Removal Performance Research Articles

SO3 removal by submicron absorbents synthesized via inhibition method: The product layer grows like parallel peaks

Injecting calcium hydroxide powder into the flue gas is an effective strategy for SO3 removal. However, commercial calcium hydroxide has several disadvantages, including large particle size, low efficiency, and unsuitability for excessive grinding. In this work, sub-micron calcium hydroxide was synthesized by an inhibition method and its performance for SO3 removal from flue gas was investigated on a pilot-scale platform (120 Nm3/h). When the concentration of sodium alginate solution was 100 mg/L, the average particle size of calcium hydroxide decreased from 13.66 µm to 0.84 µm, which improved the SO3 removal (92.1 %) and conversion of the absorbent. The results of the fixed-bed experiments indicate that the absorption kinetics of the reaction is consistent with the Bangham model. In addition, density functional theory verifies that calcium hydroxide captures SO3 by chemisorption. The AFM image shows that the calcium sulfate whiskers produced during the reaction grow like parallel peaks on the adsorbent surface. The calculations suggest that the driving force for SO3 adsorption originates from Ca-p orbital (Ca(OH)2) and O-s orbital (SO3) hybridization. This study complements the island growth mechanism for gas-solid two-phase reactions and provides an effective method for removing SO3 from flue gas in coal-fired power plants. In addition, it will provide an important reference for the development of submicron adsorbents.

Exploring photocatalytic tetracycline removal performance under simulated sunlight irradiation: Milling time effect on metallic reduction of MnO/ZrO2 mixed oxide

In the present research, it is reported that ball milling technique can be applied to enhance the photocatalytic properties of MnO and ZrO2 metal oxide powders (MZOx) furthermore the fabricated photocatalyst can be used for the degradation of tetracycline (TTC). XRD analyses revealed that increasing the milling time resulted in the formation of a pure metallic Mn crystal phase, which boosted the antibiotic degradation rate. It was confirmed by SEM technique that the morphological structures of the particles were generally small and uniform. The band gap energy was calculated as 3.70 eV for the hybrid metal oxide. Additionally, the adsorptive and photoluminescence features were illuminated via DRS and PL analyses. The effect of milling time had a major impact on the photodegradation rate of TTC, and the 8 h milling sample (MZOx-8h) exhibited the highest catalytic degradation activity (79.4 %). Low photocatalytic activity was obtained at acidic pHs and increased at alkaline pHs. The presence of H2O2 sharply decreased photocatalytic process time (60 min) and 94.3 % of the TTC was degraded at 7.5 mM H2O2. The photocatalytic degradation process proceeded through superoxide radicals and was supported by holes. The stability of MZOx-8h almost remained constant (70.02 %) even after seven cycles. It was determined that the presence of oxalic acid positively affected the progress of TTC degradation reactions. Further, practical application areas were investigated and MZOx-8h doped on support materials was found to be suitable for such applications in proportion to the doping ratio. Finally, it was demonstrated that MZOx-8h exhibited remarkable performance in photocatalytic reactions of different types of organic pollutants. The synergistic nature of MnO and ZrO2 with the contribution of ball milling time effect resulted in high photocatalytic activity.

Performance evaluation and microbial community analysis of a continuous stirred tank reactor–anaerobic ceramic membrane bioreactor system for practical swine wastewater treatment

To treat swine wastewater from a practical piggery, a continuous stirred tank reactor (CSTR)–anaerobic ceramic membrane bioreactor (AnCMBR) was operated for 201 days. A high chemical oxygen demand (COD) removal efficiency of 95 % and biogas production rate of 0.31 L/L·d were achieved at an organic loading rate (OLR) of 1.19 g-COD/L·d. Although the free ammonia concentration reached a maximum of 200 mg/L during the last operational phase, no evident inhibitory effect on AnCMBR performance was observed. Microbial community analyses indicated that six bacterial phyla were responsible for the hydrolysis, acidification, and fermentation of organics and environmental stabilization. Hydrotrophic methanogenic archaea were dominant, indicating that the main methane production pathway involved the use of H2 and CO2 as substrates. The results demonstrated that CSTR–AnCMBR systems exhibit excellent organics removal performance and energy recovery at high organic concentrations and possess strong anti-shock ability. Thus, they represent alternative green and sustainable anaerobic technologies for practical swine wastewater treatment.

