Microbial electrolysis cell device, scale-up design method and application of hydrogen production from kitchen waste leachate

Abstract

This invention discloses a microbial electrolysis cell device, a scale-up design method, and its application in hydrogen production from kitchen waste leachate. The device employs a dual-chamber reactor structure, with the anode and cathode chambers separated by an anion exchange membrane. The cathode is a spiral nickel mesh wound based on Archimedes' spiral equation, and the anode is a multi-carbon brush assembly. The scale-up design method determines the optimal design parameter α—combining coulombic efficiency, energy efficiency, hydrogen yield, and hydrogen purity—by systematically optimizing the ratio of the cathode's projected area to the effective volume of the anode chamber in a small reactor. The reactor is then scaled up based on this optimal α value while maintaining this ratio constant. Under optimal conditions, the maximum current density reaches 295.7 A / m³. 3 The hydrogen production rate reached 2.75 m³. 3 / m 3 •d, with a purity >94%, enables efficient hydrogen production from kitchen waste leachate, providing a clear design method for the large-scale application of microbial electrolysis cells.

Description

Technical Field

[0001] This invention relates to the field of bioelectrochemical technology, specifically to microbial electrolysis cell devices, scale-up design methods, and applications of hydrogen production from kitchen waste leachate. Background Technology

[0002] Food waste is a major type of solid waste in cities. It has a high organic content and is easily degradable. my country's annual output exceeds 120 million tons and continues to grow. Its leachate has high COD and BOD concentrations, is acidic, and is rich in volatile fatty acids, proteins, oils, and salts. Improper treatment can easily lead to eutrophication of water bodies, soil acidification, and malodorous pollution.

[0003] Traditional treatment technologies have significant drawbacks: anaerobic digestion is slow to start up, prone to acidification, and has a low gas production rate; aerobic treatment has high energy consumption and a large amount of sludge; and physicochemical methods are costly and do not achieve complete degradation. The industry urgently needs efficient and low-consumption resource recovery technologies.

[0004] Microbial electrolyzers (MECs) can utilize microorganisms to degrade organic matter to produce hydrogen. They have advantages such as high conversion efficiency, high hydrogen purity, and mild conditions, making them an important technological direction for the energy utilization of organic waste.

[0005] However, MEC performance degrades significantly after scale-up, with a marked decrease in current density and hydrogen production rate. The core reasons are imbalances in reactor configuration, electrode area-to-volume ratio, and increased internal resistance. Current research focuses primarily on materials and catalysts, lacking systematic engineering scale-up methods.

[0006] Platinum-carbon cathodes offer excellent activity but are expensive. Nickel-based materials, on the other hand, are low-cost, highly active, and have good mechanical properties, making them an ideal alternative. Nickel exhibits a high hydrogen evolution overpotential and is easily passivated at neutral pH, while its activity is even better under alkaline conditions. However, current technologies have not systematically optimized the matching relationship between nickel mesh configuration and reactor size.

[0007] Hydrogen production in MECs is susceptible to competition from methanogens, leading to reduced hydrogen purity and energy efficiency. Existing suppression methods are energy-intensive, complex to operate, and have unstable effects; targeted high-yield hydrogen production under mild conditions remains a key challenge.

[0008] Existing related patents mostly target methane production and water purification, use carbon-based / stainless steel electrodes, do not use spiral nickel mesh cathodes, do not involve α parameter optimization, and have not verified the scale-up effect above 10 L, which is significantly different from the route of this invention.

[0009] In summary, existing technologies lack methods for large-scale MEC (Mechanical Engineering of Concentrated Organic Cells) production and hydrogen production-oriented synergistic optimization strategies, and the spiral electrode has not achieved reliable scale-up. This invention, based on α-parameter optimization, provides an engineerable, high-efficiency hydrogen production technology from kitchen waste leachate. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the above technical defects and provide a spiral nickel mesh cathode microbial electrolyzer based on the optimized parameter of the ratio of cathode projected area to anode liquid volume (α), a microbial electrolyzer device for reliable reactor scale-up through α value, a scale-up design method, and an application for hydrogen production from kitchen waste leachate.

