The regulation mechanism of transition metal doping on Hg0 adsorption and oxidation on Ce/TiO2(001) surface: A DFT study.

The mercury oxidation performance of Ce/TiO2 catalyst can be further enhanced by transition metal modifications. This study employed density functional theory (DFT) calculations to investigate the adsorption and oxidation mechanisms of Hg0 on Ce/TiO2(001) and its transition metal modified surfaces. According to the calculation results, Ru-, Mo-, Nb-, and Mn-doping increased the affinity of the Ce/TiO2(001) surface towards Hg0 and HCl, thereby facilitating the efficient capture and oxidation of Hg0. The increased adsorption energy (Eads) of the intermediate HgCl on the modified surfaces could promote its conversion to the final product HgCl2. The modification of transition metals impeded the desorption of the final products HgCl2 and HgO, but it did not serve as the rate-determining step. The oxidation of Hg0 by lattice oxygen and HCl followed the Mars-Maessen and Langmuir-Hinshelwood mechanisms, respectively. HCl exhibited higher mercury oxidation ability than lattice oxygen. The reactivity of lattice oxygen could be further improved by doping transition metals, their promotion order was Ru > Nb > Mo > Mn. In a HCl atmosphere, Mn modification could significantly reduce the energy barrier for HCl activation and HgCl2 formation, providing the optimal enhancement for the mercury oxidation ability of Ce/TiO2 catalyst. The screening method of transition metal modified components based on surface adsorption reaction and oxidation energy barrier was proposed in this study, which provided theoretical guidance for the development of CeTi based catalysts with high mercury oxidation activity.

Multifunctional Bacterial Cellulose/Covalent Organic Framework Composite Membranes with Antifouling and Antibacterial Properties for Dye Separation.

Covalent organic frameworks (COFs) have a wide application prospect in wastewater treatment because of their unique structure and properties; however, the preparation of pure COF membranes remains a great challenge by reason of the insolubility and unprocessability of COF powders formed at high temperature and high pressure. In this study, a continuous and defect-free bacterial cellulose/covalent organic framework composite membrane was prepared by using bacterial cellulose (BC) and a porphyrin-based COF with their unique structures and hydrogen bonding forces. The dye rejection rate of this composite membrane toward methyl green and congo red was up to 99%, and the permeance was about 195 L m-2 h-1 bar-1. It showed excellent stability under different pH conditions, long-time filtration, and cyclic experimental conditions. In addition, the hydrophilicity and surface negativity of the BC/COF composite membrane made it have certain antifouling performance, and the flux recovery rate can reach 93.72%. More importantly, the composite membrane exhibited excellent antibacterial properties due to the doping of the porphyrin-based COF, and the survival rates of both Escherichia coli and Staphylococcus aureus were less than 1% after exposure to visible light. The self-supporting BC/COF composite membrane synthesized by this strategy also has outstanding antifouling and antibacterial properties, in addition to excellent dye separation effects, which greatly broaden the application of COF materials in water treatment.

Complete catalytic reaction of mercury oxidation on CeO2/TiO2 (001) surface: A DFT study.

CeO2/TiO2 catalyst is a promising material for realizing the integration of denitrification and mercury removal to reduce mercury emissions. Oxidation mechanism of Hg0 on CeO2/TiO2 (001) surface in the presence of HCl and O2 was studied by density functional theory (DFT). The results indicated that Hg0 was physically adsorbed on CeO2/TiO2 (001) surface. As an important intermediate, HgCl was adsorbed on the surface of CeO2/TiO2 (001) utilizing enhanced chemisorption, while the adsorption energy of HgCl2 was only -57.05 kJ/mol. In the absence of HCl, mercury oxidation followed the Mars-Maessen mechanism with a relatively high energy barrier, and the product (HgO) was difficult to desorb, which hindered the reaction process. When HCl existed, reactive chlorine (Cl*) would be produced by the dissociation of HCl, and the mercury oxidation would follow the Langmuir-Hinshelwood mechanism. The co-existence of HCl and O2 had no significant effect on the adsorption of Hg0, but reduced the reaction energy barrier and the final product (HgCl2) was more easily desorbed from the catalyst surface. In addition, two complete cyclic reaction pathways for catalytic oxidation of Hg0 on CeO2/TiO2 (001) surface were constructed to clarify the detailed reaction process.

Highly efficient absorption of nitric oxide by RuIII(edta) aqueous solutions at low concentrations.

In this paper, RuIII(edta) was used as a highly efficient absorbent for the removal of NO due to its desirable properties of high NO affinity and oxygen insensitivity. The effects of the RuIII(edta) concentration, reaction temperature, initial solution pH, oxygen concentration, inlet NO concentration, and liquid-to-gas ratio on denitration performance were examined. The results indicated that RuIII(edta) showed excellent denitration performance at low concentrations and that an increase in the concentration of RuIII(edta) resulted in an increase in NO removal efficiency. In addition, NO removal efficiency increased to its optimum value at first and then declined as both the reaction temperature and initial solution pH rose. The optimal reaction temperature and ideal initial solution pH were determined to be 45°C and 5.0 respectively. The suitable liquid-to-gas ratio was found to be 51.5 L/m3. NO removal efficiency was less affected by the oxygen concentration in the range of 0-12% due to a superior anti-oxidation performance at pH = 5.0. Furthermore, the NO removal efficiency decreased significantly as the inlet NO concentration increased. The addition of 5 wt% urea to an aqueous solution of RuIII(edta) enhanced denitration performance, and an RuIII(edta) and urea mixed solution were able to exceed 65.07% NO removal efficiency within 30 min under optimal experimental conditions. This work proposed an alternative absorbent for NO removal and provided fundamental data for industrial denitration with RuIII(edta) absorbents.

Transition-metal-free KI-catalyzed regioselective sulfenylation of 4-anilinocoumarins using Bunte salts.

An efficient and eco-friendly protocol for the KI-catalyzed regioselective sulfenylation of 4-anilinocoumarins with Bunte salts was established. The reaction worked smoothly under metal-free conditions and afforded a wide range of sulfenylated 4-anilinocoumarins with potential bioactivity in moderate to excellent yields. This method would expand the still limited scope of synthesis methods for C-S bond formation using Bunte salts.