A protamine-chitosan complex and a preparation method and application thereof

Abstract

The application discloses a protamine-chitosan compound and a preparation method and application thereof, and relates to the technical field of biological resource utilization and wastewater treatment. 60 After Co irradiation and compounding, the protamine-chitosan compound is freeze-dried, and can be used as a flocculant for removing arsenic from wastewater. The flocculant is environment-friendly, the arsenic removal process is simple, the arsenic removal efficiency is high, the flocculant has a certain desorption capacity, can be reused, and cost reduction is achieved.

Description

Technical Field

[0001] This invention relates to the field of biological resource utilization and wastewater treatment technology, and more specifically to a protamine-chitosan complex, its preparation method and application. Background Technology

[0002] Arsenic, commonly known as arsenic trioxide, is a nonmetallic element frequently used in pesticides, herbicides, insecticides, and many alloys. Its compound, arsenic trioxide, is known as arsenic trioxide, a highly toxic substance.

[0003] The most abundant form of arsenic in the aquatic environment is inorganic arsenic, and trivalent arsenic is more toxic and more soluble in water than pentavalent arsenic. After arsenic enters the human body, only a small portion is metabolized and excreted; the vast majority accumulates in various organs, posing a health risk. Residual arsenic in the body often binds to enzyme systems in cells. If left unchecked, this can lead to the inactivation of many enzymes, stimulating the nervous system and affecting red blood cells over time. It may even induce malignant tumors, and in severe cases, can cause death.

[0004] Therefore, removing arsenic ions from water is crucial for human health. However, existing arsenic removal methods suffer from problems such as low adsorption capacity, poor adsorbent stability, high risk of desorption pollution, and low adsorption efficiency of arsenic in its oxidized state.

[0005] Therefore, how to provide a flocculant that is simple to process and environmentally friendly is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a protamine-chitosan complex, its preparation method, and its application. The preparation method of the present invention is simple and easy to promote. The prepared protamine-chitosan complex can effectively remove arsenic with high arsenic removal efficiency, no secondary pollution, and is environmentally friendly.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A protamine-chitosan complex, comprising protamine and chitosan mixed in a mass ratio of 4-6:1, and then subjected to... 60 It is obtained by lyophilization after Co irradiation recombination.

[0009] To address the problems in the background technology, the inventors creatively employed a compound of protamine and chitosan. Both protamine and chitosan are byproducts of aquatic product processing, natural components, environmentally friendly and pollution-free. Furthermore, they eliminate the need for multiple flocculations in wastewater to remove arsenic, simplifying the operation and achieving highly efficient arsenic removal. Protamine is a protein, primarily composed of polycationic peptides, typically formed by the condensation of only about 30 amino acids, mainly arginine. It possesses strong alkalinity and positive charge, and when added to wastewater, it can pass through its positively charged amino groups (-NH3). + ) and negatively charged arsenate (AsO4) 3- Protamine can bind to arsenic through electrostatic attraction and coordination with arsenic or arsenous acid (H3AsO3); however, although protamine has excellent adsorption properties for arsenic, its small molecular weight and high water solubility make it difficult for adsorbed protamine to be removed from wastewater, thus failing to achieve the true purpose of arsenic removal. Accordingly, the inventors combined protamine with chitosan. On the one hand, protamine provides a high density of positively charged sites, efficiently capturing arsenic ions. On the other hand, chitosan enhances the chelation ability for arsenic through its network structure and hydroxyl / amino active sites. At the same time, as a macromolecular backbone, it endows the complex with flocculation properties. The combination of the two can not only significantly improve the adsorption capacity and rate of arsenic, but also achieve rapid solid-liquid separation through flocculation and sedimentation. Furthermore, in this invention, the two are not simply mixed, but irradiation technology is used to crosslink chitosan and protamine to form a protamine-chitosan complex, which further enhances the positive charge of the complex (by irradiation inducing the amino and hydroxyl groups to form covalent bonds, exposing more active sites), improving the specific adsorption capacity for arsenic. At the same time, as a flocculant, it can be easily separated after adsorption (the complex forms large flocs, which can be quickly removed by conventional filtration or centrifugation).

[0010] Preferably, protamine solid and chitosan are mixed at a mass ratio of 4 to 6:1 to ensure that the complex has the best charge density and flocculation structure balance. If the amount of protamine solid added is too much (>6:1), it will lead to too many free amino groups in the complex. Although it can increase the arsenic adsorption capacity, the excessive positive charge may cause excessive dispersion of colloids, which will reduce the flocculation and sedimentation efficiency. If the proportion of protamine is too low (<4:1), the chitosan skeleton will account for too much of the effective adsorption sites, weaken the specific binding ability to arsenic, and the floc structure will be too loose and difficult to separate quickly.

