A critical review on the technique and mechanism of microwave-based denitrification in flue gas

Microwave radiation has received extensive attention due to its significant thermal and nonthermal effects, and the development of MW-based denitrification in flue gas has become one of the most promising methods to avoid the defects of ammonia escape, high temperature and cost in traditional SCR. This review introduces the thermal and non-thermal effects of microwaves and divides MW-based denitrification methods into MW reduction and oxidation denitrification, systematically summarizes these denitrification methods, including MW discharge reduction, MW-induced catalytic reduction using active carbon, molecular sieves, metal oxides(transition metals, perovskites, etc.), MW-induced oxidation denitrification with and without additional oxidant, and discusses their removal pathway and mechanism. Finally, several research prospects and directions regarding the development of microwave-based denitrification methods are provided.

Enhancement of ionic conductivity and fracture toughness by infiltrating porous Li_(0.33)La_(0.56)TiO_(3) pellets

Although solid-state lithium electrolytes have the potential to reduce the safety issues associated with organic liquid electrolytes,disadvantages such as low total conductivity,large interface impedance,and delamination of the interface due to cyclic stress still need to be addressed.The solid-state lithium-ion conductor Li_(0.33)La_(0.56)TiO_(3)(LLTO) was prepared via a hydrothermal route by using CTAB as templates in this paper.Perovskite LLTO with micro-porous channels was obtained and the total conductivity is comparable to the non-porous LLTO.Porous LLTO pellets are infiltrated with the non-porous LLTO precursor solution,and the total conductivities of the infiltrated porous LLTO are all higher than those without infiltration.After infiltration,the porous LLTO calcined at 600℃ achieves the highest total conductivity,7.88×10^(-5) S/cm.The fracture toughness of the infiltrated LLTO is higher than that of the non-porous LLTO.The results demonstrate a new way to prepare solid-state lithium-ion conductors with high ionic conductivity and great tolerance to cyclic stress.

Insight study of rare earth elements in PM_(2.5)during five years in a Chinese inland city:Composition

The booming development of rare earth industry and the extensive utilization of its products accompanied by urban development have led to the accelerated accumulation of rare earth elements(REEs)as emerging pollutants in atmospheric environment.In this study,the variation of REEs in PM_(2.5)with urban(a non-mining city)transformation was investigated through five consecutive years of sample collection.The compositional variability and provenance contribution of REEs in PM_(2.5)were characterized,and the REEs exposure risks of children and adults via inhalation,ingestion and dermal absorption were also evaluated.The results showed an increase in the total REEs concentration from 46.46±35.16 mg/kg(2017)to 81.22±38.98 mg/kg(2021)over the five-year period,with Ce and La making the largest contribution.The actual increment of industrial and traffic emission source among the three pollution sources was 1.34 ng/m^(3).Coal combustion source displayed a downward trend.Ingestion was the main exposure pathway for REEs in PM_(2.5)for both children and adults.Ce contributed the most to the total intake of REEs in PM_(2.5)among the population,followed by La and Nd.The exposure risks of REEs in PM_(2.5)in the region were relatively low,but the trend of change was of great concern.It was strongly recommended to strengthen the concern about traffic-related non-exhaust emissions of particulate matter.

Preparation of hybrid perovskite-type Li_(0.33)La_(0.56)TiO_(3)by adding ionic liquids

Perovs kite-type Li_(0.33)La_(0.56)TiO_(3)(LLTO)shows greate r advantages than organic liquid electrolytes to be used in all-so lid-state lithium-ion batteries with high energy densities.Ionic liquid[BMIM][BF4]was used to improve the properties of Li_(0.33)La_(0.56)TiO_(3)by attrition milling in this study.The microstructure,crystallinity and lithium-ion conductivity of the samples were measured by scanning electron microscopy(SEM),X-ray diffraction(XRD),and impedance spectroscopy(IS).The total ionic conductivities of the samples LLTO+x wt%[BMIM][BF4]increase upon adding[BMIM][BF4]and the maximum conductivity reaches4.71×10^(-4)S/cm when x=12.5 wt%.The enhancement of the total conductivity is ascribed to the bridging role of the ionic liquid among grains,as evidenced by the low activation energy of 0.17-0.25 eV and the SEM observation.The Li+transference numbers of the hybrid samples are all lower than that of the pure LLTO,indicating the existence of electronic conductions.The hybrid mate rial with a mixed conductivity and good stability in the atmosphere can find uses in all-solid-state lithium-ion batteries to improve the interface contact between electrolytes and electrodes.

