Iodine Determination by Microwave Plasma Torch Atomic Emission Spectrometer Coupled with Online Preconcentration Vapor Generation Technique

This article focuses on iodine determination by microwave plasma torch atomic emission spectrometry （MPT-AES） coupled with online preconcentration vapor generation method. A new desolvation device, multistrand Nafion dryer, was used as the substitute for condenser desolvation system. Some experimental conditions, such as preconcentration time, acidity of sample solution, rinsing solution acidity and dynamic linear range were investigated and optimized. The new desolvation system eliminates the problem of decreasing emission intensity of I（I） 206.238 nm line with the increase of working time on a conventional condenser desolvation system, thus greatly improving the reproducibility.

Bioinspired design of integral molded Janus silk fibroin-MXene evaporator for efficient solar vapor generation

Solar vapor generation is a promising sustainable technology that uses solar distillation to produce fresh water from seawater and wastewater,helping relieve global water resource shortage.Here,inspired by naturally grown integrally molded mulberry leaves with a Janus hydrophilic and hydrophobic structure,a novel,simple,and efficient integrated molding method is proposed to break through the limitations of the traditional split manufacturing strategy and realizes the integrated formation of Janus evaporator.Based on the spontaneous sedimentation characteristics of MXene in silk fibroin solution and its regulation of mesoscopic structure and hydrophilicity of silk fibroin,layered structures with different compositions and hydrophilicities were obtained in one step.Meanwhile,ethanol and glutaraldehyde were added to construct a physical crystallization-chemical crosslinking dual stabilization structure in silk fibroin.Our evaporator has the evaporation rate of 3.07 kg·m^(-2)·h^(-1) and the efficiency of 86.8%under 1 sun and maintains high evaporation performance under various extreme test conditions including vigorous washing,repeated compression,and high-intensity ultraviolet(UV)irradiation.Additionally,the evaporator performs well in practical application scenarios,its evaporation rate in the simulated Dead Sea seawater exceeds 2.13 kg·m^(-2)·h^(-1),and more than 99.9%of the salt,heavy metal ions,oil pollution,and dyes are purified.

Ultrasensitive determination of mercury by ICP-OES coupled with a vapor generation approach based on solution cathode glow discharge

We herein proposed a sample introduction technique based on solution cathode glow discharge(SCGD)of a portable design for inductively coupled plasma-optical emission spectrometry(ICP-OES)and its ap-plication in sensitive determination of mercury.The products from SCGD containing mercury vapor,were transported by an Ar flow to ICP spectrometer for detection.A gas liquid separator(GLS)and a dryer were used to condense and remove most of the accompanying moisture,which greatly improved both the stability and sensitivity of the signal.The detection limit(DL)acquired by this developed method was 0.22μg/L(194.1 nm),which was nearly 82 times lower than that obtained by pneumatic nebuliza-tion(PN).The relative standard deviation(RSD)was 1.4%(n=14)for a 50μg/L standard.Blank solution(HNO_(3),pH 1)can effectively elute mercury residue.Its accuracy and practicality were also demonstrated by the determination of GBW10029(fish)certified reference material,shrimp,crawfish,soil and human hair samples.The results showed good consistency with the certified values and the values obtained us-ing inductively coupled plasma−mass spectrometry.

Novel advances in metal-based solar absorber for photothermal vapor generation

Access to safe drinking water has become an extremely urgent research topic wo rldwide.In recent years,the technology of solar vapor generation has been extensively explored as a potential and effective strategy of transforming elements content in seawater.In this review,the basic concepts and theories of metal-based photothermal vapor generation device(PVGD) with excellent optical and thermal regulatory are introduced.In the view of optical regulation,how to achieve high-efficiency localized evaporation in different evaporation system(i.e.,volumetric solar heating and interface solar heating) is discussed;from the aspect of thermal regulation,the importance of selective absorption surface for interfacial PVGD is analyzed.Based on the above discussion and analysis,we summarize the challenges of metal-based desalination device.

A sensitive and compact mercury analyzer by integrating dielectric barrier discharge induced cold vapor generation and optical emission spectrometry

An environmentally friendly,low power consuming,sensitive and compact mercury analyzer was developed for the determination of mercury in water samples by integrating a thin film dielectric barrier discharge induced cold vapor reactor and a dielectric barrier discharge optical emission spectrometer into a small polymethyl methacrylate plate（10.5 cm length×8.0 cm width×1.2 cm height）.Mercury cold vapor was generated when standard or sample solutions with or without formic acid were introduced to the reactor to form thin film liquid and exposed to microplasma irradiation and subsequently separated from the liquid phase for transport to the microplasma and detection of its atomic emission.Limits of detection of 0.20 μg L^-1 and 2.6 μg L^-1 were obtained for the proposed system using or not using formic acid,respectively.Compared to the conventional microplasma optical emission spectrometry used for mercury analysis,this system not only retains the good limit of detection amenable to the determination of mercury in real samples,but also reduces power consumption,eliminates the generation of hydrogen and avoids the use of toxic or unstable reductant.Method validation was demonstrated by analysis of a certified reference material of water sample and three real water samples with good spike recoveries（88-102%）.

