环境•农林最新文献

The conversion of agricultural residues into high-value materials represents a sustainable pathway for environmental remediation. In this study, rice husk ash (RHA), an abundant agro-industrial by-product, was valorized into high-purity NaY zeolite through a sol–gel-assisted hydrothermal process. The resulting zeolite exhibited a Si/Al ratio of 7, a surface area of 154.4 m²/g, and a micropore size of 1.19 nm. XRD and SEM analyses confirmed the formation of a highly crystalline FAU-type framework with cauliflower-like cubic aggregates (~ 2 µm) and rough porous surfaces favorable for ion exchange. Batch adsorption experiments revealed strong pH dependence, with optimal metal uptake at pH 4, achieving removal efficiencies of 91.9% (Cu²⁺), 72.9% (Zn²⁺), and 15.0% (Ni²⁺). Kinetic data were well described by the pseudo-second-order model (R² = 0.99), suggesting that the adsorption rate is governed by interactions associated with ion-exchange processes, while the Langmuir isotherm (R² > 0.99) described monolayer adsorption with maximum capacities of 49.0, 8.7, and 4.5 mg/g for Cu, Zn, and Ni, respectively. Under three adjusted real wastewater systems, simulating increased heavy-metal loadings (Cu:Zn:Ni = 10:10:2, 50:50:2, 50:50:5 mg/L), total adsorption capacities reached 22.5–48.3 mg/g, with Cu–Zn–Ni accounting for over 70% of total uptake. Ion release analyses (Na⁺, Al³⁺, Si⁴⁺) confirmed ion exchange as the dominant mechanism. These results highlight the potential of RHA-derived NaY zeolite as a cost-effective, eco-friendly, and robust adsorbent, providing a circular economy approach to agricultural waste valorization and sustainable wastewater treatment.

Contamination from heavy metal ions and effluents from agriculture is one of the most significant environmental restrictions to crops' productivity. In this study, Chitin nanoparticles (ChNPs), Chitosan nanoparticles (CsNPs), Zinc oxide nanoparticles (ZnONPs), and Chitosan/zinc oxide nanocomposites (Cs/ZnO NCs) have been synthesized using Acheta domesticus L. extract. Characterization was carried out using ultraviolet–visible (UV–Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). According to the results of UV–Vis, the spectra showed characteristic bands within the wavelength range of 296–356 nm, indicating the presence of nanoparticles. FTIR analysis provided information about the functional groups responsible for nanoparticle stability and interaction of chitosan with ZnO, while XRD showed semi-crystallinity of ChNPs and CsNPs and crystallinity of ZnONPs. The particle size varied from 10 to 100 nm using SEM and TEM analysis techniques. After that, the synthesized nanomaterials were examined for their potential to reduce the stress caused by Pb and wastewater in Brassica campestris L. Plants' growth, biomass, chlorophyll, soluble sugars, proteins, phytohormones and electrolytes were decreased due to Pb and wastewater, and on the other hand, oxidative stress was enhanced due to Pb and wastewater. In all tested materials, Cs/ZnONCs demonstrated maximum efficiency in the protection of plants. Under Pb-stressed conditions, Cs/ZnONCs increased shoot and root lengths up to 6.0 and 6.2 cm, respectively, against 2.9 and 3.2 cm of Pb-stressed plants. Furthermore, fresh and dry weights were raised to 0.48 and 0.049 g, respectively, against 0.20 and 0.021 g of Pb-stressed plants. Additionally, Cs/ZnONCs increased the content of soluble sugars and proteins up to 59 and 185 µg/g, respectively, against 22 and 130 µg/g of Pb-stressed plants. Also, chlorophyll a and total chlorophyll content increased from 2.50 and 6.10 mg/g of fresh weight in the presence of Pb stress to 5.30 and 11.80 mg/g of fresh weight, respectively, after Cs/ZnO NCs application. In addition, Cs/ZnONCs improved the concentration of indole-3-acetic acid and gibberellic acid but decreased the level of abscisic acid production. Overall, Cs/ZnONCs showed higher efficacy than the isolated nanoparticles of ChNPs, CsNPs, and ZnONPs and could be a potential nanomaterial to ameliorate Pb and wastewater stress in B. campestris L.

