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This review explores the expanding role of electrochemical sensors across diverse domains such as environmental monitoring, medical diagnostics, and food quality assurance. In recent years, iron-based electrocatalysts have emerged as promising candidates for enhancing sensor performance. Notable for their non-toxicity, abundance, catalytic activity, and cost-effectiveness, these materials offer significant advantages. However, further investigation is needed to fully understand how iron-based materials' physical, chemical, and electrical properties influence their catalytic performance in sensor applications. It explores the overview of electrochemical sensor technology, examines the impact of iron-based materials and their characteristics on catalytic activity, and investigates various iron-based materials, their advantages, functionalization, and modification techniques. Additionally, the review investigates the application of iron-based electrode material composites in electrochemical sensors for real sample detections. Ultimately, continued research and development in this area promise to unlock new avenues for using iron-based electrode materials in sensor applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The expanding global population and the use of conventional agrochemical pesticides have led to the loss of crop yield and food shortages. Excessive pesticide used in agriculture risks life forms by contaminating soil and water resources, necessitating the use of nano agrochemicals. This article focuses on synthesis moiety and use of nanopesticides for enhanced stability, controlled release mechanisms, improved efficacy, and reduced pesticide residue levels. The current literature survey offered regulatory frameworks for commercial deployment of nanopesticides and evaluated societal and environmental impacts. Various physicochemical and biological processes, especially microorganisms and advanced oxidation techniques are important in treating pesticide residues through degradation mechanisms. Agricultural waste could be converted into nanofibers for sustainable composites production, new nanocatalysts, such as N-doped TiO 2 and bimetallic nanoparticles for advancing pesticide degradation. Microbial and enzyme methods have been listed as emerging nanobiotechnology tools in achieving a significant reduction of chlorpyrifos and dimethomorph for the management of pesticide residues in agriculture. Moreover, cutting-edge biotechnological alternatives to conventional pesticides are advocated for promoting a transition towards more sustainable pest control methodologies. Application of nanopesticides could be critical in addressing environmental concern due to its increased mobility, prolonged persistence and ecosystem toxicity. Green synthesis of nanopesticides offers solutions to environmental risks associated and using genetic engineering techniques may induce pest and disease resistance for agricultural sustainability. Production of nanopesticides from biological sources is necessary to develop and implement comprehensive strategies to uphold agricultural productivity while safeguarding environmental integrity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Activated carbon (AC) based adsorbents derived from waste sludge were utilized to remediate mixed contaminants in wastewater as an integrated waste-to-resource approach promoting a paradigm shift in management of refuse sludge and wastewater. This review specifically focuses on the remediation of constituents of landfill leachate by sludge-based activated carbon (SBAC). The adsorption effectiveness of SBAC for the exclusion of leachate characters including heavy metals, phenols, dyes, phosphates, and phosphorus were explored with regard to modifiers such as pH, temperature, properties of the adsorbent including functional groups, initial doses of absorbent and adsorbate, and duration of exposure to note the impact of each parameter on the efficiency of adsorption of the sludge adsorbent. Through the works of various researchers, it was noted that the properties of the adsorbent, pH and temperature impact the working of SBACs. The pH of the adsorbent by influencing the functional groups. Temperature was expected to have a paramount effect on the adsorption efficiency of the SBACs. The importance of the regeneration and recycling of the adsorbents as well as their leachability is highlighted. Sludge based activated carbon is recommended as a timely, resource-efficient, and sustainable approach for the remediation of wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The management of plastic waste (PW) has become an indispensable worldwide issue because of the enhanced accumulation and environmental impacts of these waste materials. Thermo-catalytic pyrolysis has been proposed as an emerging technology for the valorization of PW into value-added liquid fuels. This review provides a comprehensive investigation of the latest advances in thermo-catalytic pyrolysis of PW for liquid fuel generation, by emphasizing polyethylene, polypropylene, and polystyrene. To this end, the current strategies of PW management are summarized. The various parameters affecting the thermal pyrolysis of PW (e.g., temperature, residence time, heating rate, pyrolysis medium, and plastic type) are discussed, highlighting their significant influence on feed reactivity, product yield, and carbon number distribution of the pyrolysis process. Optimizing these parameters in the pyrolysis process can ensure highly efficient energy recovery from PW. In comparison with non-catalytic PW pyrolysis, catalytic pyrolysis of PW is considered by discussing mechanisms, reaction pathways, and the performance of various catalysts. It is established that the introduction of either acid or base catalysts shifts PW pyrolysis from the conventional free radical mechanism towards the carbonium ion mechanism, altering its kinetics and pathways. This review also provides an overview of PW pyrolysis practicality for scaling up by describing techno-economic challenges and opportunities, environmental considerations, and presenting future outlooks in this field. Overall, via investigation of the recent research findings, this paper offers valuable insights into the potential of thermo-catalytic pyrolysis as an emerging strategy for PW management and the production of liquid fuels, while also highlighting avenues for further exploration and development., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Owing to the ever-increasing generation of plastic waste, the need to develop environmentally friendly disposal methods has increased. This study explored the potential of waste plastic straw to generate valuable light olefins and monocyclic aromatic hydrocarbons (MAHs) via catalytic pyrolysis using high-silica zeolite-based catalysts. HZSM-5 (SiO 2 /Al 2 O 3 :200) exhibited superior performance, yielding more light olefins (49.8 wt%) and a higher MAH content than Hbeta (300). This was attributed to the increased acidity and proper shape selectivity. HZSM-5 displayed better coking resistance (0.7 wt%) than Hbeta (4.4 wt%) by impeding secondary reactions, limiting coke precursor formation. The use of HZSM-5 (80) resulted in higher MAHs and lower light olefins than HZSM-5 (200) because of its higher acidity. Incorporation of Co into HZSM-5 (200) marginally lowered light olefin yield (to 44.0 wt%) while notably enhancing MAH production and boosting propene selectivity within the olefin composition. These observations are attributed to the well-balanced coexistence of Lewis and Brønsted acid sites, which stimulated the carbonium ion mechanism and induced H-transfer, cyclization, Diels-alder, and dehydrogenation reactions. The catalytic pyrolysis of plastic straw over high-silica and metal-loaded HZSM-5 catalysts has been suggested as an efficient and sustainable method for transforming plastic waste materials into valuable light olefins and MAHs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Using bone char for contaminated wastewater treatment and soil remediation is an intriguing approach to environmental management and an environmentally friendly way of recycling waste. The bone char remediation strategy for heavy metal-polluted wastewater was primarily affected by bone char characteristics, factors of solution, and heavy metal (HM) chemistry. Therefore, the optimal parameters of HM sorption by bone char depend on the research being performed. Regarding enhancing HM immobilization by bone char, a generic strategy for determining optimal parameters and predicting outcomes is crucial. The primary objective of this research was to employ artificial neural network (ANN) technology to determine the optimal parameters via sensitivity analysis and to predict objective function through simulation. Sensitivity analysis found that for multi-metals sorption (Cd, Ni, and Zn), the order of significance for pyrolysis parameters was reaction temperature > heating rate > residence time. The primary variables for single metal sorption were solution pH, HM concentration, and pyrolysis temperature. Regarding binary sorption, the incubation parameters were evaluated in the following order: HM concentrations > solution pH > bone char mass > incubation duration. This approach can be used for further experiment design and improve the immobilization of HM by bone char for water remediation., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflicts of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Bisphenols (BPs) are recognized as emerging contaminants because of their estrogenic properties and frequent occurrence in environmental matrices. Here, we evaluated the toxic effects of five common BPs on freshwater microalga Chlamydomonas mexicana and removal of the BPs by the alga. Bisphenols -AF (BPAF), -B (BPB), and -Z (BPZ) (96 h, EC 50 1.78-12.09 mg·L -1 ) exhibited higher toxicity to C. mexicana compared to bisphenol -S (BPS) and -F (BPF) (96 h, EC 50 30.53-85.48 mg·L -1 ). In contrast, the mixture of BPs exhibited acute toxicity (96 h, EC 50 8.07 mg·L -1 ). After 14 days, C. mexicana had effectively removed 61%, 99%, 55%, 87%, and 89% of BPS, BPF, BPAF, BPB, and BPZ, respectively, at 1 mg L -1 . The biotransformed products of all five BPs were analyzed using UHPLC QTOF, and their toxicity was predicted. All biotransformed products were observed to be less toxic than the parent compounds. The fatty acid composition of C. mexicana after exposure to the BP mixture was predominantly palmitic acid (34.14%), followed by oleic acid (18.9%), and γ-linolenic acid (10.79%). The results provide crucial information on the ecotoxicity of these five BPs and their removal by C. mexicana; the resulting biomass is a potential feedstock for producing biodiesel., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Crop residues are representative agricultural waste materials, massively generated in the world. However, a large fraction of them is currently being wasted, though they have a high potential to be used as a value-added carbon-rich material. Also, the applications of carbon-rich materials from agricultural waste to industries can have economic benefit because waste-derived carbon materials are considered inexpensive waste materials. In this review, valorization methods for crop residues as carbon-rich materials (i.e., biochars) and their applications to industrial toxic gas removals are discussed. Applications of crop residue biochars to toxic gas removal can have significant environmental benefits and economic feasibility. As such, this review discussed the technical advantages of the use of crop residue biochars as adsorbents for hazardous gaseous pollutants and greenhouse gases (GHGs) stemmed from combustion of fossil fuels and the different refinery processes. Also, the practical benefits from the activation methods in line with the biochar properties were comprehensively discussed. The relationships between the physico-chemical properties of biochars and the removal mechanisms of gaseous pollutants (H 2 S, SO 2 , Hg 0 , and CO 2 ) on biochars were also highlighted in this review study. Porosity controls using physical and chemical activations along with the addition of specific functional groups and metals on biochars have significantly contributed to the enhancement of flue gas adsorption. The adsorption capacity of biochar for each toxic chemical was in the range of 46-76 mg g -1 for H 2 S, 40-182 mg g -1 for SO 2 , 80-952 μg g -1 for Hg 0 , and 82-308 mg g -1 CO 2 , respectively. This helps to find suitable activation methods for adsorption of the target pollutants. In the last part, the benefits from the use of biochars and the research directions were prospectively provided to make crop residue biochars more practical materials in adsorption of pollutant gases., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

To remove harmful volatile organic compounds (VOCs) including 2-butanone (methyl ethyl ketone, MEK) emitted from various industrial plants is very important for the clean air. Also, it is worthwhile to recycle porous spent fluid catalytic cracking (SFCC) catalysts from various petroleum refineries in terms of reducing industrial waste and the reuse of discharged resources. Therefore, Mn and Mn-Cu added SFCC (Mn/SFCC and Mn-Cu/SFCC) catalysts were prepared to compare their catalytic efficiencies together with the SFCC catalyst in the ozonation of 2-butanone. Since the SFCC-based catalysts have a structure similar to that of zeolite Y (Y), the Mn-loaded zeolite Y catalyst (Mn/Y) was also prepared to compare its activity for the removal of 2-butanone and ozone to that of the SFCC-based ones at room temperature. Among the five catalysts of this study (Y, Mn/Y, SFCC, Mn/SFCC, and Mn-Cu/SFCC), the Mn-Cu/SFCC and Mn/SFCC catalysts showed the better catalytic decomposition activity than the others. The increased distributions of the Mn 3+ species and the O vacancy sites in Mn/SFCC and Mn-Cu/SFCC catalysts which could supply more available active sites for the 2-butanone and ozone removal would enhance the catalytic activity of them., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