Reduction of mercury(Ⅱ)by electrons contained in carbon dots:An environmentally friendly cold vapor generation for mercury analysis

In this work,the reduction of mercury ions(Hg2+)to elemental mercury(Hg0)was easily achieved using highly reductive carbon dots(r-CDs),which synthesized from sucrose by a simple and cost-effective method.After a careful mechanistic study,the reduction was probably accomplished with the large numbers of electrons contained in r-CDs rather than the oxidation of its functional groups.Additionally,a3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay showed that the r-CDs were nontoxic to wildlife and human beings.Consequently,the r-CDs were used as an alternative to toxic reductants(SnCl2 or NaBH4)for the sensitive and in situ determination of mercury by cold vapor gene ration(CVG)coupled to a miniature point discharge optical emission spectrometer(μPD-OES).Limit of detection of 0.05μg/L was obtained for Hg2+,with relative standard deviation(RSD)less than 5.4%at a concentration of 5μg/L.The accuracy of r-CDs induced CVG-μPD-OES was validated by the determination of mercury in a certified reference material(DOLT-5,dogfish liver)and five natural water samples collected from different rivers and lakes in Chengdu City,Since r-CDs are nontoxic and prepared from abundant and inexpensive sucrose,the r-CDs induced CVG-μPD-OES retains the great potential for the inexpensive and enviro nmentally friendly field analysis of mercury in natural water.The accuracy of the proposed method was validated by the analysis of a certified reference material and several water samples with satisfactory results.

Polyoxometalates-Modulated Hydrophilic-Hydrophobic Composite Interfacial Material for Efficient Solar Water Evaporation and Salt Harvesting in High-Salinity Brine

Solar vapor generation(SVC)represents a promising technique for seawater desalination to alleviate the global water crisis and energy shortage.One of its main bottleneck problems is that the evaporation efficiency and stability are limited by salt crystallization under high-salinity brines.Herein,we demonstrate that the 3D porous melamine-foam(MF)wrapped by a type of self-assembling composite materials based on reduced polyoxometalates(i.e.heteropoly blue,HPB),oleic acid(OA),and polypyrrole(PPy)(labeled with MF@HPB-PPy_(n)-OA)can serve as efficient and stable SVC material at high salinity.Structural characterizations of MF@HPB-PPy_(n)-OA indicate that both hydrophilic region of HPBs and hydrophobic region of OA co-exist on the surface of composite materials,optimizing the hydrophilic and hydrophobic interfaces of the SVC materials,and fully exerting its functionality for ultrahigh water-evaporation and anti-salt fouling.The optimal MF@HPB-PPy_(10)-OA operates continuously and stably for over 100 h in 10wt%brine.Furthermore,MF@HPB-PPy_(10)-OA accomplishes complete salt-water separation of 10wt%brine with 3.3kgm^(-2)h^(-1)under 1-sun irradiation,yielding salt harvesting efficiency of 96.5%,which belongs to the record high of high-salinity systems reported so far and is close to achieving zero liquid discharge.Moreover,the low cost of MF@HPB-PPy_(10)-OA(2.56$m^(-2))suggests its potential application in the practical SVC technique.

Fibrous Aerogels with Tunable Superwettability for High-Performance Solar-Driven Interfacial Evaporation

Solar-driven interfacial evaporation is an emerging technology for water desalination.Generally,double-layered structure with separate surface wettability properties is usually employed for evaporator construction.However,creating materials with tunable properties is a great challenge because the wettability of existing materials is usually monotonous.Herein,we report vinyltrimethoxysilane as a single molecular unit to hybrid with bacterial cellulose(BC)fibrous network,which can be built into robust aerogel with entirely distinct wettability through controlling assembly pathways.Siloxane groups or carbon atoms are exposed on the surface of BC nanofibers,resulting in either superhydrophilic or superhydrophobic aerogels.With this special property,single component-modified aerogels could be integrated into a double-layered evaporator for water desalination.Under 1 sun,our evaporator achieves high water evaporation rates of 1.91 and 4.20 kg m^(-2)h^(-1)under laboratory and outdoor solar conditions,respectively.Moreover,this aerogel evaporator shows unprecedented lightweight,structural robustness,long-term stability under extreme conditions,and excellent salt-resistance,highlighting the advantages in synthesis of aerogel materials from the single molecular unit.