Facile fabrication of Fe/Zr binary MOFs for arsenic removal in water:High capacity,fast kinetics and good reusability

A water-stable bimetallic Fe/Zrmetal-organic framework[UiO-66(Fe/Zr)]for exceptional decontamination of arsenic in water was fabricated through a facile one-step strategy.The batch adsorption experiments revealed the excellent performances with ultrafast adsorption kinetics due to the synergistic effects of two functional centers and large surface area(498.33 m^(2)/g).The absorption capacity of UiO-66(Fe/Zr)for arsenate[As(V)]and arsenite[As(III)]reached as high as 204.1 mg/g and 101.7 mg/g,respectively.Langmuir model was suitable to describe the adsorption behaviors of arsenic on UiO-66(Fe/Zr).The fast kinetics(adsorption equilibrium in 30min,10mg/L As)and pseudo-second-ordermodel implied the strong chemisorption between arsenic ions and UiO-66(Fe/Zr),which was further confirmed by DFT theoretical calculations.The results of FT-IR,XPS analysis and TCLP test demonstrated that arsenic was immobilized on the surface of UiO-66(Fe/Zr)through Fe/Zr-O-As bonds,and the leaching rates of the adsorbed As(III)and As(V)from the spent adsorbent were only 5.6%and 1.4%,respectively.UiO-66(Fe/Zr)can be regenerated for five cycles without obvious removal efficiency decrease.The original arsenic(1.0mg/L)in lake and tapwater was effectively removed in 2.0 hr[99.0%of As(III)and 99.8%of As(V)].The bimetallic UiO-66(Fe/Zr)has great potentials in water deep purification of arsenic with fast kinetics and high capacity.

Operando reconstruction-induced CO_(2)reduction activity and selectivity for cobalt-based photocatalysis

The oxygen atom coordination inducing the structure reconstruction of the catalytic site is identified and recognized ambiguously,which is related to accurately declare the mechanism in a dynamic catalytic process.Herein,we demonstrated that the reconstructed catalytic sites would lead to a remarkable performance for photocatalytic CO_(2)reduction.At the initial 4-cycles testing,the in-situ formation of CoOx active sites on the Co(CoP)surface performed an increasing transient activity and selectivity toward CO evolution.The formation of reconstructive Co-O bond and the appearance of intermediate specie CO were simultaneously observed by the pre-operando Raman,revealing the dynamic relationship between catalytic site structure and the photocatalytic properties.Moreover,density functional theory calculations showed that the electronic structure of the reconstructive surface sites could modulate the ability of CO_(2)adsorption and CO desorption.The reduced barrier energy for the rate-determining step finally improved the activity and selectivity of CO_(2)reduction.

Aggregation and stability of selenium nanoparticles: Complex roles of surface coating, electrolytes and natural organic matter

The application of selenium nanoparticles(SeNPs)as nanofertilizers may lead to the release of SeNPs into aquatic systems.However,the environmental behavior of SeNPs is rarely studied.In this study,using alginate-coated SeNPs(Alg-SeNPs)and polyvinyl alcohol-coated SeNPs(PVA-SeNPs)as models,we systematically investigated the aggregation and stability of SeNPs under various water conditions.PVA-SeNPs were highly stable in mono-and polyvalent electrolytes,probably due to the strong steric hindrance of the capping agent.Alg-SeNPs only suffered from a limited increase in size,even at 2500 mmol/L NaCl and 200 mmol/L MgCl_(2),while they underwent apparent aggregation in CaCl_(2) and LaCl_(3) solutions.The binding of Ca^(2+) and La^(3+) with the guluronic acid part in alginate induced the formation of cross-linking aggregates.Natural organic matter enhanced the stability of Alg-SeNPs in monovalent electrolytes,while accelerated the attachment of Alg-SeNPs in polyvalent electrolytes,due to the cation bridge effects.The long-term stability of SeNPs in natural water showed that the aggregation sizes of Alg-SeNPs and PVA-SeNPs increased to several hundreds of nanometers or above 10μm after 30 days,implying that SeNPs may be suspended in the water column or further settle down,depending on the surrounding water chemistry.The study may contribute to the deep insight into the fate and mobility of SeNPs in the aquatic environment.The varying fate of SeNPs in different natural waters also suggests that the risks of SeNPs to organisms living in diverse depths in the aquatic compartment should be concerned.

