Application In Wastewater Treatment Research Articles

Anaerobic oxidation of methane coupled to reductive immobilization of hexavalent chromium by “Candidatus Methanoperedens”

The anaerobic oxidation of methane (AOM) carried out by anaerobic methanotrophic archaea (ANME) plays an important role in mitigating methane emissions from aqueous environments and has applications in bioremediation and wastewater treatment. Previous studies showed that AOM could be coupled to chromate reduction. However, the specific responsible microorganisms and the biochemical mechanisms are unclear. Herein, we showed that a consortium dominated by ANME “Candidatus Methanoperedens” was able to couple AOM to the reduction of Cr(VI) to Cr(III) at a stoichiometry close to the theoretical ratio. Quantitative distribution analysis of Cr(III) products suggested Cr(VI) was predominantly reduced via the extracellular respiratory pathways. Further Cr(III)-targeted fluorescent visualization combined with single-cell electron microscopic imaging suggested that Cr(VI) was reduced by “Ca. Methanoperedens” independently. Biochemical mechanism investigation via proteomic analysis showed proteins for nitrate reduction under nitrate-reducing conditions were significantly downregulated in Cr(VI)-reducing incubation. Instead, many multiheme cytochrome c (MHCs) were among the most upregulated proteins during the Cr(VI) reduction process, suggesting MHC-governed pathways for extracellular Cr(VI) reduction. The significant upregulation of a formate-dependent nitrite reductase during Cr(VI) reduction indicated its potential contribution to the small proportion of Cr(VI) reduction inside cells.

Advanced PPS/MOFs composite nanofiltration membranes derived from contra-diffusion synthesis for precise molecular separation

To meet the separation requirements of polyphenylene sulfide (PPS) membranes in extremely harsh environments and to enhance the separation performance of PPS membrane material, this study utilizes Zeolitic imidazolate framework (ZIF) material with a porous structure to modify the structure of the PPS membranes. Using the Contra-diffusion synthesis method, we successfully created PPS composite membranes that were modified by ZIF-8. At the end of the three-hour reaction time, a continuous and dense layer of ZIF-8 crystals with uniform crystal size and regular crystal shape was produced on the matrix membrane's surface. The permeance to rhodamine B aqueous solution is 42.54 L m−2 h−1 bar−1, and the retention rate is 99.5 %, which has high permeability and retention performance. In the anti-pollution performance test, the composite membrane's flux recovery rate is 72.9 %, which has good anti-pollution performance. After immersion in strong acids, strong alkalis, and a variety of organic solvents, the appearance shows no evident flaws, and the separation performance in strong alkalis and five different types of organic solvents stays steady, demonstrating excellent alkali and solvent resistance. This proves that composite membranes have great potential for application in dye wastewater treatment.

Highly effective catalytic degradation of bisphenol a through activation of peroxymonosulfate by an Fe-Nx structure anchored on novel lignin-based graphitic biochar: Electron transfer mechanism

A lignin-based Fe/N co-doped carbonaceous catalyst was synthesized via freeze-drying followed by pyrolysis to activate peroxymonosulfate (PMS) for efficient degradation of bisphenol A (BPA). The Fe/N co-doped biochar exhibited a high specific surface area (364.84 m2/g), hierarchical porous structures, and abundant oxygen-containing functional groups (hydroxyl and carboxyl groups), which enhancing the dispersion of Fe3O4 nanoparticle and exposure of catalytic site. The Fe8-N10-C/PMS system achieved 100 % BPA degradation within 20 min with a corresponding first-order reaction rate constant (kobs) of 0.4056 min−1, which outperformed most reported catalysts in efficiency. Quenching and EPR analyses revealed that both free radicals (•OH, SO4•−, and O2•−) and non-radical (1O2) were rate-limiting steps, while graphitic N and Fe-Nx structures facilitated direct electron transfer from BPA to PMS in electrochemical tests. XPS results confirmed that pyrrolic N, rather than pyridinic N, played a crucial role in forming the Fe-Nx structure. Moreover, the catalyst showed excellent stability, regeneration capability, and adaptability under diverse conditions, highlighting the potential of the Fe-N-C/PMS system for practical wastewater treatment applications.

