Sewage treatment and electrolytic hydrogen production synergistic process method based on pollutant oxidation reaction

Abstract

A sewage treatment and electrolytic hydrogen production synergistic process method based on pollutant oxidation reaction aims to overcome the defects that in the prior art, water electrolysis hydrogen production is large in power consumption and low in efficiency and needs to additionally consume water resources, and the process method comprises the steps that anodic oxidation decomposition of pollutants in sewage and cathode hydrogen production are achieved through sewage electrolysis; the pollutant is used as an anode regulator in the electrolytic sewage reaction; pollutants in the sewage are organic pollutants of micromolecular alcohol, aldehyde and / or acid or inorganic pollutants containing sulfide. According to the method, hydrogen is produced by electrolyzing the sewage, and when pollutants in the sewage are micromolecular alcohol, aldehyde and / or acid sewage or sulfide sewage, the pollutants are used as anode regulators during sewage electrolysis in a sewage electrolysis reaction, so that the electrolysis energy consumption can be obviously reduced; hydrogen energy can be obtained, sewage treatment can be carried out, sewage recycling is achieved, and environmental protection is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to a synergistic process method for sewage treatment and electrolytic hydrogen production based on pollutant oxidation reaction. Background Art

[0002] Hydrogen energy is one of the most promising and cleanest sustainable energy sources. Its combustion product is water and it does not emit any carbon. Due to the current resource situation in my country, which is "poor in oil, less in gas and rich in coal", the main form of hydrogen production in China at this stage is coal gasification. However, the coal gasification hydrogen production process not only consumes a large amount of fossil fuels, but also emits a large amount of greenhouse gases, which has many disadvantages.

[0003] Compared with hydrogen production from coal gasification, hydrogen production from water electrolysis consumes relatively less fossil fuels and is less likely to produce greenhouse gases. However, hydrogen production from water electrolysis has the following disadvantages: high electricity consumption and low hydrogen production efficiency.

[0004] Moreover, when producing hydrogen by electrolysis of water, additional water is consumed, which has no obvious advantages in terms of the currently advocated low carbon and environmental protection. Summary of the invention

[0005] The present invention overcomes the defects of the prior art of hydrogen production by electrolysis of water, such as large power consumption, low efficiency, additional water consumption, and lack of obvious low-carbon and environmental protection advantages, and provides a synergistic process method for sewage treatment and hydrogen production by electrolysis based on pollutant oxidation reaction.

[0006] The technical solution adopted by the present invention to achieve the purpose of the invention is: a synergistic process method for sewage treatment and electrolytic hydrogen production based on pollutant oxidation reaction, the process method is: electrolyzing sewage to achieve anodic oxidation decomposition of pollutants in sewage and cathode hydrogen production. The pollutants in the sewage are used as anode regulators in the electrolytic sewage reaction; the pollutants in the sewage are: organic pollutants of small molecule alcohols, aldehydes and / or acids or inorganic pollutants containing sulfides.

[0007] The beneficial effects of the present invention are as follows: (1) when hydrogen is produced by electrolyzing sewage, not only hydrogen energy can be obtained, but also sewage treatment can be performed, thereby realizing sewage reuse and reducing the extra consumption of pure water, which is obviously beneficial to environmental protection;

[0008] (2) When the pollutants in the sewage are small molecule alcohols, aldehydes and / or acidic sewage, or sulfide sewage, these pollutants can be used as anode regulators in the electrolysis of sewage, which can significantly reduce the electrolysis energy consumption;

[0009] (3) When the pollutants in the electrolyzed wastewater are small molecule alcohols, aldehydes and / or acids, since alcohols, aldehydes and acids are carbon-containing organic matter, they can effectively reduce the electrolysis potential of the anode reaction during the electrolysis reaction;

[0010] (4) When the pollutants in the electrolytic wastewater are sulfide wastewater, the electrolytic oxidation treatment of sulfide itself has the advantages of high efficiency and low energy consumption; and sulfide, as a soluble anode using aluminum, iron, etc., obtains a large amount of metal cations under the application of direct current, and micro-flocculation such as Al(OH)3 appears under the action of hydrolysis, which can adsorb and flocculate pollutants to achieve the desulfurization goal; and when iron acts as the anode, the Fe obtained in the reaction process 2+ Able to work with S 2- FeS is precipitated and desulfurization is achieved.

