Fe2O3-decorated hollow porous silica spheres assisted by waste gelatin template for efficient purification of synthetic wastewater containing As(V)

Utilizing Gelatin Waste for Efficient Bimodal Porous Silica Adsorbents for Carbon Dioxide Capture

This study explores the modification of pore structures in porous silica materials synthesized using sodium silicate and waste gelatin, under varying silica-to-gelatin ratios. At ratios of 1.0-1.5, bimodal porous silica with mesopores and macropores emerged due to spaces between silica nanoparticles and clusters, following gelatin elimination. The study further evaluated the obtained bimodal porous silica as polyethyleneimine (PEI) supports for CO2 capture, alongside PEI-loaded unimodal porous silica and hollow silica sphere for comparison. Notably, the PEI-loaded bimodal silica showcased superior CO2 uptake, achieving 145.6 mg g-1 at 90 °C. Transmission electron microscopy (TEM) revealed PEI's uniform distribution within the pores of bimodal silica, unlike the excessive surface layering seen in unimodal silica. Conversely, PEI completely filled the hollow porous silica's interior, extending gas molecule diffusion distance. All sorbents displayed nearly constant CO2 adsorption across 20 cycles, demonstrating outstanding stability. Notably, the bimodal porous silica displayed a negligible capacity loss, underscoring its robust performance.

Unraveling the roles of microporous and micro-mesoporous structures of carbon supports on iron oxide properties and As (V) removal performance in contaminated water

This study investigates the impact of microporous (SP-C) and micro-mesoporous carbon (DP-C) supports on the dispersion and phase transformation of iron oxides and their arsenic (V) removal efficiency. The research demonstrates that carbon-supported iron oxide sorbents exhibit superior As(V) uptake capacity compared to unsupported Fe2O3, attributed to reduced iron oxide crystallite sizes and As(V) adsorption on carbon supports. Maximum As(V) uptake capacities of 23.8 mg/g and 18.9 mg/g were achieved for Fe/SP-C and Fe/DP-C at 30 wt% and 50 wt% iron loading, respectively. The study reveals a nonlinear relationship between As(V) sorption capacity and iron oxide crystallite size after excluding As(V) adsorption capacity on carbon supports, suggesting the iron oxide phase (Fe3O4) plays a role in determining adsorption capacity. Iron oxide-loaded DP-C sorbents exhibit faster adsorption rates at low As(V) concentrations (5 mg/L) than SP-C sorbents due to their bimodal pore structure. Adsorption behavior varies at higher As(V) concentrations (45 mg/L), with Fe/DP-C reaching maximum capacity more slowly due to limited available adsorptive sites. All adsorbents maintained near-complete As(V) removal efficiency over five cycles. The findings provide insights for designing more efficient adsorbents for As(V) removal from contaminated water sources.

Fine-tuning mesoporous silica properties by a dual-template ratio as TiO2 support for dye photodegradation booster

Titanium dioxide (TiO₂) has been integrated into the surface of mesoporous silica (SMG) synthesized via the hydrothermal approach and a dual template CTAB-Gelatin. XRD, nitrogen adsorption, FTIR, SEM-EDX, and UV-Vis DR spectroscopy were performed to evaluate a 1 wt% TiO₂/SMG material. After titania incorporation, the addition of gelatin during the synthesis of SMG increases the pore volume to 0.76 cc/g. The expansion of the silica pores is caused by the development of TiO₂ crystal grains on the mesoporous silica-gelatin. An increase in the gelatin-CTAB to mesoporous silica weight ratio modifies the surface area, pore size, and particle size without compromising the meso-structure. In this research, the TiO₂/SMG composite demonstrated much greater photodegradability for methylene blue (MB) than the TiO₂/mesoporous silica sample without gelatin. The experimental results indicate that the photocatalytic activity of methylene blue from SMG titania/silica samples is reliant on the adsorption ability of the composite and the photocatalytic activity of titania, with optimal activity from samples with the highest surface area and pore volume, which directly increase the Ti: Si ratio and decrease the photodegradability of the composite when the ratio is too high or too low.

Enhancing arsenate metabolism in Microcystis aeruginosa and relieving risks of arsenite and microcystins by nano-Fe2O3 under dissolved organic phosphorus conditions

Little information is available on how nano-Fe₂O₃ substituted iron ions as a possible iron source impacting on algal growth and arsenate (As(V)) metabolism under dissolved organic phosphorus (DOP) (D-glucose-6-phosphate (GP)) conditions. We investigated the growth of Microcystis aeruginosa and As(V) metabolism together with their metabolites in As(V) aquatic environments with nano-Fe₂O₃ and GP as the sole iron and P sources, respectively. Results showed that nano-Fe₂O₃ showed inhibitory effects on M. aeruginosa growth and microcystin (MCs) release under GP conditions in As(V) polluted water. There was little influence on As species changes in GP media under different nano-Fe₂O₃ concentrations except for obvious total As (TAs) removal in 100 mg L^-1 nano-Fe₂O₃ levels. As(V) metabolism dominated with As(V) biotransformation in algal cells was facilitated and arsenite (As(III)) releasing risk was relieved clearly by nano-Fe₂O₃ under GP conditions. The dissolved organic matter (DOM) in media exhibited more fatty acid analogs containing -CO, -CH₂ =CH₂, and -CH functional groups with increasing nano-Fe₂O₃ concentrations, but the fluorescent analogs were relatively reduced especially for the fluorescent DOM dominated by aromatic protein-like tryptophan which was significantly inhibited by nano-Fe₂O_3. Thus, As methylation that was facilitated in M. aeruginosa by nano-Fe₂O₃ in GP environments also caused more organic substances to release that absorb infrared spectra while reducing the release risks of As(III) and MCs as well as protein-containing tryptophan fractions. From ¹H-NMR analysis, this might be caused by the increased metabolites of aromatic compounds, organic acid/amino acid, and carbohydrates/glucose in algal cells. The findings are vital for a better understanding of nano-Fe₂O₃ role-playing in As bioremediation by microalgae and the subsequent potential aquatic ecological risks.