Leaching Toxicity Research Articles

Reductive Immobilization of Hexavalent Chromium in Soil Using Hydrazine – Kinetics, Process Optimization, Sonochemical Enhancement, and Cost Estimation

ABSTRACT The presence of hexavalent chromium in soil poses a grave hazard to the environment and human health. This study explores the effectiveness, mechanism, and economic viability of remediation of Cr(VI)-contaminated soil by hydrazine. Soil-phase batch kinetic experiments were performed to examine the feasibility of reducing Cr(VI) while finding the effects of relevant process parameters, such as initial Cr(VI) concentration, hydrazine dosage, pH, soil-to-water ratio, and temperature. The materials were thoroughly characterized to gain insight into the mechanism. TCLP tests were done to affirm the immobilization stability. Complete Cr(VI) reduction was achieved within 3 h using a moderate 326% excess of hydrazine at neutral pH. Sonication of the soil mixed with hydrazine using a probe-type sonicator accelerated the reduction of Cr(VI) to Cr(III). Kinetic data could be adequately fitted in a second-order rate model, where the rate constant shows a linear dependency on the soil-to-water ratio. Additionally, the logarithmic rate constant demonstrates linearity within the pH range. The leaching toxicity of Cr(VI) and Crtotal complied with the USEPA regulatory limit and remained stable for 75 d. Hydrazine alone and its combination with ultrasound are sustainable and economically feasible for effective remediation of Cr(VI)-contaminated soil. The statistical analysis using RSM indicated a 99.4% reduction, aligning closely with the calculated optimized value. The optimal process conditions are easy to implement for field application at a competitive cost compared to other reductants. A simplified economic analysis was done to check the competitive acceptability of the technique, considering the construction cost of the remediation plant and its daily operational and maintenance expenses. The results show that the proposed technique will be a competitive one for field applications for the remediation of soil contaminated with Cr(VI). The data and kinetic rate equation will be useful for the process design of the remediation of soil contaminated with Cr(VI).

Effect of As and MgO addition on arsenic vitrification in copper smelting slag

The arsenic (As) vitrification in copper smelting slag derived from the FeO−SiO2−Fe2O3−B2O3−CaO− Al2O3−(MgO) system was studied. The vitrification mechanism of As was systematically investigated by XRD, SEM, FTIR and XPS analysis. It is determined that As exhibits favorable compatibility with the iron-silicate slag. FTIR and XPS analysis indicates that As can partially substitute for silicon to form the Si—O—As structure, thereby enhancing the degree of polymerization of the melt. The [BO3]3− unit tends to decrease with the increase of the As content, while the opposite behavior is observed with the addition of MgO. Additionally, MgO increases the non-bridging oxygen (NBO) number of the melt. TCLP, SPLP and pH dependence tests show that the leaching toxicity of As increases with the increase of the As content but decreases with the addition of MgO. DSC analysis demonstrates that the incorporation of both As and MgO can improve the thermal stability of the As-containing glass.

Double-edged effects of aluminosilicates formation on denitrification and desalination during the leaching process of secondary aluminum dross (SAD)

As the proportion of recycled aluminum increased, the production of secondary aluminum dross (SAD) increased dramatically, putting enormous pressure on the enterprises and environment. The utilization rate of SAD was less than 30 % due to problems such as high discharge of acidic/alkaline wastewater or restrictions on the salt content of raw materials. In a previous study, authors achieved self-driven hydrolysis of SAD by water leaching. However, the removal of Na and K was incomplete, which was also found in alkaline leaching processes and was more serious. To further identify the causes, the transformation behaviors of Al, Si, N, F, Cl, Na, and K in SAD during the water leaching process were investigated in this study. In addition, the double-edged effects of aluminosilicates formation on denitrification and desalination during the leaching process of SAD were also revealed. The results showed that the generation of Al(OH)3 inclusions during the hydrolysis of AlN inhibited the deep denitrification, while NH3 provided an alkaline driving force for the dissolution of Al(OH)3 and Si/SiO2. Dissociated Al(OH)4- and H3SiO4- reacted with Na+/K+ to form aluminosilicates, which promoted denitrification but inhibited desalination. Eventually, after 480 min of water leaching (L/S = 1.5, T = 80 °C), the denitrification was 86.39 %, the removal rate of Cl was 99.61 %, and the contents of Na and K in leaching residues were 0.39 wt% and 0.24 wt%, respectively. The leaching residues with an Al content of 37.41 wt% showed no leaching toxicity, which reached Grade I bauxite grade.