In recent years, heterogeneous catalytic oxidation technology utilizing persulfate has garnered significant attention in environmental pollution control. Within this context, the high-valent metal oxidation mechanism, prevalent in transition metal-based catalyst-activated persulfate reaction systems, stands out as a notable non-free radical oxidation pathway. Compared to free radicals, high-valent metal species, often serving as interfacial reactive oxygen species, exhibit several advantages: lower oxidation potential, longer half-life, higher steady-state concentration, and superior anti-interference ability. These characteristics endow high-valent metal oxidation with considerable research potential in addressing environmental pollution. However, the intricate heterogeneous surface structure of catalysts and the complex interactions at the “solid–liquid” interface pose significant challenges for in-depth exploration of high-valent metal oxidation. This includes understanding its derivatization, oxidation properties, stabilization, and identification. To address these challenges, this paper provides a comprehensive review of the reactive species involved in high-valent metal oxidation, their derivative mechanisms, stabilization means, recognition technologies, and oxidation characteristics, drawing from research in the field of heterogeneous persulfate catalytic activation. Based on this synthesis, the paper also outlines the research challenges and offers development suggestions for advancing the understanding of high-valent metal oxidation mechanisms.

Phytoextraction represents a cost-effective and eco-friendly strategy for the remediation of cadmium-contaminated agricultural soils. In this study, we integrated multi-omics approaches to investigate the synergistic mechanisms underlying the enhancement of Cd phytoextraction efficiency by rice straw (RS) amendment in the hyperaccumulator Sedum plumbizincicola (HSe), relative to the non-hyperaccumulator Sedum alfredii (NSe). Our results demonstrated that RS amendment drove a dynamic ‘immobilization-activation’ shift in soil Cd speciation, with immobilization occurring prior to planting and activation during plant growth. RS amendment increased shoot biomass by 59.0% in NSe and 58.0% in HSe, and shoot Cd concentration by 43.0% in NSe and 80.9% in HSe, respectively. Consequently, total shoot Cd accumulation in both ecotypes reached 2.3–2.4 times that in the control treatment, with HSe displaying superior Cd enrichment capacity. Metabolomic analysis confirmed that HSe inherently possesses a robust antioxidant defense system to alleviate Cd-induced cellular toxicity. RS amendment further reprogrammed root metabolic pathways in HSe, marked by upregulated biosynthesis of flavonoids, valine, isoleucine, and pantothenate. These metabolic adjustments collectively enhanced antioxidant defense, nitrogen metabolism, energy metabolism, and Cd uptake and translocation. Moreover, this study clarified the interactions between root metabolites and rhizosphere microorganisms. Under RS amendment, HSe selectively recruited specific microbial taxa to enhance growth performance and stress tolerance. Notably, marmesin is likely to act as a key signaling metabolite that recruits RS-specific genera and promotes nitrogen acquisition, carbon cycling, and Cd mobilization. These findings highlight that the synergistic interplay between plant genotype and RS amendment is critical for improving phytoremediation efficiency.

