Piezoelectric materials and techniques for environmental pollution remediation

Natural marmatite photocatalyst for treatment of mineral processing wastewater to help zero wastewater discharge

Mineral processing wastewater (MPW) with large discharge and high toxicity affects environmental safety, and the realizing zero discharge of MPW is of great significance for reducing environmental pollution, saving water resources, and promoting the sustainable development of the mining industry. In this study, we reported natural marmatite (NM) as a low-cost and efficient photocatalyst for the treatment of MPW to help zero wastewater discharge. The photocatalytic activity of NM was evaluated by the removal of total organic carbon (TOC) from MPW under visible-light illumination, and the optimal degradation conditions were discussed. Results showed that superoxide free radicals (·O2-) were the dominant active species responsible for organic pollutants degradation, and 74.25% TOC removal was obtained after 120 min reaction under the optimum treatment conditions. Meanwhile, the wastewater treated by NM photocatalysis can be reused in the flotation system without adverse impact on the product index. Based on these findings, a model of zero wastewater discharge for flotation with the help of photocatalytic treatment was established, it indicated that the water of the whole system can be balanced without affecting the ore dressing index, which showed that visible light-driven photocatalyst has a promising application prospect in the treatment and recycling of industrial wastewater.

Piezoelectric catalytic driven advanced oxidation process using two-dimensional metal dichalcogenides for wastewater pollutants remediation

The public and society have increasingly recognized numerous grave environmental issues, including water pollution, attributed to the rapid expansion of industrialization and agriculture. Renewable energy-driven catalytic advanced oxidation processes (AOPs) represent a green, sustainable, and environmentally friendly approach to meet the demands of environmental remediation. In this context, 2D transition metal dichalcogenides (TMDCs) piezoelectric materials, with their non-centrosymmetric crystal structure, exhibit unique features. They create dipole polarization, inducing a built-in electric field that generates polarized holes and electrons and triggers redox reactions, thereby facilitating the generation of reactive oxygen species for wastewater pollutant remediation. A broad spectrum of 2D TMDCs piezoelectric materials have been explored in self-integrated Fenton-like processes and persulfate activation processes. These materials offer a more simplistic and practical method than traditional approaches. Consequently, this review highlights recent advancements in 2D TMDCs piezoelectric catalysts and their roles in wastewater pollutant remediation through piezocatalytic-driven AOPs, such as Fenton-like processes and sulfate radicals-based oxidation processes.

Dipole Moment and Built-In Polarization Electric Field Induced by Oxygen Vacancies in BiOX for Boosting Piezoelectric-Photocatalytic Removal of Uranium(VI)

Piezoelectric-photocatalysis is distinguished by its piezoelectricity as an external force that induces deformation within the catalyst to engender a polarized electric field compared to conventional photocatalysis. Herein, the piezoelectric photocatalyst BiOBr has been expertly synthesized via a plasma process and applied for piezoelectric-photocatalysis removal of uranium(VI) for the first time. The abundant surface oxygen vacancies (OVs) could induce a dipole moment and built-in electric field, which endows BiOBr with excellent separation and transport efficiency of photogenerated charges to actuate more charges to participate in the piezoelectric-photocatalytic reduction process. Consequently, under visible light and ultrasound (150 W and 40 kHz), the removal rate constant of OVs-BiOBr-30 (0.0306 min-1) was 2.4, 30.6, and 6 times higher than those of BiOBr (0.01273 min-1), ultrasound, or photocatalysis, respectively. The piezoelectric-photocatalytic synergy is also universal for BiOX (X = Cl, Br, or I) to accelerate the reduction rate of uranium(VI). This work highlights the role of piezoelectric-photocatalysis in the treatment of uranium-containing wastewater, which is of great significance for resource conservation and environmental remediation.

