Liquid metal magnetic hydrogel microspheres, preparation method and application thereof

Abstract

This invention provides a method for preparing liquid metal magnetic hydrogel microspheres, specifically including the following steps: (1) ultrasonically dispersing sodium alginate in deionized water to obtain a sodium alginate dispersion; (2) adding liquid metal to the sodium alginate dispersion, ultrasonically dispersing and stirring evenly to obtain an SA-LM solution; (3) taking another SA-LM solution, adding a crosslinking agent and nano-Fe3O4 powder to the SA-LM solution respectively, then adding an initiator to the SA-LM solution, mixing evenly to obtain a pregel solution; (4) dropping the pregel solution into a CaCl2 solution, magnetically stirring to form polymerized liquid metal magnetic hydrogel microspheres; (5) drying the liquid metal magnetic hydrogel microspheres. Furthermore, this invention also provides a liquid metal magnetic hydrogel microsphere and its application. The hydrogel microspheres provided by this invention have higher adsorption efficiency.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and specifically relates to a liquid metal magnetic hydrogel microsphere, its preparation method, and its application. Background Technology

[0002] Environmental pollution, especially from dyes and heavy metals, is a pressing issue. Azo dyes are commonly used as food additives for coloring food, but long-term excessive use has potential liver toxicity, causing not only cancer, birth defects, and mutations, but also direct threats to life. Adsorption, photocatalytic degradation, and membrane filtration—methods using nanomaterials for dye wastewater treatment—are highly effective.

[0003] Among these methods, adsorption is more widely used due to its advantages such as diverse material sources, low cost, simple operation, high efficiency, and recyclability. Compared to traditional adsorbents, hydrogel adsorbents can achieve controllable adsorption performance by adjusting their composition and pore structure. The loose and porous structure of hydrogel adsorbents provides more adsorption sites for dye molecules, resulting in higher adsorption capacity. Their excellent hydration capacity improves their ability to stably adsorb pollutants in liquid environments. However, simple hydrogel adsorption is relatively poor, requiring the encapsulation of a certain amount of adsorbent to achieve the removal of organic pollutants. Furthermore, traditional adsorbents are difficult to separate into solid and liquid phases, easily causing secondary pollution. To address this issue, existing technologies have introduced magnetic adsorption materials prepared from paramagnetic substances.

[0004] Magnetic nanomaterials, with their nanoscale size and unique surface properties, exhibit rapid adsorption rates. Their high diffusion rates and short batch times enable rapid removal of target pollutants, achieving highly efficient adsorption. However, magnetic nanoparticles easily diffuse into the solution, making subsequent separation from the liquid difficult. Furthermore, magnetic Fe3O4 nanoparticles exposed to air are easily oxidized, prone to aggregation, and exhibit poor stability, reducing their application performance. Magnetic hydrogels combine magnetic nanoparticles with a hydrogel network structure through physical embedding or chemical grafting, giving them the properties of both hydrogels and magnetic materials. Sodium alginate possesses excellent sphericity, stability, and mass transfer capabilities. However, the adsorption efficiency of magnetic hydrogels as adsorbents is not at its peak, reaching only around 30%.

[0005] Therefore, how to improve the adsorption efficiency of hydrogel microspheres has become an urgent problem to be solved in this field. Summary of the Invention

[0006] The main objective of this invention is to provide a method for preparing liquid metal magnetic hydrogel microspheres, overcoming the shortcomings of existing technologies. This preparation method is simple, resulting in liquid metal hydrogel microspheres with high adsorption efficiency, easy separation, and suitable for industrial production.

[0007] This invention provides a method for preparing liquid metal hydrogel microspheres, specifically including the following steps:

[0008] (1) Sodium alginate was ultrasonically dispersed in deionized water to prepare sodium alginate dispersion;

[0009] (2) Add liquid metal to the sodium alginate dispersion, ultrasonically disperse and stir evenly to obtain SA-LM solution;

[0010] (3) Take another SA-LM solution, add the crosslinking agent and nano Fe3O4 powder to the SA-LM solution respectively, then add the initiator to the SA-LM solution, mix evenly, and obtain a pregel solution;

[0011] (4) The pregel solution is dropped into CaCl2 solution and magnetically stirred to form liquid metal magnetic hydrogel microspheres through polymerization.