Intensification of flocculation efficiency in multi-stage reactors by optimizing the multi-cone segment configuration

Flocculation is widely used in water treatment, and creating an optimal environment for floc growth is essential to enhancing flocculation efficiency. In this paper, we developed a multi-stage flocculation reactor (MFR) with strong, moderate, and weak mixing zones. Specifically, multi-cone structures with varying diameter ratios (DR) were incorporated in the moderate zone to promote floc growth. Computational simulations revealed that an MFR with a DR of 0.5 generated a uniform and symmetric flow field, reducing zero-velocity zones and forming distinct vortices within cones. This environment facilitated gradual floc growth while minimizing breakage. When applied to treating fracturing flowback fluid, a complex and challenging wastewater, the MFR produced larger and denser flocs, with an average chord length of 180 μm and a fractal dimension of 1.7170. These flocs exhibited high viscoelasticity, with a strength factor of 68.22 and a recovery factor of 47.77, indicating superior shear resistance and recovery ability after breakage. Consequently, the MFR achieved COD and turbidity removal rates of 92.05% and 93.61%, respectively, outperforming a stirred flocculation reactor, which achieved rates of 72.29% and 83.53% for the same parameters. Additionally, the MFR demonstrated excellent pollutant removal efficiency for both mineral processing wastewater and dyeing wastewater. With gradually decreasing energy along the flow direction, the MFR provided appropriate mixing intensities for different stages of floc growth, promoting efficient formation. These findings underscore the MFR’s potential as a highly effective solution for wastewater treatment applications.

A comparison study on hydrophobic and hydrophilic-mixed matrix membranes for diethanolamine removal

ABSTRACT This study systematically compares Polyvinylidene fluoride (PVDF) and Polysulfone (PSf) mixed-matrix membranes (MMMs) modified with graphene oxide (GO) for diethanolamine (DEA) removal. PVDF and PSf exhibit distinct interactions with GO due to their inherent hydrophobic and hydrophilic properties, respectively, influencing membrane performance. Membranes were fabricated using the phase inversion method and characterized by Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), and Contact Angle (CA) analysis. Performance testing revealed superior water permeability and DEA rejection for PSf/GO membranes. The PSf/GO-0.5 membrane achieved 91.04% DEA rejection and 47.45 L/m²·h·bar water permeability, outperforming PVDF/GO-0.5, which demonstrated 78.53% DEA rejection and 28.32 L/m²·h·bar water permeability. While GO improved membrane performance, excessive loading caused pore clogging, reducing effectiveness. This study highlights the potential of hydrophilic PSf/GO membranes for efficient amine removal, offering valuable insights for wastewater treatment applications.

Zn-MIL53(Fe) as an electro-Fenton catalyst: Application in organic pollutant degradation and pathogen inactivation

In this study, the potential of a bimetallic Metal-Organic Framework Zn-MIL53(Fe) for electro-Fenton catalysis was evaluated. After the material characterisation, its catalytic activity was validated in Fenton reaction to degrade a model organic pollutant: Rhodamine B. After that, the evaluation of Zn-MIL53(Fe) as electro-Fenton catalyst was performed and improved outcomes were reached by electro-Fenton regarding anodic oxidation. Then, electro-Fenton treatment optimisation was carried out using response surface methodology assays considering different catalyst dosages (7.2–43.2 mg), current intensities (5–45 mA) and treatment time (30–90 min) in a volume of 0.1 L. Under optimal conditions, a degradation rate over 90 % for Fluoxetine and Sulfamethoxazole in synthetic wastewater was achieved within 90 min, using graphite sheet as anode and nickel foam as cathode (25 mA), with a catalyst dosage of 43.2 mg in a volume of 0.1 L. Additionally, its application in the pathogen inactivation was evaluated using different gram-negative and gram-positive bacteria. Complete eliminations of both types of bacteria were reached in 5 min using the optimal conditions. In the end, Zn-MIL53(Fe) was proven as a reusable material, capable of performing 3 complete cycles of electro-Fenton treatment for both types of pollutants bacteria and pharmaceuticals, which makes it a promising candidate for more efficient wastewater treatment applications which involve the Fenton reaction.