Dye Removal From Tannery Wastewater Utilizing Footwear Waste: A Sustainable Approach

ABSTRACTWaste‐to‐3R (reduce, reuse, and recycle) is a promising mass balance approach in the leather sector for addressing the current challenge of overproduction of rubber sole waste in the footwear industry and dye pollution in tanneries. In this study, low‐cost charcoal derived from discarded natural rubber (NR) soles was effectively employed to remove anionic and cationic dyes from a model tannery dye solution, aligning with mass balance approaches in the leather sector. Discarded rubber charcoal (DRC) was prepared at 350°C using a self‐fabricated pyrolytic cell. The resulting charcoal was then dried, ground, and separated through 40‐mesh size lab‐scale sieves, and it was subsequently employed for the removal of dyes from tannery wastewater. The dye removal performance was optimized by adjusting parameters such as dosage, pH, contact time, and concentration. The maximum adsorption capacity and removal efficiency of the anionic acid dye (AD) were found to be 158.22 mg/g and 88.39% at pH 1, respectively, while those of the cationic methylene blue dye were 166.18 mg/g and 85.53% at pH 12, respectively, between 15 and 30 min, depending on the DRC conditions. Fresh charcoal and dye‐loaded charcoal were characterized through Fourier transform infrared spectroscopy, x‐ray diffraction, Brunauer–Emmett–Teller, scanning electron microscope (SEM), and transmission electron microscope with Energy‐Dispersive X‐ray (EDX) Spectroscopy for respective functional groups and morphology studies, and zeta potential measurements were employed to characterize the charcoal surface charge. The SEM image revealed that the shape of the DRC particles resembles a honeycomb structure, with an average size of 573.56 µm. The adsorption kinetic study indicates that the Freundlich isotherm model and pseudo‐second‐order kinetics were well‐fitted for dye removal in this study. The charcoal exhibited robust stability, retaining its capacity of 57.42 mg/g of AD and 44.94 mg/g of MB dye after four reuse cycles. This resilience was observed in treatment with various desorption agents, including HCl, CH3COOH, NaOH, and C2H5OH. The findings of this study suggest that NR‐derived charcoal could be used as a successful substitute for commercial activated carbon in wastewater treatment to get rid of the acid and basic dyes of the leather industry. Based on the observed results, a plausible mechanism was also proposed.

Rotating hydrothermal route to red mud derived uniform hierarchical porous flowerlike boehmite (γ-AlOOH) microspheres: Force analysis on formation mechanism and superior adsorption performances for anionic dyes removal

Towards increasingly severe worldwide pollution of industrial solid waste red mud (RM) released from aluminum industry, constitutional valuable element Al has been successfully separated for a novel mild rotating hydrothermal synthesis (150 °C, 12 h, 5 Hz) of the uniform hierarchical porous flowerlike boehmite (γ-AlOOH) microspheres in the presence of appropriate urea, which exhibit distinctly small average diameter (1.52 μm) and narrow particle size distribution (PSD: 1.12–1.97 μm), as well as high specific surface area (129.37 m2 g−1). On the one hand, the rotating hydrothermal synthesis promotes the mass and heat transfer, enabling γ-AlOOH microspheres at a lower temperature within a shorter time. On the other hand, moderate rotation provides predominant shear force, rendering the uniform γ-AlOOH microspheres with small average diameter and narrow PSD. The optimal AlOOH–U2M-R5Hz microspheres demonstrate satisfactory adsorption performance for Congo Red (CR) and Methyl Blue (MB), with the maximum adsorption capacities of 602.4 and 1208.7 mg g−1, respectively. Various isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich are utilized, adsorption kinetics are analyzed, adsorption mechanism is uncovered based on hydrogen bonding and electrostatic attraction. The increase in the temperature or the presence of coexisting cations facilitates the adsorption of CR, whereas coexisting anions weaken the adsorption of CR on the AlOOH–U2M-R5Hz microspheres. Furthermore, the excellent recycling performances and especially dynamic adsorption (retainment of removal efficiency of approx. 99.0% within 1000 min) as well as authentic water bodies (e.g. tap water and river water) simulated wastewater treatment undoubtedly indicate great practical applications of the AlOOH–U2M-R5Hz microspheres, towards cleaner aluminum production and cost-effective sustainable solution to anionic dye-bearing wastewater.

