Total recovery of gold,palladium, and platinum using lignophenol derivative

A tertiary amine type adsorption gel was prepared by the immobilization of dimethylamine onto crosslinked lignophenol (CLP) matrix. This novel product was studied for its adsorption behavior for Au(III), Pd(II), Pt(IV), Cu(II), Zn(II), Ni(II), and Fe(III) in 0.5–6 M hydrochloric acid medium. From our previous study, crosslinked lignophenol (CLP) is known to hold solo selectivity for Au(III). After modification to dimethylamine type adsorbent (DMA-CLP), an extended selectivity of Au(III), Pd(II), and Pt(IV) was observed. The maximum loading capacity for these three metal ions was evaluated by isotherm study. For Au(III) an impressive value of 7.2 mol/kg of DMA-CLP was observed. The feasibility of recovery of precious metals from a mixture containing several other metal ions was studied in batch mode by using both model solution and actual industrial solution obtained after aqua regia leaching of metal components in obsolate e-devices. In addition, a number of adsorption–elution cycles were produced so as to know the feasibility of multiple uses.     

Preparation of Silicon Nitride-Titanium Nitride and Titanium-Titanium Nitride Composites from (CH3)3SiNHTiCl3-Coated Si3N4 and Ti Particles

[(Trimethylsilyl)amino]titanium trichloride, (CH₃)₃-SiNHTiClj, was isolated as a red-orange crystalline solid in 58% yield from the reaction of TiCl₄ with [(CH₃)₃Si]₂NH in 1:1 molar ratio in dichloromethane at —78°C. Pyrolysis of (CH₃)₃SiNHTiCl₃ at 600°C furnished titanium nitride. This precursor is suitable for the preparation of composites and was employed to prepare Si₃N₄-TiN and Ti-TiN powders by adding Si₃N₄ particles or titanium powders to a solution of (CH₃), SiNHTiCl₃ in dichloromethane, drying and pyrolyzing the resulting solid. This precursor also has been used as a binder to prepare Si₃N₄-TiN and Ti-TiN bodies. High-resolution transmission electron microscopic studies of the Si₃N₄-TiN composite showed that titanium nitride is concentrated on the surface of the Si₃N₄ particles.     

Boundary element model of electrochemical dissolution with geometric non-linearities

Large scale changes in geometry due to corrosion of polycrystalline pure copper are modeled using the Boundary Element Method. Axisymmetric geometries are considered. A quasi-static analysis is performed and a nonlinear polarization curve is determined from experiments to impose third kind boundary conditions. Super-elements, based on a cubic spline fit interpolation, are introduced to model the motion of the boundaries. Faraday's law is used to relate boundary motion to the surface flux. An set of controlled experiments using nearly pure (99.99% and 99.9%) copper with aerated NH₄OH electrolyte was used to test the experimental methods developed for this study and to verify the functionality of the numerical code in predicting large changes in geometry due to long duration dissolution. Polarization curves were measured and input into the BEM code and recession profiles were predicted. Comparison between experiment and predictions reveal that, given the polarization curves measured in the lab, the BEM code predicts accurate recession profiles.     

Improved PID controller design for unstable time delay processes based on direct synthesis method and maximum sensitivity

In this paper, a proportional-integral-derivative controller in series with a lead-lag filter is designed for control of the open-loop unstable processes with time delay based on direct synthesis method. Study of the performance of the designed controllers has been carried out on various unstable processes. Set-point weighting is considered to reduce the undesirable overshoot. The proposed scheme consists of only one tuning parameter, and systematic guidelines are provided for selection of the tuning parameter based on the peak value of the sensitivity function (M_s). Robustness analysis has been carried out based on sensitivity and complementary sensitivity functions. Nominal and robust control performances are achieved with the proposed method and improved closed-loop performances are obtained when compared to the recently reported methods in the literature.     

Vicarious perception of postural discomfort and exertion

Perceived exertion and discomfort have been used extensively in ergonomics practice. Job incumbents typically rate their exertion on scales such as Borg's rated perceived effort (RPE) and their discomfort on scales such as Corlett and Bishop's body part discomfort scales (BPD). This study asks whether exertion and discomfort can be perceived by an external observer, i.e. is vicarious perception possible? Four participants (targets) performed 20 postural holding tasks selected from Ovako Working Posture Analysing System postures and gave RPE and BPD scores for each posture. Video clips of each target in each posture were shown to four expert ergonomists and 23 novices, who also gave RPE and BPD scores. Correlations between targets and observers scores were high, with significance exceeding p = 0.01. Observers were generally conservative, rating easy postures too high and difficult postures too low. All observers rated female targets higher than male targets. Female observers rated all targets higher then male observers. Vicarious perception of discomfort and exertion was possible, but there was not a one-to-one correspondence to ratings given by those experiencing the posture.     

Flow and heat transfer in serpentine channels

Serpentine channels are often used in microchannel reactors and heat exchangers. These channels offer better mixing, higher heat and mass‐transfer coefficients than straight channels. In the present work, flow and heat transfer experiments were carried out with a serpentine channel plate comprising of 10 units (single unit dimensions: 1 × 1.5 mm² in cross section, length 46.28 mm, D_h 1.2 mm) in series. Pressure drop and heat‐transfer coefficients were experimentally measured. Flow and heat transfer in the experimental set‐up were simulated using computational fluid dynamics (CFD) models to understand the mechanisms responsible for performance enhancement. The CFD methodology, thus, developed was applied to understand the effect of various geometrical parameters on heat transfer enhancement. A criterion was defined for evaluation of heat transfer performance (heat transfer per unit pumping power), thus, ensuring due considerations to required pumping power. The effect of geometrical parameters and the corresponding mechanisms contributing for enhancement are discussed briefly. Based on the results, a design map comprising different serpentine channels showing heat transfer enhancement with pumping power was developed for Reynolds number of 200 which will be useful for further work on flow and heat transfer in serpentine channels. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1814–1827, 2013