Heavy metal contamination impacts the environment because of the toxicity, persistence, bioaccumulation, and potential mobility of these contaminants, particularly when their concentrations exceed permissible environmental limits. The typical/conventional methods used to eliminate the toxic contaminants are highly energy-intensive, costly, and may require substantial chemical and energy inputs, and can also generate additional secondary waste. Thus, a shift to an eco-friendlier alternative becomes a necessity. One such method is the utilization of Microbial Fuel Cells (MFCs). This MFC possesses the advantage of treating water along with the simultaneous generation of bioenergy (bioelectricity). This review critically highlights the use of MFCs for the removal and recovery of heavy metals, with emphasis on MFCs mechanisms, configurations, operating parameters, and reported performance. The role of anodic oxidation, extracellular electron transfer (EET), cathodic reduction, electrodeposition, precipitation, adsorption, biosorption, and biological transformation in heavy metal remediation is also discussed. Different MFC configurations, including single, dual, benthic/sediment, and multi-chambered systems, are evaluated in relation to metal removal and electricity generation. Additionally, the effects of pH, electrode materials (anode and cathode), type of substrate, microbial community, metal type and concentration, and external resistance on MFC performance are also summarized. The reviewed studies demonstrated the potential of MFCs in remediating and recovering heavy metals, although the performance varied substantially among different MFCs configurations. However, the direct comparison across various studies is limited due to differences in microbial species, reactor configurations, operating conditions, substrate, type of metal ion and its concentration, and performance metrics. Major challenges include metal toxicity, electrode and membrane costs, exoelectrogenic biofilms, and limited long-term and large-scale validation. To advance MFC-based heavy metal remediation for practical applications, future studies could prioritize real industrial wastewater, mixed metal systems, continuous operation, scalable MFCs architecture, mechanistic validation, and resource recovery.

Graphical Abstract

Removal of toxicants from wastewater using MFC

Manganese oxide (MnO₂)-modified biochar was prepared from spent tea leaves by pyrolysis followed by co-precipitation and applied to the heterogeneous catalytic ozonation of ketoprofen (KTP). The effects of pyrolysis temperature and manganese oxide loading were first evaluated to identify the catalyst with the highest activity. Under the selected conditions, MBC900(1:20) achieved 88% KTP degradation within 10 min, which was 34% higher than the combined removal obtained from ozonation alone and adsorption. Characterization results showed that manganese oxide was mainly present in an amorphous form and was well distributed on the biochar surface and within its pores. Manganese modification also altered the pore structure and introduced Mn–O sites, while Mn³⁺ and Mn⁴⁺ were the dominant manganese species. KTP degradation was influenced by catalyst dosage, O₃ concentration, initial KTP concentration, pH, temperature, and coexisting water constituents. Radical quenching experiments and EPR measurements showed that ^•OH was the major reactive species responsible for KTP oxidation, with ¹O₂ also contributing to the reaction. The catalytic system achieved 44% TOC removal, compared with 27% for ozonation alone. Transformation-product analysis suggested that KTP degradation mainly proceeded through hydroxylation and oxidation involving the carboxyl group and aromatic rings. These results demonstrate that manganese oxide-modified biochar can effectively promote O₃ activation and KTP degradation in water.

Nanotechnology provides effective solutions for wastewater remediation. This study synthesized iron oxide (Fe₃O₄) and chitosan-coated Fe₃O₄ nanoparticles via co-precipitation to remove heavy metals from the Lower Bari Doab Canal, Pakistan, contaminated by industrial and agricultural effluents. The characterization of chitosan coated iron oxide nanoparticles was performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS). FTIR analyses confirm the presence of Fe–O group as well as C-H stretching band, C-N bending vibration and C-O band correspond to chitosan which verify the chitosan coating. XRD analysis revealed the characteristics peaks for magnetite formation and chitosan functionalization. The average crystallite size of chitosan coated Fe₃O₄ NP calculated is 13.1 nm. SEM micrographs illustrated the morphology of NPs. Batch adsorption experiments evaluated the removal of Co²⁺, Cr³⁺, Cu²⁺, and Pb²⁺ under varying operational conditions. Chitosan-coated Fe₃O₄ nanoparticles exhibited significantly higher adsorption capacities than uncoated particles, following Freundlich isotherms and the adsorption of heavy metal was better described by the pseudo-first-order-model as the calculated qe values were closer to the experimental qe values than those of the pseudo-second order model. Pb²⁺ showed the removal efficiency (62% at pH 6) in the pH experiment and the highest removal efficiency of 78% at pH 7 in the dosage experiment when the dosage concentration was 1 g of CFe₃O₄. The removal percentage of heavy metals follows the order Pb²⁺ > Cr³⁺ > Cu²⁺ > Co²⁺ when the dosage concentration is varied and with the increase in dosage the removal percentage also get increased; moreover, the removal efficiency of heavy metals increased by increasing the agitation speed which is varied (100,150,200 and 250RPM). Overall, chitosan-coated Fe₃O₄ nanoparticles demonstrate strong potential as efficient, magnetically retrievable adsorbents for heavy-metal-contaminated wastewater.

