Boosting extraction of Pb in contaminated soil via interfacial solar evaporation of multifunctional sponge

Interfacial solar water evaporation is a reliable way to accelerate water evaporation and contaminant remediation.Embracing the recent advance in photothermal technology,a functional sponge was prepared by coating a sodium alginate(SA)impregnated sponge with a surface layer of reduced graphene oxide(rGO)to act as a photothermal conversion medium and then subsequently evaluated for its ability to enhance Pb extraction from contaminated soil driven by interfacial solar evaporation.The SA loaded sponge had a Pb adsorption capacity of 107.4 mg g^(-1).Coating the top surface of the SA sponge with rGO increased water evaporation performance to 1.81 kg m^(-2)h^(-1)in soil media under one sun illumination and with a wind velocity of 2 m s^(-1).Over 12 continuous days of indoor evaporation testing,the Pb extraction efficiency was increased by 22.0%under 1 sun illumination relative to that observed without illumination.Subsequently,Pb extraction was further improved by 48.9%under outdoor evaporation conditions compared to indoor conditions.Overall,this initial work shows the significant potential of interfacial solar evaporation technologies for Pb contaminated soil remediation,which should also be applicable to a variety of other environmental contaminants.

Influence of Indian mustard (Brassica juncea) on rhizosphere soil solution chemistry in long-term contaminated soils:A rhizobox study

This study investigated the influence of Indian mustard （Brassicajuncea） root exudation on soil solution properties （pH, dissolved organic carbon （DOC）, metal solubility） in the rhizosphere using a rhizobox. Measurement was conducted following the cultivation of Indian mustard in the rhizobox filled four different types of heavy metal contaminated soils （two alkaline soils and two acidic soils）. The growth of Indian mustard resulted in a significant increase （by 0.6 pH units） in rhizosphere soil solution pH of acidic soils and only a slight increase （〈 0.1 pH units） in alkaline soils. Furthermore, the DOC concentration increased by 17-156 mg/L in the rhizosphere regardless of soil type and the extent of contamination, demonstrating the exudation of DOC from root. Ion chromatographic determination showed a marked increase in the total dissolved organic acids （OAs） in rhizosphere. While root exudates were observed in all soils, the amount of DOC and OAs in soil solution varied considerably amongst different soils, resulting in significant changes to soil solution metals in the rhizosphere. For example, the soil solution Cd, Cu, Pb, and Zn concentrations increased in the rhizosphere of alkaline soils compared to bulk soil following plant cultivation. In contrast, the soluble concentrations of Cd, Pb, and Zn in acidic soils decreased in rhizosphere soil when compared to bulk soils. Besides the influence of pH and DOC on metal solubility, the increase of heavy metal concentration having high stability constant such as Cu and Pb resulted in a release of Cd and Zn from solid phase to liquid phase.

Chemodynamics of heavy metals in long-term contaminated soils:Metal speciation in soil solution

The concentration and speciation of heavy metals in soil solution isolated from long-term contaminated soils were investigated. The soil solution was extracted at 70% maximum water holding capacity （MWHC） after equilibration for 24 h. The free metal concentrations （Cd^2＋, Cu^2＋, Pb^2＋, and Zn^2＋） in soil solution were determined using the Donnan membrane technique （DMT）. Initially the DMT was validated using artificial solutions where the percentage of free metal ions were significantly correlated with the percentages predicted using MINTEQA2. However, there was a significant difference between the absolute free ion concentrations predicted by MINTEQA2 and the values determined by the DMT. This was due to the significant metal adsorption onto the cation exchange membrane used in the DMT with 20%, 28%, 44%, and 8% mass loss of the initial total concentration of Cd, Cu, Pb, and Zn in solution, respectively. This could result in a significant error in the determination of free metal ions when using DMT if no allowance for membrane cation adsorption was made. Relative to the total soluble metal concentrations the amounts of free Cd^2＋ （3%-52%） and Zn^2＋ （11%-72%） in soil solutions were generally higher than those of Cu^2＋ （0.2%-30%） and Pb^2＋ （0.6%-10%）. Among the key soil solution properties, dissolved heavy metal concentrations were the most significant factor governing free metal ion concentrations. Soil solution pH showed only a weak relationship with free metal ion partitioning coefficients （Kp） and dissolved organic carbon did not show any significant influence on Kp.

