Method for separating biological sulphur by flocculants and electrolytic flotation

Abstract

This invention provides a flocculant and a method for separating bio-sulfur via electrolytic flotation, relating to the field of environmental protection and purification technology. The flocculant comprises metal cations and chitosan, with the metal cations complexed with the chitosan. The method for separating bio-sulfur via electrolytic flotation includes: Step 1: passing the bio-sulfur-containing material into an electrolytic reaction device; Step 2: performing an electrolytic oxidation stage; Step 3: performing an electrolytic flotation stage, wherein a flocculant is added during the electrolytic flotation stage; Step 4: collecting the bio-sulfur. This invention can rapidly and efficiently separate bio-sulfur from effluent, with a simple process, no need for electrolyte addition, small flocculant dosage, and environmental friendliness. The bio-sulfur recovery rate can reach over 97%, and the sulfur purity can reach over 92%.

Description

Technical Field

[0001] This invention relates to the field of environmental protection and purification technology, specifically to a flocculant and a method for separating biological sulfur by electrolytic flotation. Background Technology

[0002] Biological desulfurization technology, developed in the 1980s, is a new alternative to conventional desulfurization. It has many advantages, such as not requiring catalysts or oxidants, not needing to treat chemical sludge, producing very little biological pollution, low energy consumption, sulfur recovery, high efficiency, and no odor. Its disadvantages include difficulty in process control and stringent requirements for operating conditions.

[0003] In bioreactors, elemental sulfur obtained through bioconversion (bio-sulfur) differs significantly from naturally occurring chemical sulfur in several aspects. AJH Janssen et al. studied this sulfur produced through microbial transformation, indicating that the resulting sulfur particles exhibit distinct colloidal properties. A large polymeric compound surrounds the bio-sulfur particles, similar to protein polymers. Furthermore, their investigation of the interfacial characteristics of the elemental sulfur particles revealed that these bio-converted sulfur particles carry a negative surface charge, making them hydrophilic particles, entirely different from naturally occurring crystalline sulfur. Zhang Keqiang et al. explored and analyzed the characteristics of bio-sulfur produced in bioreactors during the biological treatment of sulfide-containing wastewater. They analyzed the particle size of bio-sulfur particles using dynamic light scattering (LPLS) technology, finding that the particle size ranged from approximately 0.5 to 10 μm.

[0004] Currently, commonly used methods for separating particulate matter mainly include gravity sedimentation, centrifugal sedimentation, flocculation sedimentation, and air flotation. Regarding the separation of bio-sulfur, current research mainly focuses on the separation of bio-sulfur during sulfide removal processes. Flocculation sedimentation can separate bio-sulfur particles from water, but due to the large amount of flocculant used, a large amount of flocculant can encapsulate the bio-sulfur particles, causing significant difficulties for subsequent solvent extraction, crystallization, and purification. The process of "slow filter-sand scraping-extraction-distillation" for the recovery of elemental sulfur has been found to be expensive and costly to be economically viable due to the high toxicity of extraction, thus its engineering application requires further investigation.

[0005] Therefore, there is an urgent need to develop a method for separating bio-sulfur that requires a small amount of flocculant, has a simple and efficient process, and is environmentally friendly. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide a flocculant and a method for electrolytic flotation separation of bio-sulfur, in order to solve at least one of the following problems: reducing flocculant dosage, simple and efficient process, and environmental friendliness.

[0007] The objective of this invention is mainly achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a flocculant, the method comprising the step of mixing and reacting chitosan with a metal cation salt.

[0009] In one specific embodiment of the present invention, the mass ratio of chitosan to the metal cation salt is 1:1 to 1:2.

[0010] In one specific embodiment of the present invention, the pH value of the mixed reaction is 1-3.

[0011] In one specific embodiment of the present invention, the metal cation salt is an iron salt.

[0012] In one specific embodiment of the present invention, the iron salt is one or more of Fe2(SO4)3, Fe(NO3)3 and FeCl3.

[0013] In one specific embodiment of the present invention, the temperature of the mixing reaction is 30-40°C.