[0011] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a microbial electrolysis cell device, including a reactor shell, the interior of which is divided into an anode chamber and a cathode chamber by an anion exchange membrane, and a multi-carbon brush anode and a spiral wound nickel mesh cathode respectively located in the anode chamber and the cathode chamber are also connected inside the reactor shell;

[0012] The ratio α of the projected area of ​​the spiral nickel mesh cathode to the effective volume of the anode chamber is 35-50 m². 2 / m 3 .

[0013] Preferably, the spiral-wound nickel mesh cathode is designed based on Archimedes' spiral equation r = 1.0 + 0.3θ, where:

[0014] r is the radial distance, and θ is the polar angle.

[0015] Preferably, the multi-carbon brush anode comprises multiple graphite carbon brushes uniformly distributed within the anode chamber.

[0016] Preferably, the anode chamber is used to introduce leachate from food waste with a pH of 10.0-10.5.

[0017] Another aspect of this invention discloses a method for scale-up design of a microbial electrolysis cell, comprising the following steps:

[0018] S1: Construct a prototype reactor with a volume of 100-500 ml, using a spiral-wound nickel mesh cathode, and test the ratio α of the cathode projected area to the effective volume of the anode chamber;

[0019] S2: Determine the optimal α value that combines coulombic efficiency, energy efficiency, hydrogen yield, and hydrogen purity.

[0020] S3: Based on the target reactor volume and the optimal α value, scale up the reactor proportionally while keeping the ratio constant.

[0021] Preferably, the optimal α value of S2 is 42m. 2 / m 3 .

[0022] Preferably, the effective volume of the reactor constructed in step S3 by scaling up is 5~15 L.

[0023] Another aspect of the present invention discloses the application of a microbial electrolysis cell device in the treatment of leachate from kitchen waste.

[0024] Preferred, including:

[0025] The leachate from kitchen waste with a pH of 10.0~10.5 is passed into the anode chamber, and the alkaline electrolyte is passed into the cathode chamber.

[0026] Apply an external voltage of 2.5~4.0 V, operate for 30~40 h, and collect the hydrogen gas generated in the cathode chamber.

[0027] Preferably, the applied voltage is 3.5 V and the hydrogen purity is >94%.

[0028] The advantages of this invention compared to the prior art are:

[0029] (1) Clarify the scale-up design method. Propose an α-value optimization method to achieve effective reactor scale-up.

[0030] (2) Achieve high-purity hydrogen generation. Under alkaline high-voltage conditions, the hydrogen purity of the nickel mesh cathode is >94%, which is significantly better than the existing MEC.

[0031] (3) Low cost. Nickel mesh costs two orders of magnitude less than Pt / C. Attached Figure Description

[0032] Figure 1 The schematic diagrams of the 100 mL prototype MEC device of this invention are (A) a schematic diagram of the reactor structure and (B) a spiral nickel mesh cathode.

[0033] Figure 2 The graph shows the performance comparison of 100 mL MEC at different α values, including (A) maximum current density and hydrogen concentration, and (B) coulombic efficiency and hydrogen production rate.

[0034] Figure 3 The cathode biomass of 100 mL MEC is represented by different α values.

[0035] Figure 4 The results of the microbial community structure analysis include the bacterial community composition at the (A) phylum level and (B) genus level.

[0036] Figure 5 This is a schematic diagram of the 10 L dual-chamber MEC device of the present invention, including (A) reactor cross-section, (B) spiral nickel mesh cathode configuration and (C) anode distribution position.

[0037] Figure 6 The operating performance curves of the 10 L MEC include (A) current density-time curves at different voltages, (B) hydrogen concentration and yield at different voltages, and (C) current density-time curves of the MEC at the optimal voltage of 3.5V.

