Removal Of Heavy Metals Research Articles

Scenedesmus sp. as a phycoremediation agent for heavy metal removal from landfill leachate in a comparative study: batch, continuous, and membrane bioreactor (MBR).

Improper disposal of municipal solid waste led to the release of heavy metals into the environment through leachate accumulation, causing a range of health and environmental problems. Phycoremediation, using microalgae to remove heavy metals from contaminated water, was investigated as a promising alternative to traditional remediation methods. This study explored the potential of Scenedesmus sp. as a phycoremediation agent for heavy metal removal from landfill leachate. The study was conducted in batch, continuous, and membrane bioreactor (MBR). In the batch system, Scenedesmus sp. was added to the leachate and incubated for 15days before the biomass was separated from the suspension. In the continuous system, Scenedesmus sp. was cultured in a flow-through system, and the leachate was continuously fed into the system with flow rates measured at 120, 150, and 180mL/h for 27days. The MBR system was similar to the continuous system, but it incorporated a membrane filtration step to remove suspended solids from the treated water. The peristaltic pump was calibrated to operate at five different flow rates: 0.24 L/h, 0.30 L/h, 0.36 L/h, 0.42 L/h, and 0.48 L/h for the MBR system and ran for 24h. The results showed that Scenedesmus sp. was effective in removing heavy metals such as lead (Pb), cobalt (Co), chromium (Cr), nickel (Ni), and zinc (Zn) from landfill leachate in all three systems. The highest removal efficiency was observed for Ni, with a removal of 0.083mg/L in the MBR and 0.068mg/L in batch mode. The lowest removal efficiency was observed for Zn, with a removal of 0.032mg/L in the MBR, 0.027mg/L in continuous mode, and 0.022mg/L in batch mode. The findings depicted that the adsorption capacity varied among the studied metal ions, with the highest capacity observed for Ni (II) and the lowest for Zn (II), reflecting differences in metal speciation, surface charge interactions, and affinity for the adsorbent material. These factors influenced the adsorption process and resulted in varying adsorption capacities for different metal ions. The study also evaluated the biomass growth of Scenedesmus sp. and found that it was significantly influenced by the initial metal concentration in the leachate. The results of this study suggest that Scenedesmus sp. can be used as an effective phycoremediation agent for removing heavy metals from landfill leachate.

MXene@polydopamine/oxidized sodium alginate modified collagen composite aerogel as sustainable bio-adsorbent for heavy metal ion adsorption and solar driven water evaporation

The design of an environmentally friendly bio-adsorbent for the removal of heavy metal ions from aqueous media is a sustainable strategy to ensure water safety. Herein, a three-dimensional macroscopic aerogel with photothermal conversion and heavy metal wastewater treatment capability was designed using leather collagen, MXene@polydopamine and oxidized sodium alginate as raw materials, named as MPAC composite aerogel. The applicability of the developed MPAC composite aerogel in water evaporation and heavy metal wastewater treatment was studied. MPAC composite aerogel had good Cr(VI) adsorption capacity. This article focused on the study of adsorption kinetics, isotherms and thermodynamics. The adsorption equilibrium time of MPAC composite aerogel was 60 min, and the equilibrium adsorption capacity of MPAC composite aerogel for Cr(VI) reached 80.73, 100.80 and 112.86 mg/g when the initial Cr(VI) concentration was 30, 70 and 100 mg/L, respectively. The adsorption process of Cr(VI) by MPAC composite aerogel conformed to the two-level dynamics model and the Freundlich adsorption isotherm model, and was a spontaneous endothermic reaction. Additionally, the composite aerogel had good solar-driven water evaporation ability and could enhance the water evaporation rate of Cr(VI) solution. Furthermore, the MPAC composite aerogel had high adsorption performance for Cr(VI) under solar illumination conditions. This new aerogel has the advantages of low cost, environmental friendliness, strong adsorption capacity and photothermal conversion performance and is a promising heavy metal ion adsorbent.

