Oil-water separation biomass membrane and preparation method thereof

Abstract

The present invention relates to the field of biotechnology, and in particular to a biomass membrane that can be used for oil-water separation and a preparation method thereof. The present invention adopts freezing and salting-out (sodium citrate) processes, and polyvinyl alcohol is concentrated and aggregated to form a hydrogel due to the effects of aggregation and crystallization. The concentration and aggregation of the polyvinyl alcohol hydrogel can drive palm fiber to form a dense grid structure, thereby improving its mechanical properties and regulating the pore size and being well applied to oil-water separation. The FSP-biomass membrane prepared by the present invention can be applied to the field of oil-water separation, and the preparation of the method has the advantages of simple operation, rapidity, green environmental protection and no pollution; the FSP-biomass membrane prepared by the present invention can separate oil and water by self-weight; the preparation method of the present invention improves the separation efficiency of the biomass membrane, the number of cycles, the self-cleaning ability, and the ability to resist membrane pollution, and greatly improves the mechanical properties of the biomass membrane material.

Description

Technical Field

[0001] The invention relates to the field of biotechnology, and in particular to a biomass membrane that can be used for oil-water separation and a preparation method thereof. Technical Background

[0002] In recent years, oil pollution has entered the ocean and oil spills from ships have been serious, which has not only caused losses to human property but also caused serious damage to the marine ecology. Traditional methods of dealing with oil spills basically use adsorption and combustion methods, relying on organic polymer materials. Given that these methods are generally prone to secondary pollution to the environment and low efficiency, in recent years, membrane separation has been identified as an efficient, pollution-free, low-energy consumption emulsified oil separation technology and has gradually been widely used.

[0003] Biomass materials have received extensive attention in the field of water purification due to their biodegradability, recyclability, low price and easy availability. However, due to the natural hydrophobicity and natural brittleness of most biomass, the flux, flexibility and tensile properties of biomass membrane materials limit the direct use of most biomass materials for water purification. Therefore, it is necessary to pretreat the biomass materials before application. During the treatment process, they are subjected to high temperature and strong alkali or strong acid treatment, which causes the mechanical properties of the biomass materials to deteriorate. Therefore, during the use of biomass materials, the surface wax is removed during the acid-base treatment, which makes the fiber structure easy to disperse and leads to a decrease in its recycling performance. Summary of the invention

[0004] In order to solve the above problems, the present invention adopts freezing and salting-out strategies to bionically prepare hydrogels to replace the original waxy and stable original fibers, regulates structural parameters such as the pore size and hydrogel thickness of the oil-water separation membrane, and improves the pore size, separation efficiency and separation flux of the oil-water separation membrane.

[0005] In one aspect, the present invention provides a method for preparing an oil-water separation biomass membrane, comprising the following steps:

[0006] 1) Preparation of original palm skin membrane material: firstly, the original palm skin is wiped with ethanol to remove dust and impurities on the surface of the original palm skin, to obtain the original palm skin membrane material, and then dried and stored in an incubator;

[0007] 2) Pretreatment of palm peel material: the original palm peel membrane material is added into an alkaline solution and soaked to remove part of the cuticle wax, hemicellulose and lignin; then, the original palm peel is placed into a salt solution and soaked to further remove the lignin, and the obtained sample is the pretreated palm peel membrane material;

[0008] 3) Biomimetic preparation of FSP-biomass membrane: The palm skin membrane material pretreated in step 2) is placed on the surface of the PVA aqueous solution, then frozen, and finally salted out to obtain the FSP-biomass membrane.

[0009] In some embodiments of the present invention, the alkaline solution in step 2) is a 2 wt % NaOH aqueous solution, and the alkaline solution immersion condition is immersion at 80° C. for 2.5 hours.

[0010] In some embodiments of the present invention, the salt solution in step 2) is a 2 wt % NaCl aqueous solution, and the salt solution immersion condition is immersion at 80° C. for 6 hours.

[0011] In some embodiments of the present invention, the concentration of the PVA solution in step 3) is 5 wt % PVA aqueous solution.

[0012] In some embodiments of the present invention, the freezing time in step 3) is 6 hours and the freezing temperature is -52°C.