[0038] Figure 7 The power generation curves of 100 mL MEC are shown for (A) when the cathode catalyst is carbon-supported platinum and (B) when the cathode is a spiral nickel mesh.

[0039] Figure 8 Electrochemical characteristics of nickel mesh cathode at different pH values, including (A) linear sweep voltammetry curves and (B) electrochemical impedance spectroscopy. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings.

[0041] The purpose of this invention is to provide a spiral nickel mesh cathode microbial electrolysis cell based on the optimized parameter of cathode projected area and anode chamber liquid volume ratio (α), which enables reliable reactor scale-up through the α value.

[0042] Another objective of this invention is to provide a high-purity hydrogen production method that, through the synergistic effect of nickel mesh cathode electrocatalytic activity, alkaline conditions, and high applied voltage, directionally suppresses methanogenesis.

[0043] A microbial electrolysis cell for hydrogen production includes: a reactor shell, internally divided into an anode chamber and a cathode chamber by an anion exchange membrane; and a spirally wound nickel mesh cathode disposed in the cathode chamber, wherein the α value of the nickel mesh is 35-50 μm. 2 / m 3 Eight carbon brush anodes are installed in the anode chamber. The anode chamber is circulated with leachate from kitchen waste at a pH of 10.0-10.5, and the cathode chamber is circulated with alkaline electrolyte. When an external voltage of 2.5-4.0 V is applied, the hydrogen purity is >90%.

[0044] Where the value of α is 42 m 2 / m 3 The spiral wound nickel mesh cathode is designed based on Archimedes' spiral equation r = 1.0 + 0.3θ, where r is the radial distance (cm) and θ is the polar angle.

[0045] When in use, the effective volume of the reactor is 5-15 L, the applied voltage is 3.5 V, and the hydrogen purity is >94%.

[0046] The design process includes: constructing a 100-500 mL prototype reactor, using a spiral nickel mesh cathode, and testing α values ​​of 20-60 m. 2 / m 3 The hydrogen production performance within the specified range was determined; the optimal α value was determined by combining coulombic efficiency, energy efficiency, hydrogen yield, and purity; and the reactor was scaled up and constructed proportionally based on the target reactor volume and the optimal α value.

[0047] In actual operation:

[0048] Leachate from food waste with a pH of 10.0-10.5 is introduced into the anode chamber, and alkaline electrolyte is introduced into the cathode chamber. An external voltage of 2.5-4.0 V is applied, and hydrogen gas generated in the cathode chamber is collected. The external voltage is 3.5 V, the operating cycle is 30-40 hours, the hydrogen purity is >94%, and the coulombic efficiency is >85%.

[0049] The cathodic electroactive biofilm contained bacteria of the genus Geoalkalibacter, with a relative abundance of 25.6%.

[0050] In specific implementation of the present invention, Example 1: Optimization of α parameter

[0051] The reactor was constructed as a 100 mL single-chamber bottle reactor with an effective volume of 100 mL. The anode was a carbon brush, 8 cm long and 3 cm in diameter, pretreated by calcination in a muffle furnace at 450°C for 2 hours. The cathode was a nickel mesh, 60 mesh, with a purity greater than 99%, which was sequentially ultrasonically cleaned for 20 minutes each with anhydrous ethanol, 1 M hydrochloric acid, and deionized water, and then dried before being wound into a spiral shape according to the Archimedes spiral equation r = 1.0 + 0.3θ (in cm). By adjusting the number of spiral turns and the height, values ​​of α were achieved as 12, 21, 42, and 56 m, respectively. 2 / m 3 Four cathode configurations. For example... Figure 1 The schematic diagrams of the 100 mL prototype MEC device of this invention are (A) a schematic diagram of the reactor structure and (B) a spiral nickel mesh cathode.

[0052] During the start-up and operation phase, effluent from a mature MEC (medium-carbohydrate culture medium) was inoculated. This effluent came from 100 mL of MEC that had been operating stably for over 6 months. The substrate consisted of a 50 mM carbonate buffer containing 1 g / L sodium acetate, at pH 10.5. An external voltage of 0.8 V was applied, and the temperature was controlled at 28 ± 2°C. When the current density exceeded 40 A / m³... 3 Once it has stabilized for 3 cycles, the startup is considered complete.

