Microwave hydrothermal synthesis of BiP1−xVxO4/attapulgite nanocomposite with efficient photocatalytic performance for deep desulfurization

Enhancement of the catalytic performance of UIO-66 for the CO2 synthesis of cyclic carbonate using natural nanomaterials as a carrier

One of the environmentally friendly methods is the intelligent utilization of natural one-dimensional nanomaterials as carriers to improve the CO2 catalytic performance of MOF materials. This paper reports an efficient composite catalyst preparation using a cheap and readily available magnesium-aluminosilicate nanometer, attapulgite (ATP), as a carrier for MOF materials. Due to its Lewis acidic site and unique alkaline pore structure, ATP exhibits excellent catalytic activity in the coupling reaction of CO2 with epoxy compounds, and its regular one-dimensional nanorod shape has tremendous potential as a carrier compared to other natural minerals. Given the diversity of MOF material types and structures, the design of this UIO-66/ATP nanocomposite catalyst provides both a new pathway for CO2 capture and conversion and a developmental space for the synthesis of such nanocomposites.

Olive Mill Wastewater Remediation: From Conventional Approaches to Photocatalytic Processes by Easily Recoverable Materials

Olive oil production in Mediterranean countries represents a crucial market, especially for Spain, Italy, and Greece. However, although this sector plays a significant role in the European economy, it also leads to dramatic environmental consequences. Waste generated from olive oil production processes can be divided into solid waste and olive mill wastewaters (OMWW). These latter are characterized by high levels of organic compounds (i.e., polyphenols) that have been efficiently removed because of their hazardous environmental effects. Over the years, in this regard, several strategies have been primarily investigated, but all of them are characterized by advantages and weaknesses, which need to be overcome. Moreover, in recent years, each country has developed national legislation to regulate this type of waste, in line with the EU legislation. In this scenario, the present review provides an insight into the different methods used for treating olive mill wastewaters paying particular attention to the recent advances related to the development of more efficient photocatalytic approaches. In this regard, the most advanced photocatalysts should also be easily recoverable and considered valid alternatives to the currently used conventional systems. In this context, the optimization of innovative systems is today’s object of hard work by the research community due to the profound potential they can offer in real applications. This review provides an overview of OMWW treatment methods, highlighting advantages and disadvantages and discussing the still unresolved critical issues.

Crystal phase, morphology evolution and luminescence properties of Eu3+ -doped BiPO4 phosphor prepared using the hydrothermal method

A series of Bi_1-x Eu_x PO₄ phosphors was successfully prepared using an easy citric acid- assisted hydrothermal method. The effects of synthesis temperature, amount of citric acid, and Eu³⁺ concentration on the crystal phase, morphology, and luminescence properties were investigated. X-ray diffraction results revealed that BiPO₄ :Eu³⁺ formed a hexagonal phase at 80°C, although it transformed to a monoclinic phase when the hydrothermal temperature was increased to 160°C. Moreover, it was found that a small amount of Eu³⁺ doping and the addition of citric acid introduced no secondary or related phases. The morphologies of the samples varied from nanoparticles to spherical microparticles to polyhedrons after the synthesis temperature was adjusted. Particle size was controlled by adding different amounts of citric acid. Under 394 nm excitation, the Bi_0.95 Eu_0.05 PO₄ phosphor prepared at 160°C with 0.3 g of citric acid had excellent luminescence properties. A possible crystal growth mechanism during this reaction is proposed.

Clever use of natural clay materials in the synthesis of non-symmetric carbonates by utilizing CO2 as a feedstock: Ag/attapulgite nano-catalyst

Using natural minerals seems to be one of the most novel and environmentally friendly strategies to design catalysts for CO₂ conversion. Herein, we report a facile and efficient nano-catalyst for the synthesis of non-symmetric carbonate by utilizing a magnesium-aluminium silicate nano-mineral-attapulgite (ATP). Thanks to the unique structure of ATP and its ability to absorb carbon dioxide, the Ag/attapulgite nano-catalyst has excellent catalytic activity and stability in the carbon dioxide fixation reaction. The design of this Ag/attapulgite nano-catalyst provides a novel idea for realizing CO₂ conversion and clay resource utilization.