[0011] As a preferred technical solution, the protamine and chitosan are mixed in a mass ratio of 5:1.

[0012] Another object of the present invention is to provide a method for preparing the above-mentioned protamine-chitosan complex, comprising the following steps:

[0013] (1) Weigh protamine and chitosan according to the proportion, mix them, and then add 3 to 5 times the total solid mass of plasma-activated water to homogenize the mixture. The pH of the plasma-activated water is 4.0 to 5.5.

[0014] (2) After homogenization, the liquid material is subjected to 60 Co irradiation treatment;

[0015] (3) Freeze-drying.

[0016] As a preferred technical solution, step (2) 60 The parameters for the Co irradiation treatment were as follows: a transparent glass containing protamine and chitosan was placed 40 cm above the ground and 1.4 m away from the 60Co irradiation source; the irradiation dose rate was 33 Gy / min; the irradiation time was 120 min; the irradiation non-uniformity was less than 1.0; and the irradiation ambient temperature was 18℃.

[0017] As a preferred technical solution, the freeze-drying parameters for step (3) are as follows: the irradiated mixture is pre-frozen at -40°C for 4 hours, and then transferred to a freeze dryer. Under the conditions of cold trap temperature of -50°C and vacuum degree of 10Pa, it is first kept at -30°C for 12 hours for primary drying, and then gradually heated to 25°C for secondary drying for 6 hours, finally obtaining a loose and porous protamine-chitosan complex.

[0018] As a preferred technical solution, the method for preparing the protamine is as follows: after pretreating the fish testis tissue, it is mixed with plasma-activated water at a material-to-liquid ratio of 1:9 to 11. Then, 4 to 5 times the volume of 1.0 mol / L sulfuric acid is added to the mixture, and the mixture is immediately subjected to ultrasonic treatment at 45°C. After adjusting the pH value of the ultrasonically treated mixture to 7.0, it is desalted by nanofiltration, precipitated with ethanol, and dried to obtain protamine.

[0019] The method for preparing protamine in this invention does not involve direct sulfuric acid treatment of the pretreated fish testis tissue. Instead, it uses plasma-activated water treatment. This plasma-activated water has a low pH and contains a large number of excited-state and metastable reactive particles (such as ·OH, H2O2, and NO2). - ) and charged charge (H3O) + The activated fish testes can efficiently lyse cell membranes, enhance the solubility of protamine, and selectively degrade impurities, thereby effectively improving the extraction efficiency of protamine. Furthermore, plasma-activated water treatment can protonate the basic amino acids (such as arginine guanidinoses) of protamine, enhancing its positive charge and potentially exposing more thiol (-SH) sites, further improving its adsorption capacity for arsenic ions.

[0020] More preferably, the method for pretreatment of the fish testis tissue is as follows: the fish testis tissue after impurity removal and defatting is placed in a food processor and crushed, 0.2 mol / L NaCl solution is added, mechanical homogenization is performed for 1 min, stirring is performed in an ice bath for 20 min, standing is allowed for 10 min, high-speed centrifugation is performed at 3000-5000 rpm for 10 min, the supernatant is discarded, and the precipitate is collected.

[0021] More preferably, the plasma-activated water has a pH of 4.0–5.5, a conductivity of 800–1300 μs / cm, an ORP of 450–650 mV, and a temperature of 30–45 °C.

[0022] Another object of the present invention is to provide the application of the above-mentioned protamine-chitosan complex or the protamine-chitosan complex obtained by the above preparation method as a flocculant in the adsorption and removal of arsenic from wastewater.

[0023] As a preferred technical solution, when the protamine-chitosan complex is added to wastewater for arsenic removal adsorption, the adsorption pH is controlled at 1-9, the adsorption temperature at 25℃-65℃, the adsorption time at 6-24h, and the amount added is 1-10g / L of wastewater.

[0024] More preferably, when the protamine-chitosan complex is added to wastewater for arsenic removal adsorption, the adsorption pH is controlled at 5, the adsorption temperature at 55°C, the adsorption time at 16 h, and the amount added is 7 g / L of wastewater.

