A method for treating p-chlorophenol in wastewater by direct coupling of ultraviolet catalytic oxidation and biodegradation

Abstract

The present invention discloses a method for treating para-chlorophenol in wastewater by directly coupling ultraviolet light catalytic oxidation and biodegradation. This method combines a lignin-based carbon composite catalyst with a directly coupled ultraviolet light catalytic oxidation and biodegradation method to achieve the degradation of para-chlorophenol. The photocatalysis and biofilm in the UCPB system exhibit excellent synergy, effectively degrading and mineralizing para-chlorophenol wastewater. Specifically, the photocatalytic process provides the biofilm with the carbon source required for growth, which in turn promotes the photocatalytic oxidation process. Simultaneously, the highly toxic and poorly biodegradable 4-CP is converted into a less toxic and easily degradable intermediate, reducing or preventing damage to the microbial colonies in the system by adverse substances.

Description

Technical Field

[0001] The invention relates to the treatment of p-chlorophenol wastewater, and in particular to a method for treating p-chlorophenol in wastewater by direct coupling of ultraviolet catalytic oxidation and biodegradation. Background Art

[0002] With the rapid development of industry, the treatment of wastewater containing refractory organic pollutants has seriously impacted and restricted the rapid development of my country's economy. Among these, chlorophenols (CPs), produced by industries such as pulp bleaching, organic dyes, pesticides, and printing, are environmentally persistent, mutagenic, carcinogenic, and teratogenic. Even at very low concentrations, they can damage and erode the central nervous system, kidneys, and livers of humans and animals. They have become typical refractory organic pollutants in the environment, posing a serious threat to human health and environmental safety. Papermaking bleaching wastewater reportedly contains over 300 organic pollutants, of which organic chlorides account for over two-thirds. Parachlorophenol (4-CP), a relatively high-content compound, is a potent carcinogen, teratogen, and mutagenic substance. It is also chemically and thermally stable, making it difficult to decompose or biodegrade.

[0003] In recent years, photocatalytic-biodegradation coupled (ICPB) technology has demonstrated unique advantages in the treatment of refractory wastewater and is attracting increasing attention. ICPB technology integrates the photocatalytic oxidation and biodegradation processes within a single reactor, loading the photocatalyst and biofilm onto a porous support to enable simultaneous reactions. ICPB technology has been applied to the treatment of refractory pollutants such as chlorophenols, nitrogen-containing compounds, antibiotics, and dyes. Ma Dongmei et al. (Study on the Degradation and Power Generation Characteristics of 4-Chlorophenol Using a Photocatalytic-Microbial Degradation Directly Coupled Fuel Cell [D]. Jilin University, 2017) used a photocatalytic-biodegradation coupled anode (PFMC) to degrade 4-CP. They found that the PMFC system had a high removal rate for 4-CP and effectively protected the internal microorganisms. Zhang Linlin et al. (Zhang Linlin. Research on the integrated treatment of refractory organic wastewater by photocatalysis coupled with microbial method [D]. Heilongjiang University, 2015.) used SiO2-TiO2 as catalyst to construct a photocatalytic-biological direct coupling system for the treatment of 20 mg / L 2,4,5-trichlorophenol. Under ultraviolet light irradiation for 6 h, the removal rates of 2,4,5-trichlorophenol and TOC were 94.1% and 97.5%, respectively. Zhong Lanlan et al. (China Environmental Science, 2021, 41(8): 3660-3666.) used N-TiO2 as catalyst to construct a photocatalytic-biological direct coupling system for the degradation of 4-fluorophenol (4-FP) wastewater. The system can shorten the degradation time of 50 mg / L 4-FP to 5 hours, and the biofilm content increases by 166 mg within 8 days.

[0004] Photocatalysts are a crucial component of ICPB systems, directly impacting pollutant degradation efficiency and subsequent microbial growth. Bismuth-based photocatalytic materials, with their narrow band gap, stable chemical structure, and environmentally friendly properties, are ideal semiconductor photocatalytic materials. However, bismuth-based photocatalysts often suffer from poor adsorption, weak photocatalytic properties in single-action applications, a wide spectral response range, low light absorption, and large nanoparticle size. Therefore, enhancing the adsorption and photocatalytic properties of bismuth-based photocatalysts remains a hot topic in current scientific research. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a UV catalytic oxidation-biodegradation direct coupling system to address the deficiencies of the existing technology, and further use the system to treat wastewater containing para-chlorophenol, while also improving the degradation performance and biological response behavior during the reaction process.

[0006] In order to solve the above technical problems, the present invention discloses a method for treating p-chlorophenol in wastewater by direct coupling of ultraviolet catalytic oxidation and biodegradation, comprising the following steps:

[0007] (1) loading a lignin carbon-based composite catalyst onto a polyurethane sponge carrier, then placing the catalyst-loaded polyurethane sponge carrier into acclimated aerobic sludge, aerating, completing activated sludge inoculation, and obtaining an inoculated polyurethane sponge carrier;

[0008] (2) placing the inoculated polyurethane sponge carrier into a fluidized bed reactor to culture a biofilm, and using a sequencing batch activated sludge process to culture the biofilm to obtain a polyurethane sponge carrier loaded with a catalyst and a biofilm;

[0009] (3) placing the polyurethane sponge carrier loaded with the catalyst and the biofilm in an internal circulation reactor to obtain a UV-catalytic oxidation-biodegradation direct coupling system;

[0010] (4) The wastewater to be treated is added to the internal circulation reactor of the ultraviolet photocatalytic oxidation-biodegradation direct coupling system for treatment.

[0011] Among them, the lignin carbon-based composite catalyst is an LC / ZnAl2O4 / BiPO4 ultraviolet photocatalyst, wherein the LC / ZnAl2O4 / BiPO4 ultraviolet photocatalyst is obtained by adding lignin carbon to a mixed solution during the hydrothermal method for preparing a ZnAl2O4 / BiPO4 heterojunction photocatalyst.

[0012] In the ZnAl2O4 / BiPO4 heterojunction, the mass ratio of ZnAl2O4 to BiPO4 is 0.5-1 wt%, and the mass ratio of lignin charcoal to the ZnAl2O4 / BiPO4 heterojunction is 0.1-10 wt%.

[0013] Preferably, the mass ratio of ZnAl2O4 to BiPO4 is 1 wt%, and the mass ratio of lignin char to ZnAl2O4 / BiPO4 heterojunction is 1 wt%.

[0014] In step (1), the acclimated aerobic sludge is obtained by acclimating activated sludge using wastewater containing para-chlorophenol.