Biosynthesis and Application of Biological Thin Films for Heavy Metal Ion Biosorption from Aqueous Solution

This study investigates the biosynthesis and application of Mycelium Bio-Films (MBFs) derived from pure Common oyster mushroom (COM) for heavy metal ion biosorption from aqueous solutions. The research focuses on the growth mechanism of MBFs and their potential for Cu (II) ions removal. MBFs were synthesized through a hyphae cultivation process and characterized using Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Energy-Dispersive X-ray Spectroscopy (EDS) mapping. Batch biosorption experiments were conducted to determine optimal operational parameters and adsorption mechanisms. Key findings reveal optimal biosorption conditions at pH 5, with a 40-minute contact time, and 100mg/L initial Cu (II) concentration using 0.2g of biosorbent in 10mL aqueous solution at room temperature with 150rpm agitation. Under these conditions, a maximum adsorption efficiency of 82.8% was achieved. The adsorption process best fits Pseudo-second-order kinetics and Langmuir isotherm, indicating chemisorption, complexation, and ion exchange as primary mechanisms. Functional groups involved in biosorption include carboxyl, hydroxyl, and amide groups. Importantly, MBFs demonstrate high reusability potential through diluted acid elution. This research contributes to environmental remediation by presenting a novel, sustainable biosorbent for heavy metal removal. The MBFs show promise for industrial wastewater treatment applications, offering an eco-friendly alternative to conventional adsorbents and contributing to filling the lack of biobank collections. Future studies could explore the efficacy of MBFs with other heavy metals and investigate potential scale-up for large-scale implementation.

MAl-X [M-Zn, Mg, Ni; X- Cl, NO3, CO3] layered double hydroxides: Catalytic applicability in plastic waste recycling and wastewater treatment for the sustainable environment

MAl-X [M-Zn, Mg, Ni; X- Cl, NO3, CO3] layered double hydroxides: Catalytic applicability in plastic waste recycling and wastewater treatment for the sustainable environment

Synthesis and characterization of eco-friendly cathodic electrodes incorporating nano Zero-Valent iron (NZVI) for the electro-fenton treatment of pharmaceutical wastewater

The electro-Fenton process has the potential to be an efficient effluent treatment method, contingent on effective process optimization. It relies on two critical components: efficient in-situ H2O2 generation and the integration of highly reactive heterogeneous catalysts into electrode synthesis. In this study, several cathodic electrodes were synthesized, including those using zero-valent iron nanoparticles (P-NZVI), zero-valent iron nanoparticles supported on activated carbon (AC-NZVI), and El Hamma Bentonite clay loaded with zero-valent iron nanoparticles (HB-NZVI). These electrodes were fabricated using sustainable, straightforward methods and subjected to thorough physicochemical and electrochemical characterization. The goal of this research was to develop environmentally friendly cathodes, employing either pressed catalyst techniques or supporting the catalyst on carbon felt (CF) or titanium foil. These electrodes were evaluated within a heterogeneous electro-Fenton-like process, with a boron-doped diamond (BDD) anode, targeting the efficient degradation of the pharmaceutical pollutant Antipyrine (ATP). Among the tested configurations, the AC-NZVI/CF electrode demonstrated the highest degradation efficiency. Key experimental parameters, such as pH, current density, and water matrices, were systematically studied to optimize the process. Under optimal conditions (pH 7, current density of 55 mA A/cm2), 80 % mineralization of a 40 mg/L ATP solution was achieved within 150 min, with an energy consumption of just 0.3502 kWh/g. The performance of the AC-NZVI/CF electrode remained stable when applied to real wastewater and after five consecutive cycles. Comprehensive analyses using FTIR, SEM-EDS, and XPS confirmed the stability and recyclability of the electrode, showcasing its potential for sustainable wastewater treatment applications.

Effect of irradiation on Co0.72Sr0.07Ni0.21Fe2O4 ferrite nanoparticles and their catalytic efficiency in water treatment

This study investigates the magnetic, thermal, and electrical properties of Co0.72Sr0.07Ni0.21Fe2O4 ferrite nanoparticles under different conditions, including as-prepared, irradiated (at a dose of 100 kGy in CO2 atmosphere), and aged (at 1000°C). The magnetic properties are analyzed using M-H loops, revealing that the aged sample exhibits the highest magnetization values. The observed decrease in magnetization after irradiation and increase after aging is consistent due to the presence of a new phase (γ-FeOOH) in the irradiated sample that XRD confirms. Electrical conductivity measurements demonstrate that the aging sample exhibits the highest electrical conductivity due to increased grain boundaries, while the irradiated sample shows increased conductivity attributed to oxygen vacancies. As well as the nanocomposite of PVP and Co0.72Sr0.07Ni0.21Fe2O4 nanoparticles aged (at 1000°C) is found to be effective in degrading the Toluidine Blue (TB) dye through catalytic oxidation and photodegradation mechanisms. The catalytic degradation of TB dye provides valuable insights into the potential application of these ferrite nanoparticles in environmental remediation and wastewater treatment. Also, nanocomposite demonstrated significant antimicrobial activity against five pathogenic bacterial strains commonly found in contaminated water, with superior effectiveness against Gram-negative bacteria, particularly Salmonella enterica and Pseudomonas aeruginosa, suggesting its potential as an effective water treatment agent. The novelty and the aims are to analyze the changes in magnetization and conductivity of the nanoparticles under different conditions, including as-prepared, irradiated, and aged samples. Additionally, the catalytic efficiency of the aged nanoparticles in degrading Toluidine Blue (TB) dye is examined, providing insights into their potential application in environmental remediation and wastewater treatment.

