Fe-ctab co-pillared montmorillonite composite material, and preparation method and application thereof

Abstract

This invention discloses an Fe-CTAB co-pillared montmorillonite composite material, its preparation method, and its application, belonging to the technical field of photocatalytic wastewater treatment. This invention specifically modifies montmorillonite with CTAB and iron pillars, and then co-pillars it to prepare a photocatalytic composite material of montmorillonite matrix. The modified composite material successfully introduces a large number of positively charged quaternary ammonium cation sites, while the iron oxide pillars provide electrons and holes, thereby increasing the adsorption rate and performance of metal ions in high-concentration industrial wastewater. Furthermore, it can be used to treat high-concentration hexavalent chromium industrial wastewater generated by adsorption-reduction electroplating plants under ultraviolet-visible light irradiation.

Description

Technical Field

[0001] This invention belongs to the technical field of photocatalytic wastewater treatment, specifically relating to an Fe-CTAB co-pillared montmorillonite composite material, its preparation method, and its application. Background Technology

[0002] Hexavalent chromium (Cr(VI)) is a Group 1 carcinogen. It exists in water as anion, exhibiting high solubility and strong mobility. Traditional treatment technologies (chemical reduction, adsorption, ion exchange, membrane separation) suffer from high reagent consumption, secondary pollution from iron sludge, and high operating costs. Photocatalytic reduction can convert Cr(VI) into the less toxic Cr(III), but conventional catalysts have drawbacks such as weak visible light response, rapid electron-hole recombination, and poor anion enrichment capacity.

[0003] Montmorillonite is a natural layered clay with a large specific surface area and strong cation exchange capacity, but it is negatively charged and insulating, resulting in extremely poor adsorption and photocatalytic activity for Cr(VI). While a single iron pillar can impart photocatalytic activity, interlayer expansion is limited and hydrophobic enrichment sites are lacking. Modification with CTAB alone can increase interlayer spacing and enhance adsorption, but it lacks photocatalytic ability. More importantly, even with simple physical mixing of iron-pillared montmorillonite and CTAB, CTAB molecules cannot stably embed into the interlayer domain through cation exchange, failing to form an organic-inorganic co-pillared structure with Fe2O3 nanoclusters, thus preventing the construction of continuous hydrophobic mass transfer channels. In this case, Cr(VI) still relies on diffusion from the traditional aqueous bulk to the material's outer surface, resulting in high mass transfer resistance, low local interlayer concentration, and an inability to achieve spatial coupling between adsorption sites and photocatalytically active sites, making synergistic removal difficult. Currently, there is a lack of montmorillonite-based materials that synergistically modify both materials to achieve integrated adsorption and photocatalysis, making it difficult to meet the engineering requirements for efficient, green, and low-cost treatment of Cr(VI) wastewater.

[0004] Based on the above-mentioned shortcomings, a Fe-CTAB co-pillared synergistic modification strategy is proposed to solve the performance bottleneck of single modification, which has become an urgent problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a Fe-CTAB co-pillared montmorillonite composite material, its preparation method and application, so as to solve the problems mentioned in the background art or achieve better technical effects.

[0006] To solve the above-mentioned technical problems, the inventors, through practice and summarization, derived the technical solution of this invention. This invention discloses a method for preparing Fe-CTAB co-pillared montmorillonite composite material, the steps of which are as follows:

[0007] S1: Montmorillonite and sodium carbonate are mixed at a mass ratio of 3~7:2, water is added to make a slurry, and after stirring, filtering, drying, grinding and sieving, sodium montmorillonite is obtained.

[0008] S2: Add sodium carbonate to ferric nitrate nonahydrate solution, stir and age for 24 hours to obtain a stable iron columnar solution;

[0009] S3: The sodium montmorillonite obtained in S1 is prepared into a suspension, heated and then slowly added to the iron pillar liquid obtained in S2. After reaction, it is aged, washed with water, dried, and then calcined at high temperature to obtain iron pillar montmorillonite.

[0010] S4: Disperse the iron-pillared montmorillonite obtained in S3 with CTAB in deionized water, heat and react, filter and wash until no bromide ions are present, dry, grind and sieve to obtain the Fe-CTAB co-pillared montmorillonite composite material.

[0011] Furthermore, in S1, the mass ratio of montmorillonite to sodium carbonate is 5:2.