[0012] (5) Dry the liquid metal magnetic hydrogel microspheres.

[0013] Preferably, in step (1), the sodium alginate is 15g and the mass concentration of the sodium alginate dispersion is 4.8%wt; in step (2), the liquid metal is 7.5mg; and in step (3), the SA-LM solution is 2mL.

[0014] Preferably, the crosslinking agent is one or more of acrylamide, bisacrylamide, and tetramethylethylenediamine; the acrylamide has a mass concentration of 19% wt and a volume of 2.75 mL; the bisacrylamide has a mass concentration of 2‰ and a volume of 300 μL; and the tetramethylethylenediamine has a volume of 10 μL.

[0015] Preferably, the initiator is ammonium persulfate.

[0016] Preferably, the volume of the CaCl2 solution is 5 ml.

[0017] A liquid metal magnetic hydrogel microsphere obtained by the above preparation method, wherein the surface of the liquid metal magnetic hydrogel microsphere has wrinkled pores, and metal elements are aggregated on the pore walls to form a liquid metal scaffold, and the liquid metal magnetic hydrogel microsphere has a three-dimensional network structure with large pores.

[0018] An application of the above-mentioned liquid metal magnetic hydrogel microspheres is carried out through the following steps:

[0019] (1) Take 0.01g to 0.05g of liquid metal magnetic hydrogel microspheres and add them to malachite green aqueous solution;

[0020] (2) After dispersing the liquid metal magnetic hydrogel microspheres in the solution, the adsorption is allowed to stand for 1 to 6 hours.

[0021] Compared with the prior art, the advantages of the present invention include:

[0022] This invention utilizes sodium alginate to bond with metal ions Mn+ (n>=2) to form a three-dimensional network structure with large pores. The liquid metal hydrogel microspheres prepared by this invention are dual-network hydrogels, possessing two interpenetrating network polymer chains with complementary properties, exhibiting stronger mechanical strength and adsorption efficiency than traditional hydrogels.

[0023] In this invention, liquid metal can penetrate the porous structure of hydrogels and form nanoparticles. These nanoparticles possess a high specific surface area and abundant surface active sites, which can increase adsorption capacity and improve the tunability of the hydrogel. This invention combines hydrogel, magnetic nanoparticles, and liquid metal to form a portable hydrogel adsorbent that can be extracted in situ from the test solution, saving time and economic costs. Furthermore, this invention uses SEM to characterize the morphology of the internal pores of magnetic hydrogel microspheres containing and without liquid metal. By optimizing the mass ratio of liquid metal, the optimal state of the liquid metal magnetic hydrogel microspheres is obtained, with an adsorption efficiency reaching up to 99.9%. The liquid metal hydrogel microspheres of this invention are a promising new adsorbent for solid-liquid separation pretreatment steps. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart of a method for preparing liquid metal magnetic hydrogel microspheres according to the present invention;

[0026] Figure 2 This is a flowchart illustrating the working mechanism of the liquid metal magnetic hydrogel microspheres and the adsorption process of pigment pollutants in this invention.

[0027] Figure 3 These are transmission electron microscope images and elemental analysis spectra of the magnetic hydrogel microspheres of this invention;

[0028] Figure 4 These are transmission electron microscope images and elemental analysis spectra of the liquid metal magnetic hydrogel microspheres of this invention;

[0029] Figure 5This is one of the comparison images of the adsorption of pigments by the magnetic hydrogel microspheres and liquid metal magnetic hydrogel microspheres of the present invention;

[0030] Figure 6 This is the second comparison image of the adsorption of pigments by the magnetic hydrogel microspheres and liquid metal magnetic hydrogel microspheres of the present invention.

[0031] Figure 7 These are optical microscope images of the magnetic hydrogel microspheres and liquid metal magnetic hydrogel microspheres of this invention;

[0032] Figure 8 This is a hardness diagram of the liquid metal magnetic hydrogel microspheres under different liquid metal mass concentrations according to the present invention;

[0033] Figure 9 This invention relates to the effect of different liquid metal concentrations on the decolorization rate.