Challenges in using Electrocoagulation Process in Removal of Nickel Metal in Wastewater: a Literature Review

In recent years, the surge in nickel production, driven by the growing demand for electric vehicle batteries, has raised concerns regarding environmental consequences. The nickel mining and processing industries contribute to increased nickel levels in wastewater, presenting a serious threat to aquatic ecosystems and human health. This article emphasizes the urgency of developing effective technologies for treating nickel-contaminated wastewater. Electrocoagulation emerges as a promising method, providing high efficiency, minimal sludge production, and cost-effectiveness. The article critically and systematically reviews the potential of the electrocoagulation process in nickel removal from wastewater. In the review, we identify and analyze nearly 32 studies published from 2013 to 2023. We discuss contaminant removal mechanisms and analyze trends in the use of operational parameters. This article identifies the most commonly applied conditions: aluminum electrodes, inter-electrode spacing ≥ 1 cm, current density ≤ 10 mA/cm², initial pH 6 ≤ pH < 11, electrolysis time < 60 min, batch operation, and initial nickel concentration > 50 mg/L. This comprehensive review serves as a foundational resource for advancing electrocoagulation technology in the removal of heavy metals from nickel wastewater.

Exploring bioremediation strategies for heavy metals and POPs pollution: the role of microbes, plants, and nanotechnology

Heavy metal and Persistent Organic Pollutants (POPs) pollution stemming from industrialization, intensive agriculture, and other human activities pose significant environmental and health threats. These contaminants persist in the air, soil, and water, particularly in industrialized nations, adversely affecting human health and ecosystems. While physical and chemical methods exist for detoxifying contaminated soil, they often have drawbacks such as high cost and technical complexity. Bioremediation, utilizing plants and microbes, offers a promising solution. Certain microorganisms like Streptomyces, Aspergillus and plant species such as Hibiscus and Helianthus show high metal adsorption capacities, making them suitable for bioremediation. However, plants’ slow growth and limited remediation efficiency have been challenges. Recent advancements involve leveraging plant-associated microbes to enhance heavy metal removal. Additionally, nanotechnology, particularly nano-bioremediation, shows promise in efficiently removing contaminants from polluted environments by combining nanoparticles with bioremediation techniques. This review underscores bioremediation methods for heavy metals using plants and microbes, focusing on the role of Plant Growth Promoting Rhizobacteria (PGPR) in promoting phytoremediation. It also explores the implementation of nanotechnologies for eliminating metals from polluted soil, emphasizing the significance of soil microbiomes, nanoparticles, and contaminant interactions in developing effective nano-remediation strategies for optimizing agriculture in contaminated fields.

Magnetic nanocomposite for lead (II) removal from water

A magnetic perovskite-spinel oxide nanocomposite synthesized through a sol–gel self-combustion process is used for the first time as an adsorbent to remove toxic heavy metals (i.e., Pb2+). The synthesized LaFeO3:CoFe2O4 ((LFO)1:(CFO)x) (x = 0.11–0.87) nanocomposites possess good stability, abundant oxygenated active binding sites, and unique structural features, making them suitable for removing divalent Pb2+ ions. Scanning electron microscopy, X-ray diffraction, BET surface area, magnetization measurements, zeta-potential analyses, and X-ray photoelectron spectroscopy were used to analyze the nanocomposites, and their structural changes after Pb2+ ions adsorption. Batch tests confirmed that (LFO)1:(CFO)x efficiently removes Pb2+ from water with a maximum adsorption capacity of 105.96 mg/g. The detailed quantitative study indicates that the interaction of hydroxyl groups with Pb2+ ions occurs through electrostatic interactions and complex formation. We also demonstrate a new ring-magnetic separator system that allows magnetic separation of the toxic ions at a higher speed compared to traditional block magnets. The unique structure, high porosity, large specific surface area, and oxygenated functional groups of (LFO)1:(CFO)x nanocomposites make them promising materials for removal of heavy metal ions and possibly other environmental pollutants. This study provides a new approach to preparing nanocomposites of magnetic spinel ferrites with perovskite oxides for environmental applications.