[0011] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Attached Figure 1 It is a model of experimental device for electrolysis of sewage driven by multiple solar fields.

[0013] Attached Figure 2 An outdoor experimental device for solar energy multi-field driven sewage electrolysis reaction.

[0014] Attached Figure 3 This is a solar experiment for thermoelectrochemical simulation of sulfur-containing wastewater decomposition and redox (hydrogen production per electrolysis / irradiation time) of Example 1.

[0015] Attached Figure 4 This is a solar experiment for thermoelectrochemical simulation of sulfur-containing wastewater decomposition redox according to Example 1 (sulfate concentration over electrolysis / irradiation time).

[0016] Attached Figure 5 This is the solar experiment of thermoelectrochemical simulation of sulfur-containing wastewater decomposition redox in Example 1 (potential changes with electrolysis / irradiation time).

[0017] Attached Figure 6 The figure is a comparison of hydrogen production of methanol in Example 2 at different temperatures.

[0018] Attached Figure 7 The comparison of hydrogen production yields by electrolysis / irradiation in the solar experiment of simulating hydrogen production by decomposing methanol wastewater in Example 2 is shown.

[0019] Attached Figure 8 This is the effect of electrolysis / irradiation time on methanol conversion efficiency in the simulated methanol wastewater decomposition hydrogen production solar energy test of Example 2. DETAILED DESCRIPTION

[0020] As shown in the attached drawings, this embodiment is a synergistic process method for wastewater treatment and electrolytic hydrogen production based on pollutant oxidation reaction, and the process method is: electrolyzing wastewater to achieve anodic oxidation decomposition of pollutants in the wastewater and cathode hydrogen production.

[0021] The pollutants in the sewage are used as anode regulators in the sewage electrolysis reaction; the pollutants in the sewage are: organic pollutants containing small molecule alcohols, aldehydes and / or acids or inorganic pollutants containing sulfides. In the method for producing hydrogen by electrolyzing sewage of the present invention, the temperature of the electrolyzed sewage is 25-90°C, and the time for electrolyzing sewage is 2-10h. In addition, when the pollutants in the sewage are organic pollutants containing small molecule alcohols, aldehydes and / or acids, the conditions for electrolyzing organic sewage are: voltage of 0.2-0.7V, current of 0.2mA-10mA; when the sewage is inorganic sewage containing sulfides, the conditions for sewage electrolysis are: voltage of 0.6-0.9V, current of 0.2-10mA.

[0022] When producing hydrogen by electrolyzing sulfide-containing wastewater, the anode is made of a commercial (Ti / IrO2&Ta2O5) DSA (dimensionally stable anode) electrode with a size of 2×2cm2; the cathode is a platinum sheet electrode (area 2×2cm2). Both are located parallel to each other under the electrolyte surface; the distance between the anode and cathode electrode plates is 2 cm; the gas collector is equipped with a condenser for pumping hydrogen.

[0023] When electrolyzing organic wastewater to produce hydrogen, the platinum electrode is made of 99.9% platinum sheet (thickness 2 mm) from an industrial manufacturer. The platinum sheet is cut into specified sizes and polished.

[0024] The following table 1 is water and adjusting agent S 2- ΔG of the electrochemical decomposition hydrogen production equation o 、E o *.

[0025] Table 1 Water and adjusting agent S 2- ΔG of the electrochemical decomposition hydrogen production equation o and E o *

[0026]

[0027] Table 1 summarizes the ΔG of water and anode alternative modifiers. o and E o The data show that all chemical equations are E o <0, and the process is non-spontaneous. o The values ​​can be converted to the applied cell voltage and clearly show that by using sulfide as a regulator, the anode reaction process is switched and the required electrolysis potential for the process is significantly reduced.

