Adsorbent for simultaneously removing heavy metal lead and precious metal gold, preparation method and application

Abstract

The invention discloses an adsorbent for simultaneously removing heavy metal lead and precious metal gold as well as a preparation method and application thereof, and belongs to the technical field of environmental functional materials. The technical problems of high cost, secondary pollution and the like of preparation of the heavy metal adsorption material adsorbent in the prior art are solved. The preparation method comprises the following steps: collecting leaves, pretreating the leaves, and performing ultraviolet irradiation on the pretreated leaves; carrying out freeze drying or vacuum drying on the leaves irradiated by the ultraviolet light; finally, carrying out ball milling on the dried leaves by using a ball milling instrument to obtain powdery leaves; the ball milling frequency of the ball milling instrument is 10-40 Hz, and the ball milling time is 10-120 min. In the preparation process of the adsorbent, a solvent does not need to be added, the adsorbent is obtained by combining leaf ball milling with ultraviolet irradiation and freeze drying, the operation steps are simple and green, and large-scale production is easy.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental functional materials, and in particular relates to an adsorbent capable of simultaneously removing heavy metal lead and precious metal gold, a preparation method and application thereof. Background Art

[0002] In the process of modern industry and urbanization, the pollution of heavy metals and precious metals has become a focus of global attention. The main sources of lead ion pollution come from battery manufacturing, smelting, fertilizers and fuels. People who are exposed to lead-contaminated environments for a long time may suffer from health problems such as neurological damage and cognitive decline, and also pose a serious threat to the ecological environment. Lead ion emission pollution will affect soil fertility and microbial activity, thereby affecting plant growth and ecosystem stability. Lead ion pollution in water bodies will endanger the survival of aquatic organisms and destroy the balance of aquatic ecosystems. At the same time, metal recycling is also of great significance in terms of resource conservation and economic benefits, especially the recycling of precious metals such as gold, which is crucial to reducing mineral resource mining and reducing environmental damage.

[0003] The traditional methods for removing metals from aqueous solutions can be divided into three categories: physical, chemical, and biological methods, including chemical precipitation, chemical oxidation / reduction, ion exchange, filtration, electrochemical treatment, reverse osmosis, membrane technology, and evaporation recovery. Precipitation has broad application prospects among many technologies due to its simplicity and economy. At present, a variety of adsorbents have been developed and their removal performance has been studied. However, most adsorbents, such as activated carbon, clay and zeolite, and metal-organic framework materials are expensive and produce secondary waste, requiring not only technical processing chemicals but also complex infrastructure. For example, depending on the precipitant, the removal rate of lead ions by chemical precipitation varies from 70% to 90%. The removal rate of ordinary commercial carbon materials is usually around 85%, while the removal rate of MOF (metal organic framework) materials with broad-spectrum adsorption capacity can reach 99%. However, due to the high cost of MOF materials, their application in water treatment is severely limited. As for metal recovery, existing technologies such as cyanidation and electrolysis, although they show high recovery rates under laboratory conditions, are difficult to promote on a large scale in practical applications due to environmental pollution, economic costs, and operational complexity. In particular, the potential environmental safety risks of the cyanidation method have limited its application. Therefore, it is of great application value to develop an environmentally friendly adsorption material that is simple to prepare, has abundant raw materials, and can efficiently and quickly remove heavy metal lead and adsorb and recover precious metal gold. Summary of the invention

[0004] One of the purposes of the present invention is to provide a method for preparing an adsorbent that can remove heavy metal lead and precious metal gold alone or simultaneously, which aims to solve the problems of preparation load, high cost and secondary pollution of heavy metal adsorbent materials. No solvent is added during the preparation process, and the preparation is obtained by ball milling leaves combined with ultraviolet irradiation and freeze drying. The method has simple operation steps, is green, and is easy to mass produce.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold comprises the following steps:

[0007] Step 1, collecting leaves and pre-treating them, irradiating the pre-treated leaves with ultraviolet light, the wavelength of the ultraviolet light is 190 to 400 nm, and the irradiation time is 12 to 48 hours;

[0008] Step 2, drying the leaves irradiated with ultraviolet light in step 1; the drying method is freeze drying or vacuum drying;

[0009] Step 3: Use a ball mill to ball-mill the leaves dried in step 2 to obtain powdered leaves; the ball milling frequency of the ball mill is 10 to 40 Hz, and the ball milling time is 10 to 120 min.