[0015] The polyurethane sponge carrier is a hydrophilic polyurethane sponge in the shape of a 7 mm cube. (This experiment uses a hydrophilic 7 mm cube polyurethane sponge (Jiangsu Yunhuan Environmental Protection Co., Ltd.) as a carrier, and the specific surface area of ​​the carrier is greater than 4000 m 2 / m 3 The porosity is 98%. The volume ratio of the catalyst mass: the polyurethane sponge carrier mass and the ethanol is 1:2:20 to 150. Preferably, the volume ratio of the catalyst mass: the polyurethane sponge carrier mass and the ethanol is 1:2:100.

[0016] During the biofilm cultivation process, the sequencing batch activated sludge SBR process was used to cultivate the biofilm. Cr The experimental culture medium required for biofilm formation was prepared in a ratio of N:P=200:5:1, specifically as follows: NaAc·3H2O 400mg / L, CO(NH2)219.5mg / L, Na2HPO4 7.15mg / L; during the biofilm culture process, the water temperature was maintained at 25±1℃, the dissolved oxygen content was controlled at 4±0.5mg / L, and 500mL of culture medium was replaced every 12h. The effluent COD Cr Stable, biofilm culture completed.

[0017] Preferably, in step (4), the ultraviolet photocatalytic oxidation-biodegradation direct coupling system is first stabilized with wastewater containing para-chlorophenol, and then the pH of the chlorophenol wastewater to be treated is adjusted to neutral, and then added to the inner circulation reactor of the ultraviolet photocatalytic oxidation-biodegradation direct coupling system for treatment, wherein an ultraviolet mercury lamp is used as a light source outside the inner circulation reactor, and the experimental temperature and dissolved oxygen are controlled at 25±1°C and 4±0.5 mg / L, respectively.

[0018] Beneficial Effects: Compared with existing technologies, this invention uses a direct coupling of ultraviolet photocatalysis and biodegradation to treat highly toxic and difficult-to-biodegrade 4-CP wastewater. The results compare the degradation effects of different treatment systems on 4-CP wastewater (such as removal rate, mineralization capacity, and dechlorination rate) with biodegradation, photolysis, adsorption, and photocatalytic oxidation technologies. The results also explore the changes in microbial diversity and bacterial colony structure, and propose the mechanism of action of the photocatalytic-biodegradation coupling technology. The details are as follows:

[0019] (1) The photocatalyst LP3 was loaded onto a polyurethane sponge support using a co-impregnation method. The concentration of the catalyst suspension directly affects the catalyst loading and catalytic performance. A low concentration of the catalyst in ethanol is beneficial for increasing the catalyst loading rate on the sponge support. When the concentration of the catalyst in ethanol is 1 wt%, the photocatalytic performance of the sample is the best.

[0020] (2) The UCPB system has the highest removal efficiency and mineralization degree for the degradation of 4-CP wastewater. After 12 hours, the removal rates of 4-CP, TOC and dechlorination in the wastewater by the UCPB system were 98.21%, 86.42% and 95.15%, respectively. 4-CP is a difficult-to-biodegrade organic matter, and microorganisms have limited ability to degrade it. The photocatalytic oxidation system can effectively degrade 4-CP into low-toxic and easy-to-treat intermediate species, but the mineralization effect is poor. In contrast, the photocatalytic and biofilm in the UCPB system have a good synergistic effect, which can efficiently degrade and mineralize para-chlorophenol wastewater. That is, the photocatalytic process can provide the carbon source required for the growth of the biofilm, and the biofilm can promote the photocatalytic oxidation process.

[0021] (3) The high-throughput sequencing results showed that the microbial colonies in the UCPB system were diverse and the dominant species that degraded aromatic compounds were relatively abundant. This further demonstrated that the photocatalytic-biological direct coupling system could convert the highly toxic and difficult-to-biodegrade 4-CP into a low-toxic and easily degradable intermediate, thereby reducing or avoiding the damage of adverse substances to the microbial colonies in the system.

[0022] (4) The degradation mechanism of 4-CP in the UCPB system may be: photocatalytic degradation of p-chlorophenol into intermediate products, which are then transferred to the microorganisms inside the carrier as a carbon source for growth, ultimately achieving efficient degradation and mineralization of p-chlorophenol. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 SEM (ab), TEM (cd), Mapping (e) and EDS (f) images of LP3;

[0024] Figure 2 The concentration change curves of MB photocatalytic degradation (a) and adsorption (b) by LC / ZnAl2O4 / BiPO4;

[0025] Figure 3 The cyclicity curve of the photocatalytic degradation of MB by LP3(b) catalyst;

[0026] Figure 4 This is a diagram of the internal circulation experimental device;

[0027] Figure 5 To investigate the effects of different treatment methods on the removal of 4-CP from wastewater in a stable system;

[0028] Figure 6 To investigate the effects of different treatment methods on TOC removal in 4-CP wastewater in a stable system;

[0029] Figure 7 The dechlorination effects of different systems in treating 4-CP wastewater in the fourth experiment;

[0030] Figure 8 Figure 2 shows the changes in UV-visible absorption spectra of 4-CP in adsorption (a), photolysis (b), biodegradation (c), photocatalysis (d), and UCPB (e) systems, the UV-visible absorption spectra of different degradation products (f), and the chromaticity change of 4-CP wastewater in the UCPB system (g).

[0031] Figure 9 is the distribution of internal and external biofilms in the biodegradation (ad) and UCPB (eh) systems;

[0032] Figure 10 The changes of biomass in biodegradation and photocatalysis-biodegradation direct coupling systems;

[0033] Figure 11 The changes of dehydrogenase activity under biological treatment and UCPB system;

[0034] Figure 12 The phylum-level community distribution (a) and detailed colony proportion distribution (bc) of the fourth batch of biological treatment and UCPB system. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0036] Experimental instruments:

[0037] The XRD instrument used was a Bruker D8 X-ray diffractometer, with Cu Kα as the emission source and an X-ray wavelength of The scanning range was 10 to 80°; scanning electron microscopy (SEM) was performed using a JEOL scanning electron microscope (Quanta FEG 250, USA); transmission electron microscopy (TEM) was performed using a JEOL projection electron microscope (JEM-3200FS, Japan); X-ray photoelectron spectroscopy (XPS) was performed using a Shimadzu X-ray photoelectron spectrometer (AXIS ULTRA DLD, Japan); ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) was performed using a Shimadzu UV-2550 ultraviolet-visible spectrophotometer; fluorescence spectroscopy (PL) was performed using a fluorescence spectrometer (Fluorolog-3) from Jobin Yvon Inc., USA; and photoelectrochemical performance was tested using a Shanghai Chenhua electrochemical workstation (CHI 760E).

