In Situ Synthesis of Ultrahigh Molecular Weight Polyethylene/Graphene Oxide Nanocomposite Using the Immobilized Single-site Catalyst

We address the immobilization of single-site catalyst on the graphite oxide (GO) surface using methylaluminoxane. Ethylene polymerization was performed using the immobilized catalyst and the nanocomposite of ultrahigh molecular weight polyethylene (UHMWPE)/GO with less entanglement density was obtained. It was observed that the drawability, mechanical and thermal properties of the produced polymer significantly are affected by the anchoring of polymer chains to the GO nanosheets. The orientation and location of crystalline lamellae and nanosheets were verified by microscopic techniques. Besides, X-ray analysis demonstrated the dispersion of GO within the UHMWPE phase and crystallinity of UHMWPE/GO nanocomposites enhanced during drawing process.     

Solvent effect in phase separation for fabrication of micropatterned porous scaffold sheets

Cellular orientation control is important for tissue regeneration. Design of oriented structures for cells with suitable features can be used in tissue engineering. One of the methods of cellular orientation with the aim of regenerating which damaged tissues is utilizing oriented biocompatible substrates. This paper reports a one-step method with different solvents to fabricate porous micropatterned polyhydroxybutyrate scaffold sheets. The results indicated that the porosity and pore morphology of the scaffolds are viable with respect to proliferation rate, and a micropattern for cell alignment. Stem cells culturing proved that the scaffold sheets are suitable for cell culturing. Preliminary experiments indicate that the 2-D scaffold sheets are very promising as basis for building 3-D scaffolds.     

Oxidation of Binary FeCr Alloys (Fe?C2.25Cr, Fe?C10Cr, Fe?C18Cr and Fe?C25Cr) in O2 and in O2?+?H2O Environment at 600???C

The oxidation behaviour of the binary alloys Fe?C2.25Cr, Fe?C10Cr, Fe?C18Cr and Fe?C25Cr (wt%) in dry and wet O₂ at 600???C is investigated by isothermal exposures of carefully polished samples for up to 168?h. The oxidized samples are investigated gravimetrically and the oxides formed are studied by X-ray diffraction. X-ray photoelectron spectroscopy is used for depth profiling of the thin oxides. The scale surface is imaged by SEM. Cross-sections through the scale are analyzed by SEM/EDX for imaging and for measuring the chemical composition. The oxidation behavior of the four FeCr alloys is intermediate between those of iron and chromium. Fe?C2.25Cr oxidizes in a way similar to iron in both environments, forming a poorly protective scale consisting of FeCr spinel at the bottom, magnetite in the middle and a hematite cap layer. In dry O₂, Fe?C10Cr, Fe?C18Cr and Fe?C25Cr form a thin and protective (Fe,Cr)₂O₃ oxide similar to the chromia film formed on pure chromium. In wet O₂, Fe?C10Cr, Fe?C18Cr and Fe?C25Cr initially form the same kind of protective oxide film as in dry conditions. After an incubation time that depends on alloy chromium content, all three alloys go into breakaway oxidation and form thick, poorly protective scales similar to those formed on Fe?C2.25Cr. Breakaway oxidation in wet O₂ is triggered by the evaporation of CrO₂(OH)₂ from the protective (Fe,Cr)₂O₃ oxide.     

The effect of weathering on durability and deformability properties of granitoid rocks

In this paper, the effects of weathering on durability and deformability properties for three different types of granitoid rocks were investigated. Five weathering grades ranging from fresh to completely weathered rocks were considered for each rock type. Deformability has been evaluated based on failure strain, tangent and secant modulus. For measuring these parameters, at least five uniaxial compressive strength tests with axial strain recorded were conducted on each weathering grade. To assess the weathering effect on the durability behavior of these rocks, a slake durability test was performed up to 40 cycles. The obtained results indicated that uniaxial compressive strength and elastic modulus dramatically decrease with increasing weathering grade. After moderately weathering grade, remarkable damage was observed in the structure and fabric of considered rocks. The results from slake durability tests showed that the slake durability index for each weathering grade has a certain changes trend which can be used in determination of the weathering grade and the long-term durability assessment. Moreover, the results showed that for evaluation of the long-term durability of the mentioned rock types, at least eight cycles should be considered, while two cycles were sufficient for estimation of weathering grade.     