Polysulfone membranes decorated with Fe–Mn binary oxide nanoparticles and polydopamine for enhanced arsenate/arsenite adsorptive removal

Arsenic contamination of water is a global environmental concern, and membrane technology combined with nanotechnology contributes to more efficient removal of arsenic. In this study, Fe–Mn oxide (FM), Polydopamine (PDA), and PDA-modified FM (PFM) were incorporated into polysulfone (PSF) to prepare adsorption membranes (PFMP) for arsenic removal. The prepared nanoparticles and membranes were characterized using TEM, SEM, FTIR, TGA, contact angle, and pure water flux. The introduction of particles enhanced the hydrophilicity of the membranes and significantly enhanced the pure water flux of the membranes. Adsorption experiments indicated that the PFMP membrane exhibited the best arsenic removal performance, with maximum adsorption capacities for As(III) and As(V) were 11.57 mg/g and 12.39 mg/g, respectively. The Langmuir model fitted the adsorption isotherms well, and the kinetics followed the pseudo-second-order model. The filtration experiment revealed that the PFMP membrane was capable of reducing As(III) solution (915 L/m2) and As(V) solution (1075 L/m2) from a concentration of 100 μg/L to the safe limit of As (＜10 μg/L). The As-loaded membrane was regenerated using NaOH solution (pH = 11), and the filtration experiment was repeated. FTIR and XPS demonstrated that the mechanism of the reaction between the membrane and arsenic was ligand exchange, where the arsenic ions were bonded to the oxygen ions to form Mn–O–As and Fe–O–As.

Optimal design and performance evaluation of grinding wheels with triply periodic minimal surface lattice structure

High-performance grinding wheels are critical tools for precision surface generation. In precision grinding processes, the coolant supply at the wheel-workpiece interface is critical for reducing grinding temperature and detrimental friction. For better lubrication and chip removal performance, the cavities or pores need to be generated throughout the grinding wheel. The ideal morphology of pores in grinding wheels should be inter-connected and capable of providing sufficient coolant. Conventional grinding wheel design and fabrication methods can only passively generate closed circular pores by using pore-forming agents. Increasing the percentage of pores in this way generally leads to an uncontrollable reduction in mechanical strength, while the closed pores are insufficient in cooling performance. In this paper, the grinding wheels with triply periodic minimal surface lattice structure are designed and fabricated, which achieves the regulable and inter-connected internal structure of grinding wheels. Meanwhile, to balance the relationship between the structural properties and performance indicators of porous grinding wheels, an optimal design method for the porous structure of grinding wheels is proposed. Finally, the grinding performance of the novel grinding wheels in comparison to electroplated diamond grinding wheels is investigated in terms of grinding force, specific grinding energy and ground surface roughness.

Monolayer calcium-doped layered yttrium hydroxide adsorbent for rapid and efficient removal of fluoride from industrial wastewater

Strategies for the rapid and efficient removal of fluoridated industrial wastewater are currently lacking. Herein, monolayer calcium-doped layered yttrium hydroxide (Ca-Y LRH) was synthesized through formamide exfoliation, and its removal of fluoride reached equilibrium within 4 min. The adsorption kinetics fit the pseudo-second-order kinetic model with a faster adsorption rate (KF = 0.22 mg g−1 min−1), and the adsorption isotherm followed the Langmuir model with a maximum adsorption capacity of 483.33 mg g−1. The interlayer chloride ions in the monolayer Ca-Y LRH were the main ligands for substituting fluoride, which inhibited the increase in pH and maintained the continuation of the fluoride removal process. Furthermore, the optimum fluoride removal performance of monolayer Ca-Y LRH was predicted by software-based multiparameter methods and was found to be useful for treating fluoridated industrial wastewater samples (858.17 or 8.72 mg L−1). These findings provide novel insights into the treatment of fluoridated industrial wastewater.