Elements characteristics and potential environmental risk assessment of jarosite residue and arsenic sulfide residue based on geochemical and mineralogical analysis

The waste slag known as jarosite residue (JR) and arsenic sulfide residue (ASR) were produced following the creation of zinc by hydrometallurgical procedures. The increasing annual zinc mining has led to growing pressure to dispose of the resulting JR and ASR from zinc smelting, making it crucial to assess their environmental impact and feasibility for utilization. The main components, distribution characteristics of elements, and potential environmental risks of zinc smelting wastes are studied through toxicity leaching tests, sequential extraction procedures, and various characterization technologies such as XRF, XRD, and SEM-EDS. The mineral compositions of JR are natrojarosite, franklinite, and gunningite, and zinc mainly adheres to the crevices of the natrojarosite mineral. Meanwhile, the ASR of flocculent structures is composed of orpiment, greenockite, arsenic oxide, and calvertite, and As appears in the form of the S-As-O phase. The Zn, Cu, and Cd in JR were dominated by exchangeable bound (81.53–96.6 %), and the main form of As, Cd, Se, and Tl in ASR was organic matter bound (87.0–99.21 %). The Risk Assessment Code (RAC) method confirmed the risk of Cd, Cu, Zn, and Mo in JR is high, while the risk of Cd, Pb, and Cr in ASR is moderate. Compared to the standard value of “Identification Standard for Toxicity of Hazardous Waste Leaching (GB5085.3-2007)”, the leachate concentrations of Zn in JR as well as Cd and As in ASR were exceeded, suggesting that the JR and ASR were in the type of hazardous waste and posed an environmental risk. The study provides theoretical guidance for the future rational management and effective utilization of hazardous waste.

Overlooked competition and promotion effects in electrochemical oxidation of humic acid and ammonia in landfill leachate

Electrochemical oxidation (EO) can effectively reduce the degree of humification and toxicity of landfill leachate by generating highly active oxidative species in situ. However, the selective and competitive oxidation of humic acid (HA) and ammonia (NH4+) and the role of different oxidative species during the EO process in complex aqueous conditions remain unclear. In this study, a nanostructured tin-antimony electrode (Ti/Sb-SnO2 NFs) was prepared and compared with three types of commercial electrodes (Ti/Ir-RuO2, Ti4O7, Ti/Sb-SnO2) in terms of electrochemical properties and electrocatalytic oxidation of HA and NH4+. The de-humification capacity, interactive effects of HA and NH4+ on each other's oxidation by different oxidative species, as well as the related oxidation byproducts were investigated. The differences in pollutant electrooxidation among the different electrodes were found to be insignificant. The presence of HA was found to be detrimental to NH4+ degradation while reducing the N2 conversion rate. Interestingly, NH4+ initially inhibited the degradation rates of HA while promoted the degradation and reduced the accumulation of organic chlorine during the later EO process. A proposed mechanism accounts for both competitive and promotional effects for simultaneous HA and NH4+ oxidation during the EO process.