Effect of montmorillonite modified straw biochar on transfer behavior of lead and copper in the historical mining areas of dry-hot valleys

Due to the rapid development of human beings, heavy metals are occurred in the Yunnan-Guizhou Plateau and Panxi Plateau, the special dry and hot climate areas. Pb and Cu can be quickly transferred through water-plant-animal, further harm to human health by food chain. Therefore, the study of heavy metal treatment is imminent. In this study, Biochar-montmorillonite composites were prepared by co-pyrolysis and characterized, and their ability to remove lead and copper from water-soil process were tracked. And their effectiveness in remediating soil contaminated by lead and copper was documented. The composite material has the rich pore structure, large specific surface area (81.5 m2/g) and a variety of surface functional groups such as C-C, CO, ester-metal and metal-oxygen bonds. Pb and Cu can be effectively adsorbed and fixed to the level of no harm to human health. The adsorption reaction of lead and copper on the Biochar-montmorillonite composites is more suitable to be described by Langmuir adsorption and pseudo-second-order kinetics models. The saturation adsorption capacity of the composite for Pb was measured as 212.5 mg/g. For Cu, it was 136.5 mg/g. The data were fitted by a two-compartment first-order kinetic model. ffast for Pb and Cu is estimated to be 0.81 and 0.78, respective. Fast adsorption is dominant and belongs to typical chemical adsorption, which is consistent with the second-order kinetic results. With 5 % of the composite, approximately 80 % of exchangeable heavy metals in those soils collected from the Yunnan-Guizhou Plateau and Panxi Plateau were reduced. The biochar-montmorillonite composites made Pb and Cu change to stable residual state, up to 35 %. Besides, it effectively restored the activity of urease and sucrase in soils. Results indicated that biochar-montmorillonite composites can be effectively used as an environment-friendly adsorbent or passivator to purify heavy metals in soils.

Pioneering Piezoelectric-Driven Atomic Hydrogen for Efficient Dehalogenation of Halogenated Organic Pollutants

The electrocatalytic hydrodehalogenation (EHDH) process mediated by atomic hydrogen (H*) is recognized as an efficient method for degrading halogenated organic pollutants (HOPs). However, a significant challenge is the excessive energy consumption resulting from the recombination of H* to H2 production in the EHDH process. In this study, a promising strategy was proposed to generate piezo-induced atomic H*, without external energy input or chemical consumption, for the degradation and dehalogenation of HOPs. Specifically, sub-5 nm Ni nanoparticles were subtly dotted on an N-doped carbon layer coating on BaTiO3 cube, and the resulted hybrid nanocomposite (Ni-NC@BTO) can effectively break C-X (X = Cl and F) bonds under ultrasonic vibration or mechanical stirring, demonstrating high piezoelectric driven dehalogenation efficiencies toward various HOPs. Mechanistic studies revealed that the dotted Ni nanoparticles can efficiently capture H* to form Ni-H* (Habs) and drive the dehalogenation process to lower the toxicity of intermediates. COMSOL simulations confirmed a "chimney effect" on the interface of Ni nanoparticle, which facilitated the accumulation of H+ and enhanced electron transfer for H* formation by improving the surface charge of the piezocatalyst and strengthening the interfacial electric field. Our work introduces an environmentally friendly dehalogenation method for HOPs using the piezoelectric process independent of the external energy input and chemical consumption.

A comprehensive review on the application of semiconducting materials in the degradation of effluents and water splitting

In this comprehensive review article, we delve into the critical intersection of environmental science and materials science. The introduction sets the stage by emphasizing the global water shortage crisis and the dire consequences of untreated effluents on ecosystems and human health. As we progress into the second section, we embark on an intricate exploration of piezoelectric and photocatalytic principles, illuminating their significance in wastewater treatment and sustainable energy production. The heart of our review is dedicated to a detailed analysis of the detrimental impacts of effluents on human health, underscoring the urgency of effective treatment methods. We dissected three key materials in the realm of piezo-photocatalysis: ZnO-based materials, BaTiO3-based materials, and bismuth-doped materials. Each material is scrutinized for its unique properties and applications in the removal of pollutants from wastewater, offering a comprehensive understanding of their potential to address this critical issue. Furthermore, our exploration extends to the realm of hydrogen production, where we discuss various types of hydrogen and the role of piezo-photocatalysis in generating clean and sustainable hydrogen. By illuminating the synergistic potential of these advanced materials and technologies, we pave the way for innovative solutions to the pressing challenges of water pollution and renewable energy production. This review article not only serves as a valuable resource for researchers and scholars in the fields of material science and environmental engineering but also underscores the pivotal role of interdisciplinary approaches in addressing complex global issues.

