Innovative W-doped titanium dioxide anchored on clay for photocatalytic removal of atrazine

The origin of dielectric relaxation behavior in TiO2 based ceramics co-doped with Zn2+, W6+ ions under a N2/O2 sintering atmosphere

Dense (Zn_0.5W_0.5)_xTi_1-xO₂ (ZWTO_x) ceramics were fabricated using a conventional solid state reaction method with sintering under a nitrogen atmosphere (ZWTO_x-N₂) and an oxygen atmosphere (ZWTO_x-O₂), respectively. Colossal permittivity (ε > 10⁴) and low loss (tan δ < 0.1) were simultaneously achieved in ZWTO_x-N₂ ceramics, and two types of dielectric relaxation behaviors observed were interpreted to be due to interface polarization and disassociation between oxygen vacancies and trivalent titanium ions, respectively. The impedance plots suggested that the ZWTO_x-N₂ ceramics are electrical heterostructures composed of semiconductor and insulator grain boundaries, which proved that the CP performance of ZWTO_x-N₂ ceramics almost originates from the internal barrier layer capacitance (IBLC) effect. In addition, a series of anomalous dielectric behaviors such as low permittivity and low frequency dispersion were observed for ZWTO_x-O₂ ceramics; polarization (P)-electric field (E) hysteresis loop curves were obtained for ZWTO_x-O₂ ceramics, and that impedance plots have shown that the ZWTO_x-O₂ ceramics display higher insulation resistivity. Density functional theory (DFT) calculations illustrated that the Zn²⁺-W⁶⁺ ion pairs are easy to form in ZWTO_x-O₂ ceramics, which causes destruction of the local lattice and thus leads to abnormal dielectric behavior. This work will provide a new strategy for defect engineering in TiO₂ and other CP materials.

Clay-Supported Metal Oxide Nanoparticles in Catalytic Advanced Oxidation Processes: A Review

Advanced oxidation processes (AOPs) utilizing heterogeneous catalysts have attracted great attention in the last decade. The use of solid catalysts, including metal and metal oxide nanoparticle support materials, exhibited better performance compared with the use of homogeneous catalysts, which is mainly related to their stability in hostile environments and recyclability and reusability. Various solid supports have been reported to enhance the performance of metal and metal oxide catalysts for AOPs; undoubtedly, the utilization of clay as a support is the priority under consideration and has received intensive interest. This review provides up-to-date progress on the synthesis, features, and future perspectives of clay-supported metal and metal oxide for AOPs. The methods and characteristics of metal and metal oxide incorporated into the clay structure are strongly influenced by various factors in the synthesis, including the kind of clay mineral. In addition, the benefits of nanomaterials from a green chemistry perspective are key aspects for their further considerations in various applications. Special emphasis is given to the basic schemes for clay modifications and role of clay supports for the enhanced mechanism of AOPs. The scaling-up issue is suggested for being studied to further applications at industrial scale.

Z-scheme LaCoO3/C3N5 for efficient full-spectrum light-simulated solar photocatalytic hydrogen generation

An inexpensive and efficient LaCoO3/C3N5 photocatalytic system for water splitting or other photocatalytic applications was designed. The photocatalytic reaction and mechanism of C3N5 and its complexes was verified.

Ultrathin tungsten-doped hydrogenated titanium dioxide nanosheets for solar-driven hydrogen evolution

Ultrathin tungsten-doped hydrogenated TiO2 (W-h-TiO2) nanosheets are highly efficient for photocatalytic hydrogen production by water splitting without a noble metal cocatalyst.