Strength and Contaminant Toxicity Leaching Characteristics of MgO-Solidified Silt

In this study, MgO as an environmentally friendly silt-solidifying material was first mixed with silt and then carbonized by injection with CO2. The strength and contaminant leaching characteristics of the MgO-solidified silt were studied using unconfined compressive strength and toxicity leaching tests, and the results were compared with those of cement-solidified silt. The unconfined compressive strength of the silt reached 111 kPa with 9% MgO content and a 14 d curing time. The CO2 injection further increased the unconfined compressive strength of the MgO-solidified silt by approximately 25%: the values for MgO-solidified silts without and with a CO2 injection were approximately 60% and 80%, respectively, of those of the cement-solidified silts with the same additive additions. The leaching concentrations of nutrient salts and heavy metal pollutants in the silt decreased with increased MgO content. Compared with the dredged silt, MgO solidification with carbonization reduced the leaching of total nitrogen and total phosphorus by more than 10% and 50%, respectively: these values were approximately 5% points higher than those of cement-solidified silt. Of the heavy metals, the leaching concentration of Ni was reduced the most. This study provides a theoretical basis and technical support for low-carbon treatment and green resource utilization of dredging silt.

A robust acid-resistant chelating polymer for enhanced stabilization of lead ions in fly ash

Fly ash derived from municipal solid waste incinerators (MSWIs) harbors significant quantities of heavy metals with high leaching toxicity, resulting in detrimental environmental effects. Pb2+ in fly ash is the ion most likely to exceed permissible levels. However, chemical stabilization methods demonstrate poor efficacy in stabilizing Pb2+ under acidic conditions. Herein, we have developed a robust acid-resistant chelating polymer (25DTF) for enhanced stabilization of Pb2+ in fly ash. 25DTF was synthesized through the reaction of formaldehyde with 2,5-dithiourea. 25DTF exhibited remarkable chelation efficiency, nearing 100%, for Pb2+ in fly ash. 25DTF demonstrated exceptional chelation efficiency, surpassing 99.9%, when interacting with Pb2+ in fly ash at pH ≤ 7. Even under acidic conditions, 25DTF effectively prevented the secondary dissolution of Pb2+. Additionally, it indicated outstanding Pb2+ chelation efficiency across diverse regions of China. The 25DTF chelating agent shows considerable potential in alleviating metal ion contamination in soil, wastewater, and urban environmental management, thereby fostering advancements in environmental stewardship.

The nematode Caenorhabditis elegans enhances tolerance to landfill leachate stress by increasing trehalose synthesis.

The burgeoning issue of landfill leachate, exacerbated by urbanization, necessitates evaluating its biological impact, traditionally overshadowed by physical and chemical assessments. This study harnesses Caenorhabditis elegans, a model organism, to elucidate the physiological toxicity of landfill leachate subjected to different treatment processes: nanofiltration reverse osmosis tail water (NFRO), membrane bioreactor (MBR), and raw leachate (RAW). Our investigation focuses on the modulation of sugar metabolism, particularly trehalose-a disaccharide serving dual functions as an energy source and an anti-adversity molecule in invertebrates. Upon exposure, C. elegans showcased a 60-70% reduction in glucose and glycogen levels alongside a significant trehalose increase, highlighting an adaptive response to environmental stress by augmenting trehalose synthesis. Notably, trehalose-related genes in the NFRO group were up-regulated, contrasting with the MBR and RAW groups, where trehalose synthesis genes outpaced decomposition genes by 20-30 times. These findings suggest that C. elegans predominantly counters landfill leachate-induced stress through trehalose accumulation. This research not only provides insights into the differential impact of leachate treatment methods on C. elegans but also proposes a molecular framework for assessing the environmental repercussions of landfill leachate, contributing to the development of novel strategies for pollution mitigation and environmental preservation.