[0010] In the above-mentioned method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, in step one, the leaves are selected from summer leaves or winter leaves; the step of pretreating the leaves includes: the step of washing and shearing the leaves, and obtaining leaves of equal size by shearing.

[0011] In the above-mentioned method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, the leaves are selected from summer leaves.

[0012] The above-mentioned method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, in step one, the ultraviolet light irradiation is selected from A rays with a wavelength of 315 to 400 nm, B rays with a wavelength of 280 to 315 nm, or C rays with a wavelength of 190 to 280 nm; the irradiation time is 20 to 24 hours.

[0013] The above-mentioned method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold comprises irradiating the pretreated leaves with ultraviolet light using B rays with a wavelength of 280 to 315 nm.

[0014] The above-mentioned method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, in step 2, freeze drying is performed by soaking the leaves irradiated with ultraviolet light in liquid nitrogen for drying, the vacuum drying temperature is 40-100°C, and the drying time is 10-12h; the moisture content of the leaves after drying is ≤5%.

[0015] In the above-mentioned method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, in step three, the ball milling frequency is 15 to 20 Hz, and the ball milling time is 10 to 60 min.

[0016] Another object of the present invention is to provide an adsorbent prepared by the above-mentioned method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold.

[0017] Another object of the present invention is to provide an application of the above-mentioned adsorbent, and the application steps are: adding the adsorbent to an aqueous solution containing heavy metal lead and heavy metal gold, the adsorbent dosage is 1-10 g / L; the initial pH value of the aqueous solution is 2-7, the pH value of the aqueous solution containing lead ions is 5-6, and the pH value of the aqueous solution containing gold ions is 2-3; the initial concentration of lead ions and gold ions in the aqueous solution is 100-800 mg / L.

[0018] In the above application, the initial concentration of lead ions and gold ions in the aqueous solution is 200 mg / L, the temperature of the aqueous solution is 10-100° C., and stirring is maintained during the addition of the adsorbent, with a stirring speed of 200-1000 r / min.

[0019] The preparation mechanism of the adsorbent of the present invention is as follows:

[0020] A simple green ball milling method was used to obtain universal leaf powder by combining ultraviolet irradiation and freeze drying. The results showed that the ball-milled leaf powder had excellent adsorption capacity and could effectively remove heavy metal ions. The removal rate of single-component Pb ions by ball-milled leaf powder reached more than 99%, and the adsorption effect of Au ions also reached more than 99%. The study found that there was a strong interaction between the aromatic ring structure in the leaves and heavy metal ions, and this interaction was the key to the rapid adsorption and efficient removal of heavy metal ions by leaf powder. The aromatic rings in the leaves provide abundant π electrons and oxygen-containing functional groups, which can form pocket structures with heavy metal ions, thereby enhancing the adsorption performance. In summary, the adsorption characteristics of leaf powder provide a green and efficient solution for removing heavy metal pollution.

[0021] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0022] (1) The present invention proposes a method for preparing an adsorbent that can simultaneously remove heavy metal lead and precious metal gold. The preparation method is simple to operate and low in cost, and provides a new way to utilize ordinary leaves, a natural bio-based material. Specifically, the preparation process is simple to operate, no chemical reagents are required, the raw materials are cheap and easy to obtain, the surface properties of the leaves are improved by ultraviolet irradiation, and freeze-drying maintains the microstructure of the material lignin. The adsorbent of the present invention can not only efficiently remove heavy metal lead from aqueous solutions, but also effectively adsorb and recover precious metal gold. It has broad application prospects in the fields of heavy metal polluted water treatment and precious metal recovery.

[0023] (2) The adsorbent prepared by the present invention can effectively adsorb metal lead and gold in water at the same time. Specifically, under the condition that the initial concentration of Pb(II) and Au(III) is 200 mg / L mixed solution, the adsorbent that efficiently adsorbs lead and gold reaches equilibrium within 10 seconds at the beginning of the reaction, achieving the effect of adsorption in seconds. At the same time, the removal rate of lead is as high as 95%, and the removal rate of gold is as high as 90%, achieving efficient and rapid adsorption.

[0024] (3) The adsorbent prepared by the present invention can be recycled for multiple times, with the number of cycles being as high as 30 times, while still maintaining a relatively high removal rate, which further proves that the adsorbent prepared by the present invention has good durability and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a preparation flow chart of the adsorbent of the present invention.

[0026] Figure 2 (a) and (b) are scanning electron microscope (SEM) images of the adsorbent prepared in Example 1.

