Methyl-modified, cobalt-doped silica (Co/MSiO₂) materials were synthesized by sol-gel technique calcined in N₂ atmospheres, and membranes were made thereof by coating method. The effects of Co/Si molar ratio (n_Co) on the physical-chemical constructions of Co/MSiO₂ materials and microstructures of Co/MSiO₂ membranes were systematically investigated. The gas permeance performance and hydrothermal stability of Co/MSiO₂ membranes were also tested. The results show that the cobalt element in Co/MSiO₂ material calcined at 400 °C exists not only as Si–O–Co bond but also as Co₃O₄ and CoO crystals. The introduction of metallic cobalt and methyl can enlarge the total pore volume and average pore size of the SiO₂ membrane. The activation energy (E_a) values of H₂, CO₂, and N₂ for Co/MSiO₂ membranes are less than those for MSiO₂ membranes. When operating at a pressure difference of 0.2 MPa and 200 °C compared with MSiO₂ membrane, the permeances of H₂, CO₂, and N₂ for Co/MSiO₂ membrane with n_Co = 0.08 increased by 1.17, 0.70, and 0.83 times, respectively, and the perm-selectivities of H₂/CO₂ and H₂/N₂ increased by 27.66% and 18.53%, respectively. After being steamed and thermally regenerated, the change of H₂ permeance and H₂ perm-selectivities for Co/MSiO₂ membrane is much smaller than those for MSiO₂ membrane.

Methyl-modified niobium-doped silica (Nb/SiO₂) materials with various Nb/Si molar ratios (n_Nb) were fabricated using tetraethoxysilane and methyltriethoxysilane as the silica source and niobium pentachloride as the niobium source by the sol–gel method, and the Nb/SiO₂ membranes were prepared thereof by the dip-coating process under an N₂ calcining atmosphere. Their microstructures were characterized and gas permeances tested. The results showed that the niobium element existed in the formation of the Nb-O groups in the Nb/SiO₂ materials. When the niobium doping content and the calcining temperature were large enough, the Nb₂O₅ crystals could be formed in the SiO₂ frameworks. With the increase of n_Nb and calcination temperature, the formed particle sizes increased. The doping of Nb could enhance the H₂/CO₂ and H₂/N₂ permselectivities of SiO₂ membranes. When n_Nb was equal to 0.08, the Nb/SiO₂ membrane achieved a maximal H₂ permeance of 4.83 × 10⁻⁶ mol·m⁻²·Pa⁻¹·s⁻¹ and H₂/CO₂ permselectivity of 15.49 at 200 °C and 0.1 MPa, which also exhibited great hydrothermal stability and thermal reproducibility.

Iron-manganese co-oxide film (MeO_x) has a high removal efficiency for ammonium (NH₄⁺) and manganese (Mn²⁺) in our previous studies, but it cannot effectively remove COD_Mn from water. In this study, the catalytic oxidation ability of MeO_x was enhanced by dosage with potassium ferrate (K₂FeO₄) to achieve the simultaneous removal of COD_Mn and NH₄⁺ from water in a pilot-scale experimental system. By adding 1.0 mg/L K₂FeO₄ to enhance the activity of MeO_x, the removal efficiencies of COD_Mn (20.0 mg/L) and NH₄⁺ (1.1 mg/L) were 92.5 ± 1.5% and 60.9 ± 1.4%, respectively, and the pollutants were consistently and efficiently removed for more than 90 days. The effects of the filtration rate, temperature and pH on the removal of COD_Mn were also explored, and excessive filtration rate (over 11 m/h), lower temperature (below 9.2 °C) and pH (below 6.20) caused a significant decrease in the removal efficiency of COD_Mn. The removal of COD_Mn was analyzed at different temperatures, which proved that the kinetics of COD_Mn oxidation was pseudo-first order. The mature sands (MeO_x) from column IV were taken at different times for microscopic characterization. Scanning electron microscope (SEM) showed that some substances were formed on the surface of MeO_x and the ratio of C and O elements increased significantly, and the ratio of Mn and Fe elements decreased significantly on the surface of MeO_x by electron energy dispersive spectrometer (EDS). However, the elemental composition of MeO_x would gradually recover to the initial state after the dosage of Mn²⁺. According to X-ray photoelectron spectroscopy (XPS) analysis, the substance attached to the surface of MeO_x was [(-(CH₂)₄O-)_n], which fell off the surface of MeO_x after adding Mn²⁺. Finally, the mechanism of K₂FeO₄-enhanced MeO_x for COD_Mn removal was proposed by the analysis of the oxidation process.