In this study, nickel-loaded perovskite oxides catalysts were synthesized via the impregnation of 10%Ni on XTiO 3 (X = Ce, Sr, La, Ba, Ca, and Fe) supports and employed in the catalytic steam gasification of swine manure to produce H 2 -rich syngas for the first time. The synthesized catalysts were characterized using BET, H 2 -TPR, XRD, HR-TEM, and EDX analysis. Briefly, using perovskite supports resulted in the production of ultrafine catalyst nanoparticles with a uniform dispersion of Ni particles. According to the catalytic activity test, the gas yield showed the increment as 10% Ni/LaTiO 3 < 10% Ni/FeTiO 3 < 10% Ni/CeTiO 3 < 10% Ni/BaTiO 3 < 10% Ni/SrTiO 3 < 10% Ni/CaTiO 3 . Meanwhile, zero coke formation was achieved due to the oxygen mobility of prepared catalysts. Also, the increase in the H 2 production for the applied catalysts was in the sequence as 10% Ni/CeTiO 3 < 10% Ni/FeTiO 3 < 10% Ni/LaTiO 3 < 10% Ni/BaTiO 3 < 10% Ni/SrTiO 3 < 10% Ni/CaTiO 3 . The maximum H 2 selectivity (∼48 vol%) obtained by10% Ni/CaTiO 3 was probably due to the synergistic effect of Ni and Ti on enhancing the water-gas shift reaction, and Ca on creating the maximum oxygen mobility compared to other alkaline earth metals doped at the A place of perovskite. Overall, this study provides a suitable solution for enhanced H 2 production through steam gasification of swine manure along with suggesting the appropriate supports to prevent Ni deactivation by lowering coke formation at the same time., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Dearomatization through photocatalytic oxidation is a swiftly rising phenolic compounds removal technology that works at trifling operations requirements with a special emphasis on the generation of nontoxic products. The study aims to develop a LaVO 4 /MCM-48 nanocomposite that was prepared via a hydrothermally approach assisting the employment of an MCM-48 matrix, which was then utilized for phenol degradation processes. Various techniques including UV-Vis DRS, FTIR, PL, Raman, TEM, and BET analyses are employed to characterize the developed photocatalyst. The developed photocatalyst presented remarkable characteristics, especially increased light photon utilization, and reduced recombination rate leading to enhanced visible-light-driven photodegradation performance owing to the improved specific surface area, specific porosities, and <2 eV narrow energy bandgap. The LaVO 4 /MCM-48 nanocomposite was experienced on aqueous phenol solution having 20 mg/L concentration under visible-light exposure, demonstrating exceptional performance in photodegradation up to 99.28%, comparatively higher than pure LaVO 4 . The conducted kinetic measurements revealed good accordance with pseudo first-order. A possible reaction mechanism for photocatalytic degradation was also predicted. The as-synthesized LaVO 4 /MCM-48 nanocomposite presented excellent stability and recyclability., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Nickel-impregnated TiO 2 photocatalyst (NiTP) responding to visible light was prepared by the liquid phase plasma (LPP) method, and its photoactivity was evaluated in degrading an antibiotic (oxytetracycline, OTC). For preparing the photocatalyst, nickel was uniformly impregnated onto TiO 2 (P-25) powder, and the nickel content increased as the number of LPP reactions increased. In addition, the morphology and lattice of NiTP were observed through various instrumental analyses, and it was confirmed that NiO-type nanoparticles were impregnated in NiTP. Fundamentally, as the amount of impregnated nickel in the TiO 2 powder increased sufficiently, the band gap energy of TiO 2 decreased, and eventually, the NiTP excited by visible light was synthesized. Further, OTC had a decomposition reaction pathway in which active radicals generated in OTC photocatalytic reaction under NiTP were finally mineralized through reactions such as decarboxamidation, hydration, deamination, demethylation, and dehydroxylation. In effect, we succeeded in synthesizing a photocatalyst useable under visible light by performing only the LPP single process and developed a new advanced oxidation process (AOP) that can remove toxic antibiotics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Soil contaminated with diesel fuel is a hazard to the environment and people; therefore, it needs to be remediated. Soil washing enhanced with Tween 80 (TW80), non-toxic and non-ionic surfactant, can effectively remove diesel from contaminated soils. In this study, the effects of 0.01%, 0.1%, 0.5%, 1%, and 1.5% (v/v) [TW80] concentrations; 0%, 5%, and 15% (w/w) bentonite; and variation in pH on washing efficiency were examined in a batch test. The prepared samples were physiochemically characterized on the basis of particle size, zeta potential, cation exchange capacity (CEC), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. When the bentonite content in soil was 5% or 15%, 1.5% [TW80] solution exhibited the highest washing efficiency. The diesel removal efficiencies in soil with 0% bentonite were slightly higher than those in soils with 5% and 15% bentonite because of the increase in adsorption sites by bentonite; consequently, diesel could not be easily washed out. The extracted n-alkanes showed that the percentage of carbon number 20 was higher than that of the other even-numbered carbons in the retained washed samples analyzed by gas chromatography-mass spectrometry (GC-MS). In all the washing tests, the diesel removal efficiencies in soil with 15% bentonite and 0.1% [TW80] were lower than those in soil with 15% bentonite and water because of adsorption. The bentonite samples washed with TW80 have different morphologies, with a voluminous structure composed of the fusion of all layered structures, as supported by SEM results. Changes in the diesel content and residual TW80 content in the soil before and after washing were shown by the carbon content in the EDS results. The mechanism of the washing effect was investigated by CEC and zeta potential measurements. This study may aid in selecting appropriate conditions for improving washing efficiencies in future field applications., (Copyright © 2022 Elsevier Inc. All rights reserved.)