[0025] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a protamine-chitosan complex composed of natural ingredients, which can be used as a flocculant for arsenic removal from wastewater. This flocculant is environmentally friendly, has a simple arsenic removal process, high arsenic removal efficiency, a certain desorption capacity, and can be reused to reduce costs. Moreover, the preparation method of the protamine-chitosan complex of the present invention is simple, has a short production cycle, low production cost, and is easy to promote. Attached Figure Description

[0026] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 The adsorption capacity of protamine-chitosan complex under different arsenic contents;

[0028] Figure 2 The adsorption capacity of protamine-chitosan complex under different pH conditions;

[0029] Figure 3 The adsorption capacity of protamine-chitosan complex at different adsorption temperatures;

[0030] Figure 4 The effect of different protamine-chitosan complex dosages on adsorption capacity;

[0031] Figure 5 The adsorption amount of protamine-chitosan complex at different adsorption times is represented. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention discloses a protamine-chitosan complex and its application in the adsorption and removal of arsenic from wastewater. The chitosan used in this invention is commercially available and its source is not specifically limited. Unless otherwise specified, the methods involved are conventional methods and will not be described in detail here.

[0034] Example 1

[0035] Preparation of protamine

[0036] (1) Pretreatment of fish testis tissue: After removing impurities and defatting, fish (sturgeon) testis tissue was placed in a food processor and crushed. 0.2 mol / L NaCl solution was added, and the mixture was mechanically homogenized for 1 min. The mixture was stirred in an ice bath for 20 min, allowed to stand for 10 min, and centrifuged at 3000-5000 rpm for 10 min. The supernatant was discarded and the precipitate was collected.

[0037] (2) After pretreatment of fish testis tissue, it is mixed with plasma-activated water at a material-to-liquid ratio of 1:9-11. Then, 4-5 times the volume of 1.0 mol / L sulfuric acid is added to the mixture, and the mixture is immediately incubated at 45°C with an intensity of [missing information]. The extract was extracted with ultrasonic assistance for 12 hours, allowed to stand for 1 hour, and then centrifuged at 0°C for 10-20 minutes. The filtrate was collected, and the pH of the filtrate was adjusted to 7.0 with NaOH. After nanofiltration and desalting, the filtrate was precipitated with 3 times its volume of cold ethanol. The precipitate was collected by centrifugation and dried at 30°C to obtain protamine.

[0038] The plasma-activated water has a pH of 4.0–5.5, a conductivity of 800–1300 μs / cm, an ORP of 450–650 mV, and a temperature of 30–45℃.

[0039] Example 2

[0040] Protamine-chitosan complex prepared using protamine obtained in Example 1

[0041] (1) Weigh protamine and chitosan at a mass ratio of 5:1, mix them, and then add 4 times the total solid mass (e.g., if the total mass of protamine and chitosan is 10g, then add 30-50mL) of plasma-activated water with pH 5 to homogenize. Homogenize mechanically at 20-25℃ and 6500rpm for 4 minutes.

[0042] (2) After homogenization, the liquid is then subjected to... 60 Co irradiation treatment: A transparent glass containing protamine and chitosan was placed 40 cm above the ground and 1.4 m away from a 60Co irradiation source. The irradiation dose rate was 33 Gy / min, the irradiation time was 120 min, the irradiation non-uniformity was less than 1.0, and the irradiation ambient temperature was 18℃.

[0043] (3) Freeze-drying: The irradiated mixture was pre-frozen at -40°C for 4 hours, and then transferred to a freeze dryer. Under the conditions of cold trap temperature of -50°C and vacuum degree of 10Pa, it was first kept at -30°C for 12 hours for primary drying, and then gradually heated to 25°C for secondary drying for 6 hours to obtain the protamine-chitosan complex of this embodiment.

[0044] Example 3

[0045] Weigh protamine and chitosan at a mass ratio of 4:1, mix them, and then add 3 times the total solid mass of plasma-activated water with pH 5.5 to homogenize. Homogenize mechanically for 3 minutes at 20-25℃ and 5000rpm.

[0046] The subsequent steps are the same as in Example 2 for preparing the protamine-chitosan complex of this example.

[0047] Example 4

[0048] Weigh protamine and chitosan at a mass ratio of 6:1, mix them, and then add 5 times the total solid mass of plasma-activated water with pH 4 to homogenize. Homogenize mechanically for 5 minutes at 20-25℃ and 8000rpm.

[0049] The subsequent steps are the same as in Example 2 for preparing the protamine-chitosan complex of this example.

