic acid includes the following steps:
[0025] S1. Place natural humic acid in 0.1M NaOH solution, stir well for 15 min to dissolve it, put the reaction suspension into a centrifuge, centrifuge at 10740×g for 10 min, collect the supernatant. To ensure the full separation of humic acid and impurities, after collecting the supernatant, centrifuge again and collect the supernatant;
[0026] S2. Adjust the collected supernatant to pH = 1 with 6M hydrochloric acid. At this time, the black humic acid solid precipitates from the solution. Transfer the suspension with pH = 1 to a centrifuge tube, and centrifuge it at 4650×g for 10 min using a centrifuge. Collect the centrifuged solid, disperse the collected solid in ultrapure water, and centrifuge it at 4650×g for 10 min using a centrifuge. Pour off the supernatant, and repeat this step 5 times to wash away the residual impurity ions. Finally, collect the solid and put it into an oven, and dry it at 75 °C to obtain high-purity humic acid powder;
[0027] S3. Directly put the pure humic acid powder obtained in step S2 into a muffle furnace, and calcine it at 330 °C for 6 h to promote its condensation and fixation. After the calcination is completed, collect the solid substance, disperse the solid substance in ultrapure water, adjust the suspension to pH = 8, stir it at room temperature for 48 h and let it stand for 12 h, and remove the overlying solution to remove the slightly soluble humic acid to obtain insoluble humic acid;
[0028] S4. Disperse the insoluble humic acid in step S3 in ultrapure water, centrifuge it using a centrifuge, separate and collect the solid, and repeat this step 3 times to remove the residual slightly soluble humic acid. Finally, freeze-dry to obtain a solid, that is, obtained.
[0029] Evaluate the synthesized humic acid
[0030] 1. Synthesis effect evaluation
[0031] Weigh a certain amount of humic acid and disperse it in ultrapure water to make the solid-liquid ratio 2.5 g / L. Observe the change of the solution with the naked eye. Figure 2 The solubility effect of humic acid in ultrapure water before and after the synthesis treatment is shown. The results show that the solution was dark brown before the treatment, indicating that a large amount of humic acid was dissolved in the water. After the treatment, the solution color was transparent and colorless, and the particle morphology was obvious, indicating that the granulation technology used in the present invention significantly reduced the solubility of humic acid.
[0032] 2. Solubility test
[0033] Weigh a certain amount of humic acid particles and disperse them in ultrapure water to make the solid-liquid ratio 2.5 g / L. Adjust the pH of the suspension to 4 - 10, put it into a constant temperature shaking incubator, set the reaction temperature to 25 °C, the shaking speed of the shaker to 120 r / min, and the reaction duration to 48 h. After the reaction is completed, centrifuge the suspension (rotation speed 10740×g, centrifuge for 10 min), then take the supernatant, and use a TOC analyzer to test the dissolved organic carbon (TOC) concentration. By comparing the total TOC concentration of the fully dissolved sample with the TOC concentration data of the above experimental samples, the dissolution percentage is obtained.
[0034] The experimental results are as Figure 3 shown. In order to compare the improvement effect of the present invention, Figure 3The solubility data (hollow origin in the figure) of the patent (application number 2024117995877) is cited. Figure 3 It shows that as the pH increases, the solubility of humic acid increases; the firing media (anhydrous and 2M CaCl2) significantly affect the solubility of humic acid products. Although the CaCl2 synthesis scheme proposed in the patent (application number 2024117995877) submitted by the inventor significantly reduces the solubility of humic acid (from 22% to 2%), there is still 2% solubility in an alkaline environment. The anhydrous firing scheme proposed in the present invention reduces the solubility to 0.2%, achieving stability within the entire environmental pH range.
[0035] 3. Stabilization effect evaluation 1 - FTIR
[0036] The Fourier transform infrared spectrum (FTIR) of humic acid before and after firing based on the method of the present invention was measured using a Thermo Fisher NICOLET iS10 FT-IR instrument, and the results are as Figure 4 shown. To highlight the improved characteristics of the present invention, the FTIR spectrum of slightly soluble humic acid prepared by the process of the patent (application number 2024117995877) is synchronously cited in the figure. Analysis shows that the core characteristic peaks of the FTIR spectra before and after firing remain highly consistent, confirming that the heating condensation reaction does not change the essential structural characteristics of humic acid, and the resulting product is still humic acid. It is worth noting that compared with the dissolved humic acid before firing and the slightly soluble humic acid of the patent (application number 2024117995877), the carbonyl C=O stretching vibration absorption peak (about 1710 cm-1) of the product of the present invention is significantly weakened, indicating that this method can efficiently remove the carbonyl functional group in humic acid. Since the carbonyl is one of the key functional groups conferring water solubility to humic acid, the decrease in its content directly leads to a decrease in the solubility of the product.
[0037] 4. Stabilization effect evaluation 2 - Element determination
[0038] The CHO element composition of humic acid before and after firing based on the method of the present invention was analyzed using an Agilent ICP-MS7800 instrument; to compare the improvement of the present invention, the CHO element composition of slightly soluble humic acid prepared by the process of the patent (application number 2024117995877) was synchronously measured, and the analysis results of the humic acid element composition are shown in Table 1:
[0039] Table 1 Changes in CHO elements of different humic acids prepared by the present invention and humic acids prepared in the comparative example
[0040]
[0041] Both the humic acid before and after firing maintain typical elemental composition characteristics, with the main components being carbon (53 - 65%), oxygen (26 - 31%), and hydrogen (3 - 4%). The firing treatment has a significant regulatory effect on the elemental ratios: in the untreated dissolved humic acid, the carbon, oxygen, and hydrogen contents are 52.8%, 30.8%, and 3.7% respectively; after firing, the oxygen content (23 - 26%) and hydrogen content (about 3%) of the insoluble humic acid sample decrease synchronously, indicating the preferential removal of oxygen- and hydrogen-containing functional groups (such as hydroxyl and carboxyl groups). It should be noted that the oxygen and hydrogen contents of the insoluble humic acid prepared by the present invention show the most significant decrease, proving that this method has the best removal efficiency for hydrogen- and oxygen-containing functional groups (such as carbonyl and carboxyl groups), and the resulting solubility reduction effect is also the most prominent.