Fragmentation of polypropylene into microplastics promoted by photo-aging; release of metals, toxicity and inhibition of biodegradability

The widespread presence of microplastics (MP) in water represents an environmental problem, not only because of the harmful effects of their size and potential to vector other pollutants, but also because of the release of additives, degradation products and residues contained in the polymer matrix. The latter includes metallic catalysts, which are often overlooked. This study focuses on the photo-aging of polypropylene (PP) and the resulting structural changes that promote its fragmentation microplastics (PP-MPs) and release of metals, as well as the resulting toxicity of leachates and their potential to inhibit biodegradation of organics in water. The pristine, photo-aged and waste PP are ground under the same regime to assess susceptibility to fragmentation. Obtained PP-MPs are submitted to leaching tests; the release of organics and metals is monitored by Total Organic Carbon (TOC) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis, respectively. The leachates are assessed for their toxicity against Vibrio fischeri, Daphnia magna and Pseudokirchneriella subcapitata and their influence on the biodegradability of the glucose solution. Photo-aging induced changes in the crystallinity and morphology of the PP and manifested in the abundance of smaller MPs, as revealed by the particle size distribution. In the case of pristine PP, all particles were > 100 μm in size, while aged PP yielded significant mass fraction of MPs <100 μm. The toxicity of leachates from aged PP-MPs is higher than that of pristine and exhibits a positive correlation with portion of metals released. The biodegradability of glucose is strongly inhibited by PP-MPs leachates containing a mixture of metals in trace concentrations.

Ecological risk assessment of heavy metals in coal gasification slags and their leaching toxicity

ABSTRACT The coal gasification process produces a large amount of coal gasification slag (CGS), which accumulates heavy metals from the raw coal. The CGS not only occupies land resources during long-term storage but also poses potential ecological pollution risks. In this study, eight different CGS samples from various regions of China were analyzed to determine their chemical composition and evaluate their environmental risks. Two leaching methods recommended by the Ministry of Ecology and Environment of China were employed to conduct leaching experiments, aiming to assess the hazardous waste level of CGS. The results indicated that the risk index of YL-FS and XJ-CS reached 101.87 and 87.15, respectively, classifying them as medium-risk materials. The remaining samples were categorized as low-risk materials. CGS itself is not classified as hazardous solid waste. The leaching results revealed that the concentration of Be in the leaching solution of NMG-CS and XJ-CS exceeded 0.005 mg/L, placing them in Class II of general industrial solid waste. The remaining samples exhibited minimal leaching toxicity and were classified as Class I general industrial solid waste.

Synergistic preparation of geopolymer using electrolytic manganese residue, coal slag and granulated blast furnace slag

To improve the utilization rate of industrial solid waste and the sustainable development of geopolymer research and development, this article uses electrolytic manganese residue (EMR), coal slag (CS), and granulated blast furnace slag (GGBS) as raw materials to prepare a new eco-friendly geopolymer cementitious material (GOCM). The mechanical properties, phase composition, and microstructure of GOCM are measured and analyzed using methods such as compressive bending strength test, X-ray diffraction, scanning electron microscopy, mercury intrusion test, and Fourier transform infrared spectroscopy. The effects of material ratio, water cement ratio, and alkali activator content on GOCM are explored. Meantime, the environmental characteristics of GOCM were also investigated through toxicity leaching experiments. Results show that CS improves the flowability and late compressive strength of GOCM, and EMR reduces the setting time of the slurry, the maximum strength of GOCM was observed when the contents of EMR, CS, and GGBS were 25 %, 55 %, and 20 %, the mass fraction of alkaline activator was 14 %, and the W/C was 0.45. and the maximum compressive strength reaches 22.8 MPa. The hydrates in GOCM are composed of flocculent, cluster, block C–S–H gel. The hydrates formed have excellent stabilization effect on heavy metals in raw materials. When the GOCM material ratio is optimal (the contents of EMR, CS, and GGBS were 25 %, 55 %, and 20 %), the leaching concentration of Cd, Cr, and Mn is lower than the limit values (Cd < 0.001 mg/L, Cr < 0.01 mg/L, Mn < 0.05 mg/L) specified in GB/T14848-2017.