[0014] Secondly, the present invention provides a flocculant prepared according to the above preparation method, the flocculant comprising a metal cation and chitosan, wherein the metal cation and the chitosan are complexed.

[0015] Thirdly, the present invention provides a method for electrolytic flotation separation of bio-sulfur, comprising the following steps:

[0016] Step 1: Pass the material containing bio-sulfur into the electrolysis reactor;

[0017] Step 2: Perform the electrolytic oxidation stage;

[0018] Step 3: Perform the electrolytic flotation stage, during which the flocculant is added;

[0019] Step 4: Collect bio-sulfur.

[0020] In one specific embodiment of the present invention, the electrolysis reaction device includes electrodes, the electrodes including a cathode and an anode.

[0021] In one specific embodiment of the present invention, the electrode is a graphite electrode.

[0022] In one specific embodiment of the present invention, the distance between the cathode and the anode is 1-3 cm.

[0023] In a specific embodiment of the present invention, in step 1, the bio-sulfur-containing material contains 0.1-10 g / L of bio-sulfur, and / or the bio-sulfur particles in the bio-sulfur-containing material have a particle size of less than 10 μm.

[0024] In one specific embodiment of the present invention, in step 2, the current density of the direct current applied during the electrolytic oxidation stage is 0.5-2 mA / cm². 2 And / or, in step 2, the electrolysis time of the electrolytic oxidation stage is 10-20 min.

[0025] In one specific embodiment of the present invention, in step 3, the current density of the direct current applied during the electrolytic flotation stage is 3-6 mA / cm². 2 And / or, in step 3, the electrolysis time of the electrolytic flotation stage is 5-15 min; and / or, in step 3, the mass ratio of bio-sulfur to the flocculant in the electrolytic flotation stage is 1000:(1-10).

[0026] Fourthly, the present invention provides a bio-sulfur separated according to the above method.

[0027] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0028] A) The flocculant provided by this invention is a complex of chitosan and metal cations. This complex binds to bio-sulfur through chitosan and promotes the binding of metal cations to the bio-sulfur. Based on this, when this flocculant is applied to the electrolytic flotation separation of bio-sulfur, the metal cations in the solution migrate towards the cathode during electrolysis, and hydrogen bubbles are generated at and concentrated near the cathode. This causes more bio-sulfur to float to the surface with the help of the hydrogen bubbles, thus improving the recovery rate of bio-sulfur.

[0029] B) The electrolytic flotation method for separating bio-sulfur provided by this invention can quickly and efficiently separate bio-sulfur from effluent. The process is simple, requires no electrolyte addition, requires a small amount of flocculant, is environmentally friendly, and the bio-sulfur recovery rate can reach over 97%, with a sulfur purity of over 92%. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the electrolysis reaction apparatus provided by the present invention;

[0031] Among them, 1-electrolytic cell; 2-electrode; 3-power supply; 4-overflow weir; 5-collection tank. Detailed Implementation

[0032] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0033] Air flotation is a process that uses a large number of highly dispersed microbubbles as carriers to adhere tiny suspended particles in a liquid or emulsified oil in wastewater, forming a float with a density less than water that floats on the water surface, thus achieving solid-liquid or liquid-liquid separation. The Dutch company Shell-Paques uses air flotation to recover biogenic sulfur particles. This involves using pressurized air flotation or dissolved air flotation to blow the biogenic sulfur particles to the water surface, followed by further centrifugal separation.

[0034] Electrolytic flotation involves electrolyzing wastewater to produce microbubbles containing H2, O2, and CO2. These microbubbles have significant buoyancy and act as flotation agents. Suspended particles in the wastewater adhere to these microbubbles and float to the surface, thus being removed and achieving water purification. Compared to the commonly used pressurized dissolved air flotation method, this method offers advantages such as producing tiny bubbles, generating intermediate products that have a certain oxidizing effect on organic pollutants, and having a compact device with a small footprint.

[0035] In a first aspect, the present invention provides a method for preparing a flocculant, comprising the step of mixing and reacting chitosan with a metal cation salt, thereby complexing the metal cation with the chitosan.