[0027] Figure 3 This is a graph showing the test results of the effect of different ultraviolet light-prepared adsorbents on heavy metal lead in Example 1.

[0028] Figure 4 This is a graph showing the test results of the effect of adsorbents prepared from different leaves on heavy metal lead in Example 1.

[0029] Figure 5 (a) is a test result diagram of the effect of different doses of adsorbent on the adsorption of heavy metal lead in Example 2, and (b) is a test result diagram of the effect of different doses of adsorbent on the adsorption of precious metal gold.

[0030] Figure 6 (a) is a test result diagram of the effect of different ion concentrations on the adsorption of heavy metal lead in Example 2, and (b) is a test result diagram of the effect of different ion concentrations on the adsorption of precious metal gold.

[0031] Figure 7(a) is a test result diagram of the effect of different reaction solution pH on the adsorption of heavy metal lead in Example 2, and (b) is a test result diagram of the effect of different reaction solution pH on the adsorption of precious metal gold.

[0032] Figure 8 (a) is a test result diagram of the effect of different reaction times on the adsorption of heavy metal lead in Example 3, and (b) is a test result diagram of the effect of different reaction times on the adsorption of precious metal gold.

[0033] Fig. 9 This is a test result diagram of the cyclic adsorption effect of heavy metal lead in Example 4.

[0034] Fig.10 This is a test result diagram of the adsorption effect of the coexistence of heavy metal lead and precious metal gold in Example 5. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0036] In the description of this application, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a way to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0037] The technical solution of the present application is further described in detail below in conjunction with the accompanying drawings.

[0038] The raw materials described in the present invention can be purchased through commercial channels.

[0039] Embodiment 1:

[0040] like Figure 1 As shown, the present invention provides a method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, which specifically comprises the following steps:

[0041] Step 1: Wash the collected leaves with deionized water, cut the washed leaves into small pieces of similar size with scissors, and then place them under ultraviolet lamps of different wavelengths for irradiation, namely A rays (315-400nm), and the time is set to 24h;

[0042] Step 2: freeze drying for 12 hours.

[0043] Step 3: The obtained solid is ball-milled using a high-speed vibrating ball mill at a vibration frequency of 20 Hz for 120 min.

[0044] The SEM image of the adsorbent prepared in this example is as follows Figure 2 As shown. Figure 2 (a) and (b) show that the adsorbent surface is smooth and has no obvious pore structure.

[0045] Embodiment 2:

[0046] The present invention discloses a method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, which specifically comprises the following steps:

[0047] Step 1: Wash the collected leaves with deionized water, cut the washed leaves into small pieces of similar size with scissors, and then place them under ultraviolet lamps of different wavelengths for irradiation, B rays (280-315nm), and the time is set to 20h;

[0048] Step 2: freeze drying for 10 hours.

[0049] Step 3: The obtained solid is ball-milled using a high-speed vibrating ball mill at a vibration frequency of 15 Hz for 30 min.

[0050] Embodiment 3:

[0051] The present invention discloses a method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, which specifically comprises the following steps:

[0052] Step 1: Wash the collected leaves with deionized water, cut the washed leaves into small pieces of similar size with scissors, and then place them under ultraviolet lamps of different wavelengths for irradiation, C rays (190-280nm), and the time is set to 22h;

[0053] Step 2: freeze drying for 11 hours.

[0054] Step 3: The obtained solid is ball-milled using a high-speed vibrating ball mill at a vibration frequency of 18 Hz for 50 min.

[0055] The adsorption effects of the adsorbents prepared in Examples 1 to 3 are compared. Figure 3 As shown, the adsorption effect of the adsorbent is best when irradiated by B rays (280-315 nm), the effect of A rays is not significantly improved compared with that of no irradiation, and the excessive power of C rays destroys its structure, resulting in poor effect. The results show that appropriate ultraviolet light irradiation can improve its adsorption performance.

[0056] Embodiment 4:

[0057] The present invention discloses a method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, which specifically comprises the following steps:

[0058] Step 1: Wash the collected summer leaves with deionized water, cut the washed leaves into small pieces of similar size with scissors, and then place them under ultraviolet lamps of different wavelengths for irradiation, B rays (280-315nm), and the time is set to 20h;

[0059] Step 2: freeze drying for 10 hours.

[0060] Step 3: The obtained solid is ball-milled using a high-speed vibrating ball mill at a vibration frequency of 15 Hz for 10 min.