[0053] Run for at least three stable cycles under each α value condition, monitoring current density, coulombic efficiency, hydrogen yield, hydrogen purity, and energy efficiency. Figure 2 As shown, the results indicate that α is 12 m. 2 / m 3 At that time, the maximum current density was 68.2 A / m. 3 The coulombic efficiency is 108.2%, and the hydrogen yield is 0.27 m³. 3 / m 3 ·d, hydrogen purity 96.7%. α is 21 m 2 / m 3 At that time, the maximum current density increased to 73.0 A / m. 3The coulombic efficiency is 116.2%, and the hydrogen yield is 0.37 m³. 3 / m 3 ·d, hydrogen purity 94.4%. α is 42 m 2 / m 3 At that time, the maximum current density reached 83.7 A / m. 3 The coulombic efficiency is 121.5%, and the hydrogen yield is 0.39 m³. 3 / m 3 ·d, hydrogen purity 95.3%. α is 56m 2 / m 3 At that time, the maximum current density further increased to 94.9 A / m. 3 However, the coulombic efficiency decreased to 120.9%, and the hydrogen yield decreased to 0.35 m³. 3 / m 3 ·d, hydrogen purity 95.3%.

[0054] Based on comprehensive comparison, α is 42 m. 2 / m 3 The overall performance is optimal at this α value. Although the maximum current density is slightly lower than α at 56m³, this value indicates optimal overall performance. 2 / m 3 The group showed the highest coulombic efficiency and hydrogen yield, with a stable hydrogen purity greater than 95%. α was 12 and 21 m. 2 / m 3 At this time, the current density and hydrogen production rate are significantly lower. α is 56 m. 2 / m 3 At that time, while the current density increased, the energy efficiency decreased, and the cathode biomass was too low, which was not conducive to long-term stable operation. Therefore, a 42 m [structure / scale] was determined. 2 / m 3 This is the optimal value for α. Example 2: Analysis of cathode biofilm

[0055] Biomass at nickel mesh cathodes with different α values ​​was determined using the Coomassie Brilliant Blue method. For example... Figure 3 As shown, the measurement results indicate that α is 12 m. 2 / m 3 The biomass was 0.35 mg / cm³. 2 α is 21 m 2 / m 3 The concentration was 0.31 mg / cm³. 2 α is 42 m 2 / m 3 The concentration was 0.29 mg / cm³. 2 α is 56 m 2 / m 3 The concentration was 0.11 mg / cm³. 2 .

[0056] For α = 42 m 2 / m 3 High-throughput sequencing of 16S rRNA was performed on the anode and cathode biofilms of the group, such as... Figure 4 As shown, in the cathode bacterial community, Proteobacteria accounted for 68.0% and Desulfobacterota for 22.9%, making them the dominant phylum; at the genus level, Dethiobacter accounted for 27.9% and Geoalkalibacter for 25.6%, both typical electroactive bacteria adapted to alkaline environments. In the anodic bacterial community, Proteobacteria accounted for 46.1% and Bacteroidota for 37.8%, making them the dominant phylum; at the genus level, Geobacter accounted for 20.6% and Paracoccus for 13.6%. Example 3: Laboratory-scale MEC validation

[0057] The reactor shell is made of plexiglass, with an inner diameter of 20 cm and a height of 35 cm. The effective volume of the anode chamber is 10 L. The cathode chamber is an annular cavity surrounding the anode chamber, with an effective volume of approximately 2 L. The two chambers are separated by an anion exchange membrane. Figure 5 This is a schematic diagram of the 10 L dual-chamber MEC device of the present invention, including (A) reactor cross-section, (B) spiral nickel mesh cathode configuration and (C) anode distribution position.