Enhancing Tannic Acid-Arginine Complex Loading in Ultraporous PA6 Nanofibers through NH3 Foaming for Efficient Heavy Metal Removal from Textile Wastewater.

Metal-containing dyes in the textile industry release heavy metal ions into wastewater, posing significant environmental risks and complicating treatment processes. Among various removal methods, chemical adsorption through functional groups that form stable complexes is one of the most effective. Tannic acid (TA), renowned for its strong chelation of metal ions via phenolic hydroxyl groups, faces challenges in operation and recycling in its powdered form. Electrospun polyamide 6 (PA6) nanofiber membranes, characterized by high surface area and structural stability, offer a promising platform. However, achieving an optimal TA loading remains a technical hurdle for industrial applications. To address this, we developed an arginine (l-Arg) bridging strategy to enhance the TA loading on PA6 nanofibers. Additionally, we implemented an NH3 escape foaming technique to increase membrane porosity by 20% and quadruple pore size, enhancing surface roughness and resulting in a 70% increase in TA loading. The optimized adsorbent demonstrated the effective removal of various heavy metal ions, achieving over 95% removal efficiency for five different metals. Even after five adsorption-desorption cycles, the membrane retained over 92% efficiency, translating to a treatment capacity of 12.5 tons of wastewater per kilogram of foaming fiber, underscoring its potential for practical wastewater treatment applications.

Asymmetric Membranes Obtained from Sulfonated HIPS Waste with Potential Application in Wastewater Treatment

Asymmetric Membranes Obtained from Sulfonated HIPS Waste with Potential Application in Wastewater Treatment

Selective removal and monitoring of Pb(II) ions in wastewater using fluorescence-enhanced silicon quantum dot composites

In this study, we developed a novel composite film composed of silicon quantum dot (SiQD)-nanoSiO2-polyvinyl alcohol (PVA) (referred to as SSP). This composite film exhibits dual functionality for monitoring and removing heavy metal ions from wastewater. The composition and structure of the SSP composite film were confirmed through various techniques, such as via Fourier-transform infrared spectroscopy, thermogravimetry/differential scanning calorimetry, scanning electron microscopy SEM, and X-ray photoelectron spectroscopy. The evaluation of film adsorption performance revealed that the thermodynamic behavior of the adsorption process was consistent with the theoretical predictions of the Freundlich model. However, the adsorption kinetics were more accurately described by the Elovich model. At pH 6.0, SSP achieved a maximum adsorption capacity of 263.66 mg/g at 20 °C, as determined by the Langmuir model. Additionally, the adsorption of Pb(II) ions increased the fluorescence intensity of the composite material, enabling the monitoring of Pb(II) ion concentrations in wastewater. This composite film efficiently removed Pb(II) ions with high selectivity and sustained strong adsorption performance through five cycles, emphasizing its outstanding regeneration capability. Therefore, the proposed composite material exhibits significant potential for practical applications in wastewater treatment.

The Biochar Derived from Pecan Shells for the Removal of Congo Red: The Effects of Temperature and Heating Rate

Organic pollutants, especially dyes, are seriously hazardous to the aquatic system and humans due to their toxicity, and carcinogenic or mutagenic properties. In this study, a biochar prepared from agricultural waste (pecan shells) via pyrolysis was applied to remove the dye pollutant Congo Red from wastewater to avoid a negative effect to the ecosystem. This study also investigated the effect of preparation conditions (temperature and heating rate) on the physicochemical properties and the adsorption performance of biochars. The physicochemical properties of the biochar were characterized using scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The adsorption performance of the biochar was evaluated for Congo Red removal. The results showed that biochar prepared at 800 °C with a heating rate of 20 °C/min (PSC-800-20) exhibited a higher specific surface area of 450.23 m2/g and a higher adsorption capacity for Congo Red (130.48 mg/g). Furthermore, adsorption experiments indicated that the pseudo-second-order and Langmuir models fitted well with the adsorption kinetics and isotherms of the biochar derived from pecan shells, respectively. Additionally, the PSC-800-20 biochar demonstrated a stable adsorption capacity over multiple cycles, suggesting its potential for regeneration and reuse in wastewater treatment applications. Therefore, the biochar derived from agricultural waste presents a promising and sustainable solution for the removal of toxic dye pollutants from wastewater.

