In-situ identification of iron electrocoagulation speciation and application for natural organic matter (NOM) removal

In this work, iron speciation in electrocoagulation (EC) was studied to determine the impact of operating parameters on natural organic matter (NOM) removal from natural water. Two electrochemical EC parameters, current density (i) and charge loading rate (CLR), were investigated. Variation of these parameters led to a near unity current efficiency (φ = 0.957 ± 0.03), at any combination of i in a range of 1–25 mA/cm² and CLR in a range of 12–300 C/L/min. Higher i and CLR led to a higher bulk pH and limited the amount of dissolved oxygen (DO) reduced at the cathode surface due to mass transfer limitations. A low i (1 mA/cm²) and intermediate CLR (60 C/L/min) resulted in low bulk DO (<2.5 mg/L), where green rust (GR) was identified by in-situ Raman spectroscopy as the primary crystalline electrochemical product. Longer electrolysis times at higher i led to magnetite (Fe₃O₄) formation. Both higher (300 C/L/min) and lower (12 C/L/min) CLR values led to increased DO and/or increased pH, with lepidocrocite (γ-FeOOH) as the only crystalline species observed. The NOM removal of the three identified species was compared, with conditions leading to GR formation showing the greatest dissolved organic carbon removal, and highest removal of the low apparent molecular weight (<550 Da) chromophoric NOM fraction, determined by high performance size exclusion chromatography.     

Computational fluid dynamics modeling of immobilized photocatalytic reactors for water treatment

A computational fluid dynamics (CFD) model for the simulation of immobilized photocatalytic reactors used for water treatment was developed and evaluated experimentally. The model integrated hydrodynamics, species mass transport, chemical reaction kinetics, and irradiance distribution within the reactor. The experimental evaluation was performed using various configurations of annular reactors and ultraviolet lamp sizes over a wide range of hydrodynamic conditions (350 < Re < 11,000). The evaluation showed that the developed CFD model was able to successfully predict the photocatalytic degradation rate of a model pollutant in the analyzed reactors. In terms of hydrodynamic models, the results demonstrated that the laminar model performs well for systems under laminar flow conditions, whereas the Abe‐Kondoh‐Nagano low Reynolds number and the Reynolds stress turbulence models give accurate predictions for photoreactors under transitional or turbulent flow regimes. The performed analysis confirmed that degradation rates of organic contaminants in immobilized photocatalytic reactors are strongly limited by external mass transfer; as a consequence, the degradation prediction capability of the CFD model is largely determined by the external mass transfer prediction performance of the hydrodynamic models used. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Attributing the resistance against simulated tree gum of an acrylic/melamine film loaded with an active silicone additive to its surface free energy

The present work reports preparation of acrylic/melamine based clearcoats with different loadings of a functionalized polysiloxane additive. The resulting films were applied over a black basecoat automotive coating system. Dynamic mechanical thermal analysis (DMTA), contact angle measurement, optical microscopy and gonio-spectrophotometery were utilized to investigate the mechanical (viscoelastic/viscoplastic), surface and optical properties of the coating system before and after exposure to Arabic gum (simulated tree gum). The resistance of film surface against gum attack showed high dependence on gum adhesion to the films. It was revealed that depreciation of surface free energy of additive loaded films could greatly improve their behavior against gum, apparently due to their enhanced non-stick characteristic. Tg and loss peak height also increased, indicating that additive did not negatively influence coating curing state. However, at loading contents exceeding 4 wt% both Tg and loss peak height decreased, revealing that a phase separation had occurred. The improved resistance of films against Arabic gum was corresponded to the low clearcoat shrinkage and crack formation. Weaker interactions between gum and clearcoat surface was seen in presence of additive. The shape and size of defects (of gum exposed films) were also significantly changed.     

Polypropylene/clay nanocomposite: kinetic and thermodynamic of dyeing with various disperse dyes

The preparation of polypropylene/clay nanocomposite fibers is interesting from the point of dyeability. This paper investigated the kinetics and the thermodynamic parameters of polypropylene/nanoclay dyeing with three disperse dyes as common dyestuffs for non-polar polymer (C.I. Disperse Blue 60, C.I. Disperse Red 324, and C.I. Disperse Yellow 211). The physicochemical parameters of dyeing are calculated in terms of sorption isotherm, standard affinity, enthalpy and entropy changes, and diffusion coefficient as well as activation energy of the diffusion. The sorption of disperse dye on polypropylene/nanoclay composite shows the linear isotherm. The value of dyeing rate constant and diffusion coefficient of dye molecules increases with the dyeing temperature. The standard affinity of Disperse Red 324 to polypropylene/nanoclay fiber is higher than the two other dyes due its higher partially polarity.     

A Nonvolatile Spintronic Memory Element with a Continuum of Resistance States

A continuum of stable remanent resistance states is reported in perpendicularly magnetized pseudo spin valves with a graded anisotropy free layer. The resistance states can be systematically set by an externally applied magnetic field. The gradual reversal of the free layer with applied field and the field‐independent fixed layer leads to a range of stable and reproducible remanent resistance values, as determined by the giant magnetoresistance of the device. An analysis of first‐order reversal curves combined with magnetic force microscopy shows that the origin of the effect is the field‐dependent population of up and down domains in the free layer.     