Synergistic SiC/Co3O4 composites for enhanced microwave-assisted benzene catalytic removal performance

Microwave-assisted catalysis is a promising technique for enhancing catalytic reactions through selective heating, potentially leading to improved reaction rates and energy efficiency. However, understanding the complex interactions between microwave absorption and catalytic performance in composite catalysts remains a challenge. In this study, Cobalt oxide(Co3O4)/silicon carbide(SiC) composite catalysts with varying SiC content were synthesized and characterized to investigate the relationship between their microwave absorption properties and catalytic performance. Quantitative analysis revealed that SiC and Co3O4 absorb microwave energy through relaxation polarization and magnetic loss mechanisms, respectively. Increasing SiC content enhanced the dielectric and magnetic loss capabilities of the composites, with the Co3O4/SiC composite containing 10 wt% SiC (Co3O4/SiC-10) exhibiting a dielectric loss tangent of 3.87 and a minimum reflection loss of −35dB. However, higher SiC content decreased the surface chemically adsorbed oxygen, surface oxygen mobility, and benzene adsorption capacity, weakening the catalytic activity under conventional heating. The Co3O4/SiC-10 sample achieved a significantly better balance between microwave absorption and catalytic performance, significantly outperforming the original Co3O4 sample under microwave irradiation. These founding establishes a quantitative research methodology that correlates dielectric loss tangent, reflection loss, and other crucial parameters with microwave absorption performance and further catalytic properties, providing insights for the rational design of catalysts that optimize both microwave absorption and catalytic activity.

Improved performance and mechanism of the long-term vanadium(V) remediation by immobilization of rice washing waste

There is an urgent need to develop more efficient microbial technologies suitable for vanadium (V) stressed environments. In this study, rice washing waste (RWW) was utilized as both the carbon and microbial sources immobilized together with sludge to treat V-containing wastewater. Continuous flow reactors were operated, and V(V) removal efficiencies (30 d) with polyvinyl alcohol (PVA) and chitosan as embedded carriers achieved 9.0% and 79.4%, respectively. A superior V(V) removal performance (91.45%) was achieved in the continuous flow reactors with chitosan-based immobilized materials (70 d). V was detected on the surface and within the material, and V(IV) was found, indicating that both adsorption and microbes were able to contribute to V(V) remediation. Increase in the fractions of some functional microbes were observed in response to V(V) stress (unclassified_f_Comamonadaceae, unclassified_f_Enterobacteriaceae) and ammonia stress (unclassified_f_Hungateiclostridiacea). RWW could serve as suitable carbon and microbial sources for long-term operation and enhance V(V) removal by immobilized together with sludge, thereby unveiling a new method for both food and V contaminants.

External circuit loading mode regulates anode biofilm electrochemistry and pollutants removal in microbial fuel cells

This study investigated the effects of different external circuit loading mode on pollutants removal and power generation in microbial fuel cells (MFC). The results indicated that MFC exhibited distinct characteristics of higher maximum power density (Pmax) (named MFC-HP) and lower Pmax (named MFC-LP). And the capacitive properties of bioanodes may affect anodic electrochemistry. Reducing external load to align with the internal resistance increased Pmax of MFC-LP by 54.47 %, without no obvious effect on MFC-HP. However, intermittent external resistance loading (IER) mitigated the biotoxic effects of sulfamethoxazole (SMX) (a persistent organic pollutant) on chemical oxygen demand (COD) and NH4+-N removal and maintained high Pmax (424.33 mW/m2) in MFC-HP. Meanwhile, IER mode enriched electrochemically active bacteria (EAB) and environmental adaptive bacteria Advenella, which may reduce antibiotic resistance genes (ARGs) accumulation. This study suggested that the external circuit control can be effective means to regulate electrochemical characteristics and pollutants removal performance of MFC.