[0028] Decomposition reaction of hydrogen sulfide: H2S(g)=S(s)+H2(g), ΔG 0 =33kJ / mol Compared with the electrolysis of water, it is thermodynamically easier to occur.

[0029]

[0030] because Less than direct Therefore, the addition of sulfide transforms the hydrogen production process from water decomposition to sulfide oxidation (elimination) process with smaller applied voltage and higher efficiency, and high temperature can also assist the process.

[0031] Therefore, when electrolyzing sulfide-containing wastewater, the actual electrolysis potential can be significantly reduced to below 1.0V, while the traditional water electrolysis reaction is 1.5V. The electrolysis of sulfide-containing wastewater to produce hydrogen consumes significantly less electricity, and it also treats wastewater and reduces the consumption of pure water.

[0032] The following table 2 shows the electrochemical decomposition reaction equation of water and small molecule organic matter, ΔG o 、E o .

[0033] Table 2 Electrochemical decomposition reaction equations and ΔG of water and small organic molecules o 、E o

[0034]

[0035]

[0036] From the analysis of Table 2, we can see that except for formic acid and formaldehyde, the rest of the chemical reactions This indicates that these reactions are non-spontaneous.

[0037] Reactions involving small organic molecules: organic matter → CO2 + H2O, with ΔG° in the range of -46 to 97 kJ / mol, are thermodynamically easier to occur than the single water electrolysis hydrogen production reaction: H2O(l) = 1 / 2O2(g) + H2(g), ΔG° = 273.2 kJ / mol.

[0038] Due to the change in the anode half-reaction potential, it is obvious that Anode half reaction H2O→1 / 2O2+ Easily oxidized organic matter, the anode reaction is replaced by: organics → CO2 therefore, Less than The lower applied potential will mainly reduce the electrical input for the produced hydrogen (required to be no more than 6 kWh / m 3 ).

[0039] Moreover, different functional groups and different molecular sizes show different potentials. The potential of C1 organic matter is lower than that of C2 organic matter, such as methanol (0.016V) / ethanol (0.085V) and formic acid (-0.017V) / acetic acid (0.098V); in addition, the carbon content of organic matter will also affect its potential.

[0040] According to the above thermodynamic data analysis, the slow kinetics of oxygen evolution reaction (OER) can be controlled by selecting a suitable electron donor as a regulator. Compared with the 1.5V of the conventional water electrolysis reaction, the electrolysis potential during the actual electrolysis of wastewater containing the above organic matter can be significantly reduced to below 0.6V on the basis of heating. Therefore, by adding an organic matter regulator, the organic matter in the wastewater can be oxidized and decomposed at a lower voltage with higher efficiency, and the hydrogen production process of water electrolysis can be transformed into a more efficient hydrogen production pathway through the substitution reaction of the anode regulator.

[0041] In the process of hydrogen production by electrolysis of sewage, the reaction potential decreases with the increase of temperature; in addition, the addition of anode regulators changes the redox reaction and electrolysis potential. The electrolysis potential of organic matter is lower than that of water alone, which shows that the addition of anode regulators is conducive to reducing the electrolysis voltage and improving the efficiency of hydrogen production. The reduction of electrolysis potential makes it possible to produce hydrogen by electrolysis of sewage through solar energy drive in the future. Both solar thermal assistance and regulators will reduce the electrolysis potential (from 1.229V to 0.40~0.6V), and then convert the oxygen evolution reaction into the anodic oxidation reaction of organic molecules.

[0042] In the method of producing hydrogen by electrolyzing wastewater, the required potential is low, and the electrolysis of wastewater to produce hydrogen can be carried out by using solar multi-field driving. The electrolysis of wastewater to produce hydrogen by using solar multi-field driving includes the following steps:

[0043] S1. Constructing a solar photovoltaic system and a solar thermal chemical utilization system; the solar photovoltaic system includes: a solar photovoltaic array; the solar thermal chemical utilization system includes: a solar collector.