[0050] Comparative Example 1

[0051] Replace chitosan with carboxymethyl cellulose, and follow the same steps as in Example 2.

[0052] Comparative Example 2

[0053] Step (2) omitted 60 Co irradiation treatment, with other steps the same as in Example 2.

[0054] Experimental Example 1:

[0055] The protamine-chitosan complex prepared in Example 2 was used to determine the arsenic removal effect in wastewater.

[0056] Preparation of arsenic-containing simulation solution (stock solution): Accurately weigh 0.25g of arsenic trioxide (As2O3) using an electronic balance and dissolve it in 2.5M NaOH solution. Add deionized water until the solution volume is 30mL. Then, take an appropriate amount of 6M HCl solution and 2M NaOH solution to adjust the pH of the solution to 6.5. Then add 0.2g of NaHCO3 solid. After the sodium salt dissolves in the water, finally make up the volume to 50mL with deionized water to obtain a 5g / L As(III) standard stock solution.

[0057] Adsorption experiment: The protamine-chitosan complex was pulverized to 100 mesh, and 0.250 g of each was placed in a 50 ml centrifuge tube. A diluent containing 100 mg / L As was added. The mixture was incubated at 25 °C with constant shaking (180 r / min) for 12 h, and then centrifuged at 8000 r / min for 10 min. The supernatant was collected to determine the metal concentration.

[0058] Desorption experiment: The filter residue left after centrifugation in the adsorption experiment was washed twice with saturated NaCl, and then centrifuged at 12000 r / min. The saturated NaCl washing solution was then poured off. For each heavy metal adsorption experiment, 25 mL of 0.1 mol / L NaOH was used as the desorbent and the mixture was shaken at a constant temperature (180 r / min) for 12 h. The centrifuge tubes were then removed and centrifuged at 8000 r / min for 10 min. The supernatant was then used to measure the As concentration.

[0059] Adsorption isotherm determination: Weigh 0.250 g of protamine-chitosan complex powder into a 50 ml centrifuge tube, and add 25 mL of As solution with initial concentrations of 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 mg / L, respectively, with a pH of 5.0. Incubate in a benchtop constant-temperature shaker at 25 °C (180 r / min) for 12 h, filter, collect the filtrate, and simultaneously perform a blank control without material. Use the Langmuir equation to describe the adsorption process using adsorption isotherms.

[0060] Arsenic determination: After ensuring the filtrate is clear, the arsenic content is determined using hydride-atomic fluorescence spectrometry (AFS-8220, Beijing Jitian). The pre-reducing agent before instrumentation is 10% thiourea and 10% ascorbic acid. During instrumentation, the reducing agent is 20% potassium borohydride + 5% potassium hydroxide, the current carrier is 5% hydrochloric acid solution, the instrument's negative high voltage is 240–270V, and the lamp current is 50mA.

[0061] 1. The effect of arsenic content in water

[0062] Weigh 0.25 g of protamine-chitosan complex powder into a 50 mL centrifuge tube, and add 25 mL of As solution with initial concentrations of 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 mg / L, respectively, with a pH of 5.0. Incubate in a benchtop constant-temperature shaker at 25 °C (180 r / min) for 12 h, filter, and collect the filtrate. A blank control without material is also provided. After the process, a certain amount of the supernatant is filtered through a 0.45 μL filter membrane, and the arsenic concentration is determined by HG-AFS (see Table 1 and Appendix). Figure 1 ).

[0063] Table 1

[0064]

[0065] As shown in Table 1, the protamine-chitosan complex has a good adsorption effect on arsenic, and the adsorption capacity increases with the increase of arsenic concentration in water.

[0066] 2. Effect of pH

[0067] Five 100 mg / L arsenic solutions were prepared, and the pH was adjusted to 1, 3, 5, 7, and 9 using NaOH and hydrochloric acid, respectively. 5 g of protamine-chitosan complex was added, and the solutions were incubated at 25 °C and 150 rpm for 12 h in a constant-temperature shaker. Adsorption and desorption performance were tested at different pH values. After the process, a certain amount of the supernatant was filtered through a 0.45 μL filter membrane, and the arsenic concentration was determined by HG-AFS (see Table 2 and Appendix). Figure 2 ).

[0068] Table 2

[0069]

[0070] As shown in Table 2, the protamine-chitosan complex has a high adsorption capacity for arsenic at pH 5.