This research studied the catalytic pyrolysis of oil sludge (OS) over metal-loaded HZSM-5 catalysts, an eco-friendly and cost-effective technology to produce value-added aromatics such as benzene, toluene, ethylbenzene, and xylene (BTEXs). In particular, it evaluated the respective effects of the experimental parameters: the type and amount of the metal loaded, the reaction temperature, and the OS/catalyst ratio, on the BTEXs yield sequentially to achieve optimum conditions. This evaluation showed that the highest yields of the BTEXs (6.61 wt%) and other aromatics were achieved when Ni was incorporated into the HZSM-5 (Ni/HZSM-5) followed by the corresponding yields of Ga/HZSM-5 and Fe/HZSM-5, due to a better distribution of Ni on the support surface and an enhanced acidity strength of this catalyst. Further, increase in Ni loading (up to 10 wt% Ni/HZSM-5) increased the BTEXs yield to 13.48 wt%. However, the excessive Ni loading (15 wt% Ni/HZSM-5) resulted in a reduced BTEXs yield due to the blockage of the zeolite channels. Next, an increase in the reaction temperature from 500 °C to 600 °C increased the yield of the BTEXs and other aromatics. However, a further increase in the reaction temperature to 650 °C decreased slightly their yield because of the stimulating secondary reactions at high temperatures. The increase of catalyst amount (OS/catalyst of 1/3) also maximized the BTEXs yield (30.50 wt%)., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Polycyclic aromatic hydrocarbons (PAHs) are known as a hazardous group of pollutants in the soil which causes many challenges to the environment. In this study, the potential of biochar (BC), as a carbonaceous material, is evaluated for the immobilization of PAHs in soils. For this purpose, various bonding mechanisms of BC and PAHs, and the strength of bonds are firstly described. Also, the effect of impressive criteria including BC physicochemical properties (such as surface area, porosity, particle size, polarity, aromaticity, functional group, etc., which are mostly the function of pyrolysis temperature), number of rings in PAHs, incubation time, and soil properties, on the extent and rate of PAHs immobilization by BC are explained. Then, the utilization of BC in collaboration with biological tools which simplifies further dissipation of PAHs in the soil is described considering detailed interactions among BC, microbes, and plants in the soil matrix. The co-effect of BC and biological remediation has been authenticated by previous studies. Moreover, recent technologies and challenges related to the application of BC in soil remediation are explained. The implementation of a combined BC-biological remediation method would provide excellent prospects for PAHs-contaminated soils., (Copyright © 2022 Elsevier Inc. All rights reserved.)

A huge amount of palm waste generated daily represents a problematic high-moisture waste to be disposed of, yet it also represents a promising biomass resource to be transformed into a value-added product. A single-mode microwave hydrothermal carbonization process incorporating steam purging was developed and utilised to convert high-moisture palm waste into hydrochar over a range of process temperatures from 150 to 300 °C. The microwave hydrothermal carbonization recorded a shorter process duration (10 min) and prevented the occurrence of hot spots within the reactor. The resulting hydrochar showed up to 94.3 wt% of mass yield, 69.2 wt% of fixed carbon, and 412.3 m 2 /g of surface area. The subsequent application of the hydrochar in de-chlorination of domestic water demonstrated an impressive removal performance of up to 98.9% of free chlorine, exhibiting 435 min of breakthrough time, and 40.0 mg/g of bed capacity in continuous column operation. The results show great promise of microwave hydrothermal carbonization as a desirable approach to produce desirable hydrochar for de-chlorination application., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Microalgae are drawing attentions among researchers for their biorefinery use or value-added products. The high production rate of biomasses produced are attractive for conversion into volatile biochar. Torrefaction, pyrolysis and hydrothermal carbonization are the recommended thermochemical conversion techniques that could produce microalgal-based biochar with desirable physiochemical properties such as high surface area and pore volume, abundant surface functional groups, as well as functionality such as high adsorption capacity. The characterizations of the biochar significantly influence the mechanisms in adsorption of pollutants from wastewaters. Specific adsorption of the organic and inorganic pollutants from the effluent are reviewed to examine the adsorption capacity and efficiency of biochar derived from different microalgae species. Last but not least, future remarks over the challenges and improvements are discussed accordingly. Overall, this review would discuss the synthesis, characterization and application of the microalgal-based biochar in wastewater., (Copyright © 2021 Elsevier Inc. All rights reserved.)

This study proposes a method to valorize hazardous waste such as used COVID-19 face mask via catalytic gasification over Ni-loaded ZSM-5 type zeolites. The 25% Ni was found as an optimal loading on ZSM-5 in terms of H 2 production. Among different zeolites (ZSM-5(30), ZSM-5(80), ZSM-5(280), mesoporous (m)-ZSM-5(30), and HY(30)), 25% Ni/m-ZSM-5(30) led to the highest H 2 selectivity (45.04 vol%), most likely because of the highest Ni dispersion on the m-ZSM-5(30) surface, high porosity, and acid site density of the m-ZSM-5(30). The content of N-containing species (e.g., caprolactum and nitriles) in the gasification product was also reduced, when steam was used as gasifying agent, which is the source of potentially hazardous air pollutants (e.g., NO x ). The increase in the SiO 2 /Al 2 O 3 ratio resulted in lower tar conversion and lower H 2 generation. At comparable conditions, steam gasification of the mask led to ~15 vol% higher H 2 selectivity than air gasification. Overall, the Ni-loaded zeolite catalyst can not only suppress the formation of hazardous substances but also enhance the production of hydrogen from the hazardous waste material such as COVID-19 mask waste., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Microwave co-pyrolysis was examined as an approach for simultaneous reduction and treatment of environmentally hazardous hospital plastic waste (HPW), lignocellulosic (palm kernel shell, PKS) and triglycerides (waste vegetable oil, WVO) biowaste as co-feedstock. The co-pyrolysis demonstrated faster heating rate (16-43 °C/min) compared to microwave pyrolysis of single feedstock (9-17 °C/min). Microwave co-pyrolysis of HPW/WVO performed at 1:1 ratio produced a higher yield (80.5 wt%) of hydrocarbon liquid fuel compared to HPW/PKS (78.2 wt%). The liquid oil possessed a low nitrogen content (< 4 wt%) and free of sulfur that could reduce the release of hazardous pollutants during its use as fuel in combustion. In particular, the liquid oil obtained from co-pyrolysis of HPW/WVO has low oxygenated compounds (< 16%) leading to reduction in generation of potentially hazardous sludge or problematic acidic tar during oil storage. Insignificant amount of benzene derivatives (< 1%) was also found in the liquid oil, indicating the desirable feature of this pyrolysis approach to suppress the formation of toxic polycyclic aromatic hydrocarbons (PAHs). Microwave co-pyrolysis of HPW/WVO improved the yield and properties of liquid oil for potential use as a cleaner fuel, whereas the liquid oil from co-pyrolysis of HPW/PKS is applicable in the synthesis of phenolic