Synergistic optimization of baffles and aeration to improve the Light/Dark cycle of microalgae photobioreactor for enhanced nitrogen removal performance: Computational fluid dynamics and experimental verification

Microalgae photobioreactor (PBR) is a kind of efficient wastewater treatment system for nitrogen removal. However, there is still an urgent need for process optimization of PBR. Especially, the synergistic effect and optimization of light and flow state poses a challenge. In this study, the computational fluid dynamics is employed for simulating the optimization of the number and length of the internal baffles, as well as the aeration rate of PBR, which in turn leads to the optimal growth of microalgae and efficient nitrogen removal. After optimization, the Light/Dark cycle of the reactor B is shortened by 51.6 %, and the biomass increases from 0.06 g/L to 3.94 g/L. In addition, the removal rate of NH4+-N increased by 106.0 % to 1.56 mg L−1 h−1. This work provides a feasible method for optimizing the design and operational parameters of PBR aiming the engineering application.

Treatment of Domestic Wastewater in Colombia Using Constructed Wetlands with Canna Hybrids and Oil Palm Fruit Endocarp

Untreated domestic wastewater from rural areas poses significant risks to ecosystems and human health. Constructed wetlands (CWs) are a viable alternative for this wastewater treatment, enhancing nitrogen removal using substrates as carbon sources. This process is particularly beneficial for wastewater with low carbon-to-nitrogen (C/N) ratios, making the treated water suitable for agricultural irrigation. In this study, a Horizontal Subsurface Flow CW (HSF-CW) was evaluated using Canna hybrids and a mixed substrate of gravel and endocarp from oil palm fruit (EOP) as a carbon source to leverage its abundance in the region. It was also determined that the effluent complies with the permissible limits set by Resolution 1207 of 2014 from the Colombian Ministry of Environment and Sustainable Development, which establishes environmental standards for wastewater treatment to ensure environmental protection and enable safe reuse in agricultural irrigation. The key parameters analyzed included organic contaminants, heavy metals, nutrients, and microbiological indicators. Removal efficiencies of up to 91%, 94%, 98%, 52%, 73%, 78%, and 75% were achieved for BOD, TSS, total phosphorus, nitrates, nitrites, ammonium, and total nitrogen, respectively, demonstrating the CW’s strong performance in contaminant removal and meeting most standards for agricultural irrigation. Although the carbon source was not highly efficient, the overall system performance supports its viability for improving water quality and promoting sustainable agricultural practices in rural areas.

Activation of H2O2 using a single-atom Cu catalyst for efficient tetracycline degradation

The abuse of antibiotics has caused serious harm to the ecological environment and human health. Fenton-like advanced oxidation technology is a green and effective treatment means, but how to improve the Fenton reaction efficiency and wide pH adaptability is still a big challenge. Herein, we designed and developed a single-atom catalyst Cu1-CN with graphite-phase carbon nitride as the carrier by loading a low amount of metal Cu. The N atom anchors the copper atom in the form of a coordination bond, and the single atom Cu site has excellent performance in activating H2O2. Not only a short period of time (10 min) oxidation degradation of tetracycline (degradation rate 80 %), and in a broad range of pH (3.2 ∼ 9.5) still maintaining high removal performance (efficiency more than 70 %). Combined with X-ray absorption fine structure characterization and density functional theory (DFT) calculations, it is considered that isolated Cu atom and N atom cooperate to construct highly reactive Cu-N4 active centre, which completes the task of H2O2 activation. This study provides a new theoretical basis and technical support for the degradation of antibiotic pollutants by single-atom Fenton-like reaction.

