Ultraviolet activation of monochloramine to treat contaminants of emerging concern: reactions, operating parameters, byproducts, and opportunities.

The presence of CECs in aquatic systems has raised significant concern since they are potentially harmful to the environment and human health. Eliminating CECs has led to the development of alternatives to treat wastewater, such as advanced oxidation processes (AOPs). The ultraviolet-mediated activation of monochloramine (UV/NH2Cl) is a novel and relatively unexplored AOPs for treating pollutants in wastewater systems. This process involves the production of amino radicals (•NH2) and chlorine radicals (Cl•) from the UV irradiation of NH2Cl. Studies have demonstrated its effectiveness in mitigating various CECs, exhibiting advantages, such as the potential to control the amount of toxic disinfection byproducts (TDBPs) formed, low costs of reagents, and low energy consumption. However, the strong influence of operating parameters in the degradation efficiency and existence of NH2Cl, the lack of studies of its use in real matrices and techno-economic assessments, low selectivity, and prolonged treatment periods must be overcome to make this technology more competitive with more mature AOPs. This review article revisits the state-of-the-art of the UV/NH2Cl technology to eliminate pharmaceutical and personal care products (PPCPs), micropollutants from the food industry, pesticides, and industrial products in aqueous media. The reactions involved in the production of radicals and the influence of operating parameters are covered to understand the formation of TDBPs and the main challenges and limitations of the UV/NH2Cl to degrade CECs. This review article generates critical knowledge about the UV/NH2Cl process, expanding the horizon for a better application of this technology in treating water contaminated with CECs.

Influence of Pressure and Temperature on the Flexible Behavior of Iron-Based MIL-53 with the CO2 Host: A Comprehensive Experimental and DFT Study.

This research focuses on developing MIL-53-type compounds with Fe obtained with ligands derived from PET waste, followed by the controlled addition of hydrofluoric acid (HF). Incorporating HF into the MOF structure induced substantial changes in the material textural properties, resulting in a significant change in CO2 adsorption. Furthermore, a distinctive structural alteration (breathing effect) was observed in the CO2 isotherms at different temperatures; these structural changes have not been observed by X-ray diffraction (XRD) because this characterization has been performed at room temperature, whereas the adsorption experiments were conducted at 260, 273, and 303 K and different pressures. Subsequently, DFT studies were performed to investigate the CO2-filling mechanisms and elucidate the material respiration effect. This approach offers promising opportunities for sustainable materials with improved gas adsorption properties.

S-incorporated TiO2 coatings grown by plasma electrolytic oxidation for reduction of Cr(VI)-EDTA with sunlight.

The plasma electrolytic oxidation (PEO) technique was used to prepare photocatalytic S-TiO2 coatings on Ti sheets; the incorporation of the S ions was possible from the electrolyte for modifying the structural and optics characteristics of the material. In this work, substrates of Ti (ASME SB-265 of 20 × 20 × 1 mm) were used in a PEO process in 10 min, using constant voltage pulses of 340 V with frequency of 1 kHz and duty cycles of 10% and of 30%. Solutions with H2SO4 (0.1 M) and CH4N2S (52 and 79 mM) were used as electrolytes. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (EDS) were utilized to analyze the surface morphology, crystalline phase, and chemical composition of the samples. According to the results, the catalyst coatings had microporous structure and contained anatase-rutile TiO2 nanocrystalline mixture, until 73.2% rutile and 26.8% anatase in the samples grown with 30% duty cycle and the lowest concentration of CH4N2S. From the EDS measurements, the incorporation of sulfur ions to the coatings was 0.08 wt%. 99.5% reduction efficiency of Cr(VI)-EDTA with sunlight was observed after 2 h; it was determined by diphenyl carbazide spectrophotometric method. These coatings have potential for effective sunlight heterogeneous photoreduction of this toxic, cumulative, and non-biodegradable heavy metal that contaminates the soil and water and is a serious risk to sustainability, ecosystems, and human health.