[0036] It should be noted that the flocculant provided by this invention is a complex of chitosan and metal cations. This complex binds to bio-sulfur through chitosan and promotes the binding of metal cations to the bio-sulfur. Based on this, when the flocculant is applied to the electrolytic flotation separation of bio-sulfur, the metal cations in the solution migrate towards the cathode during electrolysis, and hydrogen bubbles are generated at and concentrated near the cathode. This causes more bio-sulfur to float to the surface with the action of the hydrogen bubbles, thus improving the recovery rate of bio-sulfur.

[0037] In one specific embodiment of the present invention, the mass ratio of chitosan to metal cationic salt is 1:1 to 1:2, for example 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, preferably 1:1.6 to 1:1.9, and more preferably 1:1.8.

[0038] In one specific embodiment of the present invention, the metal cation salt is an iron salt; preferably, the iron salt is one or more of Fe2(SO4)3, Fe(NO3)3 and FeCl3.

[0039] As a specific embodiment of the present invention, the conditions for the reaction of chitosan with metal cation salt include:

[0040] The reaction time is 1-5 hours, such as 1, 2, 3, 4, 5 hours, preferably 2-4 hours, and more preferably 3 hours;

[0041] The pH value is 1-3, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, etc., preferably 2.0-2.5, more preferably 2.2;

[0042] The temperature is 30-40℃, such as 31, 32, 33, 34, 35, 36, 37, 38, 39℃, etc., preferably 30-35℃, and more preferably 32℃.

[0043] Secondly, the present invention provides a flocculant that can be prepared by the above preparation method. The flocculant is a chitosan-modified cationic flocculant, which includes metal cations and chitosan, wherein the metal cations are complexed on the chitosan molecules.

[0044] In one specific embodiment of the present invention, the metal cation is Fe. 3+ , of which Fe 3+ Chitosan complexed with chitosan molecules yields chitosan-complexed Fe(III) flocculants.

[0045] Thirdly, the present invention provides a method for electrolytic flotation separation of bio-sulfur, the purpose of which is to disrupt the stability of the bio-sulfur colloidal system, accelerate the flocculation and aggregation of sulfur particles and solid-liquid separation, and improve the recovery rate and purity of bio-sulfur.

[0046] The technical solution of this invention is implemented as follows: Bio-sulfur-containing materials from a biological desulfurization process enter an electrolytic reaction device. During electrolysis, intermediate products generated on the anode surface, such as hydroxyl radicals and nascent oxygen, have strong oxidizing effects. The structure of the macromolecular polymers attached to the surface of the bio-sulfur particles is oxidized and destroyed, causing them to detach from the sulfur particle surface. Then, a flocculant is added to rapidly increase the particle size of the sulfur particles. Microbubbles generated by the electrodes are used as flotation carriers, causing the sulfur particles to float and separate from the water. Finally, the sulfur is collected from the top overflow weir, yielding bio-sulfur.

[0047] It should be noted that, in this invention, the materials containing bio-sulfur typically also contain desulfurizing microorganisms and salts, such as anionic sulfur. 2- SO4 2- CI - SO3 2- etc., cation Na + Mg 2+ Cu 2+ Zn2+ Fe 3+ These salts originate from added biological nutrient solutions and are generated during the metabolism of organisms.

[0048] As a specific embodiment of the present invention, the method for electrolytic flotation separation of bio-sulfur includes the following steps:

[0049] Step 1: Pass the material containing bio-sulfur into the electrolysis reactor;

[0050] Step 2: Perform the electrolytic oxidation stage to destroy the structure of the biopolymers attached to the surface of the sulfur particles;

[0051] Step 3: In the electrolytic flotation stage, the above-mentioned flocculant is added to cause the bio-sulfur particles to float and separate.

[0052] Step 4: Collect bio-sulfur.

[0053] It should be noted that the electrolytic flotation method for separating bio-sulfur provided by this invention can quickly and efficiently separate bio-sulfur from bio-sulfur-containing effluent. The process is simple, requires no electrolyte addition, uses a small amount of flocculant, is environmentally friendly, and the bio-sulfur recovery rate can reach over 97%, with a sulfur purity of over 92%.