Calcium oxide adsorption of gas phase PCDD/Fs and its impact on the adsorption properties of activated carbon

Calcium oxide (CaO), utilized in semi-dry/dry desulfurization systems at municipal solid waste incineration (MSWI) plants, demonstrates some capability to remove polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study assessed the gas-phase PCDD/F removal performance of CaO, activated carbon (AC) and CaO-AC mixtures. Alone, CaO achieved removal efficiencies of only 31.9% for mass and 50.8% for I-TEQ concentration. However, CaO-AC mixtures exhibited significantly higher efficiencies, reaching 96.0% and 92.5% for mass and I-TEQ concentrations, respectively, surpassing those of AC alone, which were 74.7% and 58.5%. BET analysis indicated that CaO's limited surface area and pore structure are major constraints on its adsorption performance. Density functional theory (DFT) calculations revealed that the π-π electron donor-acceptor (EDA) interaction enhances the adsorption between AC and PCDD/F, with adsorption energies ranging from −1.02 to −1.24 eV. Additionally, the induced dipole interactions between CaO and PCDD/F contribute to adsorption energies ranging from −1.13 to −1.43 eV. Moreover, with increasing chlorination levels, PCDD/F molecules are more predisposed to accept electron transfers from the surfaces of AC or CaO, thereby facilitating adsorption. The calculation for mixed AC and CaO showed that CaO modifies AC's properties, enhancing its ability to adsorb gas phase PCDD/Fs, with the higher adsorption energy and more electrons transfer, aligning with gas phase PCDD/Fs adsorption experiments. This study provides a comprehensive understanding of how CaO influences the PCDD/F adsorption performance of AC.

Highly selective and efficient Pb2+ capture using PO4-loaded 3D-NiFe layer double hydroxides derived from MIL-88A

Lead (Pb) contamination in water requires improved decontamination technologies. The addition of phosphate to precipitate Pb2+ is a widely used method for remediating Pb in soil and water, though it has certain limitations. This study focuses on novel 3D mesoporous layered double hydroxide (LDH) sorbents functionalized with phosphate anions for Pb2+ removal from contaminated waters. Our innovative strategy involves converting a sacrificial template metal-organic frameworks (MOFs) structure (MIL-88A(Fe)) into NixFe LDH, followed by an anion exchange reaction with phosphate anions. This process preserves the 3D microrod architecture of MIL-88A and prevents deleterious LDH particle aggregation. The synthesis results in stable microrod crystals, 1–2 μm long, composed of 3D assemblies of NixFe-PO4 LDH nanoplatelets with a specific surface area exceeding 110 m2/g. The novel LDH materials display fast adsorption kinetics (pseudo-second order model) and remarkably high Pb2+ removal performances (Langmuir isotherm model) with a capacity of 538 mg/g, surpassing other reported adsorbents. LDH-PO4 exhibits high selectivity for Pb2+ over competing ions like Ni2+ and Cd2+ (selectivity order is: Pb2+ > Ni2+ > Cd2+). Removal of Pb2+ from NixFeLDH/88A-PO4 involves various mechanisms, including surface complexation and surface precipitation of lead phosphate or lead hydroxide phases as revealed by structural characterization techniques.

A novel piezoelectric fenton-like process mediated by FeOCl for efficient contaminant removal

Ferric oxychloride (FeOCl), an iron-based catalyst with a unique coordination structure, has demonstrated effective pollutant removal capabilities in various reaction systems such as photo-Fenton, Fenton-like, and electro-Fenton processes. However, in previous studies, little or no attention has been paid by researchers to the piezoelectric properties of FeOCl and the pollutant removal performance exhibited in the presence of piezoelectric fields. In this study, we observed that the piezoelectric effect significantly enhanced the Fenton-like reaction process of FeOCl. Whereas the piezoelectric properties of FeOCl have not been reported in the previous research. The process significantly enhances the kinetic removal rate of pollutant, which is 3.12 times higher than the Fenton process and 18 times higher than the Fenton-like process for FeOCl. Furthermore, we observed a significant increase in the kinetic removal rate of pollutant after lattice distortion of FeOCl under the piezoelectric field and revealed how this process mediates the ultrafast oxidative removal process. Notably, we also detect the formation of pollutant polymeric products during the piezoelectric enhancement process, confirming the existence of a pollutant polymerization pathway during piezoelectric catalysis. The piezoelectric-enhanced FeOCl Fenton-like process constructed in this study not only provides important theoretical support for the practical application of FeOCl but also opens new research perspectives for the application of FeOCl in the field of piezoelectric catalysis.