Advances in Nanohybrid Membranes for Dye Reduction: A Comprehensive Review

Separating valuable materials such as dyes from wastewater using membranes and returning them to the production line is a desirable environmental and economical procedure. However, sometimes, besides filtration, adsorption, and separation processes, pollutant destruction also can be suitable using photocatalytic membranes. The art of producing nanohybrid materials in contrast with nanocomposites encompasses nanomaterial synthesis as a new product with different properties from raw materials for nanohybrids versus the composition of nanomaterials for nanocomposites. According to the findings of this research, confirming proper synthesis of nanohybrid is one challenge that can be overcome by different analyses, other researchers' reports, and the theoretical assessment of physical or chemical reactions. The application of organic-inorganic nanomaterials and frameworks is another challenge that is discussed in the present work. According to the findings, Nanohybrid Membranes (NHMs) can achieve 100% decolorization, but cannot eliminate salts and dyes, although the removal efficiency is notable for some salts, especially divalent salts. Hydrophilicity, antifouling properties, flux, pressure, costs, usage frequency, and mechanical, chemical, and thermal stabilities of NHMs should be considered.

Efficient decontamination of organic pollutants from wastewater by covalent organic framework-based materials

Covalent organic frameworks (COFs), assembling through covalent bonds, are a rising class of porous materials. Nowadays, various COFs are widely applied in organic pollutants decontamination due to the outstanding capabilities of large surface area, multiple functional groups, porous structure, excellent absorptivity, flexible design and so on. This review concentrates on the applications of COFs in different decontamination technologies such as solid-phase extraction, membrane filtration and sieving, adsorption, and catalysis reaction. The factors influencing water chemistry, such as pH, temperature, salt concentration and natural organic matter, are summarized in terms of their impact on decontamination performance and the extraction mechanisms for the diverse analytes. The interaction mechanisms between COFs and organic pollutants were hydrogen bonding, π-π stacking, hydrophilic, hydrophobic, and electrostatic interactions. Furthermore, a perspective on current obstacles and upcoming developments of COFs for organic pollutant removal has been provided. Due to their adaptable and versatile design as well as elaborate and diverse functionalization, COFs possess significant possibility in ameliorating environmental pollution.

Flexible Composites for Piezocatalysis

Despite piezoelectric materials have a long history of application, piezoelectric catalysis has continued to be a hot topic in recent years. Flexible piezoelectric materials have just emerged in recent years due to their versatility and designability. In this paper, we review the recent advances in flexible piezoelectric materials for catalysis, discuss the fundamentals of the catalytic properties of composite materials, and detail the typical structures of these materials. We pay special attention to the types of filler in flexible piezoelectric composites, their role and the interaction between the particles and the flexible substrate. Notable examples of flexible piezoelectric materials for organic pollutants degradation, enhanced piezo-photocatalysis and antibacterial applications are also presented. Finally, we present key issues and future prospects for the development of flexible piezoelectric catalysts.

Enhanced biodegradation of endocrine disruptor bisphenol A by food waste composting without bioaugmentation: Analysis of bacterial communities and their relative abundances

Composting with food waste was assessed for its efficacy in decontaminating Bisphenol A (BPA). In a BPA-treated compost pile, the initial concentration of BPA 847 mg kg-1 fell to 6.3 mg kg-1 (99% reduction) over a 45-day composting period. The biodegradation rate was at its highest when bacterial activity peaked in the mesophilic and thermophilic phases. The average rate of total biodegradation was 18.68 mg kg-1 day-1. Standard methods were used to assess physicochemical parameters of the compost matrix and gas chromatography combined with mass spectrometry (GC/MS) was used to identify BPA intermediates. Next-generation sequencing (NGS) was used to detect BPA degraders and the diverse bacterial communities involved in BPA decomposition. These communities were found consist of 12 phyla and 21 genera during the composting process and were most diversified during the maturation phase. Three dominant phyla, Firmicutes, Pseudomonadota, and Bacteroidetes, along with Lactobacillus, Proteus, Bacillus, and Pseudomonas were found to be the most responsible for BPA degradation. Different bacterial communities were found to be involved in the food waste compost biodegradation of BPA at different stages of the composting process. In conclusion, food waste composting can effectively remove BPA, resulting in a safe product. These findings might be used to expand bioremediation technologies to apply to a wide range of pollutants.