Recent Advances in Synthesising and Applying Magnetic Ion-Imprinted Polymers to Detect, Pre-Concentrate, and Remove Heavy Metals in Various Matrices

Magnetic ion-imprinted polymers (MIIPs) are an innovative material that combines the selectivity of ion imprinting with the ease of separation provided by magnetic properties. Recent advancements in MIIPs have shown that they have higher selectivity coefficients compared to non-imprinted materials. The synthesis of MIIPs involves creating specific recognition sites for target ions in magnetic nanomaterials. Various nanomaterials, such as graphene oxide, carbon nanotubes, and silica, have been incorporated into the IIPs to improve their analytical performance for different environmental applications, including metal extraction, monitoring, detection, and quantification. This review stresses the need to develop new monomers with a high affinity for the target analyte and to find supporting materials with groups that facilitate the effective removal of the target analyte. It also explores the influence of experimental parameters on metal determination.

Magnetic Mesoporous Silica Functionalized with Amine Groups for Efficient Removal of Heavy Metals and Bacterial Inhibition

Magnetic Mesoporous Silica Functionalized with Amine Groups for Efficient Removal of Heavy Metals and Bacterial Inhibition

Fabrication and catalytic activity of TiO2/Fe3O4 and Fe3O4/β-cyclodextrin nanocatalysts for safe treatment of industrial wastewater

The rapid industrial growth has led to increased production of wastewater containing pollutants like heavy metals and organic compounds. These pollutants pose risks to human health and the environment if not properly treated. Engineered nanocatalyst materials (ENMs) are a burgeoning technology that show promise for treating industrial wastewater. Metal oxide ENMs, such as Fe3O4@β-cyclodextrin and Fe3O4@TiO2, have demonstrated efficient removal of heavy metals and methylene blue from wastewater. Fe3O4@TiO2 was found to be more effective than Fe3O4@β-cyclodextrin in removing these pollutants. The highest removal efficiencies were observed at a concentration of 40 mg/g and pH 8. Copper showed the highest removal efficiency (160.5 mg/g), followed by nickel (77.09 mg/g), lead (56.0 mg/g), and cadmium (46.05 mg/g). For methylene blue, the highest removal efficiency was also observed at a concentration of 40 mg/g and pH 8 (91.16 %). Lead (90.5 %), copper (90.48 %), nickel (83.34 %), and cadmium (77.58 %) were also efficiently removed. These findings highlight the potential of Fe3O4@TiO2 as a promising material for industrial wastewater treatment, offering cleaner and safer water for human health and the environment. ENMs have the potential to revolutionize wastewater treatment processes.

One-pot fabrication of highly permeable P84/UiO-66-NH2-PEI membrane for the efficient removal of heavy metals from wastewater

Heavy metal pollution threatens water bodies and public health, necessitating the exploration of advanced technologies to effectively remove heavy metals from wastewater. In this study, a one-pot approach was employed to fabricate a positively charged membrane using P84 as the substrate, and UiO-66-NH2 nanoparticles and PEI as crosslinkers. Introducing UiO-66-NH2 with inherent porous structures can create nanopores and gaps within the PA layer, providing extra pathways for water molecules to permeate the membrane. Moreover, the UiO-66-NH2 nanoparticles imparted hydrophilicity and a positive charge to the resulting membrane. Compared to the blank membrane without UiO-66-NH2 nanoparticles, the optimal membrane demonstrated a significant increase of 44 % in water flux (52.4 L m−2h−1) while maintaining a remarkable removal performance for CuCl2 (99.5 %), PbCl2 (99.4 %), Ni(NO3)2 (98.6 %), and ZnCl2 (98.4 %) at 4 bar. Furthermore, the UiO-66-NH2 nanoparticles can cross-link with the P84 polymer, ensuring a stable attachment between the polyamide (PA) layer and the P84 substrate by covalent bonds, preventing the potential conventional nanoparticle leakage. Additionally, three different fabrication methods were employed to explore the optimal approach for incorporating UiO-66-NH2 nanoparticles, with each method resulting in a distinct distribution of nanoparticles within the membrane. This study highlights the potential of the resultant membranes in addressing the challenges of wastewater treatment, offering a facile and promising avenue for heavy metal removal.

