Latest ArticlesThe textile industry spreads globally with the challenges of its wastewater treatment, especially dyes, which are difficult to degrade. To improve coagulation-flocculation process in dye wastewater treatment, an intercalation process was employed to prepare a new efficient coagulant of lithium borohydride-iron oxychloride (LiBH4_FeOCl) in this study. The layered crystal pristine iron oxychloride (FeOCl) material was prepared by chemical gas phase migration. LiBH4 was introduced into the layers of two dimensional (2D) FeOCl nanosheets by a simple method of liquid phase insertion. The samples were characterized by a field emitting scanning electron microscopy (SEM), a rotating anode X-ray powder diffractometer (XRD), etc. The cationic dye was employed as the simulated pollutant. A coagulation and decolorization experimental device was built to study the coagulation performance of the new coagulant LiBH4_FeOCl. It is found that the intercalation modified LiBH4_FeOCl exhibits the characteristics of crystal structure, and the layered structure of FeOCl is preserved. LiBH4_FeOCl, as an insoluble inorganic solid coagulant, performs well for dye pollutants of methyl red, basic yellow 1, methylene blue, rhodamine B, ethyl violet and Janus green B. The reaction rate is significantly 68% higher than the current commercial coagulants of Al2(SO4)3. The mechanism analysis reveals that LiBH4_FeOCl breaks and disperses rapidly in the water environment. Its negatively charged material particles can be electrostatically adsorbed with dye pollutant molecules through electrostatic action. The above collaborative actions of breaking, dispersion and electrostatic adsorption are the main coagulation mechanisms of LiBH4_FeOCl. The solid inorganic coagulant of LiBH4_FeOCl provides a competitive alternative for traditional inorganic salts and organic coagulants.
MnOx-CeO2 catalysts are developed by hydrolysis driving redox method using acetate precursor (3Mn1Ce-Ac) and nitrate precursor (3Mn1Ce-N) for the selective catalytic reduction (SCR) of NOx by NH3. A counterpart sample (Cop-3Mn1Ce) was prepared by the NH3·H2O co-precipitation method for comparison purpose. Combining the results of physicochemical properties characterization and performance test, we find that the 3Mn1Ce-Ac catalyst with some nanorod structures is highly active for the deNOx process. The SCR activity of the 3Mn1Ce-Ac catalyst is more admirable than the 3Mn1Ce-N and the Cop-3Mn1Ce catalysts due to plentiful Lewis acid sites, excellent low-temperature reducibility, and superior surface area resulted from O2 generation during the preparation procedure. The 3Mn1Ce-Ac still exhibits the greatest performance for the deNOx process when gaseous acetone is in the SCR feed gas. The NOx conversion and N2 selectivity over the 3Mn1Ce-Ac are both improved by gaseous acetone above 150 ℃ due to the inhibition of SCR undesired side reactions (NSCR & C-O reactions) and "slow-SCR" process.
In this study, Mn catalysts have been designed based on manganese oxide octahedral molecular sieve (OMS-2) supports to optimize the catalytic activity in the degradation of organic pollutants. Herein, two different synthetic strategies: Pre-incorporation vs. wet-impregnation have been employed to synthesize [PW]-OMS-2 and [PW]/OMS-2. For [PW]-OMS-2, energy dispersive X-ray spectroscopy (EDX) confirmed that dispersed granular phosphotungstic acid attached and located at the surface of OMS-2, meanwhile some W atoms have been doped into frameworks of OMS-2. However, for [PW]/OMS-2, the W atoms cannot enter the OMS-2 frameworks. A correlation has been established between the different synthetic strategies and catalytic activities. The [PW]-OMS-2 is the most highly effective and stable over than [PW]/OMS-2 and OMS-2 itself for the organic pollutants removal. This may be caused not only by the synergetic effect of [PW] and OMS-2, but also by doping W into frameworks of OMS-2. Therefore, this work provides a new environmentally-friendly and heterogeneous PMS activator and it may be put into practice to degrade organic pollutants.