Driven by the global demand for public health security, ultraviolet C light-emitting diode (UVC-LED) disinfection technology has emerged as a promising mercury-free alternative to conventional methods. Adopting a wavelength-based comparative framework, this review systematically synthesizes the disinfection characteristics of four mainstream UVC-LED wavelength bands (233 nm, 254 nm, 260–270 nm, and 270–280 nm), facilitating direct cross-band comparison of inactivation mechanisms, biosafety profiles, and practical applicability. Each band presents distinct trade-offs shaped by wavelength-dependent optical properties: 233 nm far-UVC offers favorable tissue safety via stratum corneum protein absorption but is significantly attenuated by organic loads; 254 nm, constrained by low external quantum efficiency (EQE), remains the least studied; 260–270 nm, overlapping with the nucleic acid absorption peak and lying within a relatively transparent spectral window in absorptive media, generally achieves the highest broad-spectrum inactivation efficiency; and 270–280 nm, the most mature in fabrication, delivers strong protein damage and irreversible DNA lesions with superior energy efficiency. Microbial sensitivity follows a pattern modulated by genomic and strain-level factors, while environmental matrices and carrier properties substantially attenuate disinfection efficacy, though process-assisted strategies can partially mitigate these effects. Despite progress toward municipal-scale deployment, wall-plug efficiency (WPE) remains substantially below that of conventional mercury lamps, and the feasibility of scenario-based wavelength selection is constrained by considerable heterogeneity in experimental parameters across studies. By critically examining these challenges and limitations, this review aims to provide a reference for the further development and broader application of UVC-LED disinfection technology.

Diclofenac sodium (DCF), as a frequently detected pharmaceutical and personal care products (PPCPs), is difficult to remove effectively using conventional water treatment processes and therefore requires efficient and stable treatment strategies. In this study, two ZnIn₂S₄-based bismuth heterojunction photocatalysts, ZnIn₂S₄/BiOBr (B–Z) and ZnIn₂S₄/Bi₂O₂S (S–Z), were constructed via a facile hydrothermal method for visible-light-driven DCF degradation. The morphology, crystal structure, surface chemical states, optical absorption, and photoelectrochemical properties of both catalysts were characterized by XRD, SEM, XPS, UV–vis DRS, transient photocurrent response, and electrochemical impedance spectroscopy. The results demonstrated intimate interfacial coupling, enhanced visible-light absorption, and accelerated photogenerated charge separation in both heterojunction systems. Photocatalytic experiments were performed using DCF as the target pollutant, the effects of component ratio, catalyst dosage, initial DCF concentration, and solution pH on photocatalytic performance were comprehensively evaluated. The optimized B–Z and S–Z heterojunctions, with BiOBr/ZnIn₂S₄ and Bi₂O₂S/ZnIn₂S₄ molar ratios of 5:1 and 7:1 individually, exhibited superior visible-light photocatalytic activity, removing 92.73% and 92.24% of DCF within 180 min at a catalyst dosage of 20 mg. Under a catalyst loading of 80 mg, an initial DCF concentration of 50 mg/L, and intrinsic solution pH, the DCF removal efficiencies further increased to 98.90% and 94.60%, respectively. Cycling experiments indicated good stability and reusability of both heterojunction photocatalysts. Radical trapping and high-resolution mass spectrometry analyses revealed that DCF degradation mainly proceeded through hole (h⁺)-dominated primary oxidation, followed by superoxide-radical (·O₂⁻)-assisted transformation and deep conversion of intermediate. This study provides an effective strategy for constructing visible-light-responsive ZnIn₂S₄-based heterojunction photocatalysts for highlight their potential for the treatment of PPCP-contaminated wastewater.