[0054] In one specific embodiment of the present invention, in step 1, the bio-sulfur-containing material can originate from the sulfur recovery treatment unit in a microbial desulfurization process for natural gas, biogas, coal-fired flue gas, or sulfur-containing wastewater. Generally, the surface of the sulfur particles in the material is coated with biopolymers, such as polysaccharides, proteins, and lipids.

[0055] In one specific embodiment of the present invention, in step 1, the bio-sulfur-containing material contains 0.1-10 g / L of bio-sulfur, more preferably 0.5-5 g / L. The bio-sulfur content is determined using the sulfite method, as described in the literature: Reduction of produced elementary sulfur indenitrifying sulfide removal process. Environmental biotechnology, 2011, 90: 1129-1136.

[0056] In one specific embodiment of the present invention, the bio-sulfur-containing material has a particle size of less than 10 μm.

[0057] It should be noted that the present invention does not impose any special limitations on the electrode reaction device, as long as it can perform the electrolysis reaction and collect bio-sulfur. For illustrative purposes, the electrolysis reaction device provided by the present invention can be as follows: Figure 1As shown. (Refer to...) Figure 1 The electrolysis reactor includes an electrolytic cell 1, electrodes 2, a power supply 3, an overflow weir 4, and a collection tank 5. The electrolytic cell 1 is made of plexiglass, with dimensions of 15-30 cm in height and 10-15 cm in diameter. An overflow weir 4 is installed at its top, and a collection tank 5 is installed on the outside, with a height of 5-10 cm and a diameter of 15-20 cm, extending 3-6 cm above the overflow weir. The electrolytic cell 1 contains materials containing bio-sulfur. The electrodes 2 are vertically placed and include an anode and a cathode, with an electrode plate spacing of 1-3 cm. Both the anode and cathode are made of graphite. The electrolysis reactor uses a DC regulated power supply with an output voltage of 0-30V and an output current of 0-5A.

[0058] It should be noted that the electrode plate spacing has a certain impact on air flotation. When the spacing is small, the dispersion of electrolytic bubbles is poor, which affects the air flotation effect; however, the larger the spacing, the greater the power consumption. Therefore, the present invention controls the electrode plate spacing to be 1-3 cm.

[0059] In one specific embodiment of the present invention, in step 2, the current density of the direct current applied during the electrolytic oxidation stage is 0.5-2 mA / cm². 2 For example, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 mA / cm 2 The electrolysis time is 10-20 minutes.

[0060] It should be noted that in the electrolytic flotation method for separating bio-sulfur provided by this invention, during the electrolytic oxidation stage of step 2, [O], [Cl] or ·OH, H2O2, HO2 are generated on the anode surface. - Intermediate low-state particles have strong oxidizing properties, which can destroy the structure of biopolymers attached to the surface of sulfur particles.

[0061] It should be noted that in the electrolytic oxidation stage of step 2, as the current density increases, the current density exceeds 2 mA / cm². 2 The bubbles generated during electrolytic flotation become increasingly dense. Therefore, the current density can be controlled during this stage to reduce bubble formation and maximize the oxidation effect of the electrodes. Thus, this invention controls the current density during the electrolytic oxidation stage to 0.5-2 mA / cm². 2 In the electrolytic oxidation stage of step 2, the control of the electrolysis time depends on the time required to destroy the structure of the biopolymers attached to the surface of the sulfur particles. If it is too short, the sulfur purity will not be sufficient, and if it is too long, it will increase energy consumption. Therefore, the control time is 10-20 minutes.

[0062] In one specific embodiment of the present invention, during the electrolytic flotation stage of step 3, the aforementioned flocculant is added, and the DC current density applied during the electrolytic flotation stage is 3-6 mA / cm². 2 For example, 3.5, 4.0, 4.5, 5.5 mA / cm 2 The electrolysis time is 5-15 minutes.

[0063] It should be noted that in the electrolytic flotation stage of step 3, under the action of flocculant, the particle size of bio-sulfur rapidly increases from below 10μm to about 30μm. Using the microbubbles generated by the electrodes as flotation carriers, the sulfur particles float to the surface and separate from the water, finally flowing out from the top overflow weir for collection.