Environmental risks posed by discharge of the emerging contaminant antimony (Sb) into water bodies have raised global concerns recently. The toxicity of Sb has been shown to be species-dependent, with Sb(III) demonstrating much greater toxicity than Sb(V). Here, we proposed an electrochemical filtration system to achieve rapid detoxification of Sb(III) via a non-radical pathway. The key to this technology was an electroactive carbon nanotube filter functionalized with nanoscale Ti-Ce binary oxide. Under an electric field, in situ generated H2O2 could react with the Ti-Ce binary oxide to produce hydroperoxide complexes, which enabled an efficient transformation of Sb(III) to the less toxic Sb(V) (τ < 2 s) at neutral pH. The impact of important operational parameters was assessed and optimized, and system efficacy could be maintained over a wide pH range and long-term operation. An optimum detoxification efficiency of > 90% was achieved using lake water spiked with Sb(III) at 500 μg/L. The results showed that Ti/Ce-hydroperoxo surface complexes were the dominant species responsible for the non-radical oxidation of Sb(III) based on extensive experimental evidences and advanced characterizations. This study provides a robust and effective strategy for the detoxification of water containing Sb(III) and other similar heavy metal ions by integrating state-of-the-art advanced oxidation processes, electrochemistry and nano-filtration technology.
To enhance the photodegradation ability of CeO2 for organic dyes, an effective strategy is to introduce oxygen vacancies (Vo). In general, the introduced Vo are simultaneously present both on the surface and in the bulk of CeO2. The surface oxygen vacancies (Vo-s) can decrease the band gap, thus enhancing light absorption to produce more photogenerated e− for photodegradation. However, the bulk oxygen vacancies (Vo-b) will inhibit photocatalytic activity by increasing the recombination of photogenerated e− and Vo-b. Therefore, regulating the concentrations of Vo-s to Vo-b is a breakthrough for achieving the best utilization of photogenerated e− during photodegradation. We used an easy hydrothermal method to achieve tunable concentrations of Vo-s to Vo-b in CeO2 nanorods. The optimized CeO2 presents a 70.2% removal of rhodamine B after 120 min of ultraviolet−visible light irradiation, and a superior photodegradation performance of multiple organics. This tuning strategy for Vo also provides guidance for developing other advanced metal-oxide semiconductor photocatalysts for the photodegradation of organic dyes.
Bimetallic nanoparticles modified hollow-structured nanoporous carbons (NPCs) have been fabricated via a convenient one-step carbonizing strategy derived from covalent organic framework. The Pd/Fe/NPCs, Pt/Fe/NPCs and Rh/Fe/NPCs were obtained and can be used as Fenton-like catalysts with good stability and reusability. The catalytic activity was evaluated by the degradation of 2, 4-dichlorophenl (2, 4-DCP). These fabricated bimetallic catalysts exhibited much higher catalytic activity than Fe/NPCs at room temperature. The enhancement of catalytic ability was benefited from synergetic catalytic effect of bimetallic nanoparticles and accelerated mass transfer of hollow structure. Additionally, the enhanced catalytic mechanism of bimetallic catalysts was studied in detail and the reasonable reaction pathway was proposed. Besides, the bimetallic catalysts were successfully used for degradation of 2, 4-DCP in actual industrial wastewater and the removal efficiency could reach 74.3% within 120 min, which demonstrated the promising potential application of bimetallic catalysts in the removal of pollutants in environment.