[0038] Experimental methods:

[0039] (1) 4-CP Detection: 4-CP concentration was determined using a high performance liquid chromatograph (HPLC, Agilent 1260). The specific method was as follows: 1.5 mL of the sample was filtered through a 0.22 μm water filter membrane, placed in a test bottle, and tested using HPLC. The HPLC operating conditions were: a C18 column, a measurement wavelength of 280 nm, a mobile phase of methanol:water = 60:40, a flow rate of 0.5 mL / min, an injection volume of 10 μL, and a column temperature of 25°C.

[0040] (2) Dissolved organic carbon (DOC) analysis: DOC in water samples was measured using a total organic carbon (TOC) analyzer (Elementar, Germany, Multi N / C 2100). Specifically, 5 mL of the sample was filtered through a 0.45 μm water filter membrane and then measured using an Elementar TOC analyzer. TOC was determined using the non-purgeable organic carbon analysis method (NPOC).

[0041] (3) Chloride ion (Cl - ) content determination: Cl - The content is determined by the molar method in the national standard "Determination of chloride ions in industrial circulating cooling water and boiler water" (GB / T 15453-2018).

[0042] (4) Biomass determination: The biomass loaded on the carrier was determined by the drying method. That is, after the experiment, 30 sponge carriers were taken out of the reaction system and dried at 80°C to constant weight. The obtained mass was the sum of the biomass, the mass of the sponge carrier, and the mass of the catalyst.

[0043] (5) Biological activity analysis

[0044] Dehydrogenase activity (DHA) is usually used to evaluate microbial activity, mainly using the 2,3,5-triphenyltetrazolium chloride (TTC) colorimetric method to determine [152,153 The basic principle is that TTC acts as a hydrogen acceptor and will be reduced to red triphenylformazan (TF) after receiving hydrogen in microbial cells. The red TF will crystallize in the microbial cells and can be extracted by organic solvents. The corresponding equation is as follows:

[0045]

[0046] a. Establishment of standard curve

[0047] Take 1, 2, 3, 4, 5, and 6 mL of a 1 g / L TTC-glucose standard solution, add 2 mL of Tris-HCl buffer and 1 mL of a freshly prepared 10 wt% Na2S solution, shake thoroughly until a red color develops, then accurately add 5 mL of toluene to extract the TF from the solution. Allow the solution to stand for 15 minutes until complete separation. The supernatant is then measured for absorbance at 492 nm. One unit of enzyme activity is calculated as 1 μg of TF produced in 1 hour. Using a blank as a control, plot the dehydrogenase activity to establish a standard curve.

[0048] b. Biofilm activity test

[0049] The specific method of dehydrogenase activity test is as follows: 30 sponge carriers were taken out from the UCPB reaction device and placed in a 100 mL centrifuge tube. 2.5 mL of distilled water, 5 mL of TTC solution (5 g / L), 2 mL of glucose solution (0.1 mol / L), and 2 mL of Tris-HCl buffer solution (1 mol / L, pH = 8.5) were added in sequence. The centrifuge tube was capped and placed in a water bath shaker at 200 r / min for 30 minutes. After that, it was placed in a 37°C constant temperature incubator and incubated for 1 hour. After that, 2 drops of concentrated sulfuric acid were added to terminate the reaction. Then, 5 mL of toluene solution was accurately added to extract TF from the mixture. The centrifuge tube was continued to be placed in a shaker at 200 r / min for 30 minutes. After that, the centrifuge tube was ultrasonicated for 5 minutes and then centrifuged in a centrifuge (4000 r, 5 minutes, 28 ± 2°C). The supernatant was taken and its absorbance at a wavelength of 492 nm was measured. The size of the DHA in the biofilm was calculated by comparing it with the standard curve.

[0050] (6) SEM observation: SEM was used to observe the distribution of microorganisms and catalysts on the inner and outer surfaces of the sponge carrier. The sponge carrier needed to be pretreated before testing. The specific method is as follows

[154] Sponge carriers from the fourth batch of experiments were used as samples. They were first washed four to five times with 0.1 mol / L PBS (pH 7.2) buffer solution and fixed with 2.5 wt% glutaraldehyde solution for 4 hours. The fixed carriers were then frozen in a -80°C refrigerator for one day to set their shape. The fixed carriers were quickly cut with a sterile scalpel blade, and the collected sections were rinsed with PBS solution. The fixed carriers were then fixed with 4 wt% paraformaldehyde solution for 4 hours. The fixed carriers were rinsed twice with 0.1 mol / L PBS solution for 10 minutes each. The carriers were then dehydrated in 50%, 75%, and 100% ethanol, one time each for 10 minutes each. The dehydrated carriers were then sprayed with gold for observation.

[0051] (7) Chemical Demand (COD) Cr ) Detection: COD Cr The determination was carried out according to the national standard GB11914-89 potassium dichromate titration method.

[0052] (8) Biological Demand (BOD5) Test: The biological demand is tested using the dilution and inoculation method in accordance with the national standard GB7488-87.

[0053] (9) Analysis of biological colony structure: The changes in the biofilm colonies on the sponge carriers were detected using high-throughput metagenomic classification and sequencing technology. The specific steps are as follows: 30 sponge carriers were taken out of the experimental reactor and placed in a centrifuge tube. They were then washed three times with PBS solution and placed in a shaker. After shaking at 200 r / min for 30 minutes, the shaken biofilm was centrifuged and immediately frozen at -80°C. The gene sequencing was subsequently commissioned to Shanghai Meiji Biotechnology Co., Ltd. The genome of the sponge carrier biofilm was extracted using a DNA extraction kit, and then PCR amplification was performed on the V3-V4 region of the bacterial 16s RNA using 338F and 806R as primers. Finally, the original DNA sequence was obtained using the Miseq sequencing platform (Illumina, USA).

[0054] Example 1 Preparation and Performance Study of Lignin Carbon-based Composite UV Photocatalyst

[0055] (1) Preparation of LC / ZnAl2O4 / BiPO4 composite photocatalyst

[0056] 1) Preparation of lignin charcoal

[0057] Referring to the method disclosed in CN11579889A, lignin charcoal was prepared. By examining the performance of lignin charcoal prepared at different impregnation ratios and activation temperatures, it was found that with the gradual increase of the impregnation ratio and activation temperature, the specific surface area and pore volume of the lignin charcoal material first increased and then decreased. At the same time, the pore structure of the prepared lignin charcoal is mainly mesopores, and the volume of micropores accounts for a relatively small proportion. When the impregnation ratio is 1.5:1 and the activation temperature is 550°C, the specific surface area and pore volume of the lignin charcoal are the largest, which are 1862.9m 2 / g and 0.9361cm 3 In subsequent experiments, lignin charcoal was prepared with an impregnation ratio of 1.5:1 and an activation temperature of 550 °C, which was recorded as lignin charcoal (LC(1.5)-550).