Porous carbon-based thermally conductive materials:Fabrication,functions and applications

The demand for electronic devices has dramatically increased in the past few years.Efficient electronic devices require excellent thermal management systems to extend their operation time and prevent heat accumulation from affecting performance.Carbonaceous materials are considered as one of the ideal thermal management materials due to their excellent physiochemical stability.In addition,since porous-structured carbon materials typically exhibit outstanding thermal conductivity,low density,and large contact area,they have attracted considerable attention from both academia and industry in the last decades.In this review,methods and strategies for the preparation of highly thermally conductive porous carbon-based materials and the factors that influence their thermal conductivity of the materials are summarized.The thermal performance of porous carbonaceous materials fabricated by different approaches and their applications are also discussed.Finally,the potential challenges and strategies for the development and applications of highly thermally conductive porous carbona-ceous materials are discussed.

以少胜多:通过选择性去除一部分蒸发表面来增强太阳能光热蒸发

利用最少的光热材料来实现蒸发产出的最大化对于太阳能界面光热蒸发技术的实际应用来说至关重要.本文作者发现二维光热蒸发器的蒸发速率随着其面积的增加而减小.实验和理论模拟结果显示当光热蒸发器面积变大时,其中间部分其实是“蒸发死角区域”,对整个表面的蒸发贡献很小.基于此,作者选择性的将蒸发面的中间部分除去,结果与常理相反,剩余蒸发表面的蒸发速率和蒸汽产出不仅没有下降,反而都上升了.研究发现这是由于去除中间部分后,整个蒸发表面上方的对流重塑和加强了,更有利于蒸汽的逃逸使得蒸发加快.至此,本研究成功发展了一种能够在使用更少材料的情况下实现更高蒸发速率和蒸汽产出的重要策略.

利用高导热蒸发器支撑材料增强太阳能光热蒸发

界面光热蒸发是一种高效的水蒸发技术,在太阳能海水淡化和水处理方面具有广阔的应用前景.光热蒸发器设计的一个重要部分是放置于光热蒸发表面和水体之间的隔热基底/支撑材料.这种典型的设计在二维(2D)蒸发体统中最大限度地减少了从蒸发表面到水体的热传递能量损失,从而将热量集中于蒸发表面以实现高效的光热蒸发.这种设计概念随后被直接应用于三维(3D)蒸发体系中.然而,与2D蒸发器只从太阳光获取能量不同的是,3D蒸发器还可以从空气和水中获取额外能量用于促进蒸发.在这种情况下,传统的隔热基底材料的使用是不合适的,因为它会阻碍蒸发器从水体中抽取能量.因此,本文重新对3D蒸发器进行了设计,使用了高导热材料来代替隔热材料来连接蒸发表面和水体.室内和户外测试均证实,通过使用高导热基底材料可以极大地提高蒸发性能.这一发现为设计3D光热蒸发器提供了新的思路.

基于结构设计的能量调控提升太阳能光热蒸发

界面太阳能光热蒸发是一种既有潜力又经济的海水淡化和废水处理技术.这种技术通过光热材料吸收太阳光,将太阳光转化为热能并将其集中于材料表面进行水蒸发.然而,界面光热蒸发系统由于蒸发过程中的热传导、热对流和热辐射能量损失,使光热蒸发的能量效率降低.因此,高效的能量管理对提高和优化光热蒸发效率至关重要.本文通过对光热材料以及冷、热蒸发表面的精心构筑,使蒸发器的光热蒸发性能得到显著的提升.这是由于这种结构能够同时实现降低体系能量损失,增加从环境中吸取能量,回收利用蒸汽冷凝释放的潜热以及热蒸发表面的热对流和热辐射能量损失.总体来说,通过这种新颖的能量管理策略,该光热蒸发装置的蒸发速度达到了2.94 kg m^-2h^-1,其能量转化效率超过了理论极限值.