TEMPESTITE DEPOSITS ON A STORM-INFLUENCED CARBONATE RAMP: AN EXAMPLE FROM THE PABDEH FORMATION (PALEOGENE), ZAGROS BASIN, SW IRAN

The Pabdeh Formation is part of a thick carbonate‐siliciclastic succession in the Zagros Basin of SW Iran which includes carbonate reservoirs of Cretaceous and Cenozoic ages. From field observations and petrographic and facies analysis of exposures in the type section of the Pabdeh Formation, four lithofacies were recognized. These are from oldest to youngest: (i) a mottled, bioturbated bioclastic wackestone/mudstone facies; (ii) a wackestone/packstone facies with horizontal burrows on bedding planes; (iii) a thin‐bedded bioclastic wackestone/mudstone facies alternating with thin bioclastic‐oolitic‐intraclastic intervals; and (iv) a bioclastic foraminiferal / algal / peloidal packstone facies. These observations indicate that facies evolved upwards from deep outer‐ramp deposits to inner‐ramp deposits within a shoal complex, suggesting progradation of the ramp depositional system. Storm events significantly influenced the ramp system. Storm‐generated surges transported sediments from nearshore to the deeper outer‐ramp environment where they were deposited as shell‐lags, composed mostly of bioclastic packstones, rich in pelagic microfauna with sharp, undulatory erosional basal contacts. The packstones rest on outer ramp mudstones deposited below storm base level. Sedimentary structures in the Pabdeh Formation are those typical of storm deposits, such as hummocky cross‐stratification, ripple cross‐lamination, ripple marks, escape burrows on the tops of the beds, couplets of fine‐ and coarse‐grained laminae and mixed fauna, as well as intraclasts derived from underlying facies. These distinctive sequences are interpreted to have been generated by waning storm‐generated currents. The dominance of fine‐grained sediments (medium to fine sand); the lack of large‐ scale hummocky cross‐stratification; the minor amounts of intraclasts derived from underlying facies; the paucity of amalgamated tempestite beds; and the finely‐laminated (mm to cm scale) couplets of coarse and fine lamina all suggest a distal tempestite facies. Palaeogeographic reconstruction of the Zagros Basin during the Eocene indicates that the study area was situated in tropical, storm‐dominated palaeolatitudes.     

Model‐predictive safety system for proactive detection of operation hazards

A method of designing model‐predictive safety systems that can detect operation hazards proactively is presented. Such a proactive safety system has two major components: a set of operability constraints and a robust state estimator. The safety system triggers alarm(s) in real time when the process is unable to satisfy an operability constraint over a receding time‐horizon into the future. In other words, the system uses a process model to project the process operability status and to generate alarm signals indicating the presence of a present or future operation hazard. Unlike typical existing safety systems, it systematically accounts for nonlinearities and interactions among process variables to generate alarm signals; it provides alarm signals tied to unmeasurable, but detectable, state variables; and it generates alarm signals before an actual operation hazard occurs. The application and performance of the method are shown using a polymerization reactor example. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2024–2042, 2016     

AN ARTIFICIAL NEURAL NETWORK APPROACH TO CAPILLARY RISE IN POROUS MEDIA

An artificial neural network (ANN) was used to analyze the capillary rise in porous media. Wetting experiments were performed with 15 liquids and 15 different powders. The liquids covered a wide range of surface tension (15.45-71.99 mJ/m²) and viscosity (0.25-21 mPa.s). The powders also provided an acceptable range of particle size (0.012-45 μm) and surface free energy (25.5-62.2 mJ/m²). An artificial neural network was employed to predict the time of capillary rise for a known given height. The network's inputs were density, surface tension, and viscosity for the liquids and particle size, bulk density, packing density, and surface free energy for the powders. Two statistical parameters, the product moment correlation coefficient (r²) and the performance factor (PF/3), were used to correlate the actual experimentally obtained times of capillary rise to: (i) their equivalent values as predicted by a designed and trained artificial neural network; and (ii) their corresponding values as calculated by the Lucas-Washburn equation as well as the equivalent values as calculated by its various other modified versions. It must be noted that for a perfect correlation r² = 1 and PF/3 = 0. The results showed that only the present ANN approach was able to predict with superior accuracy (i.e., r² = 0.92, PF/3 = 51) the time of capillary rise. The Lucas-Washburn calculations gave the worst correlations (r² = 0.15, PF/3 = 1002). Furthermore, some of the modifications of this equation as proposed by different workers did not seem to conspicuously improve the relationships, giving a range of inferior correlations between the calculated and experimentally determined times of capillary rise (i.e., r² = 0.27 to 0.48, PF/3 = 112 to 285).     

Studying the thermodynamic parameters of disperse dyeing of modified polyethylene terephthalate sheets using hyperbranched polymeric additive as a nanomaterial

Thermodynamic parameters of disperse dyeing of modified PET sheets by various loads of a polyesteramide hyperbranched polymer are investigated in terms of standard affinity (?Δμ°), enthalpy change (ΔH°) and entropy change (ΔS°). The results show that the standard affinity of dye to the modified PET is higher than that to the virgin PET. The bath containing virgin PET displays the highest negative values of the ΔH° and ΔS°, while the bath containing the modified PET with 2% hyperbranched polymer shows the lowest negative values of them. Surface morphology and thermal properties of the samples are analyzed by AFM and DSC.