[0013] In some embodiments of the present invention, the salt solution for salting out in step 3) is a 1.5M sodium citrate aqueous solution, and the salting out time is 48 hours.

[0014] On the other hand, the present invention provides the use of the FSP-biomass membrane prepared by the above method in the field of oil-water separation.

[0015] The present invention adopts freezing and salting-out (sodium citrate) process, polyvinyl alcohol is concentrated and aggregated to form hydrogel due to aggregation and crystallization, and the concentration and aggregation of polyvinyl alcohol hydrogel can drive palm fiber to form a dense grid structure, thereby improving its mechanical properties and regulating the pore size, and is well applied to oil-water separation.

[0016] The FSP-biomass membrane prepared by the present invention can be applied to the field of oil-water separation, and the preparation method has the advantages of simple operation, rapidity, green environmental protection and no pollution; the FSP-biomass membrane prepared by the present invention can separate oil and water by its own weight; the preparation method of the present invention improves the separation efficiency, the number of recycling times, the self-cleaning ability and the ability to resist membrane pollution of the biomass membrane, and greatly improves the mechanical properties of the biomass membrane material. The FSP-biomass membrane prepared by the present invention has the advantages of simplicity, economy and environmental protection, and the FSP-biomass membrane has great practical application potential in treating oily wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The tensile stress-strain characteristics of different biofilms.

[0018] Figure 2 This is a real picture of the original palm leather.

[0019] Figure 3 This is a physical picture of FSP-biomass membrane.

[0020] Figure 4This is the SEM image of the original palm membrane surface.

[0021] Figure 5 This is the SEM image of the palm film surface after pretreatment.

[0022] Figure 6 This is the SEM image of the FSP-biomass membrane surface.

[0023] Figure 7 The hydrophilicity test diagram of the pretreated palm skin film and FSP-biomass membrane.

[0024] Among them, A-1, A-2, and A-3 are the hydrophilicity test graphs of FSP-biomass membrane, and B-1, B-2, and B-3 are the hydrophilicity test graphs of pretreated palm skin.

[0025] Figure 8 This is the self-cleaning performance diagram of FSP-biomass membrane.

[0026] Fig. 9 This is the anti-oil pollution performance diagram of FSP-biomass membrane.

[0027] Fig.10 Separation of FSP-biomass membrane in different oil-in-water emulsions.

[0028] Fig.11 is the oleophobic angle of FSP-biomass membrane at different salt concentrations.

[0029] Fig.12 This is a cycle test diagram of palm leather film after pretreatment.

[0030] Fig.13 This is the cycle test diagram of FSP-biomass membrane.

[0031] Fig.14 This is the particle size distribution diagram of the emulsion before and after separation.

[0032] A and C are before emulsified oil separation, and B and D are after emulsified oil separation. DETAILED DESCRIPTION

[0033] The following examples are used to further illustrate the present invention; however, they are not intended to limit or define the scope of the present invention.

[0034] Example 1

[0035] 1) Preparation of raw palm skin film material: First, cut the raw palm skin into 40×40mm 2 size, wipe with ethanol to remove dust and impurities on the surface of the original palm skin, obtain the original palm skin membrane material, and dry and store it in an incubator;

[0036] 2) Palm leather material pretreatment: a 40×40mm2 The original palm bark was added to a 2wt% NaOH aqueous solution and soaked at 80°C for 2.5h to remove part of the cuticle wax, hemicellulose and lignin; then, the original palm bark was placed in a 2wt% NaCl aqueous solution and soaked at 80°C for 6h to further remove lignin, and the obtained sample was the pretreated palm bark film material;

[0037] 3) Preparation of hydrogel solution: 5 g PVA was added to 95 g water, stirred, and heated in a water bath at 85° C. until the PVA was completely dissolved to obtain a 5 wt % PVA aqueous solution. The 5 wt % PVA aqueous solution was sonicated for 1 h to remove all bubbles in the hydrogel solution, and then set aside for later use;

[0038] 4) Bionic preparation of FSP-biomass membrane: 2 ml of 5 wt% PVA solution prepared in step 3) was transferred to a culture dish, the palm bark material pretreated in step 2) was placed on the surface of the PVA aqueous solution, and then frozen at -52°C for 6 h, and finally added to 10 ml of 1.5 M sodium citrate aqueous solution and immersed for 48 h. The obtained sample was marked as a strong gel-covered biomass membrane FSP-biomass membrane.