resin., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Bio-heavy oil (BHO) is a renewable fuel, but its efficient use is problematic because its combustion may emit hazardous air pollutants (e.g., polycyclic aromatic hydrocarbon (PAH) compounds, NO x , and SO x ). Herein, catalytic fast pyrolysis over HZSM-5 zeolite was applied to upgrading BHO to drop-in fuel-range hydrocarbons with reduced contents of hazardous species such as PAH compounds and N- and S-containing species (NO x and SO x precursors). The effects of HZSM-5 desilication and linear low-density polyethylene (LLDPE) addition to the feedstock on hydrocarbon production were explored. The apparent activation energy for the thermal decomposition of BHO was up to 37.5% lowered by desilicated HZSM-5 (DeHZSM-5) compared with HZSM-5. Co-pyrolyzing LLDPE with BHO increased the content of drop-in fuel-range hydrocarbons and decreased the content of PAH compounds. The DeHZSM-5 was effective in producing drop-in fuel-range hydrocarbons from a mixture of BHO and LLDPE and suppressing the formation of N- and S-containing species and PAH compounds. The DeHZSM-5 enhanced the hydrocarbon production by up to 58.5% because of its enhanced porosity and high acid site density compared to its parent HZSM-5. This study experimentally validated that BHO can be upgraded to less hazardous fuel via catalytic fast co-pyrolysis with LLDPE over DeHZSM-5., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Consumption of diverse plastics has posed an environmental threat because their disposal practices, landfilling and incineration, release toxic chemicals and microplastics into all environmental media. Indeed, heterogeneous matrix of plastic wastes makes them hard to be disposed. As such, this study aimed to introduce an environmentally benign/reliable disposal platform for complete decomposition of plastic wastes. Pyrolysis process was adapted to convert plastics into syngas, and a disposable diaper (DD) was used as model plastic waste, because it is composed of a variety of polymeric materials. Pyrolysis of DD resulted in the formation of gaseous products and pyrogenic oils, composed of (oxygenated) hydrocarbons. Nonetheless, reactivity of CO 2 as an oxidant in pyrolysis of DD was negligible. To impart the strong/desired reactivity of CO 2 , Ni-based catalyst was adopted. Ni catalyst enhanced H 2 and CO formations 4 and 15 times more than pyrolysis without catalyst at 700 °C under CO 2 . The value-added syngas production was originated from the reduction of polymeric waste, and its derivatives including aromatic compounds. Thus, CO 2 offered a strategic means to produce value-added chemicals and reduce aromaticity of pyrogenic products. The observations could offer an innovative way to control the fate of toxic chemicals derived from plastic pyrolysis., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Polychlorinated biphenyls (PCBs) are hazardous organic contaminants threatening human health and environmental safety due to their toxicity and carcinogenicity. Biochar (BC) is an eco-friendly carbonaceous material that can extensively be utilized for the remediation of PCBs-contaminated soils. In the last decade, many studies reported that BC is beneficial for soil quality enhancement and agricultural productivity based on its physicochemical characteristics. In this review, the potential of BC application in PCBs-contaminated soils is elaborated as biological strategies (e.g., bioremediation and phytoremediation) and specific mechanisms are also comprehensively demonstrated. Further, the synergy effects of BC application on PCBs-contaminated soils are discussed, in view of eco-friendly, beneficial, and productive aspects., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Recent abnormal climate changes resulted in the dramatic alternation of rainfall and flood patterns in many countries. The massive generation of flood debris, a mixture of soil (sediment), biomass, plastic, metal, and various hazardous materials, poses various environmental and public health problems. This study suggests a sustainable technical platform to convert the hazardous materials into value-added products. CO 2 -assisted pyrolysis was used to thermally convert flood debris into syngas (H 2 and CO). CO 2 enhanced the syngas production due to gas phase homogeneous reactions (HRs) between CO 2 and volatile hydrocarbons evolved from pyrolysis of flood debris. For improvement of HRs in line with enhancement of syngas production, additional thermal energy and earth abundant catalyst were used. In particular, Ni/SiO 2 catalyst increased more than one order of magnitude higher syngas production, comparing to non-catalytic pyrolysis. Synergistic effect of CO 2 and Ni catalyst showed nearly 50% more production of syngas in reference to catalytic pyrolysis under N 2 . During flood debris pyrolysis, compositional matrix of flood debris was also determined by detecting index chemicals of waste materials that cannot be identified by naked eyes. Thus, this study confirmed that CO 2 -assisted pyrolysis is a useful tool for conversion of flood debris into value-added chemicals., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this study, the role of manganese precursors in mesoporous (meso) MnOx/γ-Al 2 O 3 catalysts was examined systematically for toluene oxidation under ozone at ambient temperature (20 °C). The meso MnOx/γ-Al 2 O 3 catalysts developed with Mn(CH 3 COO) 2, MnCl 2 , Mn(NO 3 ) 2 .4H 2 O and MnSO 4 were prepared by an innovative single step solvent-deficient method (SDM); the catalysts were labeled as MnO x /Al 2 O 3 (A), MnO x /Al 2 O 3 (C), MnO x /Al 2 O 3 (N), and MnOx/Al 2 O 3 (S), respectively. Among all, MnO x /Al 2 O 3 (C) showed superior performance both in toluene removal (95%) as well as ozone decomposition (88%) followed by acetate, nitrate and sulphated precursor MnO x /Al 2 O 3 . The superior performance of MnO x /Al 2 O 3 (C) in the oxidation of toluene to CO x is associated with the ozone decomposition over highly dispersed MnO x in which extremely active oxygen radicals (O 2- , O 2 2- and O - ) are generated to enhance the oxidation ability of the catalysts greatly. In addition, toluene adsorption over acid support played a vital role in this reaction. Hence, the properties such as optimum Mn 3+ /Mn 4+ ratio, acidic sites, and smaller particle size (≤2 nm) examined by XPS, TPD of NH 3 , and TEM results are playing vital role in the present study. In summary, the MnO x /Al 2 O 3 (C) catalyst has great potential in environmental applications particularly for the elimination of volatile organic compounds with low loading of manganese developed by SDM., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Naproxen (NPX), one of the representative non-steroidal anti-inflammatory drug (NSAID) ingredients, was decomposed by plasma in liquid process (PiLP). Strongly oxidized species generated in the plasma field of the PiLP, such as OH radicals, were confirmed by optical emission spectroscopy Increasing the operation parameters (pulse width, frequency and applied voltage) of the power supply promoted plasma field generation and OH radical generation, and affected the NPX decomposition rate. Although the NPX decomposition reaction rate was improved by up to 18-30% by adding TiO 2 photocatalyst powder and H 2 O 2 to PiLP, but the optimal addition amount should be determined considering the plasma generation and scavenger effects. A decomposition pathway was proposed, in which NPX was mineralized into CO 2 and H 2 O through five intermediates mainly by decarboxylation, demethylation, hydroxylation, and dehydration reactions via hydroxyl radicals., (Copyright © 2021 Elsevier Inc. All rights reserved.)