[0044] S2. The solar energy is divided into two parts through a spectrum divider. One part is used for photovoltaic power generation through a solar photovoltaic system, and the electric energy obtained is used for the electricity required for electrolysis of sewage to produce hydrogen; the other part is converted into medium and low temperature thermal energy through a solar thermal chemical utilization system, which is used for the thermal energy required for electrolysis of sewage to produce hydrogen.

[0045] The high temperature effect will reduce the thermodynamic energy and electrolysis potential of water decomposition chemistry. Solar cogeneration can improve the comprehensive utilization efficiency of solar energy (more than 40%). For the anode half reaction of electrolysis, water molecules are oxidized to obtain oxygen. The addition of anode regulators such as small molecular organic and inorganic substances causes the anode reaction to undergo non-aqueous oxidation to O2 substitution reaction. The decomposition voltage is lower than the water decomposition voltage, which is conducive to improving the energy conversion efficiency. In addition, alcohols, organic acids, and aldehydes are the most commonly used organic donors. 2- It is a commonly used inorganic donor. These donors are widely present in sewage and biomass fermentation products. Therefore, solar multi-field driven electrolysis to produce hydrogen can be used for the treatment of such sewage.

[0046] The electrolysis of sewage to produce hydrogen is driven by solar energy in multiple fields. The integrated chemical process of thermochemistry, electrochemistry and anode reaction is driven by solar energy. By adding different anode regulators and utilizing the thermal auxiliary effect of solar energy, the electrolysis potential of the electrolysis reaction of water is reduced, and energy consumption is reduced while efficiently producing hydrogen and deeply treating sewage. This mode integrates three functions: full spectrum utilization of solar energy, sewage treatment and hydrogen production. This mode greatly improves the utilization efficiency of solar energy by utilizing the full spectrum of solar energy, and at the same time, exerts the photoelectric and photothermal coupling effects to greatly improve the hydrogen production efficiency and sewage degradation selectivity, achieving the goal of low energy consumption, environmental protection and obtaining clean energy.

[0047] like Figure 1 , Figure 2 As shown: The solar multi-field driven sewage electrolysis device integrates three parts: solar photovoltaic unit (PV module), solar thermal unit (collector) and thermally coupled electrochemical unit (electrolytic cell). The maximum temperature that the electrolytic cell can withstand is 100°C. At the same time, the polysilicon element can generate a voltage of 18V at its maximum power point. A multimeter is used to monitor the voltage and current changes during the reaction process, and a computer is used to collect data. PV cells mainly absorb energy from the sunlight zone and convert it into electrical energy and store it in the battery as a DC power supply for the reaction system; solar concentrators mainly absorb energy from the infrared zone and convert it into thermal energy to provide high temperature for the reaction system. The reactor is placed at the focus of the parabola of the solar concentrator with a diameter of 1.5m.

[0048] The solar thermal unit uses a concentrating solar reflector (equipment parameters: diameter 1.5m, radiation area 1.8m 2 , focal point maximum 1000℃ / φ6-7cm), equipped with a two-dimensional tracking reflector, the temperature of the reactor is set by adjusting the receiver to intersect the line at the required magnification. The solar power generator uses solar silicon-based photovoltaic modules (photovoltaic output V max =5V, I max =1A, radiant surface area = 589cm 2), connected to a rechargeable lithium-ion battery and a voltage regulator for electrochemical power supply and storage. The thermo-electrochemical reactor consists of a two-electrode electrochemical cell equipped with a water inlet and outlet, allowing a continuous flow from the sump to the drain and a gas outlet for gas analysis. To control the voltage and current of the cell, a regulator is installed. The reaction time is regulated by the circulation flow rate. Small amounts of solution and gas are sampled and analyzed at specified time intervals.

[0049] The advantages of the hydrogen production reaction by electrolysis of sewage driven by multiple solar fields are further illustrated by the following examples.

[0050] Example 1

[0051] The wastewater containing 100ppm sulfide was used as the research object. Sulfide was used as the anode reaction regulator. The electrolysis was assisted by solar heat to electrolyze sulfide and produce hydrogen.