[0058] Electrode design based on α = 42 m 2 / m 3 The calculated cathode projected area is 4200 cm². 2 The nickel mesh measures 60 cm by 70 cm and is wound into a spiral shape according to Archimedes' equation of spiral, where r equals 1.0 plus 0.3θ. Its outer diameter is approximately 18 cm and its height is 30 cm. The anode uses 17 carbon brushes, each 60 cm long and 3 cm in diameter, evenly distributed within the anode chamber, with a total projected area of ​​approximately 4800 cm². 2 It is matched with the cathode.

[0059] Under conditions of COD 5.5 g / L and pH 10.5, four voltage levels of 2.8 V, 3.2 V, 3.5 V, and 4.0 V were tested sequentially. Figure 6 As shown in the figure. Analysis indicates that 3.5 V is the optimal voltage. At 4.0 V, the current density increases slightly, but the hydrogen purity and coulombic efficiency decrease significantly, suggesting that the high voltage causes some electrical energy to be used for non-target reactions or biofilm damage. The maximum current density at 3.5 V is 295.7 A / m². 3 The time to reach maximum current is 8 to 12 hours, the operating cycle is 32 hours, and the final current density is 160 A / m. 3The COD removal rate was 49.5%, the COD removal rate was 4.1 g / L / d, and the hydrogen production rate was 2.75 m³ / d. 3 / m 3 •d, hydrogen purity greater than 94%, coulombic efficiency 85.8%, energy efficiency 65.2%, total energy efficiency 44.2%.

[0060] Dissolved oxygen in the anolyte was measured using a microelectrode, and the concentration remained below 0.05 mg / L throughout the process, confirming no significant water oxidation under high voltage and indicating that the anolyte biofilm effectively suppressed side reactions. Non-biological control tests showed a maximum current density of only 7.5 A / m³ under 3.5 V and no inoculation conditions. 3 Hydrogen yield 0.13 m 3 / m 3 ·d, confirming that over 95% of hydrogen originates from bioelectrochemical processes.

[0061] This invention provides a 10 L-scale MEC with an α of 42 m. 2 / m 3 Under optimized conditions of pH 10.5 and voltage 3.5 V, it was run continuously for 10 cycles, such as... Figure 6 As shown in (C), the performance is stable. The maximum current density reaches 295.7 A / m. 3 Hydrogen yield 2.75 m 3 / m 3 •d, hydrogen purity greater than 94%, coulombic efficiency 85.8%. Compared with the 100 mL prototype, after a 100-fold increase in volume, the current density increased by 3.5 times and the hydrogen yield increased by 7.1 times, achieving superlinear growth in volumetric efficiency and verifying the effectiveness of the α parameter optimization method.

[0062] Comparative Example 1: Platinum Catalyst Cathode

[0063] The nickel mesh cathode in Example 1 was replaced with a platinum-carbon cathode as a control, with a platinum loading of 0.5 mg / cm². 2 Effective area 12 cm 2 The maximum current density in the control group was 115.4 A / m. 3 Nickel mesh at α = 42 m 2 / m 3 Its performance reaches 73% to 93% of that of platinum-carbon, but at a cost two orders of magnitude lower, giving it a significant economic advantage. For example... Figure 7 As shown.

[0064] Comparative Example 2: Electrochemical Performance Analysis of Nickel Grid Cathodes at Different pH Levels

[0065] The hydrogen reduction reaction (HER) activity of the nickel mesh cathode was tested using linear sweep voltammetry. A three-electrode system was employed: the nickel mesh as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire as the counter electrode. The electrolyte was a carbonate and bicarbonate buffer solution with a pH range of 8.5 to 11.2. Figure 8 Electrochemical characteristics of nickel mesh cathode at different pH values, including (A) linear sweep voltammetry curves and (B) electrochemical impedance spectroscopy.