[0012] Further, in S2, ferric nitrate nonahydrate is first dissolved in deionized water, and then, under stirring at 60°C, it is added according to n(OH) - ) / n(Fe 3+ Add sodium carbonate slowly at a ratio of 1.5.

[0013] Furthermore, in S3, the high-temperature calcination temperature is 350~400℃, and the calcination time is 3.5~4h.

[0014] Furthermore, in S4, the mass ratio of iron-supported montmorillonite to CTAB is 3:0.7~0.84.

[0015] Furthermore, in S4, the mass ratio of iron-supported montmorillonite to CTAB is 3:0.7.

[0016] Furthermore, in S4, the heating reaction temperature is 60°C and the reaction time is 2 hours.

[0017] Furthermore, the Fe-CTAB co-pillared montmorillonite composite material prepared by any of the above-described methods;

[0018] The Fe-CTAB co-pillared montmorillonite composite material has a layered structure, with CTAB acting as an intercalation layer loaded onto the iron-pillared montmorillonite.

[0019] Furthermore, the Fe-CTAB co-pillared montmorillonite composite material is used in the removal of hexavalent chromium from wastewater.

[0020] Furthermore, the Fe-CTAB co-pillared montmorillonite composite material, as a photocatalytic composite material, adsorbs and catalytically reduces hexavalent chromium in acidic wastewater under light irradiation.

[0021] The illumination conditions are as follows: wavelength 360nm~480nm, illumination intensity 20~100mW / cm². 2 ;

[0022] The pH of the acidic wastewater is 1 to 2.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) This invention employs a two-step method of iron pillars + CTAB intercalation to prepare Fe-CTAB co-pillared montmorillonite composite material, achieving efficient removal of Cr(VI); CTAB intercalation expands the interlayer spacing, constructs hydrophobic-positively charged microregions, and strongly enriches Cr(VI) anions; Fe pillars introduce Fe2O3 nanoclusters, narrowing the band gap and extending the visible light response, generating Fe under illumination. 2+ It works synergistically with active free radicals; adsorption pre-enrichment + in-situ photocatalytic reduction to significantly improve removal efficiency and kinetic rate.

[0025] (2) In this invention, iron-supported montmorillonite and CTAB are key raw materials. Modified montmorillonite not only provides excellent adsorption capacity but also enhances the layered structure stability and durability of the composite material. The iron oxide introduced by the iron pillar can generate photogenerated electrons and active oxygen species under light conditions, reducing and fixing hexavalent chromium anions. By intercalating CTAB with iron pillars and loading them onto montmorillonite, the excellent adsorption performance of modified montmorillonite and the photocatalytic activity of iron can be effectively combined, improving the treatment efficiency through synergistic effect, thereby achieving economical, effective, rapid, and harmless treatment of high-concentration hexavalent chromium wastewater.

[0026] (3) This invention uses CTAB and iron pillars to specifically modify montmorillonite and then co-pillars it to prepare a photocatalytic composite material of montmorillonite-based matrix composite material. A large number of positive potential points of quaternary ammonium salt cations are successfully introduced into the modified composite material, while the iron oxide pillars can provide electrons and holes, thereby increasing the adsorption rate and adsorption performance of metal ions in high-concentration industrial wastewater. Under ultraviolet-visible light irradiation, it can be used to treat high-concentration hexavalent chromium industrial wastewater generated by electroplating plants: In a strongly acidic solution (pH=1), modified montmorillonite can effectively adsorb anionic compounds such as hexavalent chromium. Under the condition of increased visible light, it can stimulate certain components (iron oxides) in the iron pillars and generate electron-hole pairs in the interlayer of modified montmorillonite, promoting the reduction of hexavalent chromium. It can also make full use of natural clay mineral resources, which is in line with the concept of green chemistry and circular economy and has positive significance for environmental protection. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope image of the surface of the Fe-CTAB co-pillared montmorillonite composite material prepared in Example 2 of the present invention;

[0028] Figure 2 The infrared spectra of montmorillonite, Fe-MMT, and Fe-CTAB co-pillared montmorillonite composite materials prepared in Example 2 are shown below.