Optimal Design of Porous Media in Solar Vapor Generators by Carbon Fiber Bundles

As a means of harvesting solar energy for water treatment,solar-driven vapor generation is becoming more appealing.Due to their entangled fibrous networks and high surface area,fibers can be used as building blocks to generate water vapor.In this paper,using a two-dimensional fiber bundle model,we studied the generation of solar vapor based on the fiber height,distance between fibers,and input sun radiation.The performance of solar absorption system was also evaluated by evaluating thermal and water management.Results showed a constant increase in solar vapor generation with an increasing fiber height and decreasing inter-fiber distance.However,the gain rate of using taller and more densely packed fiber bundles dwindled quickly.On the other hand,a shorter fiber had a higher evaporation rate per fiber height.The distance between fibers had a nonlinear effect on the fiber bundle evaporation rate.A new fiber bundle design was recommended with a fiber height of 15–20 mm and an inter-fiber distance of 1.5 mm.The results of this study can provide guidelines for future fiber bundle designs with increased efficiency,reduced cost,and versatile applications(i.e.,desalination,water purification,and power generation).

Polysulfide nanoparticles-reduced graphene oxide composite aerogel for efficient solar-driven water purification

Along with the environmental pollution, the scarcity of clean water seriously threatens the sustainable development of human society.Recently, the rapid development of solar evaporators has injected new vitality into the field of water purification. However, the industry faces a considerable challenge of achieving comprehensive purification of ions, especially the efficient removal of mercury ions. In this work, we introduce an ideal mercury-removal platform based on facilely and cost-effectively synthesized polysulfide nanoparticles(PSNs). Further development of PSN-functionalized reduced graphene oxide(PSN-rGO) aerogel evaporator results in achieving a high evaporation rate of 1.55 kg m^(-2)h^(-1)with energy efficiency of 90.8% under 1 sun. With the merits of interconnected porous structure and adsorption ability, the photothermal aerogel presents overall purification of heavy metal ions from wastewater. During solar desalination, salt ions can be rejected with long-term stability. Compared with traditional water purification technologies, this highly efficient solar evaporator provides a new practical method to utilize clean energy for clean water production.

Photothermal materials for efficient solar powered steam generation

Solar powered steam generation is an emerging area in the field o f energy harvest and sustainable technologies.The nano-structured photothermal materials are able to harvest energy from the full solar spectrum and convert it to heat with high efficiency.Moreover,the materials and structures for heat management as well as the mass transportation are also brought to the forefront.Several groups have reported their materials and structures as solutions for high performance devices,a few creatively coupled other physical fields with solar energy to achieve even better results.This paper provides a systematic review on the recent developments in photothermal nanomaterial discovery,material selection,structural design and mass/heat management,as well as their applications in seawater desalination and fresh water production from waste water with free solar energy.It also discusses current technical challenges and likely future developments.This article will help to stimulate novel ideas and new designs for the photothermal materials,towards efficient,low cost practical solar-driven clean water production.

Macroporous 3D MXene architecture for solar-driven interfacial water evaporation

Interfacial water evaporation through solar heating with photothermal materials is a promising strategy for seawater desalination and wastewater purification.Tightly packed 2D membranes with high reflection losses and limited vapor escape channels result in a low evaporation rate.In this work,3D MXene architecture was fabricated by dropping the delaminated Ti_(3)C_(2)(d-Ti_(3)C_(2))nanosheets onto the carbonized melamine foam(CMF)framework.Owing to the macroporous 3D architecture,more effective broadband solar absorption and vapor escaping were achieved.As a result,the 3D CMF@d-Ti_(3)C_(2)-based evaporator delivers a water evaporation rate of 1.60 kg/m2·h with a solar-to-vapor conversion efficiency of up to 84.6%.

Facile strategy for carbon foam fabrication with lignin as sole feedstock and its applications

This research is a follow-up to our recent discovery of a facile strategy for directly converting lignin powder into carbon foam.In this work,we report that the thermal pretreatment parameters in air can remarkably influence the formation and properties of the derived carbon foam.Thermal pretreatment parameters(heating rate,temperature,and residence time)were systematically investigated and a conversion mechanism into carbon foam was proposed.During the thermal pretreatment,relatively low temperatures,low heating rates,and short residence time hindered the formation of smooth and well-connected structures in the carbon foam.The overall product yields were similar regardless of the thermal pretreatment conditions.The densities of the different carbon foams ranged 0.27–0.83 g∙cm^(−3).The carbon foams with the highest compressive strengths(>10 MPa)were KLPC280-2-5,KLPC300-0-5,and KLPC300-2-2.5.KLPC280-2-5 exhibited a high iodine sorption value(182 mg∙g^(−1)).KLPC300-2-5 exhibited a specific capacitance of 158 F∙g^(−1) at a current density of 0.05 A∙g^(−1).The maximum evaporation rates in the solar vapor generation experiments were 1.05 and 1.38 kg∙m^(−2)∙h^(−1) under 100 and 150 mW∙cm^(−2) irradiation,respectively.The good performances are attributed to the robust,porous,and continuous structure.