[0064] It should be noted that in the electrolytic flotation stage of step 3, as the current density increases, the bubbles generated by the electrolytic flotation become increasingly dense, and the rising speed of the bubbles also increases. The suspended particles are clearly carried upward by the bubbles, but when the current density is greater than 6 mA / cm³, the upward trend becomes more pronounced. 2 During this process, the rate of small bubble generation accelerates, and they easily merge into large bubbles, thus disrupting the static separation environment of the separation zone and affecting the effluent quality. In step 3, the electrolytic flotation stage, the control of the electrolysis time depends on the time required for the bio-sulfur to be carried by the bubbles to the overflow zone and discharged through the collection tank. Too short a time results in insufficient recovery, while too long a time increases energy consumption. Therefore, the electrolysis time is controlled to be 5-15 minutes.

[0065] In a specific embodiment of the present invention, in the electrolytic flotation stage of step 3, the mass ratio of bio-sulfur to the flocculant used is 1000:(1-10), for example 1000:2, 1000:3, 1000:4, 1000:5, 1000:6, 1000:7, 1000:8, 1000:9, etc. More specifically, for example, the amount of flocculant used is 1-10 mg compared to 1 g of bio-sulfur.

[0066] It should be noted that the method provided by this invention requires a small amount of flocculant, which effectively solves the problem of great difficulty in subsequent solvent extraction, crystallization and purification.

[0067] In one specific embodiment of the present invention, in step 3, electrolysis promotes the generation of bubbles in the solution, specifically the generation of hydrogen gas at the cathode, with an average diameter of 1-10 μm; and the generation of oxygen gas at the anode, with an average diameter of 20-80 μm.

[0068] It should be noted that since the biological desulfurization solution itself contains varying levels of salts, no electrolyte needs to be added during the electrolytic flotation process, and this method is largely unaffected by solution concentration. This invention can rapidly and efficiently separate biological sulfur from effluent, and is suitable for sulfur recovery units in microbial desulfurization processes for natural gas, biogas, coal-fired flue gas, and sulfur-containing wastewater. The process is simple, requires no electrolyte addition, uses a small amount of flocculant, is environmentally friendly, and achieves a biological sulfur recovery rate of over 97% and a sulfur purity of over 92%.

[0069] The following detailed description of preferred embodiments of the present invention illustrates the principles of the invention and is not intended to limit the scope of the invention.

[0070] Example 1

[0071] This embodiment provides a flocculant and a method for separating bio-sulfur by electrolytic flotation.

[0072] Firstly, a flocculant, Fe... 3+ The flocculant is complexed on chitosan molecules. The reaction conditions for preparing the flocculant are: reaction time of 3 hours, pH value of 2.2, m(chitosan):m(Fe2(SO4)3) = 1:1.8, and temperature of 32℃.

[0073] Secondly, a method for separating bio-sulfur by electrolytic flotation is provided, comprising:

[0074] Step 1: The biological sulfur-containing effluent with a biological sulfur content of 934 mg / L is fed into the electrolysis reactor. Both the anode and cathode are made of graphite electrode plates with a plate spacing of 2 cm.

[0075] Step 2: First, the electrolysis time is 10 minutes, and the current density is 1.5 mA / cm². 2 ;

[0076] Step 3: Then add 3 mg / L chitosan-modified cationic flocculant, electrolyze for 5 minutes, and use a current density of 4 mA / cm². 2 ;

[0077] Step 4: Collect bio-sulfur at the overflow weir after electrolysis.

[0078] In this embodiment, the bio-sulfur recovery rate reached 98.1%, and the sulfur purity reached 94.5%.

[0079] Example 2

[0080] Firstly, the flocculant provided in this embodiment is the same as that in Embodiment 1.

[0081] Secondly, a method for separating bio-sulfur by electrolytic flotation is provided, comprising:

[0082] Step 1: The biological sulfur-containing effluent with a biological sulfur content of 934 mg / L is fed into the electrolysis reactor. Both the anode and cathode are made of graphite electrode plates with a plate spacing of 2 cm.