[0061] Embodiment 5:

[0062] The difference from Example 4 is that winter leaves are used as raw materials.

[0063] The adsorbents prepared in Examples 4 and 5 were tested. Figure 4 As shown in the figure, adsorbents prepared from different types of leaves were used to adsorb and remove lead ions from water. The results showed that the adsorbents prepared from summer leaves and winter leaves performed similarly in terms of lead ion removal rates, both exceeding 95%. Among them, the adsorbent prepared from summer leaves performed best, with a removal rate of 99%. These results show that common leaves can be effectively used to prepare efficient adsorbents to achieve excellent removal and recovery performance for heavy metal lead and precious metal gold.

[0064] Embodiment 6:

[0065] The performance of the adsorbent prepared in Example 1 was tested from the perspective of efficient removal of heavy metal lead.

[0066] Taking the adsorbent content, metal ion concentration and adsorption solution pH value as control targets, the control results are as follows:

[0067] (1) Figure 5 As shown in (a), the effect of different adsorbent contents on the removal rate of lead ions was studied. The results show that with the increase of adsorbent content, the removal rate of lead ions gradually increases. When the adsorbent content reaches >6g / L, the removal rate tends to saturation and approaches 100%. Figure 5 As shown in (b), the effect of changing the adsorbent content on the recovery of gold ions was also studied. The results showed that as the adsorbent content increased, the removal rate of gold ions gradually increased. When the adsorbent content reached >1g / L, the removal rate reached saturation, approaching 100%. These results show that appropriately adjusting the adsorbent content can effectively optimize the removal and recovery of lead and gold ions.

[0068] (2) Figure 6As shown in (a) and (b), the effect of lead / gold ion concentration changes in the range of 100-800 mg / L on the removal rate was studied, keeping the adsorbent content unchanged. Under the same adsorption time conditions, the results show that the increase in lead / gold ion concentration will cause the removal rate to first increase and then decrease, presenting a volcano-shaped curve. The optimal lead / gold ion concentration is 200 mg / L, and the removal rate at this concentration reaches the best level.

[0069] (3) Figure 7 As shown in (a), under the condition of pH value ranging from 2 to 7, the removal rate of lead ions gradually increases with the increase of pH value. When pH is 2, the removal rate is the lowest, while when pH value is 5 to 6, the removal effect of lead ions is the best. Similarly, Figure 7 As shown in (b), within the same pH range, when the pH value is 2-3, the removal rate of gold ions shows an upward trend. As the pH value further increases, the removal rate shows a trend of repeated fluctuations, but the overall trend is downward. Finally, it was found that the pH value of 2-3 has the best adsorption and recovery effect on precious metal gold.

[0070] After the above screening experiments, the optimal adsorption conditions for heavy metal lead and precious metal gold were determined. For the adsorption and removal of heavy metal lead, the optimal conditions are: adsorbent content> 6g / L, lead ion concentration of 200mg / L, and pH value of the reaction solution range of 5 to 6. For the adsorption and recovery of precious metal gold, the optimal conditions are: adsorbent content> 1g / L, gold ion concentration of 200mg / L, and pH value of the reaction solution range of 2 to 3.

[0071] Embodiment 7:

[0072] Effect of different reaction times on the adsorption of heavy metal lead and precious metal gold

[0073] In this example, more than 6 g / L of adsorbent was added to a solution containing 200 mg / L of lead ions, the pH value was 5-6, and the reaction was carried out at 25°C and 500-800 r / min. Samples were taken at different time points (2, 5, 10, 20, 30, 40, 50, 60, 180, 300, 600 seconds) and filtered to determine the lead ion concentration in the filtrate. Figure 8 As shown in (a), the removal rate of lead ions is as high as 96% at 60 seconds, indicating that in the initial stage of the reaction, the adsorbent has an extremely high efficiency in adsorbing lead ions, which is close to completion, and then the system tends to equilibrium.

[0074] Add more than 1g / L of adsorbent to a solution containing 200mg / L of gold ions, with a pH of 2-3, and react at 25°C and 500r / min. Take samples at different time points (2, 5, 10, 20, 30, 40, 50, 60, 180, 300, 600 seconds) and filter to determine the gold ion concentration in the filtrate. Figure 8 As shown in (b), the adsorption recovery rate of gold ions was as high as 93% at 60 seconds, indicating that in the initial stage of the reaction, the adsorbent had an extremely high adsorption efficiency for lead ions, which was close to completion, and then the system tended to equilibrium.

