Functional Chitosan Derivative and Chitin as Decolorization Materials for Methylene Blue and Methyl Orange from Aqueous Solution

Dyes are classified as one of the major pollutants of water. They have negative impacts not only on environment but also on human health. In fact, wastewater that contains these harmful substances requires many types of treatments. Therefore, alternative methods and adsorption agents are needed. Herein, we propose to evaluate the decolorization of methylene blue (MB) and methyl orange (MO) as two models of soluble dyes from water using chitin and chitosan-graft-polyacrylamide. Furthermore, the applicability of these biomacromolecules as alternative adsorption agents, their sticking probability and desorption were also examined. Experimental parameters such as dye concentration, contact time, pH solution, adsorbent dosage and temperature were thoroughly examined for the grafted chitosan and chitin. The activation energy (Ea) and the thermodynamic variables (i. e., standard Gibb's free energy (D G0), standard enthalpy (D H0), and standard entropy (D S0)) were determined using the Van't Hoff and Arrhenius equations. The sticking probability (S*) model for MB and MO removal by chitin and the chitosan derivative demonstrated that both dyes were successfully removed under the proposed conditions. Desorption studies of MB and MO showed the reusability of both materials, suggesting their application for removing dyes from aqueous solution.The authors are grateful for the financial support of the Department of Education of the Basque Government (IT1008-16)

Coal ash for removing toxic metals and phenolic contaminants from wastewater: A brief review

International audienceOver the past few years, population growth, industrial progress and climate change have led to water scarcity. Thus, water pollution caused by hazardous soluble and insoluble pollutants, such as toxic metals and phenolic compounds, has become an important problem that should be dealt with urgently. For instance, new methods have been introduced to convert low-cost raw materials (i.e. coal fly ash and coal bottom ash "wastes-to-resource") into suitable materials for new cleaner production to achieve sustainability goals in wastewater-containing toxic metals and phenolic compounds purification. Obviously, the functionalization of coal fly ash and bottom ash enhances the ability of coal ash-based entities as potential materials in wastewater remediation technologies. Here, we review the application of coal ashes, including coal bottom ash and fly ash-based materials for toxic metals and phenolic compounds removal. We also examine their structural properties and functionalization to enhance their affinities toward these pollutants in aqueous environment. Even though each process has its own benefits and limitations, coal ash-based materials appear promising for the removal of toxic metals and phenolic compounds using adsorption, membrane filtration, and photocatalysis. Overall, the study on the availability of coal fly ash and bottom ash for wastewater treatment have resulted in high removal efficiencies for toxic metals and phenolic compounds. In the future, new recycling methods for coal ashes as new water purification agents should be further studied and advanced processes should be investigated in order to achieve wastewater remediation purposes

Green process of biomass waste derived fluorescent carbon quantum dots for biological imaging in vitro and in vivo

International audienceIn the context of the circular economy, the huge amounts of biomass waste should be converted into value-added materials and energy to diminish pollution, atmospheric CO2 levels and costly waste disposal. Biological imaging usually uses expensive and toxic chemicals e.g. , organic dyes, semiconductor quantum dots, calling for safer, greener, cheaper fluorescent probes for biological imaging in vitro and in vivo. In these regards, carbon quantum dots (CQDs)-based fluorescent probes using biomass waste as a precursor may have much higher potential. Here we transformed the biomass waste of peach leaves into value-added fluorescent CQDs through a low-cost and green one-step hydrothermal process. The obtained CQDs show excitation-dependent photoluminescence properties with a fluorescence lifetime of 5.96 ns and a quantum yield of 7.71% without any passivation. In addition, the CQDs have a fine size of 1.9 nm with good hydrophilicity and high fluorescent stability over pH 4.0–11.0 range. Fluorescence imaging of in vitro cell cultures and in vivo with zebrafish show that CQDs possess ultra-low toxicity and remarkable performance for biological imaging. Even when CQDs present at a concentration as high as 500 μg/mL, the organism can still maintain more than 90% activity both in vitro and in vivo , and present bright fluorescence. The cheaper, greener, ultra-low toxicity CQDs developed in this work is a potential candidate for biological imaging in vitro and in vivo

Severe metastatic calcifications in a hemodialysis patient

Tissue calcification is a common complication in patients on continuous hemodialysis (HD) for chronic renal failure; however, severe calcification is unusual. Three distinct clinical types of extraosseous calcifications are found in uremic patients: vascular calcification, periarticular (tumoral) calcification, and visceral calcification (heart, lung, and kidney). We report a case of a young chronic HD patient who presented with extensive metastatic calcifi cations both vascular, visceral specially localized in the lungs, and periarticular with progressively increasing multiple subcutaneous swellings. This evolution was secondary to noncompliance of the patient to the treatment of a malignant hyperparathyroidism with a marked elevation of phosphocalcium product