[0029] Figure 3 The ultraviolet diffuse reflectance spectra of montmorillonite, Fe-MMT photocatalytic reducing agent and photocatalytic composite material of Example 2 in this invention;

[0030] Figure 4 This is a superoxide radical diagram of the Fe-CTAB co-pillared montmorillonite composite material prepared in this invention;

[0031] Figure 5 This is a transmission electron microscope image of the Fe-CTAB-MMT of the present invention;

[0032] Figure 6 This is a schematic diagram of the mechanism of photocatalytic removal of Cr(VI) from solution by the Fe-CTAB co-pillared montmorillonite composite material of the present invention. Detailed Implementation

[0033] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0034] Unless otherwise specified, all raw materials or reagents used in the following examples are commercially available products.

[0035] A method for preparing Fe-CTAB co-pillared montmorillonite composite material, the preparation steps are as follows:

[0036] S1: Montmorillonite and sodium carbonate are mixed at a mass ratio of 5:2, deionized water is added to make a slurry, and the mixture is stirred, filtered, dried, ground and sieved to obtain sodium montmorillonite.

[0037] S2: Dissolve ferric nitrate nonahydrate in deionized water, stirring at 60°C, according to a specific alkali-ferric ratio (n(OH)). - ) / n(Fe 3+ Add sodium carbonate slowly (1.5%), stir, and age for 24 hours to obtain a stable iron columnar liquid;

[0038] S3: Prepare sodium montmorillonite into a suspension, heat it and slowly add iron-pillared liquid. After the reaction is complete, age it, centrifuge, wash it with water, dry it, and calcine it at 350~400℃ for 3.5~4h to obtain iron-pillared montmorillonite.

[0039] S4. The iron-pillared montmorillonite obtained in S3 and CTAB are dispersed in deionized water at a mass ratio of 6:1.4~1.68. The mixture is heated to 60℃ and reacted for 2 hours. After filtration and washing until no bromide ions are present, the mixture is dried and ground at 105℃ and passed through a 200-mesh sieve to obtain the Fe-CTAB co-pillared montmorillonite composite material.

[0040] Example 1

[0041] A method for preparing Fe-CTAB co-pillared montmorillonite composite material, the preparation steps are as follows:

[0042] S1: Mix montmorillonite and sodium carbonate at a mass ratio of 5:2 (e.g., 30g montmorillonite and 12g sodium carbonate), add 200mL of deionized water to make a slurry, stir for 2 hours, filter, dry at 85℃, grind, and pass through a 200-mesh sieve to obtain sodium montmorillonite.

[0043] S2: Dissolve 121.2g of ferric nitrate nonahydrate in 1000mL of deionized water, and stir at 60℃, according to a specific alkali-ferric ratio (n(OH)). - ) / n(Fe 3+ Add sodium carbonate slowly (1.5%), stir for 2 hours, and then age for 24 hours to obtain iron columnar liquid;

[0044] S3: Prepare a suspension by mixing sodium montmorillonite and water at a mass ratio of 1:10 (e.g., 25g sodium montmorillonite and 250mL deionized water), heat at 60°C, slowly add iron-supported solution, react fully for 2 hours, age for 24 hours, centrifuge, wash with water, dry at 105°C, and calcine at 400°C for 4 hours to obtain iron-supported montmorillonite.

[0045] S4. The iron-pillared montmorillonite obtained in S3 and CTAB are dispersed in 100mL of deionized water at a mass ratio of 6:1.68 (e.g., 6g iron-pillared montmorillonite and 1.68g CTAB). The mixture is heated to 60℃ and reacted for 2h. After filtration and washing until no bromide ions are found, the mixture is dried and ground at 105℃ and passed through a 200-mesh sieve to obtain the Fe-CTAB co-pillared montmorillonite composite material.

[0046] Example 2

[0047] Unlike Example 1, only the mass ratio of iron-supported montmorillonite to CTAB in S4 is changed to 6:1.4 (e.g., 6g iron-supported montmorillonite to 1.4g CTAB), while the other parts remain unchanged.

[0048] Example 3

[0049] Unlike Example 1, only the high-temperature calcination temperature in S3 is changed to 350°C, while the other parts remain unchanged.