Semiconductor-mediated photocatalysis is a promising photochemical process for harvesting inexhaustible solar energy to address the energy crisis and environmental issues. However, the low solar-light response and poor carrier migration are severe drawbacks that limit its practical application. Herein, we propose a convenient pathway for improving electron-hole separation and solar energy utilisation by engineering defective ZnIn2S4 with doping of carbon dots. The optimum ZnIn2S4/CD200 nanosheet exhibited 100% diclofenac (DCF) degradation within 12 min under visible-light. The estimated photocatalytic efficiency under natural sunlight was 98.2%. Scavenging experiments and electron spin resonance (ESR) analysis indicated that the superoxide radical (O2∙−), photoelectron (e−), hole (h+) and hydroxyl radical (∙OH) were the predominant contributions in the ZnIn2S4/CD200/DCF/visible light system. Furthermore, ZnIn2S4/CD200 exhibited excellent reusability and stability after 4 times recycling. The photodegradation routes mainly involved hydroxylation, decarboxylation, CN bond cleavage, dechlorination, ring closure, and ring-opening. The ecological risk assessment and total organic carbon (TOC) tests exhibited desirable toxicity reduction and mineralization results. These observations not only offer a facile strategy for the construction of defective ZnIn2S4, but also pioneer the direct utilisation of natural light for highly efficient environmental remediation.
Constructing a heterojunction photocatalyst is a significant method to enhance photocatalytic activity because it can promote the separation of photogenerated carriers. Herein, amorphous/crystalline contact Bi2S3/Bi4O7 heterostructure was successfully synthesized by in-situ sulfidation of Bi4O7. The amorphous Bi2S3 is diffused on the surface of Bi4O7 rod, enhancing the visible light response and improving the transport of photogenerated carriers. Various characterizations confirm that the rapid separation of photogenerated carriers leads to increased photocatalytic performance. The optimized Bi2S3/Bi4O7 heterostructure photocatalyst (BiS-0.15) exhibits the highest Cr(VI) reduction (0.01350 min−1) and RhB oxidation (0.08011 min−1) activity, which is much higher than that of pure Bi4O7 and Bi2S3/Bi4O7 mixture under visible light irradiation. This work provides new insights into the construction of efficient novel photocatalysts.
Recently, the degradation of organic compounds in saline dye wastewater by sulfate radicals (SO4·-)-based advanced oxidation processes (AOPs) have attracted much attention. However, previous studies on these systems have selected non-chlorinated dyes as model compounds, and little is known about the transformation of chlorinated dyes in such systems. In this study, acid yellow 17 (AY-17) was selected as a model of chlorinated contaminants, and the degradation kinetics and evolution of oxidation byproducts were investigated in the UV/PDS system. AY-17 can be efficiently degraded (over 98% decolorization) under 90 min irradiation at pH 2.0–3.0, and the reaction follows pseudo-first order kinetics. Cl- accelerated the degradation of AY-17, but simultaneously led to an undesirable increase of absorbable organic halogen (AOX). Several chlorinated byproducts were identified by liquid chromatography-mass spectrometry (LC–MS/MS) in the UV/PDS system. It indicates that endogenic chlorine and exogenic Cl– reacted with SO4·- to form chloride radicals, which are involved in the dechlorination and rechlorination of AY-17 and intermediates. The possible degradation mechanisms of AY-17 photooxidative degradation are proposed. This work provides valuable information for further studies on the role of exogenic chloride in the degradation of chlorinated azo dyes and the kinetic parameters in the PDS-based oxidation process.
Ynamides are electron-rich alkynes with unique reactivities and act as flexible building blocks in organic synthesis. Therefore, the investigation for transformation of ynamides with exceptional selectivity and efficiency is attractive and interesting. Herein, we report an oxoarylation of ynamides with N-aryl hydroxamic acids. In the presence of catalytic Cu(OTf)2, both the terminal and internal ynamides could undergo an addition/[3,3] sigmatropic rearrangement cascade with N-aryl hydroxamic acids to achieve oxoarylation, along with providing selective entry to (ortho-amino)arylacetamides and oxindoles. Moreover, deuterium-labelling reaction and gram-scale reaction were conducted to probe the mechanism and showcase the scalability.
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