A spent alkaline battery-based (SB) catalyst was prepared from the black mass of a spent alkaline battery to determine the potential of recycling spent alkaline batteries as catalysts for the total oxidation of hydrocarbons. Five different acids (H 2 SO 4 , HNO 3 , C 2 H 2 O 4 , HCl, and H 3 PO 4 ) were used to examine the effect of acid treatment on catalytic activity during catalyst preparation. Hexane, benzene, toluene, and o-xylene (HBTX) were adopted as the VOCs for experiments. The properties of the prepared catalysts were studied using ICP/OES, BET, XRD, ATR/FTIR, TGA, SEM, and H 2 -TPR analyses. The results showed that acid treatment significantly influenced the activity of the SB (400) catalyst, with the type of acid also found to greatly influence the activity of the catalyst. The order of activity according to the type of acid was H 2 SO 4 > HNO 3 > C 2 H 2 O 4 > HCl > H 3 PO 4 > none. Good performance of an acid-treated SB catalyst was associated with high concentrations of manganese and iron and a large BET surface area. In addition, the sequence in which the TPR peaks appeared at low temperatures according to each acid treatment was consistent with that of catalyst activity., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Five different Ru-Mn/zeolites were used to investigate their catalytic efficiencies for removing toluene (100 ppm) with ozone (1000 ppm) at room temperature. In general, most of metal oxide catalysts for removal of organic compounds need higher temperature than the ambient temperature, but Mn-based catalysts shows activity for prevalent organic pollutants even at room temperature with ozone. For the removal of toluene at room temperature without further heating, bimetallic Ru added Mn catalysts were applied in combination with different zeolite supports. The catalytic activity of the Ru-Mn catalysts strongly depended on the zeolite, of which the characteristics such as acidity and adsorption degree of toluene are dependent on the ratio of SiO 2 /Al 2 O 3 . Among the five Ru-Mn catalysts used, Ru-Mn/HY (SiO 2 /Al 2 O 3 ratio: 80) and Ru-Mn/ZSM-5 (SiO 2 /Al 2 O 3 ratio: 80) had higher toluene and ozone removal efficiencies. The toluene removal efficiency of Ru-Mn/zeolites was proportional to the pore volume and surface area. In terms of ozone degradation, Ru-Mn/HY(80) and Ru-Mn/HZSM-5(80) had the highest removal efficiencies. Overall, the catalytic ozone oxidation of toluene using Ru-Mn/zeolites seemed to be affected by a combination of the acidic properties of zeolites, Mn 3+ /Mn 4+ ratio, and concentration ratio of oxygen vacancies to oxygen lattices on the catalyst surface., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Air pollution caused by particulate matter (PM) has become a serious issue, and significant research has focused on managing large stationary emission sources, i.e., the primary sources of PM. Currently, the U.S. Environmental Protection Agency (EPA) Method 201A and ISO 23210 are predominantly employed to measure the PM emissions at large stationary sources. Method 201A is designated as a standard test method in Korea, but it is difficult to measure PM 10 and PM 2.5 simultaneously owing to the size of the full-set cyclone. In large stationary emission sources, the use of a serial connection of PM 10 and PM 2.5 cyclones is unsuitable for measurements at conventional sampling ports featuring diameters of approximately 100 mm. Therefore, in this study, PM 10 and PM 2.5 cyclones were developed to replace the cyclones currently used in Method 201A. The developed cyclones featured a cutoff diameter, which was confirmed by numerical and experimental analyses that were close to Method 201A. Moreover, there was an increase in the stiffness of collection efficiency. The hook adaptor, which is a key accessory used in Method 201A, was found to be applicable to the newly developed cyclones. This alternative method will help reduce the measurement time by simultaneously measuring TSP, PM 10 , and PM 2.5 and eliminates the costs of installing or refurbishing additional sampling ports at existing large stationary sources., (Copyright © 2020 Elsevier Inc. All rights reserved.)

In this study, red mud (RM), a highly alkaline waste generated from alumina production industries, was used as a catalytic material for both fast copyrolysis of organosolv lignin (OL) and polypropylene (PP) and toluene removal under ozone at room temperature. The RM was pretreated with HCl to investigate the effect of alkalinity. In the catalytic fast copyrolysis of the OL and PP, the acid-treated RM (HRM) produced more aromatics, phenolics, and light olefins (C 3 to C 5 ) but less oxygenates and heavy olefins (C 6 to C 46 ) than the RM. The difference in pyrolytic performance between the RM and HRM was likely attributed to the concentrated Fe 2 O 3 species in the HRM catalyst. In addition, more efficient toluene removal was observed over MnO x /HRM than over MnO x /RM owing to the large Brunauer-Emmett-Teller surface area, high amounts of Al and Fe, and optimal Mn 3+ /Mn 4+ ratio. This study demonstrates that the RM, an industrial waste, can be reused as an effective catalytic material for not only biofuel production but also pollutant removal., (Copyright © 2020 Elsevier Inc. All rights reserved.)