Comparison of polyaluminum silicate chloride and electrocoagulation process,in natural organic matter removal from surface water in Ghochan,Iran

Removal of natural organic matter (NOM) is one of the most important objectives of water treatment plants but reducing these pollutants either present in water as dissolved or suspended form is not as efficient as is required in conventional treatment plants. The purpose of this study was comparison performance of composite polyaluminum silicate chloride (PASiC) and electrocoagulation (EC) process by aluminum electrodes in NOM removal from raw surface water. In this study, the effects of turbidity, total organic compounds (carbons) (TOC), adsorption at a wavelength of 254 nm (UV254), chemical oxygen demand (COD), alkalinity, residual aluminum in finished water by application of EC process and PASiC were investigated. The results demonstrate that PASiC coagulant at optimum concentration of 1–5 ml/L was capable of removing TOC, COD, U.V., and turbidity from raw water by 93.77, 93.5, 63 and 95 %, respectively. In contrast, EC process, removed TOC, COD, UV and turbidity from raw water by 89, 99.75, 37 and 50%, respectively. The pilot-scale results demonstrated the significant advantage of PASiC compared to EC process in removal of NOM and turbidity form raw water. Residual aluminum in finished water was below the recommended WHO guidelines 0.2 mg/L for both processes. Finally it can be concluded that PASiC and EC process are reliable, efficient and cost-effective methods for removal of NOM from surface water.     

Mathematical model evaluating for degradation of azo dye in contaminated water by UV/persulfate process

In the present study, the photooxidative degradation of Acid Red 14 (AR 14) was investigated in the UV/persulfate process, and the results of the degradation rate of AR 14 were parametrically represented by ordinary differential equations to find mathematical model for the degradation rate of AR 14 in this process. Our experimental observations led to a model for AR 14 degradation in the UV/persulfate system that could be used to predict removal efficiency by changes of S₂O₈²⁻ (X₁) and dye concentration (X₂), pH (X₃), temperature (X₄) and also distance of UV lamp from solution (X₅). It was found that persulfate and dye concentrations were the most important parameters for AR 14 degradation rate. Moreover, the results showed that the degradation rate was in good agreement with the first-order kinetics for all the parameter values studied. Moreover, the results of the mathematical model agree well with the experimental values (R² = 0.96). Our findings in this study showed that degradation efficiency of UV/S₂O₈²⁻ process for AR 14 was obtained as 98%. Therefore, this model could be applicable before scaling up the AR 14 degradation using UV/persulfate process.     

Extraction and purification of penicillin G from fermentation broth by water-compatible molecularly imprinted polymers

Highly selective molecularly imprinted polymer (MIP) was synthesized by using methacrylic acid as functional monomer, trimethylolpropane trimethacrylate as cross-linker, chloroform as porogen and penicillin G potassium as template molecule. These imprinted polymers were used as solid-phase extraction sorbent for the selective extraction of penicillin G from the fermentation broth samples. Various parameters affecting the extraction efficiency of the MIP particles such as; effects of pH, wash and eluent solutions were evaluated. Molecular recognition properties and selectivity of these MIPs were estimated and the obtained results revealed high affinity for the target antibiotic. Equilibrium binding experiments were done to assess the performance of the MIP relative to non imprinted polymer (NIP). After optimizing the extraction parameters in molecularly imprinted solid-phase extraction (MISPE), successful imprinting was confirmed by comparison of the recoveries from the fermentation broth, ranging between 24–26% (RSD 4.1–4.5%, n = 4) for the NIPs and 83–88% (RSD 3.1–3.4%, n = 4) for the MIPs.     

Engineered Cobalt Single-Atoms@BiFeO3 Heteronanostructures for Highly Efficient Solar Water Oxidation

Efficient charge–carrier separation and their utilization are the key factors in overcoming sluggish four-electron reaction kinetics involved in photocatalytic oxygen evolution. Here, a novel study demonstrates the significance of Na₂S₂O₈ as a sacrificial agent in comparison to AgNO₃. Resultantly, BiFeO₃ (BFO) and titanium doped-oxygen deficient BiFeO₃ (Ti-BFO-R) nanostructures achieve ≈64 and 44.5 times higher O₂ evolution in the presence of Na₂S₂O₈ compared to AgNO₃ as a sacrificial agent, respectively. Furthermore, the presence of Co single atoms (Co-SAs) deposited via immersion method on BFO and Ti-BFO-R nanostructures led to achieving outstanding O₂ evolution at a rate of 16.11 and 23.89 mmol g⁻¹ h⁻¹, respectively, which is 153 and 227.5 times higher compared to BFO (in the presence of AgNO₃), the highest O₂ evolution observed for BFO-based materials to date. The successful deposition of Co-SAs is confirmed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) and X-ray absorption near-edge structure (XANES). The charge transfer investigations confirm the significance of Co-SAs on BFO-based photocatalysts for improved charge–carrier separation, transport, and utilization. This novel study validates the excellent role of Na₂S₂O₈ as a sacrificial agent and Co-SAs as a cocatalyst for BFO-based nanostructures for efficient O₂ evolution.