[0066] The results showed that HER activity significantly increased with increasing pH from 8.5 to 11.2. At 10 mA / cm² 2 The overpotential at current density decreased from -1.15 V at pH 8.5 to -0.78 V at pH 10.5. When the pH increased from 10.5 to 11.2, the overpotential only decreased from -0.78 V to -0.73 V, a decrease of only 6.4%. Considering both microbial tolerance and catalytic activity, pH 10.5 was selected as the optimal condition.

[0067] Electrochemical impedance spectroscopy (EIS) was used to test the resistance characteristics of the nickel mesh cathode at different pH values. At pH 8.5, the ohmic resistance was 62.3 Ω, the charge transfer resistance was 544.9 Ω, and the total internal resistance was 607.2 Ω. At pH 9.5, the ohmic resistance decreased to 53.8 Ω, the charge transfer resistance decreased to 524.2 Ω, and the total internal resistance decreased to 578.0 Ω. At pH 10.5, the ohmic resistance decreased to 33.8 Ω, the charge transfer resistance decreased to 448.6 Ω, and the total internal resistance decreased to 482.4 Ω. At pH 11.2, the ohmic resistance was 32.5 Ω, the charge transfer resistance was 411.5 Ω, and the total internal resistance was 444.0 Ω.

[0068] Analysis showed that as the pH increased from 8.5 to 10.5, the total internal resistance decreased from 607.2 Ω to 482.4 Ω, a reduction of 20.6%, mainly due to the increased solution conductivity and enhanced catalytic activity of the nickel surface. When the pH increased from 10.5 to 11.2, the total internal resistance decreased by only 7.9%, indicating diminishing marginal returns. Considering microbial activity, pH 10.5 was the optimal equilibrium point.

[0069] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0070] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A microbial electrolysis cell device, comprising a reactor shell, characterized in that: The reactor shell is divided into an anode chamber and a cathode chamber by an anion exchange membrane. The reactor shell is also connected to a multi-carbon brush anode and a spiral wound nickel mesh cathode located in the anode chamber and cathode chamber respectively. The ratio α of the projected area of ​​the spiral nickel mesh cathode to the effective volume of the anode chamber is 35-50 m². 2 / m 3 .

2. The microbial electrolysis cell device according to claim 1, characterized in that: The spiral-wound nickel mesh cathode is designed based on Archimedes' spiral equation r = 1.0 + 0.3θ, where: r is the radial distance, and θ is the polar angle.

3. The microbial electrolysis cell device according to claim 1, characterized in that: The multi-carbon brush anode consists of multiple graphite carbon brushes evenly distributed within the anode chamber.

4. The microbial electrolysis cell device according to claim 1, characterized in that: The anode chamber is used to introduce leachate from kitchen waste with a pH of 10.0-10.

5.

5. A method for scale-up design of a microbial electrolysis cell, characterized in that: Includes the following steps: S1: Construct a prototype reactor with a volume of 100-500 ml, using a spiral-wound nickel mesh cathode, and test the ratio α of the cathode projected area to the effective volume of the anode chamber; S2: Determine the optimal α value that combines coulombic efficiency, energy efficiency, hydrogen yield, and hydrogen purity. S3: Based on the target reactor volume and the optimal α value, scale up the reactor proportionally while keeping the ratio constant.

6. The method for scale-up design of a microbial electrolysis cell according to claim 5, characterized in that: The optimal α value for S2 is 42m. 2 / m 3 .

7. The method for scale-up design of a microbial electrolysis cell according to claim 5, characterized in that: The reactor constructed in S3 by scaling up the scale has an effective volume of 5~15 L.

8. The application of a microbial electrolysis cell device as described in any one of claims 1-4 in the treatment of leachate from kitchen waste.

9. The application according to claim 8, characterized in that: include: The leachate from kitchen waste with a pH of 10.0~10.5 is passed into the anode chamber, and the alkaline electrolyte is passed into the cathode chamber. Apply an external voltage of 2.5~4.0 V, operate for 30~40 h, and collect the hydrogen gas generated in the cathode chamber.

10. The application according to claim 8, characterized in that: The applied voltage is 3.5 V, and the hydrogen purity is >94%.

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