[0050] Adsorption tests were conducted on the Fe-CTAB co-pillared montmorillonite composite materials prepared in Examples 1-3 above, and the specific methods are as follows:

[0051] (1) Adsorption under dark conditions:

[0052] Two different Cr(VI) standard solutions with pH values ​​of 1 and 2 and a concentration of 100 mg / L were prepared. 100 mg of each of the three Fe-CTAB co-pillared montmorillonite composite materials prepared in Examples 1-3 were placed in Cr(VI) solutions of different pH values, with a volume of 100 mL. The solutions were allowed to stand and adsorb for 12 h in the dark. The concentration of hexavalent chromium in the solutions was then tested. The test results are shown in Table 1 below.

[0053] Table 1. Composite materials prepared in Examples 1-3 under different pH conditions

[0054] Comparison of hexavalent chromium concentration in solution after 12 hours of adsorption

[0055]

[0056] (2) Catalytic reduction under light:

[0057] Prepare a Cr(VI) standard solution with a pH of 1 and a concentration of 100 mg / L. Take 100 mg of each of the three Fe-CTAB co-pillared montmorillonite composite materials prepared in Examples 1-3 above and place them in the Cr(VI) standard solution, with a volume of 100 mL. The solution is then analyzed at 360 nm–480 nm and 20–100 mW / cm². 2 Photocatalytic reduction was performed under illumination, and the Cr(VI) concentration was measured every 10 minutes. The test results are shown in Table 2 below.

[0058] Table 2. Composite materials prepared in Examples 1-3 under light irradiation.

[0059] Changes in hexavalent chromium concentration over time in the catalytic reduction solution

[0060]

[0061] (3) Darkness and light contrast experiment:

[0062] A Cr(VI) standard solution with a pH of 1 and a concentration of 100 mg / L was prepared. The Fe-CTAB co-pillared montmorillonite composite material prepared using the optimal preparation scheme (Example 2) was then tested under both dark and visible light irradiation (360 nm ~ 480 nm, 20 ~ 100 mW / cm²). 2 The experiment was conducted under the following conditions: samples were taken every 1 hour and 10 minutes under dark and visible light conditions, respectively, to detect the concentration of Cr(VI). The test results are shown in Table 3 below.

[0063] Table 3. Fe-CTAB co-pillared montmorillonite composite material of the present invention

[0064] Comparison of Cr(VI) removal under darkness and light.

[0065]

[0066] (4) Adsorption-photocatalytic reduction cycle test of Fe-CTAB co-pillared montmorillonite composite material:

[0067] To evaluate the recyclability of the Fe-CTAB co-pillared montmorillonite composite material prepared in this invention, under optimal conditions (the Fe-CTAB co-pillared montmorillonite composite material prepared in Example 2 and pH 1), 20 consecutive adsorption-photocatalytic cycling tests were conducted on the test solution with an initial hexavalent chromium concentration of 100 mg / L (the Cr(VI) removal rate (%) was measured after 1, 5, 10, 15 and 20 cycles, respectively). The test results are shown in Table 4 below.

[0068] Table 4. Cyclicability test results of the Fe-CTAB co-pillared montmorillonite composite material prepared in this invention.

[0069]

[0070] Analysis: The Fe-CTAB co-pillared montmorillonite composite material prepared according to the optimal formulation (Example 2) was ground into powder, and its instantaneous photocurrent and absorption characteristics to visible light were analyzed. The concentration of residual hexavalent chromium in the Cr(VI) standard solution after adsorption and photocatalysis experiments was determined using a UV spectrophotometer. Adsorbents with regular morphology were selected for SEM, XRD, FT-IR, XPS, UV-visDRS, BET, and ESR analyses. The scanning electron microscope image of the Fe-CTAB co-pillared montmorillonite composite material prepared in Example 2 is shown below. Figure 1 As shown.

[0071] Table 1 shows that, under both pH=1 and pH=2 conditions, the adsorption effect of the Fe-CTAB co-pillared montmorillonite composite material on Cr(VI) was significantly better at pH=1 than at pH=2, indicating that a strongly acidic environment is more conducive to the adsorption and fixation of Cr(VI) by the material. Among the three examples, Example 2 had the lowest residual Cr(VI) concentration and the strongest adsorption and removal capacity, and can be determined as the optimal formulation.