[0034] Figure 10 This invention relates to the effect of different sodium alginate concentrations on the decolorization rate of liquid metal magnetic hydrogel microspheres.

[0035] Figure 11 This invention relates to the effect of different amounts of liquid metal magnetic hydrogel microspheres on the decolorization rate.

[0036] Figure 12 This relates to the effect of adsorption time on the decolorization rate in this invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] Please see Figure 1 This is a flowchart of a method for preparing liquid metal magnetic hydrogel microspheres according to the present invention.

[0039] This invention discloses a method for preparing liquid metal magnetic hydrogel microspheres, specifically including:

[0040] (1) Sodium alginate was ultrasonically dispersed in deionized water to prepare sodium alginate dispersion;

[0041] (2) Add liquid metal to the sodium alginate dispersion, ultrasonically disperse and stir evenly to obtain SA-LM solution;

[0042] (3) Take another SA-LM solution, add the crosslinking agent and nano Fe3O4 powder to the SA-LM solution respectively, then add the initiator to the SA-LM solution, mix evenly, and obtain a pregel solution;

[0043] (4) The pregel solution is dropped into CaCl2 solution and magnetically stirred to form liquid metal magnetic hydrogel microspheres through polymerization.

[0044] (5) Dry the liquid metal magnetic hydrogel microspheres.

[0045] Please see Figure 2 The diagram illustrates the working mechanism of the liquid metal hydrogel microspheres and the adsorption flow chart of pigment pollutants in this invention.

[0046] Liquid metal was ultrasonically dispersed in a sodium alginate solution and then uniformly mixed with a polyacrylamide (PAAM) solution and nano-Fe3O4 powder to form a pregel solution. The pregel solution was then added dropwise to a CaCl2 solution at a uniform rate, thereby polymerizing to form liquid metal magnetic hydrogel microspheres. The prepared liquid metal magnetic hydrogel microspheres were dried in an 85°C constant temperature oven to complete the preparation of the adsorbent (i.e., liquid metal magnetic hydrogel microspheres). This invention utilizes the bonding between sodium alginate and metal ions Mn+ (n>=2) to form a three-dimensional network structure with large pores.

[0047] Subsequently, a certain mass of dried magnetic hydrogel microspheres were weighed and immersed in a malachite green solution of appropriate concentration for adsorption. It was observed that the liquid metal magnetic hydrogel microspheres gradually expanded, and the malachite green solution became almost colorless, indicating that the liquid metal magnetic hydrogel microspheres had essentially completely adsorbed the malachite green. Finally, a magnet was attached to the outside of the beaker containing the malachite green solution to remove the hydrogel microspheres, and the solution was collected for analysis. This demonstrates that the present invention successfully encapsulates dispersed liquid metal within magnetic hydrogel microspheres, thereby preparing a magnetically adsorbent material capable of efficient decolorization. Under the influence of a magnetic field, this adsorbent rapidly separates the adsorbed pigment from the aqueous environment, enabling more portable and efficient extraction of malachite green dye from actual samples.

[0048] To verify the adsorption efficiency of the liquid metal magnetic hydrogel microspheres prepared by the method of the present invention, the present invention provides the following experimental examples and control examples.

[0049] Instructions for instruments, materials and reagents used

[0050] Fe3O4 nanoparticles. LM (Ga 75.5%, In 24.5%, conductivity 34,000 S cm⁻¹) was purchased from Sigma (USA); calcium chloride, N,N,N',N'-tetramethylethylenediamine (TEMED), acrylamide (AAm, ≥99%), N,N'-methylenebis(acrylamide) (MBAA, 99%), ammonium persulfate (APS), and sodium alginate (SA, 99%) were purchased from Macklin (Shanghai, China). The water used in the experiment was deionized (18.2 mΩ). Surface morphology was characterized by SEM (Zeiss, UK); elemental analysis was performed by electron dispersive spectroscopy (EDS) and characterized by scanning electron microscopy (SEM) using an EDAX Genesis X4M; the hardness of the hydrogel microspheres was tested using a physical property tester (TAXTC, Shanghai Baosheng Industrial Development Co., Ltd.); optical microscope (Leica Microsystems); and B265-S analytical balance (Mettler-Toledo Instruments (Shanghai) Co., Ltd.).