Cyano/Hydroxyl Groups Co-Functionalized g-C₃N₄ for Photocatalytic NO Removal: A Synergistic Strategy towards Inhibition of Toxic Intermediate NO₂

Photocatalytic NO removal is usually accompanied by the generation of NO2, an intermediate with a higher toxicity than NO. Therefore, it is critically important to develop new photocatalysts capable of NO selective conversion. Herein, we report on the synergistic roles of cyano and hydroxyl functional groups in photocatalytic NO removal. According to the results, the NO2 production efficiencies on cyano/hydroxyl-group-modified g-C3N4 (DCN-O-R) was limited to 4.8%, which was lower than that of cyano-group-modified g-C3N4 (DCN, 38.6%) and pure g-C3N4 (CN, 50.0%). Meanwhile, the photocatalytic NO conversion efficiency over DCN-O-R was higher than that of DCN and g-C3N4. It was found that the insertion of cyano groups favorably changes the energy band of g-C3N4 towards the generation of •O2−. NO can only be oxidized to NO2 by the photogenerated holes. When NO2 is adsorbed on the surface of hydroxyl groups, it can be further oxidized to the product NO3− by •O2−. The synergistic effect of bifunctional groups regulates the conversion pathway from NO→NO2 to NO→NO2→NO3−. This work provides a strategy to abate toxic intermediates during the NO removal process, underlining the importance of surface/interface molecular engineering in regulating catalytic reaction pathways

Turning Agroforestry Waste into Value-Added Fluorescent Carbon Quantum Dots for Effective Detection of Fe³⁺ in an Aqueous Environment

In the context of the circular economy, the high quantity of agroforestry waste should be transformed into sustainable and high-value materials to abate pollution, CO2 emissions, and expensive waste disposal. Herein, the agroforestry waste of apple leaves was initially used as a precursor to extract the value-added nanomaterial carbon quantum dots (CQDs) by way of an easy hydrothermal strategy without complicated purification processes, as extracted CQDs doped with N and P possess a typical graphite-like structure, a fine particle size of 2.0 nm, and excitation-dependent photoluminescence (PL) behavior. The doping of N and P endows CQDs with a much higher quantum yield (18.1%), good water solubility, high fluorescence stability, and specific recognition ability for the detection of Fe3+. The fluorescence of CQDs could be quickly quenched by Fe3+ within 1 min and recovered with the addition of ascorbic acid, suggesting the recyclability of the prepared CQD-based fluorescent probe. Systematic analyses support that a synergistic mechanism of static fluorescence quenching and inner filter effect was involved in the detection of Fe3+ by CQDs, showing a linear range between 0 and 160 μM and a limit of detection (LOD) of 4.0 μM. Furthermore, the feasibility of detecting Fe3+ by CQDs in practice was verified by tap water/lake water samples. The present work evinces that apple leaves are useful in producing green and low-cost CQDs as a promising fluorescent probe for sensitive, rapid, and selective detection of Fe3+ in an aqueous environment

Coal fly ash and bottom ash low-cost feedstocks for CO2 reduction using the adsorption and catalysis processes

International audienceCombustion of fossil fuels, industry and agriculture sectors are considered as the largest emitters of carbon dioxide. In fact, the emission of CO2 greenhouse gas has been considerably intensified during the last two decades, resulting in global warming and inducing variety of adverse health effects on human and environment. Calling for effective and green feedstocks to remove CO2, low–cost materials such as coal ashes “wastes–to–materials”, have been considered among the interesting candidates of CO2 capture technologies. On the other hand, several techniques employing coal ashes as inorganic supports (e.g., catalytic reduction, photocatalysis, gas conversion, ceramic filter, gas scrubbing, adsorption, etc.) have been widely applied to reduce CO2. These processes are among the most efficient solutions utilized by industrialists and scientists to produce clean energy from CO2 and limit its continuous emission into the atmosphere. Herein, we review the recent trends and advancements in the applications of coal ashes including coal fly ash and bottom ash as low–cost wastes to reduce CO2 concentration through adsorption and catalysis processes. The chemical routes of structural modification and characterization of coal ash based feedstocks are discussed in details. The adsorption and catalytic performance of the coal ashes derivatives towards CO2 selective reduction to CH4 are also described. The main objective of this review is to highlight the excellent capacity of coal fly ash and bottom ash to capture and selective conversion of CO2 to methane, with the aim of minimizing coal ashes disposal and their storage costs. From a practical view of point, the needs of developing new advanced technologies and recycling strategies might be urgent in the near future to efficient make use of coal ashes as new cleaner materials for CO2 remediation purposes, which favourably affects the rate of global warming