[0072] As shown in Table 2, under photocatalytic conditions, the removal rate of Cr(VI) in Example 2 was significantly faster than that in Examples 1 and 3, and the Cr(VI) concentration decreased most rapidly, achieving complete removal within 60 minutes. In contrast, Examples 1 and 3 still had a certain concentration residue within the same time period, and their overall removal effect was weaker than that of Example 2.

[0073] As shown in Table 3, the Fe-CTAB co-pillared montmorillonite reducing agent of Example 2 of the present invention exhibits a slow Cr(VI) removal rate under dark conditions relying solely on adsorption, and Cr(VI) is not completely removed even after 12 hours. Under light conditions, the Cr(VI) concentration decreases rapidly, dropping to 0.8 in about 50 minutes and achieving efficient removal. Light irradiation significantly improves the reaction rate and removal efficiency, demonstrating that the material has a significant adsorption-photocatalytic synergistic removal effect. The essence of this synergistic effect lies in the hydrophobic-positively charged bifunctional microdomains constructed by the co-pillared structure. The hydrophobic microdomains created by the long-chain alkyl groups of CTAB in the interlayer alter the mass transfer pathway of Cr(VI): after Cr(VI) anions are electrostatically attracted into the interlayer, they undergo interfacial enrichment in the hydrophobic microdomains, transforming their diffusion from the traditional aqueous bulk to interfacial enrichment. This significantly shortens the mass transfer distance between Cr(VI) and the photocatalytic active sites of Fe2O3, increasing the local reaction concentration in the interlayer. Under visible light irradiation, the photogenerated electrons and reactive oxygen free radicals generated by the Fe2O3 nanoclusters can reduce Cr(VI) to Cr(III) in situ near the enrichment sites. Due to the lack of hydrophobic enrichment sites, Cr(VI) in single iron-pillared montmorillonite can only diffuse to the outer surface via aqueous diffusion, resulting in high mass transfer resistance and low local concentration. Therefore, its photocatalytic efficiency is significantly lower than that of the co-pillared material of this invention.

[0074] As shown in Table 4, the removal efficiency of the photoreduction process gradually decreased from 99.8%. This moderate decrease is attributed to the partial degradation of the embedded CTAB molecules and the gradual occupation of specific active sites by residual trivalent chromium species, which were not completely removed during regeneration. However, after twenty cycles, the material still retained more than 80% of its original activity, indicating good structural stability and reusability in practical wastewater treatment applications.

[0075] Figure 2 The infrared spectra of montmorillonite, Fe-MMT, and the Fe-CTAB co-pillared montmorillonite composite material prepared in Example 2 are shown. Comparison reveals that the Fe-CTAB co-pillared montmorillonite composite material from Example 2 exhibits high infrared spectra at 3620, 3430, and 1035 cm⁻¹. -1 The peaks at these locations are -OH, -NH2, and Si-O-Si, respectively. Figure 3 The UV diffuse reflectance spectra of montmorillonite, Fe-MMT photocatalytic reducing agent, and the photocatalytic composite material of Example 2 are shown. Comparison reveals that the visible light absorption of Fe-CTAB-MMT is further enhanced, with the absorption edge band red-shifted to 620 nm, indicating that Fe... 3+ The synergistic effect of the pillar and CTAB effectively reduces the bandgap width and improves the optical response range. Figure 4The diagram shows the superoxide radicals of the Fe-CTAB co-pillared montmorillonite composite material prepared in this experiment. It can be seen that this material can generate superoxide radicals to reduce hexavalent chromium under visible light irradiation.

[0076] The material of this invention can catalytically reduce Cr(VI) under visible light irradiation under acidic and neutral conditions. Figure 5 Transmission electron microscopy (TEM) images of Fe-CTAB-MMT are presented. The images show that montmorillonite retains its typical folded lamellar structure even after being supported by iron and CTAB. This confirms that the montmorillonite did not break due to the support, indicating the strong stability of the adsorbent material. The darker areas in the image likely represent oxide particles of the active ingredient, Fe. These nanoparticles are small and uniformly distributed. TEM images further confirm that iron species are highly dispersed on the support surface in the form of nanoparticles. This high dispersion helps increase the number of active sites on the catalyst, thereby improving its catalytic performance. Simultaneously, TEM images show good bonding between the iron nanoparticles and the montmorillonite support. This interaction helps stabilize the active ingredient, preventing its loss or aggregation during the reaction. Figure 6 The diagram illustrates the Cr(VI) removal mechanism of the Fe-CTAB co-pillared montmorillonite reducing agent prepared in this experiment. First, the embedded CTAB expands the interlayer channels and imparts a permanent positive charge, thereby removing HCrO4 through electrostatic interactions. - and Cr2O7 2- Ions are pre-concentrated to establish high-concentration nanodomains at the solid-liquid interface. Secondly, under visible light excitation, the iron oxide pillars act as photoactive centers, generating electron-hole pairs. Finally, with the assistance of reactive oxygen species, these photogenerated electrons effectively reduce locally enriched Cr(VI) to the less toxic Cr(III), which is then fixed within the clay structure through in-situ precipitation.