[0058] 2) Preparation of LC / ZnAl2O4 / BiPO4 composite photocatalyst

[0059] 1 wt% ZnAl2O4 / BiPO4 (ZP3, where the ZnAl2O4 content of the total catalyst was 1 wt%) was prepared according to the method of Example 1 in CN111135843A. Various amounts of lignin char (LC(1.5)-550) were added to the mixed solution. The samples had a mass ratio of lignin char to 1 wt% ZnAl2O4 / BiPO4 of 0.1, 0.5, 1, 3, 5, and 10 wt%, respectively, and were designated LP, LP2, LP3, LP4, LP5, and LP6.

[0060] (2) Characterization and catalytic performance testing of LC / ZnAl2O4 / BiPO4 composite photocatalyst

[0061] The morphology of 1wt% LC / 1wt% ZnAl2O4 / BiPO4 (LP3) was analyzed by SEM and TEM. Figure 1 As shown. Figure 1 (ac) It can be seen that after doping with lignin carbon, the morphology of BiPO4 in the composite catalyst changed from irregular nanorods to regular rectangular or cubic shapes, the size of the nanoparticles gradually increased, and a large amount of ZnAl2O4 and lignin carbon were loaded on the surface of BiPO4. From the HR-TEM image of LP3 ( Figure 1 d) Clear boundaries can be seen between the three components of BiPO4, ZnAl2O4 and LC, where the interplanar spacings of 0.466nm, 0.248nm and 0.33nm correspond to the (011) crystal plane of BiPO4, the (311) crystal plane of ZnAl2O4 and the (002) crystal plane of LC, respectively. The element scanning energy spectrum and element distribution of LP3 are shown in Figure 4. Figure 1As shown in e, it can be seen that Bi, P, O, Zn, Al and C elements are evenly distributed in the selected area, and their corresponding EDS spectra are as follows Figure 1 As shown in Figure f, the presence of Bi, P, O, Zn, Al and C elements can also be observed. In summary, LC and ZnAl2O4 are successfully doped into the BiPO4 catalyst.

[0062] The experimental results of photocatalysis and MB adsorption of LC / 1wt% ZnAl2O4 / BiPO4 composites are shown in Figure 2. Figure 2 As shown. Figure 2 As shown in Figure 1, the introduction of lignin carbon improves the adsorption efficiency of the photocatalyst, and an appropriate amount of lignin carbon significantly enhances the photocatalytic performance of BiPO4. As the lignin carbon content gradually increases to 10wt%, the MB adsorption removal efficiency of the BiPO4-based catalyst increases from 2.73% to 34.01% after 0.5h of dark reaction. Its adsorption and photocatalytic performance initially increase and then decrease. When 1wt% lignin carbon (LP3) is doped, LP3 exhibits the best adsorption and photocatalytic effects. Its MB adsorption efficiency in the dark reaction and MB removal efficiency after 3h of photocatalysis are 10.74% and 99.87%, respectively. At 2h, LP3's MB removal efficiency is 97.83%. When the lignin carbon doping level is 10wt%, LP6 achieves a maximum MB adsorption efficiency of 34.01% after 30 minutes of dark reaction, but its MB removal efficiency is 74.06% after 3h of photocatalysis. In order to further explore the performance of adsorption in the photocatalytic process, we conducted pure adsorption experiments on lignin carbon-based composite catalysts. Figure 2 b. Table 1 shows the detailed data of the adsorption and photocatalytic experiments of LC / ZnAl2O4 / BiPO4. It can be seen that when the lignin carbon content is higher than 3wt%, the photocatalytic performance of the lignin carbon-based composite material is severely inhibited, mainly due to adsorption. Due to the good electron transfer performance of the lignin carbon structure and the difference in energy band potential between the components in the composite material, the photogenerated electrons and holes in the composite catalyst can be quickly transferred under light, so the introduction of an appropriate amount of lignin carbon can improve the photocatalytic performance of the composite catalyst. However, when the lignin carbon content is excessive, the lignin carbon will cover the active sites of BiPO4 and hinder the absorption of light, resulting in a decrease in photocatalytic performance.

[0063] Table 1 Adsorption and photocatalytic MB removal efficiency of LC / ZnAl2O4 / BiPO4 composite catalyst (3.5h,%)

[0064]

[0065] *After LP3 catalyst photocatalytically degraded MB solution for 2 h, the MB removal rate reached 97.83%.

[0066] The stability and reusability of the catalyst can be examined through cycle experiments. The specific results are as follows: Figure 3 As shown in the figure, after 4 cycles of reaction, the LP3 heterojunction catalyst still showed a high degradation effect (96.63%). This shows that the prepared LP3 has good photocatalytic stability.

[0067] To further investigate the mechanism of ZnAl2O4 / BiPO4 catalyst in the photodegradation of MB, free radical capture experiments were conducted on BiPO4 and LP3 catalysts. The results showed that for the LP3 composite catalyst, when BQ, EDTA-2Na, and IPA were added, the MB removal efficiency of LP3 decreased to 78.32%, 60.23%, and 43.26%, respectively, compared with that without the addition of a capture agent. 2- 、h + and ·OH are the main active species in the photocatalytic degradation process of LP3 composite materials.

[0068] Example 2 Startup and acclimatization of the photocatalytic-biological treatment direct coupling (UCPB) system

[0069] 1wt% LC / 1wt% ZnAl2O4 / BiPO4(LP3)) was used as the catalyst for UCPB. The catalyst was loaded by the co-impregnation method. Specifically: 1g of the catalyst was placed in a beaker, and anhydrous ethanol in different proportions was added. After vigorous stirring for 8h, it was ultrasonicated for 2h to make the catalyst evenly dispersed in the anhydrous ethanol. 2g (220±10) 7mm cubic polyurethane sponge carriers were placed in the above suspension and vigorously stirred for 12h. The beaker was sealed with Parafilm sealing film during the whole process to prevent the volatilization of alcohol during stirring and ultrasonication. The beaker was then placed on a 70℃ magnetic heating table to evaporate the ethanol while stirring. In order to make the catalyst evenly loaded on the surface of the carrier, when the volume of ethanol was small, a glass rod was used to continue stirring until the ethanol was completely volatilized. The sponge carrier loaded with the catalyst was placed in an 80℃ oven for drying. After drying, the carrier was washed with distilled water and ultrasonicated to remove the catalyst that was not firmly loaded. Finally, it was placed in an oven and dried to constant weight, and its loading rate was calculated. The loading rate calculation formula is as follows:

[0070]

[0071] Among them, C is the loading rate, m1 is the mass of the carrier loaded with catalyst, m0 is the initial mass of the carrier, and m c is the initial mass of the catalyst.