[0051] Experimental Example

[0052] Liquid metal magnetic hydrogel microspheres: 15 g of sodium alginate (4.8% wt) and 7.5 mg of liquid metal (LM) were mixed to obtain a liquid metal-sodium alginate mixed solution (LM-SA solution) with a concentration of 0.05% wt. Separately, 2 mL of LM-SA, 2.75 mL of acrylamide (19% wt), 300 μL of 2‰ bis-acrylamide, 70 μL of 0.2 M ammonium persulfate, 10 μL of N,N,N',N'-tetramethylethylenediamine, and 40 mg of nano-Fe3O4 were mixed thoroughly to obtain a pre-gelling solution. The pre-gelling solution was then slowly added dropwise to a 5 M CaCl2 solution, magnetically stirred for 1 h, and the solution was filtered to obtain hydrogel microspheres. After drying the surface moisture of the obtained hydrogel microspheres, liquid metal hydrogel microspheres are obtained.

[0053] Comparison Example

[0054] Magnetic hydrogel microspheres: Take 2 mL of 4.8% wt sodium alginate, 2.75 mL of 19% wt acrylamide, 300 μL of 2‰ bis-acrylamide, 70 μL of 0.2M ammonium persulfate, 10 μL of N,N,N',N'-Tetramethylethylenediamine, and 40 mg of nano-Fe3O4. Mix thoroughly to obtain a mixed solution. Slowly add the mixed solution dropwise to a 5M CaCl2 solution, stir magnetically for 1 h, and filter the solution to obtain hydrogel microspheres. Dry the surface moisture of the obtained hydrogel microspheres to obtain magnetic hydrogel microspheres.

[0055] The products obtained from the above experimental and control examples were further studied as follows:

[0056] Study 1: Product Characterization

[0057] To understand the surface morphology of the magnetic hydrogel microspheres and further determine whether the liquid metal was successfully incorporated into the hydrogel network in the experimental example, the products were characterized by transmission electron microscopy (SEM). Before taking SEM images, the hydrogel microspheres needed to be freeze-dried and then sputter-coated with gold.

[0058] Please see Figure 3 and Figure 4 In the experimental example, the magnetic hydrogel microspheres containing liquid metal had many wrinkled pores on their surface. Elemental analysis of the magnetic hydrogel microspheres showed that Ga elements accumulated on the pore walls, forming a liquid metal scaffold that supported the pores and created deeper channels, thus increasing the specific surface area of ​​the hydrogel microspheres. This provided more adsorption sites for malachite green, thereby improving adsorption efficiency.

[0059] Meanwhile, please see Figure 3 In contrast, the magnetic liquid metal hydrogel microspheres in the control example had a rough surface with tiny pores and a solid interior. This clearly demonstrates that the liquid metal magnetic hydrogel microspheres were successfully prepared in the experimental example, and that the addition of liquid metal formed a scaffold between the hydrogel pore walls, providing more adsorption sites for malachite green and thus improving the adsorption effect on malachite green.

[0060] Therefore, it can be proven that in the product obtained by the preparation method of liquid metal magnetic hydrogel microspheres disclosed in this invention, liquid metal is successfully incorporated into the hydrogel network, and liquid metal magnetic hydrogel microspheres are successfully prepared by the preparation method of liquid metal magnetic hydrogel microspheres disclosed in this invention.

[0061] Study 2: Hardness Testing

[0062] Products from both the experimental and control examples, each approximately 2 mm in diameter, were selected and placed horizontally in the center of the sample stage of the physical property testing instrument. A TA / 0.5 gel probe was used. A single compression test was performed on each product at a test speed of 0.5 mm / s and a trigger force of 5 g, with each compression displacement being 2 mm. This compression test was repeated three times for each product.