Adsorption Properties of Fishbone and Fishbone-Derived Biochar for Cadmium in Aqueous Solution

Cadmium (Cd) contamination in aquatic ecosystems is a serious global environmental issue. Biochar derived from agricultural wastes has recently attracted remarkable attention as it is used as an absorbent in combating heavy metal contamination of water bodies. In the present study, the absorption efficacy of fish bone (FBM) and fishbone-derived biochar prepared at 200 °C, 400 °C, 600 °C, and 800 °C (referred to as B200, B400, B600, and B800, respectively) for the Cd ion (Cd2+) in aqueous solution was investigated. The results showed that high-temperature pyrolysis could optimize the pore structure and specific surface area of FBM, and Cd2+ successfully adsorbed onto FBM and fishbone-derived biochar. High-temperature pyrolysis significantly increased the FBM adsorption capacity for Cd2+ by 49.5–135.1%, with the optimal pyrolysis temperature being 600 °C. Furthermore, the kinetic data of FBM and fishbone-derived biochar for Cd2+ were in better alignment with the pseudo-second-order model, their adsorption isotherms were better in accordance with the Langmuir models, and the thermodynamic analysis showed that the adsorption process was monolayer and favorable adsorption. Moreover, the potential adsorption mechanisms of Cd2+ on FBM and fishbone-derived biochar might be related to pore filling, ion exchange, complexation with oxygen functional groups, and precipitation with the minerals on the biochar surface. Fishbone-derived biochar has significant potential for wastewater treatment and agricultural waste applications.

Efficient Removal of Cationic Dye by Biomimetic Amorphous Calcium Carbonate: Behavior and Mechanisms.

The search for efficient, environmentally friendly adsorbents is critical for purifying dye wastewater. In this study, we produced a first-of-its-kind effective biomimetic amorphous calcium carbonate (BACC) using bacterial processes and evaluated its capacity to adsorb a hazardous organic cationic dye-methylene blue (MB). BACC can adsorb a maximum of 494.86 mg/g of MB, and this excellent adsorption performance was maintained during different solution temperature (10-55 °C) and broad pH (3-12) conditions. The favorable adsorption characteristics of BACC can be attributable to its hydrophobic property, porosity, electronegativity, and perfect dispersity in aqueous solution. During adsorption, MB can form Cl-Ca, S-O, N-Ca, and H-bonds on the surface of BACC. Since BACC has excellent resistance to adsorption interference in different water bodies and in real dye wastewater, and can also be effectively recycled six times, our study is an important step forward in dye wastewater treatment applications.

P-doped g-C3N4/BiOCl Z-type heterojunction with N and O double vacancies and synergistically enhanced photocatalytic activity under sunlight irradiation

The use of inexhaustible natural sunlight is a highly effective method for wastewater treatment. In this study, P-doped g-C3N4/BiOCl Z-type heterojunction semiconductor photocatalyst with N and O double vacancies was constructed through calcination and coprecipitation. The obtained results revealed that the degradation rate of Rhodamine B (Rh B) reached 0.05642 min −1 within 60 min under visible light irradiation with a 300 W xenon lamp (λ≥400 nm), which was 73 and 8 times that of pure CN and BiOCl, respectively. Under natural sunlight irradiation, Rh B was almost completely degraded within 6 min, and its degradation rate reached 0.95641 min−1, which was 17 times that of Rh B simulated by visible light in the laboratory. The doping of non-metallic P and construction of a heterojunction significantly improved the photocatalytic activity of P-doped g-C3N4/BiOCl, which could be attributed to the synergistic effect of N, O vacancies and heterojunction structure interfaces on the composite material surface, which apparently expanded the light absorption range, promoted the transfer of charge, increased the quantity of active sites for the light-induced reaction, and improved the redox ability of the catalyst. The heterojunction semiconductor with surface defects prepared in this study provides a green approach for future wastewater treatment applications.