A review on occurrence of emerging pollutants in waters of the MENA region

Little is known about the occurrence of emerging pollutants (EPs) in waters in the Middle East and North Africa (MENA) region despite the extensive use of low-quality water there. Available data dealing with the sources, occurrence and removal of EPs within the MENA region in different categories of water is collected, presented and analyzed in this literature review. According to the collected database, the occurrence and removal efficiency of EPs in the water matrix in the MENA region is available, respectively, for 13 and six countries of the 18 in total; no available data is registered for the rest. Altogether, 290 EPs have been observed in different water matrices across the MENA countries, stemming mainly from industrial effluents, agricultural practices, and discharge or reuse of treated wastewater (TWW). Pharmaceutical compounds figure among the most frequently reported compounds in wastewater, TWW, surface water, and drinking water. Nevertheless, pesticides are the most frequently detected pollutants in groundwater. Worryingly, 57 cases of EPs have been reported in different fresh and drinking waters, exceeding World Health Organization (WHO) and European Commission (EC) thresholds. Overall, pharmaceuticals, organic compounds, and pesticides are the most concerning EP groups. The review revealed the ineffectiveness of treatment processes used in the region to remove EPs. Negative removals of some EPs such as carbamazepine, erythromycin, and sulfamethoxazole were recorded, suggesting their possible accumulation or release during treatment. This underlines the need to set in place and strengthen control measures, treatment procedures, standards, and policies for such pollutants in the region.

Titania-Clay Mineral Composites for Environmental Catalysis and Photocatalysis

The use of titania-based composite materials in the field of heterogeneous catalysis and photocatalysis has a long and rich history. Hybrid structures combining titania nanoparticles with clay minerals have been extensively investigated for nearly four decades. The attractiveness of clay minerals as components of functional materials stems primarily from their compositional versatility and the possibility of using silicate lamellae as prefabricated building blocks ready to be fitted into the desired nanoconstruction. This review focuses on the evolution over the years of synthetic strategies employed for the manufacturing of titania–clay mineral composites with particular attention to the role of the adopted preparative approach in shaping the physical and chemical characteristics of the materials and enabling, ultimately, tuning of their catalytic and/or photocatalytic performance.

Probing the formation and optical properties of Ti3+–TiO2 with (001) exposed crystal facet by ethanol-assisted fluorination

(001)-faceted TiO₂ with Ti³⁺ defects that are exclusively embedded in the bulk lattice near the surface was synthesized.

Z-Scheme LaCoO3/g-C3N4 for Efficient Full-Spectrum Light-Simulated Solar Photocatalytic Hydrogen Generation

Photocatalytic decomposition of water is the most attractive method for the sustainable production of hydrogen, but the development of a highly active and low-cost catalyst remains a major challenge. Here, we report the preparation of LaCoO3/g-C3N4 nanosheets and the utilization of LaCoO3 instead of noble metals to improve the photocatalytic activity for the production of hydrogen. First, LaCoO3 was successfully prepared by the sol-gel method, and then a series of highly efficient Z-scheme LaCoO3/g-C3N4 heterojunction photocatalysts were synthesized by the solvothermal method. Various characterization techniques (X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (DRS), photoluminescence (PL), transient photocurrent response test, electron paramagnetic resonance (EPR)) confirm that the heterostructure and interfacial interaction had been formed between LaCoO3 nanoparticles and g-C3N4 nanosheets. In the photocatalytic water splitting test, LaCoO3/g-C3N4-20 wt % exhibited the highest photocatalytic activity of 1046.15 μmol h-1 g-1, which is 3.5 and 1.4 times higher than those of LaCoO3 and g-C3N4, respectively. This work leads to an inexpensive and efficient LaCoO3/g-C3N4 photocatalysis system for water splitting or other photocatalytic applications.

Removal of Pharmaceutical Contaminants in Wastewater Using Nanomaterials: A Comprehensive Review

BACKGROUND

The limitless presence of pharmaceutical contaminants in discharged wastewater has emerged as a threat to aquatic species and humans. Their presence in drinking water has although raised substantial concerns, very little is known about the fate and ecological impacts of these pollutants. As a result, these pollutants are inevitably introduced to our food chain at trace concentrations. Unfortunately, the conventional wastewater treatment techniques are unable to treat pharmaceuticals completely with practical limitations. The focus has now been shifted towards nanotechnology for the successful remediation of these persistent pollutants. Thus, the current review specifically focuses on providing readers brief yet sharp insights into applications of various nanomaterials for the removal of pharmaceutical contaminants.

METHODS

An exhaustive collection of bibliographic database was done with articles having high impact and citations in relevant research domains. An in-depth analysis of screened papers was done through standard tools. Studies were categorized according to the use of nanoscale materials as nano-adsorbents (graphene, carbon nanotubes), nanophotocatalysts (metal, metal oxide), nano-filtration, and ozonation for promising alternative technologies for the efficient removal of recalcitrant contaminants.

