Role of bentonite adsorbent sub-layer in the photocatalytic-adsorptive removal of methylene blue by the immobilized TiO<Subscript>2</Subscript>/bentonite system

An immobilized clay composite (BEN–PVAG) on a glass plate (GP) was fabricated using bentonite powder (BEN) and glutaraldehyde cross-linked polyvinyl alcohol (PVAG) as the adsorbent and adhesive, respectively. The immobilized bentonite composite (BEN–PVAG) was characterized using SEM, EDX, FTIR, and BET analysis. The adsorption capacity of BEN–PVAG was examined using methylene blue (MB) as the model pollutant. The results indicated that the adsorption of MB onto BEN–PVAG obeyed pseudo-second-order kinetics. In addition, the adsorption of MB by the immobilized BEN–PVAG was controlled by intra-particle diffusion. In contrast, the adsorption of MB by the suspended BEN–PVAG composite was dominated by film diffusion. The immobilized BEN–PVAG was then applied as the adsorbent sub-layer for the fabrication of P-25TiO₂/BEN–PVAG/GP bilayer system where P-25TiO₂ was deposited as the top layer. The fabricated bilayer system exhibited synergistic photocatalytic-adsorptive removal of MB upon irradiation with a light source, while experiment in the dark yielded only adsorption process. The rate of the synergistic photocatalytic-adsorptive removal of MB by the P-25TiO₂/BEN–PVAG/GP was 5.3 times faster than the suspended P-25TiO₂. The result implied the positive impact of the BEN–PVAG adsorbent sub-layer on the immobilized P-25TiO₂ photocatalyst. Most important, the immobilized P-25TiO₂/BEN–PVAG/GP provided a convenient reuse of the catalyst over time where the treated water could be directly discharged without the need of filtration.     

Applying disk-based discontinuous deformation analysis (DDA) to simulate Donghekou landslide triggered by the Wenchuan earthquake

In this paper, for the first time, disk-based discontinuous deformation analysis (DDA) is applied to simulate a real landslide triggered by an earthquake. For this purpose, the kinematic behaviour of the Donghekou landslide triggered by the Wenchuan earthquake is simulated and the results obtained using disk-based DDA are compared with actual data. The comparisons show that there is a good agreement between the results obtained using disk-based DDA and observed data. The simulation results provided an understanding of the failure behaviour and temporal evolution of the landslide. This study shows that disk-based DDA is a practical numerical tool that can be used to simulate the post-failure behaviour of landslides triggered by an earthquake.     

Assessment of the selected trace metals in relation to long-term agricultural practices and landscape properties

Understanding of the landscape response to agricultural practices mainly in relation to soil trace metals requires particular attention. Consistent with this, the trend and possible pollution of total and DTPA fraction of Mn, Zn, Cu, and Cd in the agricultural soils developed on different landscape positions involving piedmont alluvial plain (PAP), river alluvial plain (RAP), plateau (PL), and lowland (LL) were investigated. The content of the metal in different soil profiles, grouped by landscape positions, varied in the following orders: total and DTPA-Mn as LL > PAP > RAP > PL, total Zn and Cu as PAP > RAP > LL > PL, total Cd as RAP > PAP > PL > LL, DTPA-Zn as RAP > PAP > PL > LL, and DTPA-Cu as RAP > LL > PL > PAP. A wide variation in the total fraction of Mn (89–985 mg kg^?1), Zn (24–152 mg kg^?1), Cu (8–27 mg kg^?1), and Cd (0.6–1.7 mg kg^?1) and in the DTPA fraction of Mn (1.2–11 mg kg^?1), Zn (0.3–4.4 mg kg^?1), Cu (0.3–3 mg kg^?1), Cd (0.03–0.09 mg kg^?1) observed as a result of the effects of agricultural practices and landscape properties. The values of both total and DTPA-extractable Mn, Zn, and Cu were enriched in the AP horizon probably due to anthropogenic activities particularly successive use of agrochemical compounds and manure during numerous years. Using soil pollution indices [single pollution (PI) and comprehensive pollution (PIN)], the study soils were categorized mainly as low to moderate pollution and Zn was identified as the major element affecting on the yield of these indices.     

Synthesis and characterization of reusable nano-order SO<Subscript>3</Subscript>H-KIT-5 as a heterogeneous catalyst for eco-friendly synthesis of 1,4-dihydropyridines

A novel nanocatalyst silica-bonded sulfuric acid supported on KIT-5 as an organic–inorganic hybrid with high activity was prepared successfully. The KIT-5 with high surface area was reacted with chlorosulfonic acid via simple and rapid method. This efficient and reusable heterogeneous catalyst sulfuric acid nanocatalyst catalyzed one-pot synthesis of β-dicarbonyl compounds, aldehyde and ammonium acetate in the presence of 0.05 g of nanocatalyst at room temperature via solvent-free conditions to afford excellent yields of 1,4-dihydropyridines. This nanocatalyst was fully characterized by XRD, SEM–EDXS and Map analyses. The morphology of the catalyst surface by SEM images shows all porous of KIT-5 after the reaction was filled with the SO₃H groups. The average size determines around 22–24 nm. This catalyst can be reused five times without any significant loss of activity, too. The ease of separation, high activity, high surface area and reaction under open air condition are the main advantages of this catalyst.