[0063] As can be seen, the experimental product remained intact after testing, while the control product was pulverized. Therefore, the test results show that the experimental product (i.e., the product prepared by the liquid metal magnetic hydrogel microsphere preparation method disclosed in this invention) has stronger mechanical strength than the control product (i.e., conventional hydrogel). The liquid metal magnetic hydrogel microspheres prepared by the liquid metal magnetic hydrogel microsphere preparation method disclosed in this invention have stronger mechanical strength.

[0064] Study 3: Adsorption Efficiency Test

[0065] Accurately weigh 10 mg of malachite green crystal powder, dilute to 100 mL with ultrapure water, sonicate for 10 min and shake well to prepare a 100 mg / L malachite green aqueous solution.

[0066] Using pure water as a blank control, a full wavelength scan of 190–1100 nm was performed using a UV-Vis spectrophotometer. The scan results showed that malachite green had a significant peak at a wavelength of 618 nm, so subsequent experiments were conducted at this wavelength to measure absorbance.

[0067] In five 25 mL colorimetric tubes, 100 mg / L malachite green solution was added and successively diluted and brought to volume to prepare 1–5 mg / L malachite green standard solutions for the purpose of plotting the adsorption performance standard curve. The standard curve equation is A = 0.02124C + 0.09r. 2 =0.9992 (A is absorbance, C is concentration of malachite green solution). The decolorization efficiency (η,%) of the hydrogel microspheres adsorbing the dye malachite green is calculated according to formula (1):

[0068]

[0069] In the formula: C0 is the mass concentration (mg / L) of malachite green in the solution before adsorption; C e The value represents the mass concentration (mg / L) of malachite green in the solution after adsorption.

[0070] The decolorization efficiency of the liquid metal magnetic hydrogel microspheres prepared in the experimental and control examples was compared under the same conditions. Please refer to [link to relevant documentation]. Figure 5 and Figure 6The experimental product, liquid metallic magnetic hydrogel microspheres, swelled fully after adsorption, and the solution was colorless and transparent. In contrast, the control product, magnetic hydrogel microspheres, were dense, and the solution was blue-green.

[0071] Please see Figure 6 Calculations showed that the decolorization rate of the magnetic hydrogel microspheres was only 33%, while that of the liquid metal magnetic hydrogel microspheres was nearly 100%. This indicates that the experimental product, the liquid metal magnetic hydrogel microspheres, has a higher decolorization efficiency, and that the liquid metal plays a role in enhancing the adsorption efficiency within the magnetic hydrogel microspheres. Furthermore, the physically stable liquid metal possesses good fluidity and deformability, which can promote the formation of uniform pores.

[0072] Study 4: Liquid Metal Addition Amount

[0073] Liquid metal serves as the primary pore-forming agent in magnetic hydrogel microspheres. Different amounts of liquid metal added can improve the mechanical strength of the microspheres (i.e., the adsorbent), thus affecting the adsorption efficiency. Please refer to [link to relevant documentation]. Figure 7 In a dry state, the surface of the liquid metal magnetic hydrogel microspheres prepared in the experimental example was sharper than that of the magnetic hydrogel microspheres prepared in the control example.

[0074] In addition, the amount of liquid metal added in the experimental examples was adjusted separately. That is, while keeping other conditions unchanged, the amount of liquid metal added in the experimental examples was adjusted (0 wt% liquid metal; 0.05 wt% liquid metal; 0.07 wt% liquid metal; 0.1 wt% liquid metal) to obtain the products. The hardness of the products was then tested. Please refer to [link / reference]. Figure 8 As can be seen, the gel spheres with 0.05 wt% liquid metal added are less hard than those without liquid metal (0 wt%). This is because an appropriate amount of liquid metal supports the hydrogel network in the middle, forming a fluffy network. However, adding too much liquid metal may cause the network to become too large and collapse, thus failing to maintain the pore structure and having a significant impact on the decolorization rate.

[0075] In addition, please see Figure 9 When the amount of liquid metal added exceeds 0.05 wt%, the decolorization rate decreases from 100% to 65%. Excessive liquid metal filling the pores of the adsorbent (i.e., liquid metal magnetic hydrogel microspheres) reduces the decolorization rate and easily leads to excessive waste of adsorbent material. Considering various indicators such as hardness and adsorption efficiency, experiments show that the optimal amount of liquid metal added is 0.05 wt%.