Acute toxicity of petroleum asphalt seal coat leachates to Ceriodaphnia dubia is linked to polymer preservatives

Low-VOC waterborne asphalt-emulsion (AE) seal coat is considered more sustainable than solvent-based coal-tar emulsion seal coat because asphalt emulsions contain negligible amounts of carcinogenic PAHs and release fewer harmful volatile organic compounds. Yet, many low-VOC coatings leach water-soluble substances under outdoor conditions. To investigate the chemical composition of seal coat leachates, three AE formulations were cured under natural weathering conditions and exposed to simulated runoff over a 10-day field trial. Runoff was collected and concentrated using ion-exchange solid-phase extraction (SPE) and analyzed using gas chromatography/mass spectrometry (GC–MS). Leached compounds included hydrocarbons, esters, amines, siloxanes, plasticizers, biocides, polyethylene glycol (PEG) ethers, urethanes, and toluene diisocyanate (TDI). Glycol ethers comprised 29–97 % of the measured leachate mass. Two seal coat formulations contained isothiazolinone biocides, methylchloro- and methylisothiazolinone (CMIT/MIT; 0.5 mg/L in runoff), while a third seal coat formulation continuously leached TDI, a reactive polyurethane (PU) precursor (0.7 mg/L in runoff). Biocide-containing leachates showed acute toxicity to the freshwater water flea, Ceriodaphnia dubia after 48 h, while TDI-containing leachate showed no acute toxicity, suggesting that leachate toxicity was due to in-can polymer preservatives. As biocides are implicated in impaired reproductive signaling, these results support the use of alkaline pH to avoid biofouling and reinforce the goal of reducing and/or avoiding the use of biocides altogether, especially for environmentally friendly products.

Ultra-high performance concrete with metal mine tailings and its properties: a review

Abstract Metal mine tailings (MMT) are a kind of industrial solid waste, with an increasing accumulation year by year, which has seriously damaged the ecological environment. Incorporating MMT in ultra-high performance concrete (UHPC) is an effective means to achieve green sustainable development, which can not only make wastes be resources and prevent pollution but also save raw material costs and reduce energy consumption. However, metal mine tailings contain complex and diverse metal oxides and other chemical substance and even contain certain radioactive elements and heavy metal ions. These factors can affect the corrosion resistance of UHPC, accelerate its aging and damage, and in addition may have serious impacts on the environment and human health. This paper summarizes the material properties of MMT and its application in UHPC; analyzes the effects of MMT as powder or fine aggregate on the workability, mechanical properties, durability, and leaching toxicity of UHPC; and elaborates the hydration products, interfacial transition zone, and pore structure of UHPC incorporating MMT (MMT-UHPC). Based on previous research results, the relationship between flowability, flexural strength, porosity, and compressive strength of MMT-UHPC is established.

Immobilization properties and reaction mechanism of municipal solid waste incineration fly ash with alkali activation technology

Municipal solid waste incineration fly ash (MSWIFA) needs proper treatment prior to security landfilling because of considerable amounts of heavy metals and soluble chloride. Nowadays, alkali activation technology has become an effective solidification/stabilization (S/S) technology for MSWIFA. But few studies have been systematically carried out on the preparation techniques and reaction mechanism of MSWIFA S/S body. The effects of the technical parameters (alkali activator, sodium silicate modulus, alkali equivalent, water-solid ratio, curing regime) on the immobilization properties (compressive strength and heavy metal leaching toxicity) of MSWIFA S/S bodies were studied in this work. The hydration characteristics and reaction mechanism were also explored in depth based on the structure properties and microstructure characterization. Ca2+, Na+, SiO42−, [Al(OH)4]-, OH− dissociated from MSWIFA and alkali activator solution chemical reaction to form the silicates, aluminates and aluminosilicates with lower polymerization, and promoted the gel hydration products formation via depolycondensation. Lower Ca/Si molar ratio was conductive to the formation of amorphous substance, compactness of matrix pore structure and immobilization properties. Compared to the hydration products including halite, sylvine, glauberite, gypsum, calcite crystal, C–S–H gel contributed much more to the pore structure and strength improvement of MSWIFA S/S bodies. These findings will provide valuable theoretical basis for MSWIFA management and resource utilization promotion.