[0075] The above experimental results show that the adsorbent has the effect of rapid adsorption, recovery and removal of heavy metal lead and precious metal gold.

[0076] Embodiment 8:

[0077] This example is a test of the adsorption effect of the coexistence of heavy metal lead and precious metal gold.

[0078] like Fig. 9 The results show that the adsorbent exhibits excellent stability in multiple cycles, with a high removal efficiency of up to 30 cycles. This shows that the adsorbent has good durability and economy while efficiently removing heavy metals, effectively solving the problems of traditional materials in terms of load, cost and secondary pollution, and significantly improving the professionalism and sustainability of heavy metal treatment.

[0079] Embodiment 9:

[0080] This example is a test of the adsorption effect of the coexistence of heavy metal lead and precious metal gold.

[0081] This example mainly illustrates that the adsorption of single-component metal ions and the coexistence of two-component metal ions have different effects. Fig.10 As shown in the figure, the adsorption removal rate of lead / gold ions in the single component is >99%. When heavy metal lead and precious metal gold coexist, the adsorption treatment rate of lead ions decreases slightly, still 95%, while the adsorption recovery efficiency of gold ions remains at a high level, reaching more than 99%. It can be seen that the coexistence effect has little effect on the adsorbent. This shows that water bodies contaminated by multiple heavy metals can be effectively treated at the same time.

[0082] Parts not described in the present invention can be implemented by referring to the existing technology.

[0083] It should be noted that those skilled in the art should recognize that the above implementation modes are only used to illustrate the present application and are not used to limit the present application. As long as they are within the essential spirit of the present application, appropriate changes and modifications made to the above embodiments should fall within the scope of protection of the claims of the present application.

Claims

1. A method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold, characterized in that: The following steps are involved: Step 1, collecting leaves and pre-treating them, irradiating the pre-treated leaves with ultraviolet light, the wavelength of the ultraviolet light is 190 to 400 nm, and the irradiation time is 12 to 48 hours; Step 2, drying the leaves irradiated with ultraviolet light in step 1; the drying method is freeze drying or vacuum drying; Step 3: Use a ball mill to ball-mill the leaves dried in step 2 to obtain powdered leaves; the ball milling frequency of the ball mill is 10 to 40 Hz, and the ball milling time is 10 to 120 min.

2. The method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold according to claim 1, characterized in that: In step 1, the leaves are selected from summer leaves or winter leaves; The step of pre-processing the leaves includes: washing and cutting the leaves, and obtaining leaves of equal size by cutting.

3. The method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold according to claim 2, characterized in that: The leaves are selected from summer leaves.

4. The method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold according to claim 1, characterized in that: In step 1, the ultraviolet light irradiation is selected from A rays with a wavelength of 315 to 400 nm, B rays with a wavelength of 280 to 315 nm, or C rays with a wavelength of 190 to 280 nm; the irradiation time is 20 to 24 hours.

5. The method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold according to claim 4, characterized in that: The pretreated leaves are irradiated with ultraviolet light using B rays with a wavelength of 280 to 315 nm.

6. The method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold according to claim 1, characterized in that: In step 2, freeze drying is performed by soaking the leaves irradiated with ultraviolet light in liquid nitrogen for drying. The drying temperature of vacuum drying is 40 to 100° C. and the drying time is 10 to 12 hours. After drying, the moisture content of the leaves is ≤5%.

7. The method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold according to claim 1, characterized in that: In step 3, the ball milling frequency is 15 to 20 Hz, and the ball milling time is 10 to 60 min.

8. An adsorbent prepared according to the method for preparing an adsorbent for simultaneously removing heavy metal lead and precious metal gold according to any one of claims 1 to 7.

9. The use of the adsorbent according to claim 8, characterized in that: The application steps are as follows: adding the adsorbent to an aqueous solution containing heavy metal lead and heavy metal gold, the adsorbent dosage being 1-10 g / L; the initial pH value of the aqueous solution being 2-7, the pH value of the aqueous solution containing lead ions being 5-6, and the pH value of the aqueous solution containing gold ions being 2-3; the initial concentrations of lead ions and gold ions in the aqueous solution being 100-800 mg / L.

10. The use according to claim 9, characterized in that: The initial concentration of lead ions and gold ions in the aqueous solution is 200 mg / L, the temperature of the aqueous solution is 10-100° C., and stirring is maintained during the addition of the adsorbent, with a stirring speed of 200-1000 r / min.

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