Constructing electron-enriched Cu-Mn binuclear sites for enhanced catalytic ozonation toward wastewater purification

Rational construction of electron-enriched active sites in single-atom catalysts to accelerate interfacial electron transfer and boost catalytic ozonation activity is still a challenging task. Herein, electron-enriched Cu-Mn binuclear sites were successfully immobilized onto defect-rich N-doped carbon (Cu-Mn/NvC) in activating O3 for degradation of organic pollutants with high ionization potential from water. The Cu-Mn/NvC with Cu-Nv-Mn sites achieves almost 100 % removal of 4-chlorophenol in 60 min by catalytic ozonation with a degradation rate of 0.067 min−1, which is 3.94 times faster than Mn/NC, exceeding the reported values. The nonradicals of surface atomic oxygen species (*O/*OO) and singlet oxygen (1O2) are the dominant ROS responsible for contaminants degradation. The Cu-Nv-Mn sites can capture electrons from nitrogen vacancies, acting as electron enrichment centers that provide more electrons to O3. The Cu doping elevates Mn d-band center closer to the Fermi energy level and decreases the adsorption energy by 0.494 eV, significantly accelerating electron transfer from the Mn d-bands to the 2p orbital of O3, which enhances the activation of O3 to generate *O/*OO and 1O2 and thus improves the degradation of organic pollutants. Additionally, the excellent catalytic activity towards real wastewater and exceptional reusability after ten cycles demonstrate the superiority of the proposed system for practical application in wastewater treatment. This study provides an efficient pathway for activating O3 by accelerating interfacial electron transfer via the design of electron-rich metal dual-atom sites in carbon-based catalysts.

Engineering cellulose aerogel composites for mercury ion sequestration and aquatic real time monitoring based on the immobilization of metal-organic frameworks

Industrial wastewater effluents containing elevated levels of mercury are a significant menace to both the ecosystem and human health. Despite the advent of metal-organic frameworks (MOFs) as promising adsorbents, their application in treatment of industrial wastewater has been impeded by the challenges associated with handling their powdered form. In this work, we introduce a straightforward method for fabricating MOF composite cellulose aerogels (5MM-101@CA). The resulting adsorbent showed a high adsorption capacity of 409.84 mg/g for Hg (II), with over 75 % removal efficiency maintained after five consecutive adsorption-desorption cycles. Furthermore, the material exhibited high sensitivity for the real-time detection of Hg (II), with a detection limit as low as 6.89×10−8 M. The adsorbent also showed remarkable fluorescence stability for up to a week, indicative of its excellent optical performance. Dynamic adsorption demonstrated the adsorbent's ability to sustain continuous and stable system operation without compromising adsorption efficiency. These findings underscore the effectiveness of post-synthetic modification (PSM) technology in enhancing the performance of MOFs, while highlighting the utility of low-cost cellulose as an effective carrier. Thus, the composite material developed in this work is promising as it not only maximizes the adsorption capabilities of MOFs but also circumvents the risk of secondary pollution.

Remarkable recycling processes of conjugated polymers with titanium dioxide quantum dots as photocatalysts for photodegradation of hazardous industrial wastewater

This study presents the synthesis and characterization of a novel polyaniline-titanium dioxide quantum dot (PA-TQD) composite for enhanced photocatalytic degradation of hazardous industrial wastewater. The composite was synthesized via in-situ polymerization and characterized using FTIR, XRD, TEM, BET, and TGA, confirming the integration of TiO₂ quantum dots (2.8–5.3 nm) into the polyaniline matrix (particle size 35–40 nm). BET analysis revealed a surface area of 50.30 m²/g for PA-TQD, significantly higher than 28.18 m²/g for pure polyaniline, contributing to its improved photocatalytic activity. Photocatalytic degradation experiments on methyl orange dye demonstrated a 60.1% degradation efficiency under xenon irradiation, compared to 35% for polyaniline alone. The photocatalytic rate constant of PA-TQD was 0.032 min⁻¹, indicating enhanced performance.In recycling tests, PA-TQD retained 73.8% of its photocatalytic efficiency after four cycles, showcasing strong reusability. TGA analysis confirmed the composite's enhanced thermal stability, with minimal weight loss up to 250 °C. COD analysis of real industrial wastewater samples showed effective pollutant reduction, with COD values for PA-TQD ranging from 756 to 1212 ppm. However, further optimization is needed to meet regulatory limits set by Saudi environmental laws (<1000 ppm COD). The synergy between polyaniline and TiO₂ quantum dots enhances charge separation, increases active sites, and makes PA-TQD a promising recyclable photocatalyst for sustainable wastewater treatment applications.