[0083] Step 2: First, the electrolysis time is 10 minutes, and the current density is 1.5 mA / cm². 2 ;

[0084] Step 3: Then add 8 mg / L chitosan-modified cationic flocculant, electrolyze for 5 minutes, and use a current density of 4 mA / cm². 2 ;

[0085] Step 4: Collect bio-sulfur at the overflow weir after electrolysis.

[0086] In this embodiment, the bio-sulfur recovery rate reached 98.7%, and the sulfur purity reached 93.2%.

[0087] Example 3

[0088] Firstly, the flocculant provided in this embodiment is the same as that in Embodiment 1.

[0089] Secondly, a method for separating bio-sulfur by electrolytic flotation is provided, comprising:

[0090] Step 1: The biological sulfur-containing effluent with a biological sulfur content of 934 mg / L is fed into the electrolysis reactor. Both the anode and cathode are made of graphite electrode plates with a plate spacing of 2 cm.

[0091] Step 2: First, the electrolysis time is 15 minutes, and the current density is 1 mA / cm². 2 ;

[0092] Step 3: Then add 3 mg / L chitosan-modified cationic flocculant, electrolyze for 10 min, and use a current density of 3 mA / cm². 2 ;

[0093] Step 4: Collect bio-sulfur at the overflow weir after electrolysis.

[0094] In this embodiment, the bio-sulfur recovery rate reached 98.6%, and the sulfur purity reached 94.8%.

[0095] Example 4

[0096] Firstly, the flocculant provided in this embodiment is the same as that in Embodiment 1.

[0097] Secondly, a method for separating bio-sulfur by electrolytic flotation is provided, comprising:

[0098] Step 1: The biological sulfur-containing effluent with a biological sulfur content of 934 mg / L is fed into the electrolysis reactor. Both the anode and cathode are made of graphite electrode plates with a plate spacing of 2 cm.

[0099] Step 2: First, the electrolysis time is 15 minutes, and the current density is 1 mA / cm². 2 ;

[0100] Step 3: Then add 8 mg / L chitosan-modified cationic flocculant, electrolyze for 10 min, and use a current density of 3 mA / cm². 2 ;

[0101] Step 4: Collect bio-sulfur at the overflow weir after electrolysis.

[0102] In this embodiment, the bio-sulfur recovery rate reached 99.1%, and the sulfur purity reached 93.6%.

[0103] Example 5

[0104] Firstly, the flocculant provided in this embodiment is the same as that in Embodiment 1.

[0105] Secondly, a method for separating bio-sulfur by electrolytic flotation is provided, comprising:

[0106] Step 1: The biological sulfur-containing effluent with a biological sulfur content of 3862 mg / L is fed into the electrolysis reactor. Both the anode and cathode are made of graphite electrode plates with a plate spacing of 2 cm.

[0107] Step 2: First, the electrolysis time is 15 minutes, and the current density is 2 mA / cm². 2 ;

[0108] Step 3: Then add 15 mg / L chitosan-modified cationic flocculant, electrolyze for 10 min, and use a current density of 6 mA / cm². 2 ;

[0109] Step 4: Collect bio-sulfur at the overflow weir after electrolysis.

[0110] In this embodiment, the bio-sulfur recovery rate reached 97.5%, and the sulfur purity reached 92.9%.

[0111] Example 6

[0112] Firstly, the flocculant provided in this embodiment is the same as that in Embodiment 1.

[0113] Secondly, a method for separating bio-sulfur by electrolytic flotation is provided, comprising:

[0114] Step 1: The biological sulfur-containing effluent with a biological sulfur content of 3862 mg / L is fed into the electrolysis reactor. Both the anode and cathode are made of graphite electrode plates with a plate spacing of 2 cm.

[0115] Step 2: First, the electrolysis time is 15 minutes, and the current density is 2 mA / cm². 2 ;

[0116] Step 3: Then add 30 mg / L chitosan-modified cationic flocculant, electrolyze for 10 min, and use a current density of 6 mA / cm². 2 ;

[0117] Step 4: Collect bio-sulfur at the overflow weir after electrolysis.

[0118] In this embodiment, the bio-sulfur recovery rate reached 98.7%, and the sulfur purity reached 92.5%.