In-situ synthesized 2D MXene/TiO2/Fe hybrid with (001)-(101) surface heterojunction for degradation of tetracycline under visible light

Tetracycline (TC) as a common antibiotic has adverse effects on human healthy and biological survival. In this study, a novel MXene/TiO2/Fe hybrid was designed and successfully synthesized by combination method of calcination and hydrothermal reduction. The photocatalysts were characterized by PXRD, SEM, TEM, VSM and XPS, etc. It was found that MXene/TiO2/Fe exhibited 2D multilayer structure like MXene. The in-situ synthesized TiO2 through calcinating MXene exhibited an octahedral biconical structure with exposed (001) and (101) facets. Surface heterojunction of (001) and (101) facets was formed within TiO2, which enhanced the separation of photogenerated electrons and holes. The residual MXene could play a role in co-catalyst to capture the photo-generated electrons from TiO2. Moreover, Fe nanoparticles not only optimize the band gap structure and increase the specific surface area, but also store the electrons as a good electrons acceptor, which further promote the separation of electrons and holes. The TC removal efficiency of optimal MXene/TiO2/Fe could reach 92% within 120 min. Moreover, the influence of external environment factors such as pH, catalyst dosages and common anions were investigated in detail. Mechanism analysis show that h+, •OH and •O2- are the main active substances. Finally, the degradation pathways were proposed according to LC-MS.

Recent progress on plant extract-mediated biosynthesis of ZnO-based nanocatalysts for environmental remediation: Challenges and future outlooks

The plant extract mediated green synthesis of nanomaterials has attracts enormous interest due to its cost-effectiveness, greener, and environmentally friendly. It is also considered as an alternative and facile method in which the phytochemicals can be used as a natural capping and reducing agents and helped to produce nanomaterials with high surface area, different sizes, and shapes. One of the materials fabricated using green methods is zinc oxide (ZnO) semiconductor due to its enormous applications in different field areas. In this review, an overview of recent progress on green synthesized ZnO-based catalysts and various modification methods for the purpose of enhancing the catalytic activity of ZnO and the corresponding structural-activity and interactions towards the removal of pollutants are highlighted. Particularly, the plant extract mediated ZnO-based photocatalysts application for the removal of pollutants via photocatalytic degradation, reduction reaction, and adsorption mechanism are demonstrated. Besides, the opportunities, challenges, and future outlooks of ZnO-based materials for environmental remediation with green and sustainable methods are also included. We believe that this review is a timely and comprehensive review on the recent progress related to plant extract mediated ZnO-based nanocatalysts synthesis and applications for environmental remediation.

Intrinsically morphological effect of perovskite BaTiO3 boosting piezocatalytic uranium extraction efficiency and mechanism investigation

Developing a convenient, efficient and eco-friendly approach for the recovery of U(VI) ion is a key measure to solve the environmental problems arising from the utilization of nuclear energy. Herein, the high efficiency of uranium extraction is realized by the piezo property of perovskite BaTiO₃, revealing the intrinsically morphological engineering effect on the piezocatalytic performance. Especially, BaTiO₃ nanowires (BTO NWs) exhibit not only an excellent piezocatalytic activity with U(VI) extraction rate of 96.8% in a UO₂(NO₃)₂ aqueous solution compared to 71.3% of BaTiO₃ nanoparticles (BTO NPs), but also a promising piezocatalyst for U extraction in a real U-mining wastewater with various pH ranges. Piezo response force microscopy and finite elemental simulation show that the piezo response of BTO NWs is much higher than BTO NPs. Additionally, some factors (pH, various ions, different powers) are explored on piezocatalytic efficiency for U(VI) extraction. The results from electron spin resonance and the charge/radical capture experiments confirm that the active species (e^-, •O^2-, •OH) stemmed from the piezo induction of BTO NWs and BTO NPs in the piezocatalytic U(VI) reduction process. The present work reveals the structure-performance correlation during piezocatalysis and highlights the crucial role of piezocatalysis in dealing with environmental problems.