Remediation of Heavy Metal Pollution from Coal Mine Effluent Using Metal-Organic Frameworks (MOF): Impact of Water Media, Operational Factors and Metal Characteristics

The energy sector is the sector that generates the highest amount of environmental contamination, especially in water sources, mostly in the case of coal-based energy production. The aim of this study was to examine a significant contamination source, heavy metal contamination, in coal mining effluents. The current investigation introduces an MOF platform based on zirconium clusters and isophthalic acid with NH2-MIP-SO3H mixed amine and sulfonic acid functional groups in order to remove the most common heavy metal ions in coal mining effluents, including Hg, Cd, Pb, and Cu ions. The water matrix and the operational conditions were identified to be very influential in the removal process, such as the pH of water, the initial metal concentration and operating time. NH2-MIP-SO3H offers a great removal efficiency of metals starting from 745.83 mg/g for Cd, 673.67 mg/g for Cu, 589.85 mg/g for Hg, and 481.66 mg/g for Pb ions, with the Langmuir equation for equilibrium and pseudo-second-order equation for kinetics being the ideal models to express the equilibrium and kinetic data, respectively. A significant impact of water pH was found to occur, with the NH2-MIP-SO3H platform performing best at pH 6. Reuse of NH2-MIP-SO3H demonstrates excellent reusability, sustaining 90% of initial performance over eight regeneration cycles. The interaction of functional group-functional metal was the dominant mechanism in the removal process. The NH2-MIP-SO3H unique approach to heavy metal removal provides a very hopeful outlook for additional investigations in larger-scale studies.

Bioremediation of chromium(VI) and arsenic(III) using isolated microalgal (Chlorella thermophilia): Analysis of growth, biomolecular compositions (carbohydrate, protein, chlorophyll) and biosorption kinetics

Microalgae are under research focus for the production of bio-fuels by bioremediation of different kinds of wastewater like industry and municipality and other sources. The current study deals with investigations towards the capability of isolated microalgae (Chlorella thermophilia) for the removal of Cr(VI) and As(III) by re-modeling their extracellular and intracellular compositions. This isolated microalgae was able to grow in the presence of Cr(VI) up to 1 mg L−1 concentration and As(III) up to 15 mg L−1 concentration. Carbohydrate content in microalgae increased to 28 % in 0.4 mg L−1 of Cr(VI) and 46 % in 10 mg L−1 of As(III) respectively as compared to control. The protein content of Chlorella thermophilia grown in Cr(VI) [1 mg L−1] and As(III) [15 mg L−1] containing media decreased by almost 61 % and 9 % respectively as compared to control. Growth kinetics results revealed the decline in biomass to 10 % and 15 % under exposure of Cr(VI) [0.6 mg L−1] and As(III) [10 mg L−1] respectively compared to control. Chlorella thermophilia showed the removal of As(III) within the range of 70–91 % [at an As(III) concentration of 0.5–10 mg L−1], while removal of Cr(VI) was within 50–65 % [at a Cr(VI) concentration of 0.2–0.6 mg L−1]. Interestingly, almost 60 % of Cr(VI) was removed within 6 days of microalgae growth while removal of As(III) was slow and steadily increased to 80 % in 30 days. Our results showed the prospects of Chlorella thermophilia as a sustainable resource for the removal of heavy metals [Cr(VI) and As(III)] from wastewater. In addition, the enrichment of carbohydrates in microalgae during their growth would be supportive for the production of biofuels.