[0072] The results showed that the lignin carbon-based composite catalyst was loaded on the sponge carrier by the co-impregnation method, and an experiment was carried out to explore the effect of catalyst suspension concentration on catalyst loading rate and performance. The specific conditions are shown in Table 2.

[0073] Table 2 Effect of catalyst suspension concentration on loading rate

[0074]

[0075] Table 2 shows that the loading rate of the lignin carbon-based catalyst on the polyurethane sponge support gradually increases with increasing ethanol content (i.e., decreasing catalyst concentration). The loading efficiency of the two catalysts on the support is essentially the same, indicating that a low-concentration catalyst suspension is beneficial for increasing the catalyst loading rate. When the ethanol volume is 100 mL and the catalyst weight is 1 g, the loading rate of LP3 on the support is 47.16 ± 3.57%, respectively.

[0076] Subsequently, a series of photocatalytic degradation experiments were conducted to further investigate the effect of catalyst loading on 4-CP degradation performance. The results showed that removal initially increased and then decreased with increasing catalyst loading. This is likely due to excessive catalyst loading on the support, which reduces the number of adsorption sites and specific surface area. PCP-3 achieved the highest 4-CP removal efficiency of 99.55% after 12 hours of illumination.

[0077] (2) Microbial inoculation and biofilm cultivation

[0078] The microbial inoculation sludge comes from the aerobic pool of a large papermaking wastewater treatment plant in northern Jiangsu. Since parachlorophenol (4-CP) is highly toxic and difficult to biodegrade, it has a serious inhibitory effect on microorganisms. Therefore, 4-CP needs to be added to the culture medium to acclimate the microorganisms in the activated sludge. 5 mg / L 4-CP is added to the reaction system every 3 to 4 days to enable the microorganisms to adapt to the environment required for the experiment. The unloaded and loaded catalyst sponge carriers are put into the above-mentioned acclimated aerobic sludge and aerated for 24 hours to complete the activated sludge inoculation. The inoculated sponge carrier is placed in a fluidized bed reactor to culture the biofilm. The specific device is as follows: Figure 4 As shown. In order to facilitate UV transmission during the experiment, the UCPB reaction device is made of quartz glass. It consists of a hollow cylinder with an effective volume of 540mL, of which the inner and outer diameters are 70mm and 75mm respectively, and the column height is 180mm. A 40mm circular aeration disk is installed at the bottom of the reactor to provide oxygen required for the aerobic process. The biofilm is cultivated using the sequencing batch activated sludge (SBR) process. According to COD CrThe experimental culture medium required for biofilm formation was prepared in a ratio of N:P = 200:5:1, specifically as follows: NaAc·3H2O 400mg / L, CO(NH2)2 19.5mg / L, Na2HPO4 7.15mg / L. During the biofilm culture process, the water temperature was maintained at 25±1℃, the dissolved oxygen content was controlled at 4±0.5mg / L, and 500mL of culture medium was replaced every 12h. To prevent the catalyst from damaging the biofilm under light conditions, the reactor was placed in a dark environment. The COD of the inlet and outlet water was measured every day. Cr The changes of COD in the effluent were monitored and the growth of biofilm was observed under a microscope. Cr Basically stable, at this time the biofilm culture is basically completed, and a large amount of biofilm is attached to the inside and outside of the sponge carrier.

[0079] Prepared 4-CP wastewater was added to an internal circulation reactor containing a sponge carrier containing a cultured biofilm. Because the microorganisms needed to gradually adapt to the para-chlorophenol wastewater treatment environment, 250 mL of 20 mg / L 4-CP water samples were exchanged every 12 hours during the initial cycle. After the system stabilized, the corresponding UV photocatalysis-biodegradation direct coupling experiment was carried out.

[0080] In order to explore the degradation effect of UCPB on 4-CP, comparative experiments such as photolysis (P), adsorption (AD), biodegradation (B) and photocatalytic oxidation (PC) were carried out, as shown in Table 3. Figure 4 The device shown was used. A UV photocatalytic-biological direct coupling system (UCPB) was constructed using LP3 as a catalyst, and the light source used was an UV mercury lamp (6w, 365nm, Shanghai Jiguang Instrument Co., Ltd.). During the experiment, 500mL of 20mg / L 4-CP wastewater was replaced each time, and the experimental temperature and dissolved oxygen were controlled at around 25±1℃ and 4±0.5mg / L. Samples were taken at reaction times of 0h, 2h, 4h, 6h, 8h, 10h, 12h and 24h to test the 4-CP concentration, dissolved organic carbon (DOC) and chloride ion content (Cl - ).

[0081] Table 3 UCPB system comparative experimental operating conditions

[0082]

[0083] Example 3 Performance of the UCPB system in degrading bamboo pulp ECF bleaching wastewater (1) Study on the degradation effect of the UCPB system on 4-CP wastewater

[0084] Depend on Figure 5As can be seen, the sponge carrier's adsorption of 4-CP wastewater remained generally stable across the four experimental batches, with a 4-CP removal rate remaining stable at around 8%. The polyurethane sponge carrier achieved a high 4-CP adsorption rate of 53% after 12 hours (data from the first batch of sponge carrier adsorption), indicating that the sponge carrier had a strong initial adsorption effect on 4-CP. However, after multiple experiments, the sponge carrier's adsorption of 4-CP wastewater reached near saturation, resulting in minimal changes in 4-CP concentration after the adsorption system stabilized. The experimental data indicate that 4-CP is difficult to desorb once adsorbed onto the sponge carrier, indicating that the sponge carrier's adsorption and desorption performance for 4-CP is not significant. In the single-use illumination system, both UV and visible light had very weak removal effects on 4-CP wastewater, and the photolysis effect was essentially negligible, indicating that photolysis cannot degrade 4-CP. In the single biological treatment experiment, the microbial removal rate of 4-CP was very low, remaining below 20%. Furthermore, the process also involves adsorption of the catalyst and the sponge carrier, demonstrating that the biofilm's ability to treat this substance is actually very limited. The test results show that the COD of 20mg / L 4-CP wastewater Cr is 31.7 mg / L, BOD5 is 1.04 mg / L, so the BOD5 / COD of 4-CP wastewater is Cr It is 0.033, indicating that 4-CP is a difficult-to-biodegrade organic matter and has a pungent and unpleasant odor, making it difficult to degrade through biological treatment methods.