[0071] Table 3

[0072]

[0073] The Langmuir model is a classical theory for describing monolayer adsorption. Proposed in 1916 by American physical chemist Irving Langmuir based on the kinetic theory of molecules and some assumptions, it is now widely used in adsorption chemistry. This model is primarily used to study the adsorption behavior of gases or liquids on solid surfaces and is applicable to monolayer adsorption cases involving either chemisorption (chemical bonding) or physisorption (van der Waals forces). As shown in Table 3, the maximum adsorption capacity of the protamine-chitosan complex in this invention is derived to be 63.3 mg / g, consistent with the measured results in Table 2.

[0074] 3. Effect of adsorption temperature

[0075] Five 100 mg / L arsenic solutions were prepared, and the pH was adjusted to 7 using NaOH and hydrochloric acid. 5 g of protamine-chitosan complex was added, and the solutions were reacted for 12 h at 25℃, 35℃, 45℃, 55℃, and 65℃ in a constant-temperature shaker at 150 r / min. Adsorption and desorption performance were tested at different temperatures. After the process, a certain amount of the supernatant was filtered through a 0.45 μL filter membrane, and the arsenic concentration was determined by HG-AFS (see Table 4 and Appendix). Figure 3 ).

[0076] Table 4

[0077]

[0078]

[0079] As shown in Table 4, the adsorption capacity of the protamine-chitosan complex is affected by temperature, and it has a high adsorption capacity for arsenic at 35℃.

[0080] 4. Effect of compound dosage

[0081] Five 100 mg / L arsenic solutions were prepared, and the pH was adjusted to 7 using NaOH and hydrochloric acid. 1 g, 3 g, 5 g, 7 g, and 10 g of protamine-chitosan complex were added respectively, and the mixture was reacted in a constant temperature shaker at 35℃ and 150 r / min for 12 h to test the adsorption and desorption performance at different dosages. After the process, a certain amount of the supernatant was filtered through a 0.45 μL filter membrane, and the arsenic concentration was determined by HG-AFS (see Table 5 and Appendix). Figure 4 ).

[0082] Table 5

[0083]

[0084] As shown in Table 5, the adsorption capacity of the protamine-chitosan complex for arsenic increases with the amount of complex added.

[0085] 5. Effect of adsorption time

[0086] Five 100 mg / L arsenic solutions were prepared, and the pH was adjusted to 7 using NaOH and hydrochloric acid. 5 g of protamine-chitosan complex was added to each solution, and the adsorption and desorption performance were tested at different adsorption times (6 h, 12 h, 16 h, 20 h, and 24 h) in a constant temperature shaker at 25 °C and 150 r / min. After the process, a certain amount of supernatant was filtered through a 0.45 μL filter membrane, and the arsenic concentration was determined by HG-AFS (see Table 6 and Appendix). Figure 5 ).

[0087] Table 6

[0088]

[0089] As shown in Table 6, the adsorption capacity of the protamine-chitosan complex for arsenic increases with the extension of adsorption time, and the growth rate slows down after 16 hours. Considering the time cost, 16 hours of adsorption is considered to be the optimal time.

[0090] 6. Orthogonal experiment

[0091] Using the amount of protamine-chitosan complex added (A), adsorption pH (B), adsorption temperature (C), and adsorption time (D) as the research objects, a four-factor, three-level orthogonal experiment was designed. The factor level table is shown in Table 7. The optimal adsorption scheme was determined by using adsorption capacity and adsorption-desorption efficiency as evaluation indicators.

[0092] Table 7

[0093]

[0094] Table 8

[0095]

[0096]

[0097] As shown in Table 8, the order of influence of different factors on adsorption capacity is: compound dosage > adsorption time > adsorption pH > adsorption temperature. The optimal extraction process is A3B2C2D2, i.e., compound dosage of 7g, adsorption pH of 5, adsorption temperature of 35℃, and adsorption time of 16h. The order of influence of different factors on desorption efficiency is: adsorption pH > adsorption temperature > compound dosage > adsorption time. The optimal extraction process is A1B3C3D1, i.e., compound dosage of 3g, adsorption pH of 5, adsorption temperature of 45℃, and adsorption time of 12h. Considering that the desorption efficiency of composite materials is relatively low and the material is not easy to desorb, the adsorption capacity is selected as the main result. Finally, the optimal adsorption pH, compound dosage of 7g, adsorption temperature of 35℃, and adsorption time of 16h are determined.

[0098] Experimental Example 2

[0099] Using the optimal process conditions obtained in Example 1, the arsenic removal efficiency of the complexes obtained in Examples 1-4 and Comparative Examples 1-2 was tested by atomic fluorescence spectrometry, wherein As(III) was pre-oxidized to As(V) before treatment. The results are shown in Table 9.