[0039] The oil-water separation performance of existing biomaterials was compared with that of the FSP-biomass membrane prepared by the present invention. The results are shown in Table 1. The results show that the filtration flux of the FSP-biomass membrane is higher than that of other biomass materials; the FSP-biomass membrane prepared by the present invention has good separation efficiency and number of cycles for treating water-in-oil emulsions.

[0040] Table 1

[0041]

[0042] "-" indicates not mentioned in the text.

[0043] References

[0044] [1]H.Guan, Z.Cheng,

[0045] [2] J. Gao, J. Wang, Q. Xu, S. Wu, Y. Chen, Regenerated cellulose strongly adhered by a supramolecular adhesive onto the PVDF membrane for a highly efficient oil / water separation, Green Chem. 23 (2021) 5633–5646.

[0046] https: / / doi.org / 10.1039 / D1GC01998H.

[0047] [3]J.Xu,R.Cao,M.Li,G.Chen,J.Tian,Superhydrophobic and superoleophiliccuttlebone with an inherent lamellar structure for continuous and effective oil spill cleanup,Chemical Engineering Journal.420(2021)

[0048] 127596. https: / / doi.org / 10.1016 / j.cej.2020.127596.

[0049] [4] F. Liu, R. Lu, Q. Pan, Juncus Pith: A Versatile Material for Automatic and Continuous Separation of Various Oil–Water Mixtures, ACS SustainableChem. Eng.5 (2017) 922–928. https: / / doi.org / 10.1021 / acssuschemeng.6b02232.

[0050] The tensile stress-strain properties of the original palm bark, pretreated palm bark and FSP-biomass membrane were recorded using an Instron electronic tensile testing machine (Instron 3365, USA). Figure 1As shown, inspired by the plant cuticle, a simple, convenient and general strategy for fabricating green, efficient and gravity-driven oil-water filtration membrane (named FSP-palm peel) was developed by coating a high-strength hydrogel on the palm peel membrane using a freezing and salting-out strategy, which improved the antifouling property of palm peel and the tensile property by 227% compared with the pretreated palm peel membrane.

[0051] The surface morphology of the original palm peel and FSP-biomass film was photographed by a digital camera. Figure 2-3 shown.

[0052] The surface morphology of the original palm peel membrane, pretreated palm peel membrane and FSP-biomass membrane was examined by scanning electron microscopy (SEM, FEG250, Quanta, USA). Figure 4-6 ,It was observed through scanning electron microscopy that the surface structure of palm peel underwent tremendous changes after palm peel film treatment. Figure 4 It is shown that the original palm skin membrane has a three-dimensional network structure, and the fibers in the palm skin are tightly wrapped by wax, such as Figure 5 As shown, there are exposed fibers on the surface of the pretreated palm skin membrane, indicating that the structure of the alkali-treated palm skin fibers is similar to that of rattan, and the structure of the dispersed fibers may lead to reduced strength. The reduced strength of the pretreated palm skin leads to poor reusability for separation of the oil-in-water emulsion. Figure 6 As shown in the figure, after the pre-treated palm skin is treated with alkali, the wax on the surface of the pre-treated palm skin is removed, and the internal fibers can be seen on the surface of the pre-treated palm skin. Figure 6 We can find that Figure 6 The fibers seemed to be re-fixed, thus greatly improving the mechanical strength of the biomass material through the salting-out and freezing-biomimetic strategy.

[0053] The water contact angle (WCA) of the membrane was measured using a JY-82 contact angle meter (Hebei Chengdu Dingsheng Co., Ltd.). Figure 7 As shown, Figure 7 A-1, A-2, and A-3 are the FSP-biomass membrane hydrophilicity test graphs. Figure 7 The hydrophilicity test chart of palm leather pretreated with B-1, B-2, and B-3, from Figure 7 It can be seen that the hydrophilicity of FSP-palm skin is significantly better than that of the pretreated palm skin film.