[0085] For the single photodegradation oxidation system, the removal rate of 4-CP was very stable in the four batches of experiments. After 12 hours, the removal rate of 4-CP by LP3 photocatalytic degradation was basically maintained at 95%. This was due to the high loading rate of LP3 on the sponge carrier and the high UV photocatalytic efficiency of LP3 and the generation of active oxidative species (·O2 - 、h +and ·OH) are relatively abundant, resulting in better photocatalytic performance. When coupled with the biofilm, the UCPB system's effectiveness in treating 4-CP gradually improved, with a higher 4-CP removal rate. In the first two experiments, the UCPB system composed of the LP3 catalyst exhibited less 4-CP treatment efficiency than the corresponding photocatalytic oxidation systems (PCP and PCM). Starting from the third experiment, the UCPB system's 4-CP removal rate gradually surpassed that of the photocatalytic oxidation system. This is primarily due to the biofilm encapsulating part of the photocatalyst in the initial UCPB experiments, resulting in less exposure and relatively low photocatalytic performance. However, as the reaction progressed, the biofilm encapsulating the catalyst on the sponge support gradually shed due to the shear force of the water flow and the influence of photocatalytically active species, exposing more catalyst to the support's outer surface, thereby improving photocatalytic performance. Simultaneously, the biofilm within the support gradually adapted to the water quality environment and rapidly metabolized photocatalytic degradation products, thus avoiding competition between intermediates and active species and allowing more active free radicals to treat the para-chlorophenol wastewater.

[0086] (2) Study on the mineralization effect of UCPB system on 4-CP wastewater

[0087] The TOC value of wastewater in the stabilization system was measured to study the mineralization degree of 4-DCP wastewater in different treatment systems. The experimental results of the corresponding four batches are as follows: Figure 6 As shown in the figure, in the single adsorption system, the TOC degradation pattern in 4-CP wastewater is basically consistent with the change in concentration. After the initial circulation and test process, the sponge carrier's adsorption of 4-CP is basically saturated, and the change in TOC is very small. For the single photolysis system, TOC remains basically unchanged, further proving that photolysis has no degradation effect on 4-CP wastewater. In the single biodegradation system, the TOC removal rate is basically around 20%. Since this substance is a difficult-to-biodegrade organic matter, it is difficult for microorganisms to degrade it even after long-term acclimation and operation, resulting in relatively small changes in its TOC.

[0088] As can be seen from the figure, the mineralization degree of 4-CP wastewater by the photocatalytic oxidation system is good and stable. The removal rate of 4-CP by the PCP system photocatalytic oxidation is basically maintained at 95% after 12 hours. Figure 6The TOC removal rate in the PCP system remained essentially constant at 41% over the 12-hour period, indicating that 4-CP was not fully mineralized during the photocatalytic oxidation process, but was instead converted into an intermediate product. Furthermore, the TOC removal rate of the PCP system for 4-CP photocatalytic oxidation increased rapidly during the first 6 hours, but then decreased slowly with increasing reaction time, further demonstrating the low mineralization efficiency of 4-CP and its intermediates by the photocatalytic oxidation system alone. The direct photocatalytic-biocoupled system significantly improved TOC removal in the 4-CP wastewater. In the first batch of experiments, the UCPB system's mineralization efficiency for 4-CP was slightly lower than that of the photocatalytic system (PC). However, starting in the second batch, the UCPB system's 4-CP removal efficiency gradually surpassed that of the photocatalytic system. In the fourth batch of experiments, the UCPB system achieved TOC removal rates of 51.46% and 86.42% for 4-CP wastewater at 12 and 24 hours, respectively. This indicates that the intermediates generated during the photocatalytic oxidation process both provide a usable carbon source for the biofilm and are simultaneously metabolized and degraded by it. The reduction of intermediates can reduce competition among active species during the photocatalytic oxidation of 4-CP, allowing more active species to oxidize 4-CP. This indicates that photocatalysis and the biofilm in the UCPB system form a good synergistic effect, that is, the photocatalytic process can provide the carbon source necessary for the growth of the biofilm, and the biofilm can promote the photocatalytic oxidation process.

[0089] (3) Study on the chloride ion concentration of 4-CP wastewater by UCPB system

[0090] In order to further verify the degradation effect of 4-CP, the chloride ion content of the fourth batch of water samples was measured. The results are as follows: Figure 7 As shown in the figure, during the degradation of 4-CP, the C-Cl bond breaks, which causes the Cl in p-chlorophenol to - Released into the reaction solution. As can be seen from the figure, the dechlorination efficiency in different systems is basically consistent with the change trend of 4-CP concentration. For the adsorption system alone, the wastewater basically does not contain chloride ions, indicating that the sponge carrier only adsorbs 4-CP and cannot degrade it. For the photolysis system alone, the chloride ion content is also very low, indicating that light alone has little effect on the degradation of 4-CP. The dechlorination rate of wastewater in the biodegradation system is also very low, which further illustrates that it is difficult for the biological treatment system to degrade 4-CP. The photocatalytic oxidation and UCPB systems have significant effects on the removal of chloride ions in 4-CP wastewater, and the dechlorination effect of the UCPB system is better than that of the photocatalytic oxidation system. At 12h, the dechlorination rates in the UCPB system were 95.15%.

[0091] (4) Changes in UV-visible absorption spectra of parachlorophenol wastewater in the UCPB system

[0092] Figure 8The following graph shows the changes in the UV-visible absorption spectra and wastewater color of 4-CP in different systems from the fourth batch. The UV-visible absorption spectrum of the 4-CP wastewater exhibits two characteristic absorption peaks at wavelengths of 225nm and 280nm. As can be seen, the UV absorption spectra of the 4-CP wastewater in the adsorption, photolysis, and biodegradation systems show only a slight decrease in absorbance at the characteristic absorption wavelengths, with no other changes. This further demonstrates that adsorption and photolysis have no degradative effect on 4-CP. The reduction in 4-CP concentration in the biodegradation system is primarily related to adsorption by the carrier and biofilm.