[0100] Table 9

[0101]

[0102]

[0103] According to the results in Table 9, although As(III) was pre-oxidized before being treated with the complex for arsenic removal, its removal rate was still lower than that of As(V). This may be because the change in water pH after oxidation with H2O2 weakened the arsenic removal effect of the protamine-chitosan (5:1) complex. However, overall, the protamine-chitosan (5:1) complex in Example 2 showed the best arsenic removal effect.

[0104] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0105] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A protamine-chitosan complex, characterized in that, Protamine and chitosan are mixed in a mass ratio of 4–6:1, and then... 60 After Co irradiation and recombination, it is obtained by freeze drying; The preparation method specifically includes the following steps: (1) Weigh protamine and chitosan according to the proportion, mix them, and then add 3 to 5 times the total solid mass of plasma-activated water with pH 4.0 to 5.5 to homogenize. Homogenize mechanically at 20 to 25°C and 5000 to 8000 rpm for 3 to 5 min. (2) After homogenization, the liquid material is subjected to 60 Co irradiation treatment: A transparent glass containing protamine and chitosan was placed 40 cm above the ground. 60 Co irradiation source 1.4 m, irradiation dose rate 33 Gy / min, irradiation time 120 min, irradiation non-uniformity less than 1.0, irradiation ambient temperature 18℃; (3) Freeze-drying.

2. The protamine-chitosan complex according to claim 1, characterized in that, The protamine and chitosan were mixed in a mass ratio of 5:

1.

3. The method for preparing the protamine-chitosan complex according to claim 1 or 2, characterized in that, Includes the following steps: (1) Weigh protamine and chitosan according to the proportion, mix them, and then add 3 to 5 times the total solid mass of plasma-activated water with pH 4.0 to 5.5 to homogenize. Homogenize mechanically at 20 to 25°C and 5000 to 8000 rpm for 3 to 5 min. (2) After homogenization, the liquid material is subjected to 60 Co irradiation treatment: A transparent glass containing protamine and chitosan was placed 40 cm above the ground. 60 Co irradiation source 1.4 m, irradiation dose rate 33 Gy / min, irradiation time 120 min, irradiation non-uniformity less than 1.0, irradiation ambient temperature 18℃; (3) Freeze-drying.

4. The method for preparing the protamine-chitosan complex according to claim 3, characterized in that, Step (3) freeze-drying parameters: The irradiated mixture was pre-frozen at -40℃ for 4 h, and then transferred to a freeze dryer. Under the conditions of cold trap temperature of -50℃ and vacuum degree of 10 Pa, it was first kept at -30℃ for 12 h for primary drying, and then gradually heated to 25℃ for secondary drying for 6 h, finally obtaining a loose and porous protamine-chitosan complex.

5. The method for preparing the protamine-chitosan complex according to claim 3, characterized in that, The method for preparing protamine is as follows: after pretreating fish testis tissue, it is mixed with plasma-activated water at a material-to-liquid ratio of 1:9 to 11. Then, 4-5 times the volume of 1.0 mol / L sulfuric acid is added to the mixture, and the mixture is immediately subjected to ultrasonic treatment at 45°C. After adjusting the pH value of the ultrasonically treated mixture to 7.0, it is desalted by nanofiltration, precipitated with ethanol, and dried to obtain protamine.

6. The method for preparing the protamine-chitosan complex according to claim 5, characterized in that, The plasma-activated water has a pH of 4.0–5.5, a conductivity of 800–1300 μs / cm, an ORP of 450–650 mV, and a temperature of 30–45℃.

7. The application of the protamine-chitosan complex according to claim 1 or 2, or the protamine-chitosan complex obtained by any of the preparation methods according to claims 3-6, as a flocculant in the adsorption and removal of arsenic from wastewater.

8. The application according to claim 7, characterized in that, When the protamine-chitosan complex is added to wastewater for arsenic removal adsorption, the adsorption pH is controlled at 1–9, the adsorption temperature at 25℃–65℃, the adsorption time at 6–24 h, and the dosage is 1–10 g / L of wastewater.

9. The application according to claim 8, characterized in that, When the protamine-chitosan complex was added to wastewater for arsenic removal adsorption, the adsorption pH was controlled at 5, the adsorption temperature at 35℃, the adsorption time at 16 h, and the dosage was 7 g / L of wastewater.

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