RESULTS

A total of 365 research articles were selected. The contemporary advancements in the field of nanomaterials for drinking and wastewater treatment have been thoroughly analyzed along with their future perspectives.

CONCLUSION

The recommendations provided in this article will be useful to adopt novel strategies for on-site removal of the emerging contaminants in pharmaceutical effluents and related industries.

A Review on Recent Treatment Technology for Herbicide Atrazine in Contaminated Environment

Atrazine is a kind of triazine herbicide that is widely used for weed control due to its good weeding effect and low price. The study of atrazine removal from the environment is of great significance due to the stable structure, difficult degradation, long residence time in environment, and toxicity on the organism and human beings. Therefore, a number of processing technologies are developed and widely employed for atrazine degradation, such as adsorption, photochemical catalysis, biodegradation, etc. In this article, with our previous research work, the progresses of researches about the treatment technology of atrazine are systematically reviewed, which includes the four main aspects of physicochemical, chemical, biological, and material-microbial-integrated aspects. The advantages and disadvantages of various methods are summarized and the degradation mechanisms are also evaluated. Specially, recent advanced technologies, both plant-microbial remediation and the material-microbial-integrated method, have been highlighted on atrazine degradation. Among them, the plant-microbial remediation is based on the combined system of soil-plant-microbes, and the material-microbial-integrated method is based on the synergistic effect of materials and microorganisms. Additionally, future research needs to focus on the excellent removal effect and low environmental impact of functional materials, and the coordination processing of two or more technologies for atrazine removal is also highlighted.

Sustainable production of nanoporous carbons: Kinetics and equilibrium studies in the removal of atrazine

Nanoporous carbons have been prepared from mangosteen peels-derived chars by physical activation under CO₂ flow as a function of temperature. As an example of circular bioeconomy, these sustainable adsorbents were used to remove atrazine, a common pesticide from the agroindustry. Several adsorption models such as Langmuir (two parameter), Sips and Redlich-Peterson (three parameters) were applied to verify the influence of carbon's properties on the uptake of atrazine. Additional kinetic models (pseudo-first order, pseudo-second order and Avrami's) allowed to establish that a mixture of physisorption and chemisorption describes the interaction between the nanoporous carbons and atrazine. As a general fact, an important diffusion of atrazine from the bulk of solution to the surface of carbons was observed. All samples were able to remove atrazine, but the highest uptake was found in the carbon with the highest contribution of micropores to the total pore of volume and with the lowest content of basic surface groups. Several correlations between the kinetic and equilibrium parameters for the atrazine adsorption were found as a function of the textural properties and surface chemistry. Based on the kinetics and equilibrium parameters, the present work proposes a mechanism for the atrazine adsorption on nanoporous carbons contributing to the understanding of the interactions between pollutant molecules and the surface functional groups on nanoporous carbons in the liquid-solid interface.

Effects of Ca2+ and fulvic acids on atrazine degradation by nano-TiO2: Performances and mechanisms

In this study, the adsorption and UV photocatalytic degradation of atrazine using nano-TiO₂ particles were studied systematically, and the colloidal stability of nano-TiO₂ particles in solution was also investigated to reveal the removal mechanism. Experiments which contained the first 6.0 hours darkness and 4.0 hours UV illumination later were conducted at different concentrations of Ca²⁺ and/or fulvic acids (FA) at pH = 7.0. Results showed that the adsorption rate of atrazine onto nano-TiO₂ particles decreased with the increase of Ca²⁺ and/or FA concentrations, which could be explained well by the colloidal stability of nanoparticles. When the solution contained Ca²⁺ or Ca²⁺-FA, the nanoparticles were aggregated together leading to the decrease of the contact surface area. Besides, there existed competitive adsorption between FA and atrazine on the particle surface. During photocatalytic degradation, the increase of Ca²⁺ and/or FA concentration accelerated the aggregation of nano-TiO₂ particles and that reduced the degradation efficiency of atrazine. The particle sizes by SEM were in accordance with the aggregation degree of nanoparticles in the solutions. Sedimentation experiments of nano-TiO₂ particles displayed that the fastest sedimentation was happened in the CaCl₂ and FA coexistent system and followed by CaCl₂ alone, and the results well demonstrated the photodegradation efficiency trends of atrazine by nano-TiO₂ particles under the different sedimentation conditions.