Understanding the effects of co-exposed facets on photocatalytic activities and fuel desulfurization performance in BiOCl singlet-crystalline sheets

Two kinds of well-crystallized BiOCl singlet-crystalline sheets (BOC-01 with twin-facet co-exposure of {001} and {110} and BOC-02 with tri-facet co-exposure of {001}, {110}, and {010}) were prepared and characterized. The photocatalytic desulfurization performance of BOC-01 and BOC-02 was tested by using n-decane and tetradecane as model oil containing heterocyclic sulfur-containing compounds (benzothiophene, or dibenzothiophene, or 4,6-dimethyldibenzothiophene). The desulfurization performance showed that twin-facet co-exposed BOC-01 had a slightly higher photocatalytic activity than tri-facet co-exposed BOC-02. The differences of photocatalytic activity between BOC-01 and BOC-02 were further explored by paramagnetic resonance spectroscopy, ultraviolet diffuse reflectance spectroscopy, steady-state and time-resolved prompt fluorescencespectra. The results disclosed that the exciton effect in BOC-01 played a key role in photocatalytic activation of molecular oxygen, while BOC-02 mainly produced reactive oxygen species by charge transfer. Theoretical calculations further indicated that the photogenerated electrons are mainly distributed on the {110} facets and the photogenerated holes are mainly distributed on the {001} facets in BOC-01 and BOC-02. This work provides a useful clue for an in-depth understanding of the effects of co-exposed facets in BiOCl on photocatalytic performance.

Full spectrum driven SCR removal of NO over hierarchical CeVO4/attapulgite nanocomposite with high resistance to SO2 and H2O

Removal of hazardous NO at low temperature via photo-assisted selective catalytic reduction (photo-SCR) strategy is promising, however fully harvesting of solar energy and achieving high SO₂/H₂O tolerance still remain a challenge. Herein, the phosphoric acid modified natural attapulgite(P-ATP) was employed as a matrix to immobilize CeVO₄ by microwave hydrothermal method. Results show that P-ATP provides abundant active sites facilitating the in situ grow of CeVO₄ nanorods on its surface which hierarchically construct a dendritic-like photocatalyst. The near-infrared (NIR) light is upconverted to visible and UV light through CeVO₄ which not only broaden the absorption range of solar light, but also build Z-scheme heterostructure with P-ATP enhancing the redox potential of charge carriers. The CeVO₄/P-ATP nanocomposite can reach as high as 92 % for NO conversion under full-spectrum solar irradiation, while retaining nearly 60 % conversion under NIR light. Moreover, the catalyst exhibits outstanding tolerance with SO₂ and H₂O due to the presence of Ce species which can prevent NH₃ from being sulfated, while ATP prevent catalyst from being corroded by H₂O. This work may open up a new window for full-spectrum driven SCR of NO based on cost-effective mineral catalyst.

Z-Scheme Photocatalyst Constructed by Natural Attapulgite and Upconversion Rare Earth Materials for Desulfurization

The Er³⁺:CeO₂/ATP (attapulgite) nanocomposites were prepared by a facile precipitation method. The samples were characterized by various measurements. XRD and TEM showed that Er³⁺:CeO₂ nanoparticles were well-crystallized and loaded on the surface of ATP. The visible light was converted into ultraviolet light by Er³⁺:CeO₂ as evidenced by upconversion photoluminance (PL) analysis. The mass ratio of Er³⁺:CeO₂ to ATP on the desulfurization efficiency was investigated. Results showed that the desulfurization rate reached 87% under 4 h visible light irradiation when the mass ratio was 4:10. The mechanism was put forward as follows. Er³⁺:CeO₂ and ATP formed Z-scheme heterostructure intermediated by oxygen vacancy, leading to the enhanced separation of photogenerated charges and preservation of high oxidation-reduction potential, both of which favored for the generation of radicals to oxidize sulfur species.