[0042] 5. Evaluation of the adsorption and fixation effect on heavy metal Zn 2+
[0043] The adsorption experiment was used to evaluate the fixation effect of humic acid on the typical heavy metal Zn 2+ . The adsorption experiment was carried out by the batch method at 25°C. Heavy metal Zn 2+ was used as the adsorbate and was prepared by dissolving Zn(NO3)2·6H2O in deionized water. Before the adsorption reaction, the insoluble humic acid powder was suspended in a NaNO3 background electrolyte solution with a pH of 7.5 overnight. Subsequently, a certain volume of Zn stock solution was added dropwise to make the Zn concentration reach 0.1 - 0.8 mM, the background electrolyte concentration was 0.1 M, and the solid-liquid ratio was 0.125 g / L. During the reaction process, the pH was precisely controlled at 7.5 ± 0.2 by adding 10 mM NaOH / HNO3 solution. After the reaction for 48 h, the suspension was centrifuged to separate the solid and the supernatant, and the Zn 2+ concentration was measured using an inductively coupled plasma optical emission spectrometer, and the adsorption percentage was calculated. To compare the effect of the synthesis treatment on the ability of humic acid to adsorb / complex metal ions, an ultrafiltration experiment was also carried out. The experimental conditions were the same as those of the adsorption experiment, except that the particulate humic acid was replaced with dissolved humic acid, and ultrafiltration was used to separate the humic acid-complexed zinc and free ionic zinc.
[0044] The isotherm results of humic acid adsorbing zinc are as Figure 5 shown. At low Zn 2+ concentrations (≤0.4 mM), the adsorption capacities of IHA and PHA for Zn 2+ are comparable. However, when the initial Zn 2+ concentration increases (≥0.6 mM), IHA shows a significantly enhanced Zn 2+ adsorption capacity. For example, when the initial Zn 2+ concentration is 0.8 mM, the Zn 2+ The adsorption capacity is 2.1 times that of PHA. This result indicates that the humic acid synthesized in the present invention has a higher heavy metal adsorption and fixation ability and can be used for adsorption theoretical research and the green remediation of heavy metal pollution.
[0045] The above are only embodiments of the present invention, and common general knowledge of specific technical solutions or characteristics in the solutions is not described in detail herein. It should be noted that without departing from the technical solution of the present invention, those skilled in the art can make several deformations and improvements to it, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope claimed in this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.
Claims
1. An improved synthesis method of insoluble humic acid, characterized in that , including the following steps: S1. Purify natural humic acid to obtain highly pure soluble humic acid; S2. Prepare insoluble humic acid from the highly pure soluble humic acid obtained in S1, specifically as follows: S2.
1. Directly put the highly pure humic acid powder obtained in step S2 into a muffle furnace for anhydrous firing to promote its condensation and granulation; S2.
2. After the firing is completed, collect the solid substance, disperse the solid substance into ultrapure water, adjust the suspension to pH = 8, stir for 48 h at room temperature and then let it stand for 12 h, and remove the overlying solution to remove slightly soluble humic acid; S2.
3. Disperse the humic acid solid in step S2.2 into ultrapure water, use a centrifuge to centrifuge, separate and collect the solid, repeat this step 3 times to remove residual insoluble humic acid, and finally freeze-dry the obtained solid to obtain it.
2. The insoluble humic acid prepared by the improved synthesis method of insoluble humic acid according to claim 1, wherein: This insoluble humic acid is applied to adsorb and fix Zn 2+ .
3. An improved synthesis method of insoluble humic acid according to claim 1, characterized in that , the firing temperature in step S2.1 is 330 °C and the firing duration is 6 h.
4. An improved synthesis method of insoluble humic acid according to claim 1, characterized in that , the specific operation of S1 is as follows: S1.
1. Place natural humic acid in a 0.1 M NaOH solution, stir for 15 min to promote its dissolution, put the reacted suspension into a centrifuge, use the centrifuge to centrifuge, and collect the supernatant; S1.
2. Adjust the collected supernatant to pH = 1 with 6 M hydrochloric acid. At this time, the black humic acid solid precipitates from the solution. Transfer the suspension with pH = 1 to a centrifuge tube, use the centrifuge to centrifuge, and collect the solid after centrifugation; S1.
3. Disperse the collected solid in ultrapure water, use the centrifuge to centrifuge again, pour out the supernatant, and repeat this step 5 times to wash away residual impurity ions; S1.
4. Finally, collect the solid and put it into an oven to dry it at 75 °C to obtain pure humic acid powder.
5. According to the method for preparing insoluble humic acid described in claim 4, after collecting the supernatant in step S1.2, centrifuge again and collect the supernatant to ensure the full separation of humic acid and impurities.
6. An improved synthesis method of insoluble humic acid according to claim 4, characterized in that: In steps S1.1 and S1.2, in step S1.1, the centrifuge centrifuges at 10740×g for 10 min, and in step S1.2, the centrifuge centrifuges at 4650×g for 10 min.