Insights into vanadium removal performance and mechanism in aqueous solution by one-step pyrolysis prepared Phytolacca acinosa biochar composite

Iron-loaded biochar (FBC) was synthesized via the dry-mixed co-pyrolysis of Phytolacca acinosa, Fe2(SO4)3 and NaOH and then used to remove aqueous vanadium (V (V)). FBC demonstrated the optimal adsorption performance for V (V) (57.67 mg/g) due to the loading of iron oxide, which increased the number of oxygen-containing functional groups. The adsorption of V (V) on FBC was pH-dependent, and the adsorption rate was high in the pH range of 2–8. Common cations and anions in water did not affect the adsorption of V (V) onto FBC, while NH4+, Na+, Ca2+, and Cd2+ can promoted its adsorption. The adsorption mechanism of FBC mainly included chemical adsorption, electrostatic adsorption, oxygen-containing functional group complexation and ion exchange. The easy preparation method, high adsorption capacity and adaptability makes FBC an ideal material for removing V (V) from wastewater.

Migration characteristics of polypropylene (PP) microplastics and effects on pollutants removal performance of bioretention cells

Polypropylene microplastics (PP-MPs) particles, the most common microplastics in the aquatic environment, can cause serious harm to the aquatic environment when they enter natural water bodies with urban stormwater runoff. It has been proved that bioretention cells can effectively retain PP-MPs. However, the influence of the migration and accumulation of PP-MPs in the filler on the pollutant removal effect of the bioretention cell is still unclear. Four bioretention devices were constructed, and different concentrations of PP-MPs (particle size range 30–100 μm) were input in the form of disordered dry-wet alternating rainfall, to explore the migration pattern of PP-MPs and its influence on the purification effect of bioretention cells. The results showed that PP-MPs were effectively retained in the surface layer (0–5 cm) of the bioretention filler (>99 %). Increasing concentrations of PP-MPs were detrimental to their vertical transport in the filler. PP-MPs improved the removal of nitrate nitrogen (73.82–94.22 %) and total nitrogen (24.75–53.14 %) from the bioretention cells and substantially attenuated the negative effects of the dry period on the pollutant removal effect. Compared with the low concentration (250 mg/L), the total nitrogen removal efficiency of high concentration PP-MPs (500–1000 mg/L) decreased by 12.90–28.39 %, and the concentration had no obvious effect on the removal of total phosphorus. In summary, the bioretention cell demonstrated good retention capacity of PP-MPs. And the long-term accumulation of PP-MPs promoted the nitrogen removal effect of the bioretention cells and had little effect on the phosphorus removal effect.

Photocatalytic nanohybrid UV-light-driven PVDF/GO-NiFe@SiO2 membrane coupled with bentonite adsorption and ozonation process for a sustainable textile wastewater treatment

The textile industries face significant environmental challenges due to the presence of complex pollutant dyes in its wastewater, making it one of the world's major sources of industrial water pollution. Numerous studies have been employed to overcome this problem, including physical, chemical, and biological treatments. However, most of those methods still suffered to achieve higher dye removal performance. This study provides new insight regarding textile wastewater treatment containing indigo red as the main colorant by carrying out a hybrid process combining bentonite adsorption, ozonation, and photocatalytic membrane filtration. For the membrane, we propose a modified polyvinylidene fluoride (PVDF) membrane incorporated with graphene oxide (GO) and nickel-iron doped silica (NiFe@SiO2) photocatalyst, which is named PVDF/GO-NiFe@SiO2 membrane. The membrane was employed under different sets of filtrations (dark and under ultraviolet irradiation) to treat natural dye wastewater from textile industry effluent. Further improvement was achieved when UV light irradiation was subjected to the process. This sequential adsorption-ozonation-membrane process under UV exposure exhibited improved dye removal from 55.11 % to 97.22 %. The results show that the proposed hybrid process successfully improved the membranes' antifouling behavior, thus boosting the membranes' performance and durability. From a broader perspective, our work promotes new insights for the integration of other physical, chemical, and biological treatment methods to improve the performance and durability of membrane-based processes, particularly for dye wastewater treatment.