Synergetic effect of ZnIn2S4 nanosheets with metal-organic framework molding heterostructure for efficient visible- light driven photocatalytic reduction of Cr(VI)

Metal organic framework anchored onto biowaste mediated carbon material (rGO) for remediation of chromium (VI) by the photocatalytic process

Groundwater contaminated with hexavalent chromium Cr(VI) causes serious health concerns for the ecosystem. In this study, a hybrid amino functionalized MOF@rGO nanocatalyst was produced by utilization of a biowaste mediated carbon material (reduced graphene oxide; rGO) and its surface was modified by in situ synthesis of a nanocrystalline, mixed ligand octahedral MOF containing iron metal and NH2 functional groups and the prepared composite was investigated for Cr (VI) removal. The photocatalytic degradation of Cr(VI) in aqueous solutions was carried out under UV irradiation. Using a batch mode system, the effect of numerous control variables was examined, and the process design and optimization were carried out by response surface methodology (RSM). The photocatalyst, NH2-MIL(53)-Fe@rGO, was intended to be a stable and highly effective nanocatalyst throughout the recycling tests. XRD, SEM, EDS, FTIR examinations were exploited to discover more about surface carbon embedded with MOF. 2 g/L of NH2-MIL-53(Fe)/rGO was utilized in degrading 200 mg/L of Cr(VI) in just 100 min, implying the selective efficacy of such a MOF-rGO nanocatalyst. Moreover, the Eg determinations well agreed with the predicted range of 2.7 eV, confirming its possibility to be exploited underneath visible light, via the Tauc plot. Thus, MOF anchored onto biowaste derived rGO photo-catalyst was successfully implemented in chromium degradation.

Construction of UiO-66-NH2 decorated by MoS2 QDs as photocatalyst for rapid and effective visible-light driven Cr(VI) reduction

The photoactive metal-organic frameworks (MOFs) are good candidates for photocatalysts, but the quick electron-hole pairs recombination has greatly restricted the photocatalytic ability of MOFs. To improve the photoactivity of MOFs, MOFs-based composite materials have been extensively studied. Here, we successfully integrated MoS2 quantum dots (QDs) with UiO-66-NH2 for the first time under hydrothermal conditions. The as-prepared MoS2 QDs/UiO-66-NH2 (MS-U) had good visible light response ability (absorption edge at 445 nm), and charge separation and transfer ability, which lays the foundation for the photocatalytic Cr(VI) reduction. Photocatalytic studies revealed that MoS2 QDs-5/UiO-66-NH2 (MS-U-5) had superior Cr(VI) reduction activity than pure MoS2 QDs and UiO-66-NH2. MS-U-5 could remove 98% Cr(VI) at pH= 2 with visible light irradiation for 20 min, which is the fastest visible light driven Cr(VI) reduction rate among the reported MOFs-based composite photocatalysts without the presence of any cocatalysts or scavengers as far as we know. Importantly, MS-U-5 could be reused at least three times. In the end, the possible electron transfer path and mechanism of Cr(VI) reduction was also investigated.

Functionalized Fe3O4-based methyl methacrylate Pickering PolyHIPE composites costabilized by fluorinated block copolymer for oil/water separation

High internal phase emulsion (HIPE) technology has been emerged as a prodigious source to create tailor-made porous structures. This type of emulsion contains significantly higher amount of water in it, which is only possible with special type of stabilizers. Most specifically, the monomers with sufficiently high solubility in water such as methyl methacrylate (MMA) make it more cumbersome to stabilize in the form of HIPE. Here we have reported the combination of stabilizers including fluorinated block copolymer Poly (2-dimethylamino)ethyl methacrylate-b-Poly(trifluoroethyl methacrylate) (PDMAEMA-b-PTFEMA) and humic acid modified iron-oxide (HA-Fe₃O₄) nanoparticles (NPs) to stabilize HIPE, which resulted in highly porous and interconnected products. Fluorinated block copolymers with inherent hydrophobic nature along with iron oxide nanoparticles increased the water repellency of MMA based polymeric monoliths. Increasing the amount of stabilizer increased the porosity and BET specific surface area to 83.8% and 27 ± 0.8 μm, respectively. The prepared porous materials demonstrated hydrophobic characteristics while adsorbing oil from the surface of water up to 16 g/g. Moreover, the adsorbed oil from the prepared monolith was recovered by using simple centrifugation method without damaging the structure. This research opens new avenues to prepare more useful oil and water separation materials such as membranes, pollutant adsorbers, and so on.