This study focused on the simultaneous removal of NO and SO 2 from an industrial flue gas stream. To evaluate the removal efficiency of NO and SO 2 using O 3 and NH 3 , the consumption of two reactants (O 3 and NH 3 ) in line with the conversion of NO and SO 2 was quantified experimentally. In addition, NO and SO 2 were converted to valuable fertilizers, NH 4 NO 3 and (NH 4 ) 2 SO 4 . To identify a principle strategy to enhance the generation of fertilizer, Fourier transform infrared spectroscopy was used to examine the reaction mechanisms for the formation of NH 4 NO 3 and (NH 4 ) 2 SO 4 . Acceleration of SO 2 oxidation could be achieved effectively by adding NO to a gas mixture of SO 2 , NH 3 , and O 3 . The formation of HNO 3 might be enhanced by the simultaneous feeding of NO and SO 2 . Particle generation was also 10 times higher for NH 3 /(NO + SO 2 ) than for NH 3 /NO and for NH 3 /SO 2 , which is a prominent feature of this study. Moreover, the introduction of steam had a positive influence on particle generation. This method offers dual applications for NO and SO 2 removal from a flue gas stream and direct fertilizer generation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

We investigated the catalytic efficiency of Mn-based bimetallic oxides in degrading toluene and ozone at room temperature. The room temperature-active bimetallic oxide catalysts were prepared by the addition of Fe, Cu, Ru, and Ag precursors to Mn/HZSM-5. We obtained H 2 -temperature-programmed reduction (H 2 -TPR) profiles, X-ray diffraction patterns, and X-ray photoelectron spectra to investigate the characteristics of the prepared catalysts. The catalytic efficiency of Mn-based bimetallic oxide catalysts in degrading toluene and ozone at room temperature was mostly improved by the addition of the secondary metals. The prepared bimetallic oxide catalysts, Cu-Mn/HZSM-5, Fe-Mn/HZSM-5, Ru-Mn/HZSM-5, and Ag-Mn/HZSM-5, enhanced efficiency for toluene removal compared to Mn/HZSM-5. The H 2 -TPR profiles of the Mn-based bimetallic oxide catalysts showed stronger and broader adsorption-desorption bands at lower temperatures than the profile of Mn/HZSM-5. Additionally, the ratio of the surface defective oxygen over the lattice oxygen on the bimetallic oxide catalysts was higher than that of Mn-only catalysts; the ratio of Mn 3+ over Mn 4+ was higher for all bimetallic oxide catalysts, as well. Among the bimetallic oxide catalysts, Ru-Mn/HZSM-5 showed the highest efficiency for the removal of toluene to CO x due to the synergetic effect of the oxidation state and reducible potential at room temperature., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

To valorize tea waste (TW), catalytic pyrolysis was done as a practical measure for recovering energy as a form of syngas. Considering CO 2 as a reactive gas medium in place of conventional pyrolysis gas, a sustainable pyrolysis platform was established. In addition, mechanistic effectiveness of CO 2 on TW pyrolysis was examined. In the presence of CO 2 , homogeneous reaction with volatile organic compounds (VOCs) derived from TW pyrolysis contributed to CO formation. To enhance the formation of syngas at low pyrolysis temperature, catalytic pyrolysis over a Ni/SiO 2 was investigated. The synergistic effects of Ni/SiO 2 catalyst and CO 2 promoted thermal cracking of VOCs and further homogeneous reaction with CO 2 , thereby resulting in the substantial enhancement (28 times more) of H 2 and CO production than non-catalytic pyrolysis. It was also confirmed that CO 2 could be considered a reactive gas medium to produce biochar (34-35 wt.% yield), having competitive porosity and surface area, in comparison to that from pyrolysis in N 2 . Therefore, CO 2 can be employed to build a sustainable waste conversion platform for energy and biochar production through pyrolysis instead of using N 2 ., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Hydrogen production from water was investigated by applying liquid plasma (LPP) to photocatalytic splitting of water. The optical properties of LPP due to water emission were also evaluated. The correlation between the optical properties of plasma and the formation of active species in water was investigated with the photocatalytic activity of hydrogen production. TiO 2 was also doped with Ag to evaluate the effect of enhancing photocatalytic activity. The photocatalytic activity was evaluated by the rate of hydrogen production, and the effect of hydrogen formation was also investigated by injecting methanol as an additive. As a result of examining the luminescence properties of LPP, it showed high luminescence in the 309 nm UV region and the 656 nm visible region. The hydrogen doping rate was increased in the Ag-doped TiO 2 photocatalyst. Ag-doped TiO 2 has wider light absorption into the visible region and narrower band gap. Due to these properties, the rate of hydrogen generation is superior to TiO 2 photocatalysts. The photochemical reaction with LPP and photocatalyst in aqueous solution with CH 3 OH showed a significant increase in hydrogen production rate. The increase in hydrogen production by injection of additives is because the optical properties of generating OH radicals are improved and CH 3 OH is decomposed to act as an electron donor to improve hydrogen production., (Copyright © 2020 Elsevier Inc. All rights reserved.)