Mg-Al layered double hydroxides modified by 2,4,6-trimercapto-s-triazine for effective removal heavy metals from soil

Since 2,4,6-trimercapto-s-triazine (TMT) possesses advantages of multiple adsorption sites and strong binding ability with heavy metals, in this study, layered double hydroxides modified by TMT are prepared (LDHs-TMT) for removing Cu(II)/Pb(II) from contaminated soil. The characterization of structure indicated TMT is intercalated between LDHs layers, and affects growth of crystal structure. The data of kinetics fits pseudo-second-order and intraparticle diffusion models. The isotherms is conformed to Langmuir model, and the adsorption capacity reaches 102.8 mg/g for Cu(II) and 105.8 mg/g for Pb(II). For adsorption mechanism, when concentration of Cu(II)/Pb(II) is low, Cu(II)/Pb(II) is preferentially immobilized by interlayered TMT molecule. As concentration increases, since adsorption sites on TMT are fully occupied, Cu(II)/Pb(II) grab the hydroxy of LDHs and form hydroxide precipitation. The effects of pH, coexistence ions, column leaching and leaching experiments are conducted. The results indicate LDHs-TMT have high adsorption stability and possesses appreciable interception for heavy metal migration.

Synthesis of green ceramic adsorbent for the treatment of tire factory effluent containing lead, zinc, aluminum, cobalt, iron and manganese ions

In this study, a novel nano-composite ceramic adsorbent was synthesized and characterized for the removal of heavy metal ions from industrial wastewater. The adsorbent was prepared using low-cost materials including clay and human hair, and hydroxyapatite nanoparticles derived from bovine bones. The synthesis method, material properties, and adsorption performance were thoroughly investigated wed XRD, FT-IR, FE-SEM and, BET. The adsorption process was optimized using Design Expert software, resulting in optimal conditions of pH 6.5, adsorbent mass of 22.5 g, temperature of 44.5 °C, initial concentration of 281 mgL−1, and retention time of 192 min. Thermodynamic parameters indicated that the adsorption process was spontaneous, endothermic, and followed the Freundlich isotherm model. The adsorption mechanism involved ion exchange, physical and chemical surface adsorption, facilitated by the unique surface properties of the nano-composite adsorbent. Moreover, the adsorbent exhibited high regeneration efficiency, with up to 73 cycles of reuse without a decrease in removal efficiency.

Heavy-Metal Ions Removal and Iodine Capture by Terpyridine Covalent Organic Frameworks.

Porous materials are excellent candidates for water remediation in environmental issues. However, it is still a key challenge to design efficient adsorbents for rapid water purification from various heavy metal ions-contaminated wastewater in one step. Here, two robust nitrogen-rich covalent organic frameworks (COFs) bearing terpyridine units on the pore walls by a "bottom-up" strategy are reported. Benefitting from the strong chelation interaction between the terpyridine units and various heavy metal ions, these two terpyridine COFs show excellent removal efficiency and capability for Pb2+, Hg2+, Cu2+, Ag+, Cd2+, Ni2+, and Cr3+ from water. These COFs are shown to remove such heavy metal ions with >90% of contents at one time after the aqueous metal ions mixture is passed through the COF filter. The nitrogen-rich features of the COFs also endow them with the capability of capturing iodine vapors, offering the terpyridine COFs the potential for environmental remediation applications.

Potential and characteristics of heavy metals electrokinetic removal from the copper-zinc mine tailings: Study on the simulated and actual tailings

Tailing ponds, as the storage of solid waste from metal mining processes, contain large amounts of residual heavy metals, potentially posing risks to the ecological environment. Despite extensive research on electrokinetic remediation of metals from tailings, comprehensive studies analyzing the migration dynamics of tailing metals under electric fields from multiple perspectives are limited. In this study, we comprehensively evaluated the removal of heavy metals from both simulated and actual tailings during the electrokinetic remediation processes. Zn, Cu, and Mn in simulated tailings showed accelerated migration rates under a 30 V two-dimensional electric field compared to the actual, achieving maximum removal efficiencies of 42.8 %, 20.1 %, and 52.1 %, respectively. This outcome was attributed to the lower effective concentration of heavy metals observed in actual tailings. Two monocotyledonous Poaceae plants, vetiver grass and sorghum, exhibited a robust growth in the remediated tailings with germination rates of 85 %. Moreover, microbial richness in these remediated tailings was clearly increased, indicating alleviation of heavy metal inhibition. The experimental results demonstrated the effective removal of residual heavy metals from tailings through electrokinetic remediation, alleviating the adverse impacts of heavy metals on both plant growth and microbial diversity, which holds significant implications for future reclamation and ecological restoration of tailing ponds. In conclusion, a comparative analysis between simulated and actual tailings, employing plant growth assessment and assessing the applicability of electrokinetic remediation for addressing metal pollution in tailing ponds from a microscopic perspective, presents a promising research direction.