[0093] For the photocatalytic and directly coupled photocatalytic-biodegradation systems, the intensities of the two characteristic absorption peaks of 4-CP gradually decreased with increasing reaction time, indicating that 4-CP was gradually degraded, consistent with the changing trend of para-chlorophenol concentration. However, during the degradation process, a new peak appeared in the 4-CP wastewater at a wavelength of 380 nm. This peak is primarily the absorption peak of an intermediate product in the degradation of 4-CP. The intensity of this peak first increased and then decreased with reaction time, indicating that 4-CP was gradually oxidized to intermediates such as quinone and 4-chlorocatechol by oxidative species. As 4-CP was completely oxidized, the content of the intermediates gradually increased. However, after 4-CP was completely degraded, the active species began to primarily attack the intermediates, eventually causing their content to gradually decrease. For the photocatalytic (PCP) system, the characteristic absorption peak of 4-CP was no longer detectable after 12 hours, but the characteristic absorption peak at 380 nm still existed. After 24 hours, the characteristic absorption peak at 380 nm was still present, indicating that this intermediate substance was still present. For the UCPB system, the intensity of the absorption peak at 380 nm was lower than that of the photocatalytic system at 12 hours, and no absorption peak at 380 nm was detected at 24 hours, indicating that the intermediates had been essentially completely converted. This further demonstrates the important role of biofilms in the degradation and mineralization of pollutants. Figure 8 Figure g shows the color change of the wastewater in the UCPB system. The color of the 4-CP wastewater in the UCPB system changes from colorless to light yellow to yellow to colorless. This, combined with the corresponding UV-visible absorption spectrum, further illustrates the overall degradation process of the 4-CP wastewater: 4-CP is first oxidized to intermediates, followed by an increase in the intermediate content, and finally, complete degradation of the intermediates. In the individual adsorption, photolysis, and biological treatment systems, the wastewater color remained unchanged throughout the process, remaining a colorless, transparent liquid. In the photocatalytic system, however, the 4-CP wastewater only changed color from colorless to yellow within 24 hours, never returning to colorless. Figure 8Figure f is the UV absorption spectrum of possible degradation products of para-chlorophenol. During the degradation of 4-CP in wastewater, the characteristic absorption peak at 250 nm gradually increases, the absorption peak at 225 nm decreases, and an isosbestic point is formed at 239 nm. This may indirectly indicate that 4-CP is converted into a benzoquinone intermediate. At 12 and 24 hours, absorption peaks below 240 nm are observed. These peaks represent the absorption peaks of different fatty acids generated by the benzene ring cleavage products, further indicating that 4-CP is gradually degraded into fatty acids and other substances.

[0094] Example 4 Analysis of biofilm response behavior during the degradation of parachlorophenol wastewater

[0095] (1) Distribution and changes of biofilm

[0096] In order to analyze the growth and distribution of biofilm in sponge carriers under different treatment systems, SEM characterization was carried out. The experimental results are as follows: Figure 9 As shown in the figure, during the UCPB culture and acclimation stage, a large amount of biofilm covered the inner and outer surfaces of the carrier, but the biomass outside the carrier was much smaller than that inside, which facilitated the full play of the synergistic effect between photocatalysis and biodegradation. The biofilm in the carrier showed different distribution after being treated with different systems. Figure 9 (ad) It can be seen that in the biological treatment 4-CP system, the biofilm on the inner and outer surfaces of the sponge carrier have severe shedding phenomenon, and only a small amount of biofilm covers the surface of the carrier. This is mainly because the difficult biodegradation of 4-CP makes it impossible for microorganisms to use it as a carbon source required for growth metabolism, resulting in the death of a large number of microorganisms and falling off due to the shear force of the water flow. In the UCPB system, it can be observed that the growth of the biofilm is relatively stable. The exterior of the sponge carrier in the UCPB system is relatively smooth, exposing a large amount of photocatalysts, which is conducive to the degradation of 4-CP into low-toxic intermediates under the action of photocatalysis. In addition, due to the shear force of the water flow and the photocatalytic process, oxidative free radicals (such as ·OH, ·O2 - and h + ), it is difficult for the biofilm to grow on the outer surface of the carrier, and only a large amount of catalysts are firmly attached to the surface of the carrier, which is more conducive to photocatalytic degradation. Figure 9 (h, l) are SEM images of the catalyst on the outer surface of the carrier. A large amount of LC / ZnAl2O4 / BiPO4(LP3) catalyst can be observed, and the morphology of the catalyst has not changed, which further proves that a large amount of catalyst is loaded on the outer surface of the carrier and the structure and performance are stable. Figure 9(f, j) It can be seen that a certain thickness of biofilm is attached to the inside of the sponge carrier in the UCPB system. Analysis shows that 4-CP can be degraded into a series of intermediates through the photocatalytic action of the catalyst on the outer surface of the carrier. These intermediates have relatively low toxicity and relatively good biochemical properties. Therefore, they can be fully utilized by the biofilm inside the carrier, which not only promotes its own growth and reproduction, but also facilitates the mineralization of organic pollutants in wastewater.

[0097] (2) Biomass changes

[0098] The biomass loaded in the sponge carrier is an important indicator for evaluating the growth status of microorganisms. Figure 10 The figure shows the changes in biomass in different batches of biodegradation and photocatalytic-biodegradation direct coupling systems. It can be seen that for the biodegradation system, the biomass in the sponge carrier decreases with the increase in the number of test batches. After the fourth batch, the biomass decreased from 4.05 mg / L to 0.32 mg / L. This is mainly due to the high toxicity of 4-CP wastewater and the difficulty of microbial degradation, which makes it impossible for microorganisms to survive. For the UCPB system, the biomass on the carrier decreased significantly in the first batch of experiments. This is mainly because after 4-CP is added to the system, it takes time for the photocatalytic conversion into intermediate products, and the microorganisms fail to adapt to the wastewater environment. Starting from the second batch of experiments, the biomass in the UCPB system gradually increased, indicating that the intermediate products after the photocatalytic degradation of 4-CP are gradually utilized by microorganisms, thereby promoting the growth of microorganisms.

[0099] (3) Changes in biological activity

[0100] A standard curve of dehydrogenase activity was established, and the equation corresponding to the standard curve is as follows:

[0101] Y=1.78629X-0.33033 R 2 =0.997 (4-3)

[0102] Where Y is the absorbance and X is the TTC concentration.

[0103] Dehydrogenases are a group of oxidoreductases within microbial cells, essential enzymes for the degradation of organic pollutants and energy production. Therefore, dehydrogenase activity can be used to assess the number of active microorganisms and their degradation activity against organic matter. It is an important indicator for evaluating the activity of degrading organisms, and dehydrogenase activity directly indicates the ability of biological cells to degrade organic matter. Figure 11The figure shows the changes in dehydrogenase activity at different reaction times in the fourth batch of biodegradation and the UCPB system. As shown in the figure, after four batches of operation, the dehydrogenase activity in the biological treatment system alone was relatively low. With increasing reaction time, the dehydrogenase activity initially decreased and then increased. This is primarily because the biofilm had difficulty utilizing the carbon source in the 4-CP wastewater, preventing the microorganisms from synthesizing dehydrogenases and carrying out metabolic activities, resulting in decreasing biological activity. At 4 hours of reaction, dehydrogenase activity significantly decreased, then gradually increased. This is primarily due to the low production of intermediates from the photocatalytic oxidation of 4-CP in the early stages of the reaction, resulting in an insufficient carbon source for the microorganisms. Furthermore, the high toxicity and poor biodegradability of the 4-CP wastewater made the microorganisms unsuitable for the water quality environment, leading to a decrease in biological activity. However, as the intermediates produced during the photocatalytic process gradually increased and their toxicity decreased, the microorganisms in the biofilm could utilize them as a carbon source, gradually increasing the dehydrogenase activity within the system.