[0076] Study 5: Sodium alginate mass concentration

[0077] Sodium alginate is one of the main components in constructing magnetic hydrogel microspheres, and its dosage affects the microsphere formation and adsorption effect. Please see [link to relevant documentation]. Figure 10 The decolorization rate of malachite green by the adsorbent (i.e., liquid metallic magnetic hydrogel microspheres) decreased with increasing sodium alginate concentration. At a sodium alginate concentration of 2.4 wt%, the adsorbent did not form; while at 9.6 wt%, the formed adsorbent exhibited tailing. Therefore, a sodium alginate concentration of 4.8 wt% was the optimal amount for this experiment.

[0078] Study 6: Adsorbent Dosage

[0079] Please see Figure 11 When the mass of the adsorbent (i.e., liquid metal magnetic hydrogel microspheres) increased from 0.01g to 0.05g, the adsorption rate increased from 15% to 75%. The decolorization rate increased significantly when the mass increased from 0.04g to 0.05g. Therefore, the amount of adsorbent added was determined to be 0.05g.

[0080] Study 7: Adsorption Time

[0081] Please refer to the effect of adsorption time. Figure 12 As the adsorption time increased from 1 hour to 6 hours, the decolorization rate increased from 53% to 100% before stabilizing. Therefore, within a certain time range, the adsorption rate of the pigment is positively correlated with the adsorption time, and the solution became clear after 6 hours of adsorption. Thus, it was determined that the adsorbent (i.e., liquid metallic magnetic hydrogel microspheres) completed the adsorption test within 6 hours.

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. The use of liquid metal magnetic hydrogel microspheres, characterized in that, the liquid metal magnetic hydrogel microspheres are prepared by a preparation method comprising the following steps: (1) ultrasonic dispersion of sodium alginate in deionized water to obtain a sodium alginate dispersion solution; (2) adding liquid metal to the sodium alginate dispersion solution, ultrasonic dispersion and uniform stirring to obtain a SA-LM solution; (3) taking another SA-LM solution, adding crosslinking agent and nano Fe3O4 powder to the SA-LM solution, then adding initiator to the SA-LM solution and mixing uniformly to obtain a pre-gel solution; (4) dropping the pre-gel solution into a CaCl2 solution while performing magnetic stirring for 1 h to form liquid metal magnetic hydrogel microspheres; (5) drying the liquid metal magnetic hydrogel microspheres; the liquid metal magnetic hydrogel microspheres have wrinkle-shaped pores on the surface, and metal elements are aggregated on the pore walls of the pores to form a liquid metal support, and the liquid metal magnetic hydrogel microspheres have a three-dimensional network structure with large pores; the use of the liquid metal magnetic hydrogel microspheres adopts the following steps: (1) taking 0.01g to 0.05g of liquid metal magnetic hydrogel microspheres and adding them to a malachite green aqueous solution; (2) dispersing the liquid metal magnetic hydrogel microspheres in the solution and then performing static adsorption, and the adsorption time is 1h to 6h.

2. Use of liquid metal magnetic hydrogel microspheres according to claim 1, characterized in that, In step (1), the sodium alginate is 15g, and the mass concentration of the sodium alginate dispersion solution is 4.8%wt; In step (2), the liquid metal is 7.5mg; In step (3), the SA-LM solution is 2mL.

3. Use of liquid metal magnetic hydrogel microspheres according to claim 2, characterized in that, The crosslinking agent is one or more of acrylamide, bisacrylamide, and tetramethyl ethylenediamine; the mass concentration of the acrylamide is 19%wt, and the volume is 2.75mL; the mass concentration of the bisacrylamide is 2‰, and the volume is 300μL; the volume of the tetramethyl ethylenediamine is 10μL.

4. Use of liquid metal magnetic hydrogel microspheres according to claim 2, characterized in that, The initiator is ammonium persulfate.

5. Use of liquid metal magnetic hydrogel microspheres according to claim 2, characterized in that, The volume of the CaCl2 solution is 5ml.

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