High efficiency and rapid treatment of naproxen sodium wastewater by dielectric barrier discharge coupled with catalysis

Pharmaceutical wastewater has the characteristics of high organic concentration and poor biodegradability, which will cause serious environmental pollution when discharged into water bodies. In this work, naproxen sodium was used to simulate pharmaceutical wastewater by dielectric barrier discharge technology. The effects of dielectric barrier discharge (DBD) and combined catalysis on the removal of naproxen sodium solution were studied. The removal effect of naproxen sodium was affected by discharge conditions, including discharge voltage, frequency, air flow rate and electrode materials. It was found that the highest removal rate of naproxen sodium solution was 98.5%, when the discharge voltage was 7000 V, the frequency was 3333 Hz, and the air flow rate was 0.3 m³/h. In addition, the effect of the initial conditions of naproxen sodium solution was studied. The removal of naproxen sodium was relatively effective at low initial concentrations as well as under the condition of weak acid or near-neutral solution. However, the initial conductivity of naproxen sodium solution had little effect on the removal rate. The removal effect of naproxen sodium solution was compared by using catalyst combined with DBD plasma and DBD plasma alone. x%La/Al₂O₃, Mn/Al₂O₃ and Co/Al₂O₃ catalysts were added. The removal rate of naproxen sodium solution reached the highest after adding 14%La/Al₂O₃ catalyst, which played the best synergistic effect. The removal rate of naproxen sodium was 18.4% higher than that without catalyst. The results showed that the combination of DBD and La/Al₂O₃ catalyst may be a promising method to remove naproxen sodium efficiently and quickly. And this method is a new attempt to treat naproxen sodium.

Progresses in lignin, cellulose, starch, chitosan, chitin, alginate, and gum/carbon nanotube (nano)composites for environmental applications: A review

Water sources are becoming increasingly scarce, and they are contaminated by industrial, residential, and agricultural waste-derived organic and inorganic contaminants. These contaminants may pollute the air, water, and soil in addition to invading the ecosystem. Because carbon nanotubes (CNTs) can undergo surface modification, they can combine with other substances to create nanocomposites (NCs), including biopolymers, metal nanoparticles, proteins, and metal oxides. Furthermore, biopolymers are significant classes of organic materials that are widely used for various applications. They have drawn attention due to their benefits such as environmental friendliness, availability, biocompatibility, safety, etc. As a result, the synthesis of a composite made of CNT and biopolymers can be very effective for a variety of applications, especially those involving the environment. In this review, we reported environmental applications (including removal of dyes, nitro compounds, hazardous materialsو toxic ions, etc.) of composites made of CNT and biopolymers such as lignin, cellulose, starch, chitosan, chitin, alginate, and gum. Also, the effect of different factors such as the medium pH, the pollutant concentration, temperature, and contact time on the adsorption capacity (AC) and the catalytic activity of the composite in the reduction or degradation of various pollutants has been systematically explained.

Application of covalent organic frameworks and metal–organic frameworks nanomaterials in organic/inorganic pollutants removal from solutions through sorption-catalysis strategies

With the fast development of agriculture, industrialization and urbanization, large amounts of different (in)organic pollutants are inevitably discharged into the ecosystems. The efficient decontamination of the (in)organic contaminants is crucial to human health and ecosystem pollution remediation. Covalent organic frameworks (COFs) and metal–organic frameworks (MOFs) have attracted multidisciplinary research interests because of their outstanding physicochemical properties like high stability, large surface areas, high sorption capacity or catalytic activity. In this review, we summarized the recent works about the elimination/extraction of organic pollutants, heavy metal ions, and radionuclides by MOFs and COFs nanomaterials through the sorption-catalytic degradation for organic chemicals and sorption-catalytic reduction-precipitation-extraction for metals or radionuclides. The interactions between the (in)organic pollutants and COFs/MOFs nanomaterials at the molecular level were discussed from the density functional theory calculation and spectroscopy analysis. The sorption of organic chemicals was mainly dominated by electrostatic attraction, π-π interaction, surface complexation and H-bonding interaction, whereas the sorption of radionuclides and metal ions was mainly attributed to surface complexation, ion exchange, reduction and incorporation reactions. The porous structures, surface functional groups, and active sites were important for the sorption ability and selectivity. The doping or co-doping of metal/nonmetal, or the incorporation with other materials could change the visible light harvest and the generation/separation of electrons/holes (e−/h+) pairs, thereby enhanced the photocatalytic activity. The challenges for the possible application of COFs/MOFs nanomaterials in the elimination of pollutants from water were described in the end.