Optimization of solidification/stabilization materials based on solid waste geopolymer

With the development of mining economy and human society, heavy metal pollution incidents have gradually increased while a large amount of mine solid waste has been produced.Red mud (RM) and blast furnace slag (BFS) are common solid wastes in mines with excellent heavy metal adsorption properties. Optimization of geopolymer solidification/stabilization(S/S) materials based on these waste materials is a good way to reduce solid waste and cure heavy metal contaminated soil, and has outstanding environmental protection significance.In this study, RM and BFS were used as geopolymer raw materials, and sodium hydroxide was used as alkali activator to prepare lead nitrate contaminated soil with Pb content of 0.5%. Laboratory tests were conducted to explore the effects of alkali-solid ratio, BFS content on the mechanical strength, toxic leaching characteristics and pH of geopolymer S/S lead contaminated soil. The optimal ratio of geopolymer is obtained. The results show that the S/S soil cured with RM and BFS geopolymer has good mechanical properties and heavy metal adsorption properties, and it has certain scientific research value and utilization prospect for the remediation of Pb contaminated soil.

Highly efficient Mn2+, Mg2+, and NH4+ recovery from electrolytic manganese residue via leaching, solvent extraction, coprecipitation, and atmospheric oxidation

Electrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, exhibits substantial leaching toxicity owing to its elevated levels of soluble Mn2+ and NH4+. The leaching and recovery of valuable metal ions and NH4+ from EMR are key to the hazard-free treatment and resource utilization of EMR. In this study, two-stage countercurrent leaching with water was used to leach Mn2+, Mg2+, and NH4+ from EMR. Subsequently, two-stage countercurrent extraction was conducted using α-hydroxy-2-ethylhexyl phosphinic acid (α-H-2-EHA) as an extractant to enrich Mn2+, and Mg2+, and NH4+ were recovered via coprecipitation. Based on the calculations for a single leaching-extraction process, the recoveries of Mn2+, Mg2+, and NH4+ ions exceeded 80%, 99%, and 90%, respectively. In addition, high-purity Mn3O4 with an Mn content of 71.61% and struvite were produced. This process represents a win-win strategy that facilitates the hazard-free treatment of EMR while simultaneously recovering valuable Mn2+, Mg2+, and NH4+ resources from waste. Thus, this study provides a novel approach to the hazard-free and resourceful management of solid waste. Environmental implicationElectrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, poses significant environmental risks due to its soluble heavy metals and ammonia nitrogen content. Efforts have been made to address this issue, but there has been no mature industrial application due to cost or processing capacity constraints. In this work, solvent extraction was first used to enrich Mn2+ from EMR leachate, and a novel α‑hydroxy‑2‑ethylhexyl phosphinic acid was used as extractant. High purity Mn3O4 and struvite was synthesized through this process. The win‑win strategy offers a novel approach for the hazard‑free and resourceful utilization of solid waste.

Investigating the potential of mineral precipitation in co-pyrolysis biochar: Development of a novel Cd (II) adsorption material utilizing dual solid waste

Ionic cadmium (Cd (II)) in water is a significant threat to ecosystems, the environment, and human health. Research is currently focused on developing efficient adsorption materials to combat Cd (II) pollution in water. One promising solution involves co-pyrolyzing solid residue from anaerobic digestion of food waste with oil-based drill cuttings pyrolysis residue to create a biochar with high organic matter content. This biochar has a lower heavy metal content and leaching toxicity compared to China's national standards, making it both safe and resourceful. It exhibits a high adsorption capacity for Cd (II) in water, reaching up to 47.80 ± 0.37 mg/g. Raising the pyrolysis temperature above 600 °C and increasing the amount of pyrolysis residue beyond 30 % enhances the biochar's adsorption capacity. The adsorption process is primarily driven by mineral precipitation, offering a promising approach for dual waste resource management and reducing heavy metal pollution.