Solar-Driven Removal of 1,4-Dioxane Using WO3/nγ-Al2O3 Nano-catalyst in Water

Increasing demand for fresh water in extreme drought regions necessitates potable water reuse. However, current membrane-based water reclamation approaches cannot effectively remove carcinogenic 1,4-dioxane. The current study reports on the solar-driven removal of 1,4-dioxane (50 mg L−1) using a homemade WO3/nγ-Al2O3 nano-catalyst. Characterization methods including scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF) analyses are used to investigate the surface features of the catalyst. The 1,4-dioxane mineralization performance of this catalyst under various reaction conditions is studied. The effect of the catalyst dosage is tested. The mean oxidation state carbon (MOSC) values of the 1,4-dioxane solution are followed during the reaction. The short chain organic acids after treatment are measured. The results showed that over 75% total organic carbon (TOC) removal was achieved in the presence of 300 mg L−1 of the catalyst with a simulated solar irradiation intensity of 40 mW cm−2. Increasing the dose of the catalyst from 100 to 700 mg L−1 can improve the treatment efficiency to some extent. The TOC reduction curve fits well with an apparent zero-order kinetic model and the corresponding constant rates are within 0.0927 and 0.1059 mg L−1 s−1, respectively. The MOSC values of the 1,4-dioxane solution increase from 1.3 to 3 along the reaction, which is associated with the formation of some short chain acids. The catalyst can be effectively reused 7 times. This work provides an oxidant-free and energy saving approach to achieve efficient removal of 1,4-dioxane and thus shows promising potential for potable reuse applications.

Photoactive nanoarchitectures based on clays incorporating TiO2 and ZnO nanoparticles

Thought as raw materials clay minerals are often disregarded in the development of advanced materials. However, clays of natural and synthetic origin constitute excellent platforms for developing nanostructured functional materials for numerous applications. They can be easily assembled to diverse types of nanoparticles provided with magnetic, electronic, photoactive or bioactive properties, allowing to overcome drawbacks of other types of substrates in the design of functional nanoarchitectures. Within this scope, clays can be of special relevance in the production of photoactive materials as they offer an advantageous way for the stabilization and immobilization of diverse metal-oxide nanoparticles. The controlled assembly under mild conditions of titanium dioxide and zinc oxide nanoparticles with clay minerals to give diverse clay-semiconductor nanoarchitectures are summarized and critically discussed in this review article. The possibility to use clay minerals as starting components showing different morphologies, such as layered, fibrous, or tubular morphologies, to immobilize these types of nanoparticles mainly plays a role in i) the control of their size and size distribution on the solid surface, ii) the mitigation or suppression of the nanoparticle aggregation, and iii) the hierarchical design for selectivity enhancements in the catalytic transformation and for improved overall reaction efficiency. This article tries also to present new steps towards more sophisticated but efficient and highly selective functional nanoarchitectures incorporating photosensitizer elements for tuning the semiconductor-clay photoactivity.

Effect of cassava waste biochar on sorption and release behavior of atrazine in soil

Biochar, can be used as a sorbent material to sequester organic contaminants in soils. In this study, the sorption-desorption behavior of atrazine (AT) was studied in latosol (L) supplemented with varying doses of cassava waste biochar (CW). Changes in the release of AT were assessed with varying aging time (0-60 days) and environmental factors (pH, ionic strength, solid-liquid ratio and disturbance intensity). Results indicate that the addition of 0.1%-5% (w/w) CW in L, promoted AT adsorption by 1.7- to 36-fold as compared with the natural soil control, after 60 days. The release of AT from biochar-amended soil was significantly affected by pH ranged from 3 to 9 and the amount of desorbed AT increased with increasing pH conditions. 0.05 mol/L Ca²⁺ enhanced AT sorption by biochar. The release of AT increased with increasing solid-liquid ratio (at the ratio of 1:10, 1:15, 1:20) and disturbance intensity, surface complexation and cation exchange were found to play important roles in sorption mechanisms.

A facile solvothermal approach for the synthesis of novel W-doped TiO2 nanoparticles/reduced graphene oxide composites with enhanced photodegradation performance under visible light irradiation

W-Doped TiO₂ nanoparticles/reduced graphene oxide composites have been synthesized for the first time. The mechanism of their high photocatalytic activity for MB has been identified and discussed.