[0052] By S 2- The redox anode half-reaction added as a regulator is dominated by the sulfide-sulfate reaction, replacing the anodic oxidation of H2O to O2. Therefore, sulfide and solar thermal utilization are the dominant factors for efficient hydrogen production and sulfide oxidation.

[0053] The experimental results of Example 1 show that: (1) at 90°C, the hydrogen yield and sulfate concentration remain unchanged after 8 hours of reaction (see Appendix Figure 3 ); (2) The hydrogen production rate and sulfate conversion rate verified the key role of inorganic anode regulator and solar thermal effect in the system (Appendix Figure 4 ); (3) Attachment Figure 5 The change in potential during the electrolysis time was tracked, indicating that: the electrolysis of sulfide-containing wastewater can proceed at an applied voltage of 0.70V to 0.90V and a constant current of 0.2mA, and that pure water decomposition to produce hydrogen is completely impossible under this condition; (4) In the solar hybrid chemical system under outdoor sunlight, the solar energy utilization rate is significant, with a hydrogen production of 0.25mL / h H2 and a sulfur conversion rate of 93%. At the same applied voltage, the amount of hydrogen obtained is much greater than that obtained by direct electrolysis of pure water (almost no precipitation) (the voltage for electrolysis of water is >1.5V).

[0054] Example 2

[0055] Methanol was used as the anode regulator and NaOH or NaSO4 was used as the electrolyte to carry out the electrolytic decomposition of methanol and hydrogen production reaction. The main conditions were as follows: Figure 2 ) was used as the research object to conduct a constant flow, constant temperature and constant volume flow experiment. The sewage was continuously pumped into a sealed, heatable reactor (50 mL) 2×2 cm equipped with two filters. 2Platinum anode and platinum cathode, sampling at 60-minute intervals. Hydrogen production and methanol concentration were monitored throughout the electrolysis / irradiation time.

[0056] As attached Figure 6 As shown, when the temperature rises, the hydrogen production rate increases. At 90°C, the hydrogen production rate of methanol aqueous solution is 2.38 times that of direct electrolysis of pure water (the hydrogen production rate of direct electrolysis of pure water is 0.16 mL / h).

[0057] As attached Figure 7 As shown in the figure, at 90°C and a constant current of 10 mA, the hydrogen production rate and methanol conversion are basically constant, reaching 3.8 mL / h. The hydrogen production rate and methanol conversion efficiency verify the key role of the anode reaction regulator and solar thermal effect in this system.

[0058] Attached Figure 8 The change of potential during the electrolysis time was tracked. The addition of methanol as a regulator greatly reduced the electrode potential of the anode reaction, which not only reduced energy consumption but also effectively treated sewage. The experimental results showed that the system H2 reached 3.85mL / h, the methanol conversion reached 30% in 10 hours, and the operation was stable. Therefore, the innovative solar thermal electrochemical system achieved a fast and stable hydrogen production method and deep treatment of methanol sewage.

[0059] When the methanol concentration was 500 mg / mL, constant current electrolysis was performed for 60 min at currents of 1, 5, and 10 mA, with the electrolyte being 0.1 mol / L NaOH and the temperature being 30°C. Table 3 lists the hydrogen production rate and methanol conversion efficiency at different currents, indicating that the greater the current, the higher the hydrogen production efficiency and the greater the voltage.

[0060] Table 3 Hydrogen production and methanol oxidation rates at different currents

[0061]

[0062] In addition, the optimal experimental conditions for the solar integrated chemical process to decompose methanol and produce hydrogen are: (1) at a temperature of 30°C, the initial concentration of methanol is 2000 mg / L, and the starting voltage of water electrolysis to produce hydrogen is about 0.7 V under a constant current of 1 mA; (2) when the reaction temperature is 90°C and the initial concentration of methanol is 2000 mg / L, the starting voltage drops to 0.2 V, while the starting voltage of water electrolysis in a direct alkaline solution without adding methanol is about 1.60 V. Under the synergistic effect of solar heat and the regulator, the experimental electrolysis voltage is reduced to 0.2 V, greatly reducing the energy consumption of the electrolytic cell.