A ubiquitous tire rubber additive induced serious eye injury in zebrafish (Danio rerio)

Previous studies have indicated that tire wear particles (TWPs) leachate exposure induced serious eye injury in fish through inhibiting the thyroid peroxidase (TPO) enzyme activity. However, the main TPO inhibitors in the leachate were still unknown. In this study, we identified 2-Mercaptobenzothiazole (MBT) as the potential TPO inhibitor in the TWPs leachate through references search, model prediction based on Danish QSAR and ToxCast database, molecular docking, and in vivo assay. We further explored the toxic mechanism of MBT under environmentally relevant concentrations. The decreased eye size of zebrafish larvae was mainly caused by the decreased lens diameter and cell density in the inner nuclear layer (INL) and outer nuclear layer (ONL) of the retina. Transcriptomics analysis demonstrated that the eye phototransduction function was significantly suppressed by inhibiting the photoreceptor cell proliferation process after MBT exposure. The altered opsin gene expression and decreased opsin protein levels were induced by weakening thyroid hormone signaling after MBT treatment. These results were comparable to those obtained from a known TPO inhibitor, methimazole. This study has identified MBT as the primary TPO inhibitor responsible for inducing eye impairment in zebrafish larvae exposed to TWPs leachate. It is crucial for reducing the toxicity of TWPs leachate in fish.

The Performance of Iron Nanocomposites as Persulfate Activators in Permeable Reactive Barrier Technology for Treatment of Landfill Leachate

Landfill leachate contains a large organic load and a wide spectrum of pollutants, and it needs appropriate treatment to reduce the severity of these contaminants. Therefore, the present study aimed to remove chemical oxygen demand (COD) and ammonia (NH3 ) as target contaminants from the landfill leachate. To this end, the zero-valent iron nanofibers/reduced ultra-large graphene oxide (ZVINFs/rULGO) and converter sludge (CS) were used as persulfate (PS) activators in permeable reactive barrier (PRB) technology for removing COD and NH3 . The Box–Behnken design (BBD) was employed to determine the possibility of using each activator and optimize three parameters: activator, pore volume (PV), and flow (mL/min) using target contaminants. In the Batch process, the effects of pH, activator concentration, and PS/COD mass ratio on COD removal were examined. The BBD experiments provided a satisfactory predictive model, indicating that ZVINFs/rULGO is superior to CS when used as activators of PS in PRB technology. The biochemical oxygen demand (BOD5 )/COD ratio increased from 0.24 in raw leachate to 0.67 in treated leachate, and leachate toxicity was reduced by more than 85%. Additionally, the ZVINFs/rULGO and CS contributed to the activation of PS.

Cocktail effects of tire wear particles leachates on diverse biological models: A multilevel analysis

Tire wear particles (TWP) stand out as a major contributor to microplastic pollution, yet their environmental impact remains inadequately understood. This study delves into the cocktail effects of TWP leachates, employing molecular, cellular, and organismal assessments on diverse biological models. Extracted in artificial seawater and analyzed for metals and organic compounds, TWP leachates revealed the presence of polyaromatic hydrocarbons and 4-tert-octylphenol. Exposure to TWP leachates (1.5 to 1000 mg peq L−1) inhibited algae growth and induced zebrafish embryotoxicity, pigment alterations, and behavioral changes. Cell painting uncovered pro-apoptotic changes, while mechanism-specific gene-reporter assays highlighted endocrine-disrupting potential, particularly antiandrogenic effects. Although heavy metals like zinc have been suggested as major players in TWP leachate toxicity, this study emphasizes water-leachable organic compounds as the primary causative agents of observed acute toxicity. The findings underscore the need to reduce TWP pollution in aquatic systems and enhance regulations governing highly toxic tire additives.