Mechanistic Insights into Micelle-Enhanced Nanofiltration for Heavy Metal Removal: Transformation of Ion Transport and Fouling Phenomena.

Toxic heavy metals are widely present in typical scenarios, such as mines and electroplating wastewater, presenting significant risks to biological and environmental safety. Membrane processes encounter a challenge in effectively intercepting heavy metals due to their small hydration radius. This research showcases the high efficiency of micelle-enhanced nanofiltration (MENF) in removing heavy metals. At the critical micelle concentration, sodium dodecyl sulfate demonstrated a high removal of Cu2+, Ni2+, Zn2+, and Cd2+ while maintaining substantial potential for complexation of heavy metals. The formation of micelles and the bonding of heavy metals with surfactants bolstered the resistance of heavy metal ions to transmembrane transport. The presence of heavy metals in ionic form in wastewater facilitated their complexation with surfactants or micelles. Notably, the valence state and concentration of interfering ions in the environment could slightly influence the removal of heavy metals by MENF. Additionally, MENF displayed remarkable antifouling properties. The loose gel layer created by surfactant molecules and the micelle enhanced the membrane permeability and reduced the scaling tendency of heavy metals. This study contributes to an improved understanding of the mechanisms involved in heavy metal rejection by using MENF.

Adsorption mechanism of Cd2+ on solid waste–based PRB composite filler and pore structure dynamic evolution laws

In this study, a composite granular filler (CGF) was prepared primarily using steel slag, fly ash, and desulphurization gypsum to remedy the default of expensive, passivation, and ease of failure for the traditional permeable reactive barrier (PRB). The adsorption characteristics of the CGF on Cd2+ were investigated by the static adsorption, and the strength loss and scatter ratio were clarified with an immersion test. Dynamic adsorption and visualization modeling were used to determine the primary factors influencing adsorption and the evolution laws of material corrosion and pore clogging. Various characterization methods were used to research the adsorption mechanism. The results showed that the CGF fit with the pseudo-second-order kinetic model and Langmuir model, and the optimal adsorption capacity reached 8.64 mg/g; the minimum ratio of scatter and strength loss were 4.95% and 6.16%, respectively. The pump speed greatly influenced the breakthrough curves. The maximum dynamic adsorption capacity reached 1.81 mg/g, and the Thomas model described the adsorption behavior well. After adsorption, the porosity increased by 7.79%, and clogging in the middle of the column was not serious. The connected pores still accounted for 99.48%, and the pore network model (PNM) maintained excellent connectivity. Hydration products generated in the CGF ensured strength and durability, and they also benefited the adsorption of Cd2+ through ion exchange, co-precipitation, and surface adsorption. This research provides a new solid-waste resource utilization method for heavy metal removal in groundwater and a theoretical basis for the long-term purification of PRB with good potential for application and economic benefits.

Heavy metal removal by porous asphalt in cyclical wetting and drying

Porous asphalt pavement (PAP) is subjected to wetting and drying cycles involving storms of varying intensity and inter-event drying periods to study the impact of continuous weather systems on heavy metal removal in runoff. Four physical models: a complete PAP system, a PAP surface, a geotextile fabric and a reservoir of cobblestone aggregate, were created at the lab-scale and tested with stormwater contaminated with dissolved Mn(Ⅱ), Zn(Ⅱ), Cu(Ⅱ), and Cr(Ⅵ). The models were exposed to repeated wetting and drying cycles spanning over 27 days in triplicate. Wetting involved light, moderate and heavy rainfall intensities. All pavement material designs performed well at removing Cu(Ⅱ) and Cr(Ⅵ). The PAP system had an overall better performance at removing Mn(Ⅱ), Zn(Ⅱ), Cu(Ⅱ), and Cr(Ⅵ) than any of the individual pavement materials but was unable to remove all of the heavy metals simultaneously to sufficiently high levels. The materials used in the filter layer and reservoir structure and their adsorption and desorption capacities should be assessed for potential contamination (leaching) of Zn(Ⅱ) and Mn(Ⅱ), respectively, prior to construction. Wetting and drying cycles had the greatest impacts on the reservoir structure’s performance versus any of the other layers. Leaching of Mn(II) observed from cobblestone aggregate was affected by the solution composition and pH. Removal of selected heavy metals was rapid in first flush and fluctuated with storm event intensity.

