利用商用凝胶型离子交换树脂实现超微纳米颗粒的大规模生产与高效水处理

纳米技术为深度水处理提供了新的机遇。然而,高活性超微(<5 nm)纳米颗粒材料的大规模生产仍存在挑战,且超微材料在实际水处理中也存在操作困难等问题,阻碍了纳米技术在水污染控制领域的推广应用。针对这些问题,我们提出了一种简便的解决方法,即以商用凝胶型离子交换树脂N201为载体合成超微纳米颗粒。N201是一种季铵化的毫米级聚(苯乙烯二乙烯基苯共聚)小球。在N2O1中通过简单的浸渍-沉淀获得了水合氧化铁(HFO)、水合氧化锰(HMO)、硫化镉(CdS)和零价铁(ZVI)等纳米颗粒,所有纳米颗粒的尺寸都小于5 nm。中试生产表明该合成方法可方便放大,并制备了大量亚5 nm HFO颗粒。关于超微纳米颗粒的合成机理,我们认为在每个在水中溶胀的N201小球内都包含连续均匀水相,使反应物可快速地扩散到树脂球内部(7 s内从小球表面扩散到中心),从而实现纳米颗粒的爆发成核,形成超窄尺寸分布的晶核。此外,交联聚合物链间还可形成狭窄的孔隙(直径<5 nm),可防止在其中形成的纳米颗粒过度生长。由于N201载体具有毫米级尺寸,所制备复合的纳米材料可方便用于连续流装置中。批次实验和柱吸附测试表明,超微HFO颗粒对As(Ⅲ/Ⅴ)的吸附性能比约17 nm的HFO显著增强。本研究有望进一步促进纳米技术在实际水处理中的推广应用。

Confinement of Fe atoms between MoS_(2) interlayers drives phase transition for improved reactivity in Fenton-like reactions

Phase manipulation of MoS_(2) from thermodynamically stable 2H phase to the unstable but more reactive 1T phase represents a crucial strategy for improving the reactivity in many reactions.The widely adopted wet chemistry approach uses intercalating entities especially alkali metal ions to achieve the phase transition;however,these entities are normally inert for the target reaction.Here,we describe the first use of iron atoms for the intercalation of 2H-MoS_(2) layers,driving the partial transition from 2H to 1T phase.Interestingly,in the peroxymonosulfate(PMS)-based Fenton-like reactions,the interlayered confinement of Fe atoms not only activates the inert basal plane,but also adds more reactive Fe sites for the formation of metal-PMS complex as primary reactive species for pollutant removal.In the degradation of a model pollutant carbamazepine(CBZ),the Fe-intercalated MoS_(2) exhibits a first order rate constant 13.3 times higher than 2H-MoS_(2).This strategy is a new direction for manipulating the phase composition and boosting the catalytic reactivity of MoS_(2)-based catalysts in various scenarios,including environmental remediation and energy applications.

Partial aging can counter-intuitively couple with sulfidation to improve the reactive durability of zerovalent iron

Sulfated zero-valent iron(SZVI)has shown promising applications in wastewater treatment.However,the rapid decline in the reactivity of SZVI with time limits its real practice.To mediate this problem,partial aging was proposed to improve the reactive durability of SZVI.Taking Cr(VI)as the target contaminant,we found that the aged ZVI(AZVI)gradually lost reactivity as aging time increased from 0.5 to 2 d.Counter-intuitively,the partially aged SZVI(ASZVI)showed greater reactivity than SZVI when exposed to oxygenated water for a period ranging from 0.5 to 14 d.In addition,the ASZVI with 0.5 d of aging time(ASZVI-0.5)not only maintained reactivity in successive runs but also increased the Cr(VI)removal capacity from 9.1 mg/g by SZVI to 19.1 mg/g by ASZVI-0.5.Correlation analysis further revealed that the electron transfer from the Fe0 core to the shell was mediated by the conductive FeS and FeS2 in the subshell of ASZVI.Meanwhile,the lepidocrocite and magnetite on the surface of ASZVI facilitated Cr(VI)adsorption and subsequent electron transfer for Cr(VI)reduction.Moreover,the iron(hydr)oxide shell could retain the conductive FeS and FeS2 in the subshell,allowing ASZVI to reduce Cr(VI)efficiently and sustainably.In general,partial aging can enhance the reactive durability of ZVI when coupled with sulfidation and this synergistic effect will be beneficial to the application of SZVI-based technology for wastewater treatment.

Weakly hydrophobic nanoconfinement by graphene aerogels greatly enhances the reactivity and ambient stability of reactivity of MIL-101-Fe in Fenton-like reaction

In the pursuit of heterogeneous catalysts with high reactivity,metal organic framework(MOF)nanomaterials have received tremendous attentions.However,many MOF catalysts especially Fe-based MOFs need to be utilized immediately after synthesis or being activated using high temperature,because of the easy loss of reactivity in humid environments resulting from the occupation of active Fe sites by water molecules.Here,we describe an inspiring strategy of growing MIL-101-Fe nanoparticles inside the three-dimensional confined space of graphene aerogel(GA),generating shapeable GA/MIL-101-Fe nanocomposite convenient for practical use.Compared to MIL-101-Fe,GA/MIL-101-Fe as catalyst demonstrates much higher reactivity in Fenton-like reaction,attributing to smaller MIL-101-Fe particle size,presence of active Fe(II)sites,and abundant defects in GA.Strikingly,the weakly hydrophobic nature of the composite greatly inhibits the loss of catalytic reactivity after being stored in humid air and accelerates the recovery of reactivity in mild temperature,by resisting the entrance of water molecules and helping to exclude water molecules.This work demonstrates that a delicate design of nanocomposite structure could not only improve the reactivity of the catalytic component,but also overcome its intrinsic drawback by taking advantage of the properties of host.We hope this functional nanoconfinement strategy could be extended to more scenarios in other fields.