As the consumption of plastic materials has been dramatically increased, the abundant presence of their debris has become a significant problem worldwide. Thus, this study proposes a sustainable plastic conversion platform for energy recovery. In detail, polystyrene pyrolysis was examined as a case study under CO 2 atmosphere in reference to N 2 condition. The major gaseous and liquid products from polystyrene pyrolysis include permanent gases (syngas and C 1-2 hydrocarbons) and condensable aromatic compounds. Under CO 2 environment, the reduction of polycyclic aromatic hydrocarbons (PAHs) was achieved during polystyrene pyrolysis, in comparison with N 2 condition. Since its slow reaction kinetics, conversion of condensable hydrocarbons into permanent gases was not fully activated. Therefore, a cheap industrial waste, steel slag (SS), was employed as a catalyst to increase reaction kinetics. The synergistic effects of SS and CO 2 contributed to doubling H 2 production, while CO formation increased more than 300 times, in reference to non-catalytic pyrolysis. Because CO 2 acted as an oxidant for CO production, control of H 2 /CO ratio was achieved in different conditions. Thus, the utilization of CO 2 would suggest a promising way to reduce the formation of PAHs, adopting the reliable platform to produce syngas from plastic waste., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Biochar production from invasive species biomass discarded as waste was studied in a fixed bed reactor pyrolysis system under different temperature conditions for value-added applications. Prior to pyrolysis, the biomass feedstock was characterized by proximate, ultimate, and heating value analyses, while the biomass decomposition behavior was examined by thermogravimetric analysis. The heating values of the feedstock biomass ranged from 18.65 to 20.65 MJ/kg, whereas the volatile matter, fixed carbon, and ash content were 61.54-72.04 wt %, 19.27-26.61 wt % and 1.51-1.86 wt %, respectively. The elemental composition of carbon, hydrogen, and oxygen in the samples was reported to be in the range of 47.41-48.47 wt %, 5.50-5.88 wt % and 46.10-45.18 wt %, respectively, while the nitrogen and sulphur content in the biomass samples were at very low concentrations, making it more useful for valorization from environmental aspects. The biochar yields were reported in the range of 45.36-58.35 wt %, 28.63-44.38 wt % and 22.68-29.42 wt % at a pyrolysis temperature of 400 °C, 500 °C, and 600 °C, respectively. The biochars were characterized from ultimate analysis, heating value, energy densification ratio, energy yield, pH, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy and energy dispersive X-ray spectrometry (SEM and EDX), to evaluate their potential for value-added applications. The carbon content, heating value, energy densification ratio, and the porosity of the biochars improved with the increase in pyrolysis temperature, while the energy yield, hydrogen, oxygen, and nitrogen content of the biochars decreased. This study revealed the potential of the valorization of underutilized discarded biomass of invasive species via a pyrolysis process to produce biochar for value-added applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

To seek an innovative way for simultaneous waste management and energy recovery, two waste materials (pine sawdust: PSD and steel slag: SS) were used in the pyrolysis process. PSD was used as a carbonaceous material for pyrolysis, and SS was used as a catalyst. Also, to achieve a more sustainable conversion system, a viable use of carbon dioxide (CO 2 ) as a raw material in the non-catalytic/catalytic pyrolysis process was evaluated. Hence, the present study laid great stress on the CO 2 effects. The present study pointed the optimistic technical features in line with the use of CO 2 in the pyrolysis process. Exploiting CO 2 in pyrolysis of PSD offered a strategic way to control carbon reallocation from liquid to gaseous pyrolysates by the gas phase reactions (GPRs). The reactions of CO 2 and volatile pyrolysates led to CO enhancement, which was only observed at ≥ 600 °C due to the slow reaction kinetics of the GPRs of volatile pyrolysates and CO 2 . Such the slow reaction kinetics was expedited remarkably when SS was acted as a catalyst. Moreover, CO 2 expedited thermal cracking of volatile pyrolysates including dehydrogenation, which led to the enhanced formation of CH 4 and H 2 ., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Microwave/Microwave discharge electrodeless lamp/Dissolved Oxygen/TiO 2 photocatalyst hybrid system was applied to evaluate the photocatalytic degradation behavior of cimetidine, one of the waste drug components. The effects of microwave intensity, pH and dissolved oxygen (DO) concentration on the reaction rate of cimetidine (CMT) degradation were experimentally evaluated. In addition, the CMT decomposition reactions were compared by the combination of unit technologies of the hybrid system. As the microwave intensity and pH of the aqueous reactant solution increased, the CMT decomposition rate increased, and the DO concentration of the aqueous reactant solution had an optimum efficiency concentration. The highest CMT degradation efficiency was obtained by microwave/microwave discharge electrodeless lamp/TiO 2 photocatalytic hybrid system at pH and DO concentration conditions (pH 10, DO 40 ppm). These results show that operation parameters and combination methods affect hydroxyl radical formation and CMT decomposition reactions on TiO 2 surfaces, and efficient CMT decomposition reactions are formed through optimized hybrid systems. CMT is mineralized to CO 2 and H 2 O through chemically active species (superoxide anion radical and hydroxyl radicals) via cimetine sulfoxide, 4-methyl-5-hydroxymethylimidazole, and sulfinyl-containing N-cyano-N',N'-dimethyl-guanidine., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Air pollution, particularly for toxic and harmful compounds to humans and the environment, has aroused increasing public concerns. Among air pollutants, volatile organic compounds (VOCs) are the main sources of air pollution. Many attempts have been made to control VOCs using catalysts, plasma, photolysis, and adsorption. Among them, oxidative catalysis by noble metals or transition metal oxides is considered one of the most feasible and effective methods to control VOCs. This paper reviews the experimental achievements on the abatement of VOCs using noble metals, transition metals and modified metal oxide catalysts. Although the catalytic degradation of VOCs appears to be feasible, there are unavoidable problems when only catalysis treatments are applied to the field. Therefore, catalysts including hybrid processes are developed to improve the removal efficiency of VOCs. This review addresses new hybrid treatments to remove VOCs using catalysts, including hybrid treatment combined with plasma, photolysis, and adsorption. The mechanism of the oxidation of VOCs by catalysts is explained by adsorption-desorption principles, such as the Langmuir-Hinshelwood, Eley-Rideal, and Mars-van-Krevelen mechanisms. A π-backbonding interaction between unsaturated compounds and transition metals is introduced to better understand the mechanism of VOC removals. Finally, several factors affecting the catalytic activities, such as support, component ratio, preparation method, metal loading, and deactivation factor, are discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)