Deep-sea microorganisms-driven V5+ and Cd2+ removal from vanadium smelting wastewater: Bacterial screening, performance and mechanism

The disorderly discharge of industrial wastewater containing heavy metals has caused serious water pollution and ecological environmental risks, ultimately threatening human life and health. Biological treatment methods have obvious advantages, but the existing microorganisms exhibit issues such as poor resistance, adaptability, colonization ability, and low activity. However, a wide variety of microorganisms in deep-sea hydrothermal vent areas are tolerant to heavy metals, possessing the potential for efficient treatment of heavy metal wastewater. Based on this, the study obtained a group of deep-sea microbial communities dominated by Burkholderia-Caballeronia-Paraburkholderia through shake flask experiments from the sediments of deep-sea hydrothermal vents, which can simultaneously achieve the synchronous removal of vanadium and cadmium heavy metals through bioreduction, biosorption, and biomineralization. Through SEM-EDS, XRD, XPS, and FT-IR analyses, it was found that V(V) was reduced to V(IV) through a reduction process and subsequently precipitated. Glucose oxidation accelerated this process. Cd(II) underwent biomineralization to form precipitates such as cadmium hydroxide and cadmium carbonate. Functional groups on the microbial cell surface, such as -CH2, C=O, N-H, -COOH, phosphate groups, amino groups, and M-O moieties, participated in the bioadsorption processes of V(V) and Cd(II) heavy metals. Under optimal conditions, namely a temperature of 40 °C, pH value of 7.5, inoculation amount of 10%, salinity of 4%, COD concentration of 600 mg/L, V5+ concentration of 300 mg/L, and Cd2+ concentration of 40 mg/L, the OD600 can reach its highest at 72 h, with the removal efficiency of V5+, Cd2+, and COD in simulated vanadium smelting wastewater reaching 86.32%, 59.13%, and 61.63%, respectively. This study provides theoretical insights and practical evidence for understanding the dynamic changes in microbial community structure under heavy metal stress, as well as the resistance mechanisms of microbial treatment of industrial heavy metal wastewater.

Feasibility of intimately coupled CaO-catalytic-ozonation and bio-contact oxidation reactor for heavy metal and color removal and deep mineralization of refractory organics in actual coking wastewater

Considering the challenges for both single and traditional two-stage treatments, advanced oxidation and biodegradation, in the treatment of actual coking wastewater, an intimately coupled catalytic ozonation and biodegradation (ICOB) reactor was developed. In this study, ICOB treatment significantly enhanced the removal of Cu2+, Fe3+, and color by 39 %, 45 %, and 52 %, respectively, outperforming biodegradation. Catalytic ozonation effectively breaking down unsaturated organic substances and high-molecular-weight dissolved organic matter into smaller, more biodegradable molecules. Compared with biodegradation, the ICOB system significantly increased the abundances of Pseudomonas, Sphingopyxis, and Brevundimonas by ∼ 96 %, ∼67 %, and ∼ 85 %, respectively. These microorganisms, possessing genes for degrading phenol, aromatic compounds, polycyclic aromatics, and sulfur metabolism, further enhanced the mineralization of intermediates. Consequently, the ICOB system outperformed biodegradation and catalytic ozonation treatments, exhibiting chemical oxygen demand removal rate of ∼ 58 % and toxicity reduction of ∼ 47 %. Overall, the ICOB treatment showcases promise for practical engineering applications in coking wastewater treatment.