[0119] Example 7

[0120] Firstly, the flocculant provided in this embodiment is the same as that in Embodiment 1.

[0121] Secondly, a method for separating bio-sulfur by electrolytic flotation is provided, comprising:

[0122] Step 1: The biological sulfur-containing effluent with a biological sulfur content of 3862 mg / L is fed into the electrolysis reactor. Both the anode and cathode are made of graphite electrode plates with a plate spacing of 2 cm.

[0123] Step 2: First, the electrolysis time is 20 minutes, and the current density is 1.5 mA / cm². 2 ;

[0124] Step 3: Then add 15 mg / L chitosan-modified cationic flocculant, electrolyze for 15 min, and use a current density of 4 mA / cm². 2 ;

[0125] Step 4: Collect bio-sulfur at the overflow weir after electrolysis.

[0126] In this embodiment, the bio-sulfur recovery rate reached 97.7%, and the sulfur purity reached 93.4%.

[0127] Example 8

[0128] Firstly, the flocculant provided in this embodiment is the same as that in Embodiment 1.

[0129] Secondly, a method for separating bio-sulfur by electrolytic flotation is provided, comprising:

[0130] Step 1: The biological sulfur-containing effluent with a biological sulfur content of 3862 mg / L is fed into the electrolysis reactor. Both the anode and cathode are made of graphite electrode plates with a plate spacing of 2 cm.

[0131] Step 2: First, the electrolysis time is 20 minutes, and the current density is 1.5 mA / cm². 2 ;

[0132] Step 3: Then add 30 mg / L chitosan-modified cationic flocculant, electrolyze for 15 min, and use a current density of 4 mA / cm². 2 ;

[0133] Step 4: Collect bio-sulfur at the overflow weir after electrolysis.

[0134] In this embodiment, the bio-sulfur recovery rate reached 98.1%, and the sulfur purity reached 92.3%.

[0135] Example 9

[0136] This embodiment is basically the same as Example 1, except that in the flocculant preparation method, m(chitosan):m(Fe2(SO4)3)=1:1.

[0137] In this embodiment, the bio-sulfur recovery rate reached 98.5%, and the sulfur purity reached 92.5%.

[0138] Example 10

[0139] This embodiment is basically the same as Example 1, except that the pH value is 1.5 in the flocculant preparation method.

[0140] In this embodiment, the bio-sulfur recovery rate reached 97.2%, and the sulfur purity reached 93.8%.

[0141] Example 11

[0142] This embodiment is basically the same as Embodiment 1, except that the temperature in the flocculant preparation method is 40℃.

[0143] In this embodiment, the bio-sulfur recovery rate reached 97.8%, and the sulfur purity reached 94.1%.

[0144] Example 12

[0145] This embodiment is basically the same as Embodiment 1, except that the current density during the electrolytic oxidation stage is 0.5 mA / cm². 2 .

[0146] In this embodiment, the bio-sulfur recovery rate reached 98.0%, and the sulfur purity reached 92.2%.

[0147] Comparative Example 1

[0148] In this comparative example, the flocculant is the same as in Example 1.

[0149] A method for separating bio-sulfur by electrolytic flotation includes: passing effluent containing bio-sulfur (934 mg / L) into an electrolytic reactor; both the anode and cathode are made of nickel-plated steel plates with a plate spacing of 2 cm; the initial electrolysis time is 10 min, and the current density is 1.5 mA / cm². 2 Then add 3 mg / L chitosan-modified cationic flocculant, electrolyze for 5 minutes, and use a current density of 4 mA / cm². 2 After electrolysis, bio-sulfur was collected at the overflow weir, with a bio-sulfur recovery rate of 95.5% and a sulfur purity of 88.7%.

[0150] It can be seen that, compared with Example 1, under the same conditions, using nickel-plated steel plate as electrode results in a lower oxygen evolution overvoltage and insufficient oxidation of the biopolymers attached to the surface of sulfur particles, leading to a sulfur purity of only 88.7%.