Biochar for the removal of contaminants from soil and water:a review

Biochar shows significant potential to serve as a globally applicable material to remediate water and soil owing to the extensive availability of feedstocks and conducive physio-chemical surface characteristics.This review aims to highlight biochar production technologies,characteristics of biochar,and the latest advancements in immobilizing and eliminating heavy metal ions and organic pollutants in soil and water.Pyrolysis temperature,heat transfer rate,residence time,and type of feedstock are critical influential parameters.Biochar’s efficacy in managing contaminants relies on the pore size distribution,surface groups,and ion-exchange capacity.The molecular composition and physical architecture of biochar may be crucial when practically applied to water and soil.In general,biochar produced at relatively high pyrolysis temperatures can effectively manage organic pollutants via increasing surface area,hydrophobicity and microporosity.Biochar generated at lower temperatures is deemed to be more suitable for removing polar organic and inorganic pollutants through oxygen-containing functional groups,precipitation and electrostatic attraction.This review also presents the existing obstacles and future research direction related to biochar-based materials in immobilizing organic contaminants and heavy metal ions in effluents and soil.

Distribution and chemical speciation of arsenic in different sized atmospheric particulate matters

The distribution and chemical speciation of arsenic(As)in different sized atmospheric particulate matters(PMs),including total suspended particles(TSP),PM_(10),and PM_(2.5),collected from Baoding,China were analyzed.The average total mass concentrations of As in TSP,PM_(10),and PM_(2.5)were 31.5,35.3,and 54.1μg/g,respectively,with an order of PM_(2.5)>PM_(10)>TSP,revealing that As is prone to accumulate on fine particles.Due to the divergent toxicities of different As species,speciation analysis of As in PMs is further conducted.Most of previous studies mainly focused on inorganic arsenite(iAs^(Ⅲ)),inorganic arsenate(iAs^(Ⅴ)),monomethylarsonate(MMA),and dimethylarsinate(DMA)in PMs,while the identification and sensitive quantification of trimethylarsine oxide(TMAO)were rarely reported.In this study,a high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry system was optimized for As speciation including TMAO in PMs.An anion exchange column was used to separate MMA,DMA and iAs^(Ⅴ),while a cation exchange column to separate TMAO and iAs^(Ⅲ).Results showed that iAs^(Ⅴ) was the dominate component in all the samples,corresponding to a portion of 79.2%±9.3%of the total extractable species,while iAs^(Ⅲ),TMAO and DMA made up the remaining 21%.Our study demonstrated that iAs^(Ⅲ) accounted for about 14.4%±11.4%of the total extracted species,with an average concentration of 1.7±1.6 ng/m^(3).It is worth noting that TMAO was widely present in the samples(84 out of 97 samples),which supported the assumption that TMAO was ubiquitous in atmospheric particles.

Microwave-assisted continuous flow phytosynthesis of silver nanoparticle/reduced graphene oxide composites and related visible light catalytic performance

The creation of an environmentally friendly synthesis method for silver nanomaterials(Ag-NPs)is an urgent concern for sustainable nanotechnology development.In the present study,a novel straightforward and green method for the preparation of silver nanoparti-cle/reduced graphene oxide(AgNP/rGO)composites was successfully developed through the combination of phytosynthesis,continuous flow synthesis and microwave-assistance.Oriental persimmon(Diospyros kaki Thunb.)extracts were used as both plant reducing and capping agents for fast online synthesis of AgNP/rGO composites.The experimental param-eters were optimized and the morphologies of the prepared materials were investigated.The characterization results reveal that spherical AgNPs were quickly synthesized and uni-formly dispersed on rGO sheets using the proposed online system.Fourier transform in-frared spectroscopy analysis confirmed that phenols,flavonoids,and other substances in the plant extracts played a decisive role in the synthesis of AgNP/rGO composites.Using sodium borohydride(NaBH4)degradation of p-nitrophenol(4-NP)as a model,the catalytic activity of the prepared AgNP/rGO materials was evaluated.The complete degradation of 4-NP was achieved within 12 min through the use of AgNP/rGO materials,and the compos-ite had a much better catalytic activity than the bare AgNPs and rGO had.Compared with the conventional chemical method,our online method is facile,fast,cost-efficient,and en-vironmentally friendly.

Selenium uptake and simultaneous catalysis of sulfite oxidation in ammonia-based desulfurization

Accelerating the(NH_4)_(2)SO_(3) oxidation gives rise to the reclaiming of byproduct, while there are secondary environmental risks from reduction of the coexisted selenium species by sulfite. In this study, a bi-functional Co-SBA-15-SH, were synthesized through Co impregnation and sulfhydryl(-SH) decoration, which can simultaneously uptake Se and accelerate sulfite oxidation efficiently. Meanwhile, the adsorption kinetics and migration mechanism of Se species were revealed through characterization and density functional calculations, with maximum adsorption capacity of 223 mg/g. The inhibition of Se~0 re-emission and poisonous effect of Se on sulfite oxidation was also investigated. Using the findings of this study, the ammonia desulfurization can be improved by enabling purification of the byproduct and lowering the toxicity of effluent by removing toxic pollutants.