[0104] Example 5 Biocolony Analysis of the Parachlorophenol Wastewater Degradation Process

[0105] (1) Biodiversity analysis

[0106] Table 4 Biodiversity index in biological treatment and UCPB system

[0107]

[0108] Biological Alpha Diversity can evaluate the abundance and diversity of microbial communities within a system. Shannon, Simpson, Ace, Chao, and Coverage indices are generally selected as commonly used indices. Among them, the Chaos and Ace indices can reflect the richness of the biological community, the Shannon and Simpson indices can reflect the diversity of the biological community, and the Coverage index is used to evaluate the coverage of the sample library. The larger the Chao index and ACE index, the greater the richness of the microbial community; while the larger the Shannon index and the smaller the Simpson index, the higher the community biodiversity. As can be seen from the table, the Coverage index of the tested samples is all above 99.8%, indicating that high-throughput sequencing can represent the main characteristics of the distribution of microbial colonies. The Chao, Ace and Shannon indices in the UCPB system were higher than those in the biological treatment system, and the Simpson index was lower than that in the biological treatment system, indicating that the richness and diversity of the biological colonies in the UCPB system were greater than those in the biological treatment system. This was mainly because the UCPB system could convert 4-CP into intermediate products such as low-toxic and easily degradable small molecules, thereby reducing the toxicity of 4-CP wastewater and thus reducing the degree of damage to the biofilm inside the carrier; while in the biological system, microorganisms directly treated highly toxic 4-CP wastewater, so it was difficult for microorganisms to adapt. Only a small number of highly adaptable microorganisms could survive, and most microbial bacteria were eliminated, resulting in a decrease in the richness and diversity of the microbial community.

[0109] (2) Changes in community structure

[0110] Figure 12The distribution of biological colonies at the phylum level in the fourth batch of biological treatment and the UCPB system is shown. The figure shows that the biological colonies in the biological treatment system are primarily composed of Proteobacteria (42.11%), Actinobacteria (42.06%), and Cyanobacteria (13.22%). The colonies are relatively homogenous, and other bacterial species are relatively rare. In contrast, the UCPB system exhibits a more diverse bacterial population. Proteobacteria and Actinobacteria remain the dominant species, but their relative abundance has decreased, while the abundance of other bacterial species has increased. Furthermore, Proteobacteria, Actinobacteria, Patescibacteria, Chloroflexi, and Bacteroidota are the dominant species. Compared to the biological treatment system, the abundance of Patescibacteria, Chloroflexi, and Bacteroidota in the UCPB system increased by 9.1%, 9.78%, and 2.32%, respectively. The decrease or disappearance of other phyla indicates that these microorganisms cannot adapt to the harmful environment and gradually die. The increase or appearance of Bacteroidota indicates that the colony is able to adapt to the environment and gradually grow. According to relevant reports, Bacteroidota plays a significant role in treating aromatic pollutants in papermaking wastewater. In summary, the diverse microbial colonies in the UCPB system, with a high relative abundance of specific bacterial species, further demonstrate that the direct photocatalytic-biological coupling system can convert the highly toxic and difficult-to-biodegrade 4-CP into a less toxic and easily degradable intermediate, reducing or preventing damage to the microbial colonies in the system by adverse substances.

[0111] The present invention provides a concept and method for treating para-chlorophenol in wastewater using a directly coupled photocatalytic oxidation-biodegradation system. While many methods and approaches exist for implementing this technical solution, the aforementioned are merely preferred embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A method for treating p-chlorophenol in wastewater by direct coupling of ultraviolet catalytic oxidation and biodegradation, characterized in that: The steps include: (1) The lignin carbon-based composite catalyst is loaded onto a polyurethane sponge carrier, and then the polyurethane sponge carrier loaded with the catalyst is put into the acclimated aerobic sludge, aerated, and the activated sludge is inoculated to obtain the inoculated polyurethane sponge carrier; (2) placing the inoculated polyurethane sponge carrier into a fluidized bed reactor to culture the biofilm, and using a sequencing batch activated sludge process to culture the biofilm to obtain a polyurethane sponge carrier loaded with a catalyst and a biofilm; (3) placing the polyurethane sponge carrier loaded with the catalyst and the biofilm in an internal circulation reactor to obtain a UV-photocatalytic oxidation-biodegradation direct coupling system; (4) adding the para-chlorophenol wastewater to the internal circulation reactor of the UV photocatalytic oxidation-biodegradation direct coupling system for treatment; The lignin carbon-based composite catalyst is a LC / ZnAl2O4 / BiPO4 ultraviolet photocatalyst, which is obtained by adding lignin carbon to a mixed solution during the hydrothermal preparation of a ZnAl2O4 / BiPO4 heterojunction photocatalyst. The polyurethane sponge carrier is a hydrophilic polyurethane sponge in the shape of a 7 mm cube, wherein the catalyst mass: the polyurethane sponge carrier mass and the ethanol volume ratio is 1: 2: 20-150; in the ZnAl2O4 / BiPO4 heterojunction, the mass ratio of ZnAl2O4 to BiPO4 is 0.5-1wt%, and the mass ratio of lignin charcoal to the ZnAl2O4 / BiPO4 heterojunction is 0.1-10wt%.

2. The method according to claim 1, characterized in that In the ZnAl2O4 / BiPO4 heterojunction, the mass ratio of ZnAl2O4 to BiPO4 is 1 wt%, and the mass ratio of lignin char to ZnAl2O4 / BiPO4 heterojunction is 1 wt%.

3. The method according to claim 1, characterized in that In step (1), the acclimated aerobic sludge is obtained by acclimating activated sludge using wastewater containing para-chlorophenol.

4. The method according to claim 1, wherein In step (4), the ultraviolet photocatalytic oxidation-biodegradation direct coupling system is first stabilized with wastewater containing para-chlorophenol, and then the pH of the chlorophenol wastewater to be treated is adjusted to neutral, and then added to the inner circulation reactor of the ultraviolet photocatalytic oxidation-biodegradation direct coupling system for treatment. An ultraviolet mercury lamp is used as a light source outside the inner circulation reactor, and the experimental temperature and dissolved oxygen are controlled at 25±1°C and 4±0.5 mg / L, respectively.

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