A photothermal reservoir for highly efficient solar steam generation without bulk water

A solid photothermal reservoir is designed to implement solar-steam generation in the absence of bulk water.The photothermal reservoir is composed of a water absorbing core encapsulated by a photothermal reduced graphene oxide based aerogel sheet which absorbs light and converts it into heat thus evaporating the stored water.The photothermal reservoir is able to store 6.5 times its own weight in water,which is sufficient for one day solar evaporation,thus no external water supplement is required.During solar-steam generation,since no bulk water is involved,the photothermal reservoir minimizes heat conduction loss,and maximizes both of the exposed evaporation surface area and net energy gain from the environment,leading to an energy efficiency beyond the theoretical limit.An extremely high water evaporation rate of 4.0 kg m-2 h-1(normalized to projection area)is achieved in laboratory studies over a cylinder photothermal reservoir with a diameter of 5.2 cm and a height of 15 cm under 1.0 sun irradiation.Practical evaluation of the photothermal reservoir outdoors as part of a desalination device demonstrates a similar evaporation rate where the salinity of the clean water produced is lower than 24 ppb.Thus the photothermal reservoir shows great potential for real world applications in portable solarthermal desalination.

Evaluation of immobilizing agents as soil quality conditioners in addition to their metal(loid) immobilizing effect

In trace metal (TM)-contaminated agricultural soils,management of TM availability is important for safe crop production.In addition,maintenance or improvement of soil quality is vital for sustainable crop cultivation.Decreased TM phytoavailability and increased soil quality can be achieved by the application of various immobilizing agents to soil,which can supply both macronutrients and organic matter.This study investigated the long-term influences of four common immobilizing agents on soil biogeochemical properties and the phytoavailability of TMs in mixed metal-contaminated soil from a cultivated upland near an abandoned mining site.Lime (L),gypsum (G),fly ash (F),and animal manure-based compost (C) were applied to pots containing contaminated soil,either individually or in combination.After incubation for three years under sequential cultivation of two crops and fallow,soil biogeochemical properties were determined,and Brassica rapa plant bioassay was performed.The phytoavailability of all TMs (both cationic metals and anionic metalloids) remained significantly lower in soils treated with immobilizing agents even after three years,when compared with the no-agent control (CK) soil.In addition,the soil quality was significantly improved by treatment with immobilizing agents.For instance,the C and L+C treatments were the most effective in improving soil physical (bulk density,porosity,and water-resistant aggregate stability),chemical (pH,organic matter,total nitrogen,cation exchange capacity,and plant-available phosphorus,magnesium,and potassium),and biological (microbial biomass carbon and dehydrogenase activity) properties.The improvement of soil properties and lowering of TM bioavailability were also consistent with the most significant increase in B.rapa biomass production observed in the C treatment,followed by the L+C,G+F,L,G,F,and L+G treatments,as compared with that in CK.These results indicate that the function of the TM-immobilizing agent as a soil quality conditioner,in addition to its TM immobilizing effect,should be considered when selecting such agents for agricultural or ecological applications.

A cobalt oxide@polydopamine-reduced graphene oxide-based 3D photothermal evaporator for highly efficient solar steam generation

Improving the evaporation rate and energy efficiency of solar steam generation is very important to facilitate real-world applications for clean water production.In this work,Co_(3)O_(4)@polydopamine(PDA)nanoparticles were synthesized and combined with reduced graphene oxide(rGO)to fabricate a new Co_(3)O_(4)@PDA-rGO photothermal aerogel.The obtained pho-tothermal aerogel sheet was thereafter used to prepare both two-dimensional(2D)and three-dimensional(3D)photothermal evaporators for solar steam generation.Due to the excellent light absorption and hydrophilicity of the photothermal aerogel,a high evaporation rate of 1.60 kg·m^(−2)·h^(−1) was achieved for the 2D photothermal evaporator.While for the 3D evaporator,the evaporation rate was dramatically increased to 3.71 kg·m^(−2)·h^(−1) with a corresponding light-to-vapor energy efficiency of 107%.This was attributed to an increased evaporation surface area,decreased energy loss from the top evaporation surface to the environment,and energy gain from the environment on the side evaporation surface.The 3D evaporator also showed excellent practical performance in seawater desalination thus demonstrating great potential for real-world applications.