Remediation techniques for elimination of heavy metal pollutants from soil: A review

Contaminated soil containing toxic metals and metalloids is found everywhere globally. As a consequence of adsorption and precipitation reactions, metals are comparatively immobile in subsurface systems. Hence remediation techniques in such contaminated sites have targeted the solid phase sources of metals such as sludges, debris, contaminated soils, or wastes. Over the last three decades, the accumulation of these toxic substances inside the soil has increased dramatically, putting the ecosystem and human health at risk. Pollution of heavy metal have posed severe impacts on human, and it affects the environment in different ways, resulting in industrial anger in many countries. Various procedures, including chemical, biological, physical, and integrated approaches, have been adopted to get rid of this type of pollution. Expenditure, timekeeping, planning challenges, and state-of-the-art gadget involvement are some drawbacks that need to be properly handled. Recently in situ metal immobilization, plant restoration, and biological methods have changed the dynamics and are considered the best solution for removing metals from soil. This review paper critically evaluates and analyzes the numerous approaches for preparing heavy metal-free soil by adopting different soil remediation methods.

Recent Progress in the Development of MOF-Based Photocatalysts for the Photoreduction of Cr(VI)

There has been a direct correlation between the rate of industrial development and the spread of pollution on Earth, particularly in the last century. The organic and inorganic pollutants generated from industrial activities have created serious risks to human life and the environment. The concept of sustainability has emerged to tackle the environmental issues in developing chemical-based industries. However, pollutants have continued to be discharged to water resources, and finding appropriate techniques for the removal and remedy of wastewater is in high demand. Chromium is one of the high-risk heavy metals in industrial wastewaters that should be removed via physical adsorption and/or transformed into less hazardous chemicals. Photocatalysis as a sustainable process has received considerable attention as it utilizes sunlight irradiation to remedy Cr^(VI) via a cost-effective process. Numerous photocatalytic systems have been developed up to now, but metal-organic frameworks (MOFs) have gained growing attention because of their unique versatilities and facile structural modulations. A variety of MOF-based photocatalysts have been widely employed for the photoreduction of Cr^(VI). Here, we review the recent progress in the design of MOF photocatalysts and summarize their performance in photoreduction reactions.

Recent advances in the application of water-stable metal-organic frameworks: Adsorption and photocatalytic reduction of heavy metal in water

Heavy metals pollution in water is a global environmental issue, which has threatened the human health and environment. Thus, it is important to remove them under practical water environment. In recent years, metal-organic frameworks (MOFs) with water-stable properties have attracted wide interest with regard to the capture of hazardous heavy metal ions in water. In this review, the synthesis strategy and postsynthesis modification preparation methods are first summarized for water-stable MOFs (WMOFs), and then the recent advances on the adsorption and photocatalytic reduction of heavy metal ions in water by WMOFs are reviewed. In contrast to the conventional adsorption materials, WMOFs not only have excellent adsorption properties, but also lead to photocatalytic reduction of heavy metal ions. WMOFs have coupling and synergistic effects on the adsorption and photocatalysis of heavy metal ions in water, which make it more effective in treating single pollutants or different pollutants. In addition, by introducing appropriate functional groups into MOFs or synthesizing MOF-based composites, the stability and ability to remove heavy metal ions of MOFs can be effectively enhanced. Although WMOFs and WMOF-based composites have made great progress in removing heavy metal ions from water, they still face many problems and challenges, and their application potential needs to be further improved in future research. Finally, this review aims at promoting the development and practical application of heavy metal ions removal in water by WMOFs.

ZnIn2 S4 -Based Photocatalysts for Energy and Environmental Applications

As a fascinating visible-light-responsive photocatalyst, zinc indium sulfide (ZnIn₂ S₄ ) has attracted extensive interdisciplinary interest and is expected to become a new research hotspot in the near future, due to its nontoxicity, suitable band gap, high physicochemical stability and durability, ease of synthesis, and appealing catalytic activity. This review provides an overview on the recent advances in ZnIn₂ S₄ -based photocatalysts. First, the crystal structures and band structures of ZnIn₂ S₄ are briefly introduced. Then, various modulation strategies of ZnIn₂ S₄ are outlined for better photocatalytic performance, which includes morphology and structure engineering, vacancy engineering, doping engineering, hydrogenation engineering, and the construction of ZnIn₂ S₄ -based composites. Thereafter, the potential applications in the energy and environmental area of ZnIn₂ S₄ -based photocatalysts are summarized. Finally, some personal perspectives about the promises and prospects of this emerging material are provided.