[0151] Comparative Example 2

[0152] A method for separating bio-sulfur by electrolytic flotation includes: passing effluent containing bio-sulfur (934 mg / L) into an electrolytic reactor; using graphite electrodes for both the anode and cathode, with a 2 cm gap between the electrodes; initial electrolysis time of 10 min and current density of 1.5 mA / cm². 2 Without adding flocculant, the electrolysis time is 5 minutes, and the current density is 4 mA / cm². 2 After electrolysis, bio-sulfur was collected at the overflow weir, with a bio-sulfur recovery rate of 87.8% and a sulfur purity of 95.1%.

[0153] It can be seen that, compared with Example 1, under the same conditions, without the addition of flocculant during electrolysis, the particle size of bio-sulfur is smaller, resulting in a bio-sulfur recovery rate of only 87.8%.

[0154] Comparative Example 3

[0155] A method for separating bio-sulfur by electrolytic flotation includes: passing effluent containing bio-sulfur (934 mg / L) into an electrolytic reactor; using graphite electrodes for both the anode and cathode, with a 2 cm gap between the electrodes; initial electrolysis time of 10 min and current density of 1.5 mA / cm². 2 Then add 3 mg / L polyaluminum chloride flocculant, electrolyze for 5 minutes, and use a current density of 4 mA / cm². 2 After electrolysis, bio-sulfur was collected at the overflow weir, with a bio-sulfur recovery rate of 92.4% and a sulfur purity of 90.6%.

[0156] It can be seen that, compared with Example 1, under the same conditions, the addition of other conventional flocculants during electrolysis, at the same dosage, is significantly less effective than the treatment of biological sulfur in Example 1.

[0157] Comparative Example 4

[0158] This comparative example is basically the same as Example 1, except that the current density during the electrolytic oxidation stage is 0.3 mA / cm². 2 .

[0159] In this embodiment, the bio-sulfur recovery rate was 97.1%, and the sulfur purity was 88.5%.

[0160] Comparative Example 5

[0161] This embodiment is basically the same as Embodiment 1, except that the current density during the electrolytic flotation stage is 2.5 mA / cm². 2 .

[0162] In this embodiment, the bio-sulfur recovery rate was 93.4%, and the sulfur purity was 91.8%.

[0163] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0164] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for separating bio-sulfur via electrolytic flotation, characterized in that, Includes the following steps: Step 1: Pass the material containing bio-sulfur into the electrolysis reactor; Step 2: Perform the electrolytic oxidation stage; Step 3: Perform the electrolytic flotation stage, in which a flocculant is added. The flocculant includes metal cations and chitosan, wherein the metal cations are complexed with the chitosan. Step 4: Collect bio-sulfur; The method for preparing the flocculant includes the step of mixing and reacting chitosan with a metal cation salt; the mass ratio of chitosan to the metal cation salt is 1:1 to 1:2; the pH value of the mixing reaction is 1 to 3; the metal cation salt is an iron salt; and the iron salt is one or more of Fe2(SO4)3, Fe(NO3)3, and FeCl3.

2. The method according to claim 1, characterized in that, The temperature of the mixing reaction is 30-40℃.

3. The method according to claim 1, characterized in that, The electrolysis reaction device includes electrodes, which include a cathode and an anode.

4. The method according to claim 3, characterized in that, The electrode is a graphite electrode; And / or, the distance between the cathode and the anode is 1-3 cm.

5. The method according to any one of claims 1-4, characterized in that, In step 1, the bio-sulfur content in the material is 0.1-10 g / L; And / or in the aforementioned bio-sulfur-containing materials, the particle size of the bio-sulfur is less than 10 μm.

6. The method according to any one of claims 1-4, characterized in that, In step 2, the applied DC current density during the electrolytic oxidation stage is 0.5-2 mA / cm². 2 ; And / or, in step 2, the electrolysis time of the electrolytic oxidation stage is 10-20 min.

7. The method according to any one of claims 1-4, characterized in that, In step 3, the DC current density applied during the electrolytic flotation stage is 3-6 mA / cm². 2 ; And / or, in step 3, the electrolysis time of the electrolytic flotation stage is 5-15 min; And / or, in step 3, during the electrolytic flotation stage, the mass ratio of bio-sulfur to the flocculant is 1000:(1-10).

8. A bio-sulfur isolated by any one of claims 1-7.

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