[0077] The Fe-CTAB co-pillared montmorillonite composite material prepared in this invention exhibits highly efficient adsorption and catalytic reduction performance for Cr(VI). This composite material also possesses excellent photocurrent response characteristics and visible light absorption capacity, thus enabling the treatment of other high-valence metal ions in solution via photocatalytic reduction. This has broad application prospects and significant implications for reducing heavy metal pollution in industrial wastewater.

Claims

1. A method for preparing Fe-CTAB co-pillared montmorillonite composite material, characterized in that, The steps are as follows: S1: Montmorillonite and sodium carbonate are mixed at a mass ratio of 3~7:2, water is added to make a slurry, and after stirring, filtering, drying, grinding and sieving, sodium montmorillonite is obtained. S2: Add sodium carbonate to ferric nitrate nonahydrate solution, stir and age for 24 hours to obtain a stable iron columnar solution; S3: The sodium montmorillonite obtained in S1 is prepared into a suspension, heated and then slowly added to the iron pillar liquid obtained in S2. After reaction, it is aged, washed with water, dried, and then calcined at high temperature to obtain iron pillar montmorillonite. S4: Disperse the iron-pillared montmorillonite obtained in S3 with CTAB in deionized water, heat and react, filter and wash until no bromide ions are present, dry, grind and sieve to obtain the Fe-CTAB co-pillared montmorillonite composite material.

2. The preparation method of the Fe-CTAB co-pillared montmorillonite composite material according to claim 1, characterized in that, In S1, the mass ratio of montmorillonite to sodium carbonate is 5:

2.

3. The method for preparing the Fe-CTAB co-pillared montmorillonite composite material according to claim 1, characterized in that, In S2, ferric nitrate nonahydrate is first dissolved in deionized water, and then, under stirring at 60°C, it is added according to n(OH) - ) / n(Fe 3+ Add sodium carbonate slowly at a ratio of 1.

5.

4. The method for preparing the Fe-CTAB co-pillared montmorillonite composite material according to claim 1, characterized in that, In S3, the high-temperature calcination temperature is 350~400℃, and the calcination time is 3.5~4h.

5. The method for preparing the Fe-CTAB co-pillared montmorillonite composite material according to claim 1, characterized in that, In S4, the mass ratio of iron-supported montmorillonite to CTAB is 3:0.7~0.

84.

6. The method for preparing the Fe-CTAB co-pillared montmorillonite composite material according to claim 5, characterized in that, In S4, the mass ratio of iron-supported montmorillonite to CTAB is 3:0.

7.

7. The method for preparing the Fe-CTAB co-pillared montmorillonite composite material according to claim 1, characterized in that, In step S4, the heating reaction temperature is 60°C and the reaction time is 2 hours.

8. The Fe-CTAB co-pillared montmorillonite composite material prepared by the preparation method of the Fe-CTAB co-pillared montmorillonite composite material according to any one of claims 1 to 7; The Fe-CTAB co-pillared montmorillonite composite material has a layered structure, with CTAB acting as an intercalation layer loaded onto the iron-pillared montmorillonite.

9. The application of the Fe-CTAB co-pillared montmorillonite composite material according to claim 8 in the removal of hexavalent chromium from wastewater.

10. The application according to claim 9, characterized in that, The Fe-CTAB co-pillared montmorillonite composite material, as a photocatalytic composite material, adsorbs and catalytically reduces hexavalent chromium in acidic wastewater under light irradiation. The illumination conditions are as follows: wavelength 360nm~480nm, illumination intensity 20~100mW / cm². 2 ; The pH of the acidic wastewater is 1 to 2.

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