Strong coupling of super-hydrophilic and vacancy-rich g-C3N4 and LDH heterostructure for wastewater purification: Adsorption-driven oxidation

High-performance nitrogen-doped carbon catalyst with Co-Cu-CuxO interfaces via bimetallic ion exchange-carbonization: Synergistic Co/Cu interactions and nonradical activation mechanism for micropollutant removal

Mono-metal active sites, with their restricted electron transfer ability, typically lead to lower redox reaction efficiency, which hampers peroxymonosulfate (PMS) activation and reduces antibiotic degradation effectiveness. In this work, a novel nitrogen-doped carbon catalyst with Co-Cu-CuxO interfaces was synthesized by pyrolyzing a Zn-based elliptical two-dimensional template through a Co2+/Cu2+ bimetallic ion exchange process. The synthesized samples were comprehensively characterized using a range of physicochemical analysis techniques. Furthermore, the catalytic performance was systematically evaluated under varying conditions, including peroxymonosulfate dosage, tetracycline concentration, solution pH, and the influence of co-existing ions and organic matter in water. The results indicated that the optimized 1:1-950 catalyst achieved over 96 % degradation of tetracycline (TC) through PMS activation, with a reaction rate constant (k) of 0.038 min-1, significantly outperforming both the mono-metal ion exchange group and the non-metal ion exchange group. This improvement was attributed to the synergistic effects of Co(II)/Co(III) and Cu(I)/Cu(II) redox reactions at the Co-Cu-CuxO interfaces. Quenching experiments, electron spin resonance (ESR), and electrochemical analyses revealed that non-radical reactive oxygen species (ROS), such as singlet oxygen (1O2) and high-valent metal-oxo species (e.g., Cu(III)-oxo and Co(IV)-oxo), played a key role in the degradation process. The degradation pathways for TC were proposed using high-performance liquid chromatography-mass spectrometry (HPLC-MS), and the environmental safety of the catalytic system was confirmed through physiological testing on mung bean growth. This work presents an efficient approach for PMS activation in TC degradation, using nitrogen-doped carbon catalysts with Co-Cu-CuxO interfaces synthesized via bimetallic ion exchange and carbonization strategy, with promising applications in advanced wastewater treatment.

Role of tea polyphenols in enhancing the performance, sustainability, and catalytic cleaning capability of membrane separation for water-soluble pollutant removal

Tea polyphenols (TPs), like green tea polyphenol (GTP) and black tea polyphenol (BTP), with phenolic hydroxyl structures, form coordination and hydrogen bonds, making them effective for bridging inorganic catalysts and membranes. Here, TPs were employed as interface agents for the preparation of TPs-modified needle-clustered NiCo-layered double hydroxide/graphene oxide membranes (NiCo-LDH-TPs/GO). The incorporation of porous guest material, NiCo-LDH-TPs, facilitated water channel expansion, enhancing membrane permeability and resulting in the development of high-performance, sustainable catalytic cleaning membranes. The introduction of TPs through coordination weakened the surface electronegativity of NiCo-LDH, promoting a uniform mixed dispersion with GO and facilitating membrane self-assembly. NiCo-LDH-GTP/GO-5 and NiCo-LDH-BTP/GO-5 membranes demonstrated permeances of 85.98 and 90.76 L m-2 h-1 bar-1, respectively, with rejections of 98.73% and 99.54% for methylene blue (MB). Notably, the NiCo-LDH-BTP/GO-5 membrane maintained a high rejection of 97.11% even after 18 cycles in the catalytic cleaning process. Furthermore, the modification of GTP and BTP enhanced MB degradation through PMS activation, resulting in a 0.33% and 0.35% increase in the reaction rate constants of NiCo-LDH, respectively, while reducing metal ion spillover. These findings highlighted the potential of TPs in enhancing the efficiency and sustainability of catalytic cleaning GO membranes for water purification and separation processes.

Unveiling glutamic acid-functionalized LDHs: understanding the Cr(VI) removal mechanism from microscopic and macroscopic view points

Interlayer functionalization modulation is essential for modifying LDHs and improving their selectivity and adsorption capacity for target pollutants. In this work, Glu@NiFe-LDH was synthesized using a simple one-step hydrothermal method and tested for its ability to remove CrO42- from wastewater. The modification significantly increased the composite material's removal ability by 2-3 times, up to 98.36 mg g-1. The behavior of CrO42- adsorption on Glu@NiFe-LDH was further studied by adjusting the affecting factors (i.e., temperature, pH, contact time, initial concentration, and interfering substance), and the adsorption behavior was confirmed as a spontaneous and chemisorption process. And the result was that Glu@NiFe-LDH demonstrated high capacity, efficiency, stability, and selectivity for the adsorption of CrO42- in a single electrolyte and natural water containing competing anions. Furthermore, molecular dynamics simulations (NVT ensemble) were employed to further reveal the mechanism of glutamic acid modification on LDH at the microscopic scale. Additionally, the IRI analysis method revealed the mechanism of weak interaction between glutamic acid molecules and CrO42-. This study provides a detailed understanding of the intercalation mechanism involved in the amino acid modification of LDHs. It explains the adsorption mechanism of metal oxo-acid radicals by amino acid-modified LDHs from a theoretical perspective. The findings offer experiments and a theoretical basis for designing targeted adsorbents in the future.