[0063] At a constant current of 1 mA, (1) at 30°C, the hydrogen production rate of direct water electrolysis was 0.16 mL / h, while the hydrogen production rate of methanol-water solution was 0.36 mL / h, which is 2.25 times that of direct water electrolysis. (2) At 90°C, the hydrogen production rate of methanol-water solution was 2.38 times that of direct water electrolysis.

[0064] The methanol concentration decreased significantly with the increase of electrolysis time, and the concentrations of intermediate formaldehyde and formic acid showed a downward trend compared with the condition of 30℃. (1) After 10 hours of electrolysis at a constant current of 10mA, the oxidation rate of 500mg / L methanol was close to 95%; (2) At 90℃, the oxidation rate of methanol was close to 95% after 8 hours. It can be seen that solar thermal assistance not only reduces the electrode potential of the reaction, but also improves the hydrogen production efficiency for the entire water electrolysis hydrogen production process.

[0065] Through the above embodiments, it can be seen that the integrated chemical process driven by multiple solar fields acts on water electrolysis to produce hydrogen and sewage treatment. This process uses solar energy as the only energy input and is a sustainable, pollution-free, green process for solar integrated chemical efficient electrolysis to produce hydrogen.

Claims

1. A synergistic process for wastewater treatment and electrolytic hydrogen production based on pollutant oxidation reaction, the process method comprising: electrolyzing wastewater to achieve anodic oxidation decomposition of pollutants in wastewater and cathode hydrogen production, characterized in that: The pollutants in the sewage are used as anode regulators in the sewage electrolysis reaction; The pollutants in the sewage are: organic pollutants containing small molecule alcohols, aldehydes and / or acids, or inorganic pollutants containing sulfides.

2. According to claim 1, a synergistic process for wastewater treatment and electrolytic hydrogen production based on pollutant oxidation reaction is characterized in that: When the sewage is organic sewage containing small molecule alcohol, aldehyde and / or acid, the conditions for electrolyzing the organic sewage are: voltage of 0.2-0.7V, current of 0.2mA-10mA, and temperature of 25-90°C.

3. The synergistic process of sewage treatment and electrolytic hydrogen production based on pollutant oxidation reaction according to claim 1 is characterized in that: When the sewage is inorganic sewage containing sulfide, the conditions for electrolyzing the inorganic sewage are: voltage of 0.6-0.9V, current of 0.2-10mA and temperature of 25-90°C.

4. The method of sewage treatment and electrolysis hydrogen production based on pollutant oxidation reaction according to claim 1 is characterized in that: The time for electrolyzing sewage is 2-10h.

5. The method of sewage treatment and electrolysis hydrogen production based on pollutant oxidation reaction according to claim 1, characterized in that: In the method for electrolyzing sewage, when the pollutant in the sewage is methanol, the electrolyte is NaOH or Na2SO4.

6. The method of sewage treatment and electrolysis hydrogen production based on pollutant oxidation reaction according to claim 1 is characterized in that: In the method for electrolyzing sewage, solar energy multi-field driving is used to carry out the sewage electrolysis reaction.

7. The method of treating wastewater and producing hydrogen by electrolysis based on pollutant oxidation reaction according to claim 6, characterized in that: The method of using solar energy multi-field drive to electrolyze sewage comprises the following steps: S1. Construct solar photovoltaic system and solar thermal chemical utilization system; S2. The solar energy is divided into two parts through a spectrum divider. One part is used for photovoltaic power generation through a solar photovoltaic system, and the electric energy obtained is used for the electricity required for the electrolysis of sewage; the other part is converted into medium and low temperature thermal energy through a solar thermal chemical utilization system, which is used for the thermal energy required for the electrolysis of sewage.

8. The method of sewage treatment and electrolysis hydrogen production based on pollutant oxidation reaction according to claim 7 is characterized in that: The solar photovoltaic system comprises: a solar photovoltaic array; the solar photothermal chemical utilization system comprises: a solar collector.

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