[0054] A digital camera was used to capture the self-cleaning performance and anti-fouling performance of the FSP-biomass membrane. Figure 8-9 As shown, Figure 8As shown in the figure, a large amount of oil beams are sprayed on the membrane surface, and these oil beams immediately rebound from the FSP-P-PS surface, and then decompose into a large number of small oil droplets floating up; the hydrophilic group of the FSP layer is the key factor in resisting oil fouling, which is of great significance for practical applications. Fig. 9 As shown, after the oil-contaminated membrane was immersed in the oil, it was immediately immersed in water. The oil on the surface floated immediately and no oil was left on the membrane surface, indicating that the biomass membrane has good anti-pollution properties.

[0055] The FSP-biomass membrane was used to separate different oil-in-water emulsions using an infrared micro-oil content analyzer (JC-oil-8, Qingdao Juchuang Instrument Co., Ltd., China). Fig.10 As shown, the separation performance study of different water-in-oil emulsions indicates that the FSP-biomass membrane is capable of purifying most water-in-oil emulsions.

[0056] The oleophobic angle of FSP-biomass membrane at different salt concentrations was measured using a JY-82 contact angle meter (Hebei Chengdu Dingsheng Co., Ltd.). Fig.11 As shown, the results show that the FSP-biomass membrane can still maintain a high oleophobic angle under different salt concentrations.

[0057] The circulation and flux of palm skin membrane and FSP-biomass membrane after pretreatment were measured using an infrared micro-oil content analyzer (JC-oil-8, Qingdao Juchuang Instrument Co., Ltd., China). The flux calculation formula is:

[0058]

[0059] J(Lm -2 h -1 ) represents the filtration flux. V(L) is the volume of liquid that passes through the filter membrane after purification. A(m 2 ) represents the effective area of ​​the separator, and Δt(h) represents the effective separation time.

[0060] The results are as follows Fig.12 and 13 As shown, the results indicate that FSP-biomass membranes can improve the recycling performance and durability of palm bark compared with simple pre-treated palm bark membranes due to the coverage of the freeze-salted FSP layer.

[0061] The particle size of the emulsified oil before and after FSP-biomass membrane separation was measured using a biological microscope (CX41-DP27, Guangmi Instrument Co., Ltd., Shanghai, China). Fig.14 As shown in B and D, the results show that the emulsified oil can basically remove most of the oil after FSP-biomass membrane separation.

[0062] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a biomass membrane for oil-water separation, Features The following steps are involved: 1) Preparation of original palm skin membrane material: First, wipe the original palm skin with ethanol to remove dust and impurities on the surface of the original palm skin, obtain the original palm skin membrane material, and dry and store it in an incubator; 2) Pretreatment of palm peel material: the original palm peel membrane material is added into an alkaline solution and soaked to remove part of the cuticle wax, hemicellulose and lignin; then, the original palm peel is placed into a salt solution and soaked to further remove the lignin, and the obtained sample is the pretreated palm peel membrane material; 3) Biomimetic preparation of FSP-biomass membrane: the palm skin membrane material pretreated in step 2) is placed on the surface of the PVA aqueous solution, then frozen, and finally salted out to obtain the FSP-biomass membrane; Wherein, the salt solution for salting out in step 3) is a 1.5 M sodium citrate aqueous solution, and the salting out time is 48 hours.

2. A method for preparing a biomass membrane for oil-water separation as claimed in claim 1, Features The alkaline solution in step 2) is a 2 wt% NaOH aqueous solution, and the soaking condition of the alkaline solution is soaking at 80° C. for 2.5 hours.

3. A method for preparing a biomass membrane for oil-water separation as claimed in claim 1, Features The salt solution in step 2) is a 2 wt% NaCl aqueous solution, and the immersion condition of the salt solution is immersion at 80° C. for 6 hours.

4. A method for preparing a biomass membrane for oil-water separation as claimed in claim 1, Features The concentration of the PVA solution in step 3) is 5 wt% PVA in water.

5. A method for preparing a biomass membrane for oil-water separation as claimed in claim 1, Features The freezing time in step 3) is 6 hours and the freezing temperature is -52°C.

6. Application of the oil-water separation biomembrane prepared by the preparation method according to any one of claims 1 to 5 in the field of oil-water separation.

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