Enzyme mass transfer coefficient in aqueous two-phase systems: Modified spray extraction columns

The fractional dispersed phase hold-up and mass transfer coefficients were measured in modified spray columns of 50 mm i.d. using an aqueous two phase system of polyethylene glycol (PEG 4000)-sodium sulphate-buffer. The mass transfer coefficients were measured for amyloglucosidase and β-galactosidase. Both co-current and countercurrent modes of operation were investigated. The dispersed phase hold-up (?_D) and the dispersed phase and the continuous phase mass transfer coefficients (k_Da, k_Ca) increased with increasing dispersed phase velocity. An increase in the phase concentration of sodium sulphate and PEG was found to reduce ?_D, k_Da, and k_Ca. The performance of the modified spray column is compared with the conventional spray column. The modifications resulted into about a ten-fold enhancement in the throughput and about a five-fold reduction in the value of the height of a transfer unit (HTU ). It has been shown that the value of HTU of the order of 1 m can be obtained. Empirical correlations for ?_D and k_Da, k_Ca have been proposed.     

Ultrasonic study on binary liquid mixtures of propiophenone with anilines and alkyl substituted anilines at T=303.15 to 318.15 K

Densities ‘ρ’, ultrasonic speeds of sound ‘u’ of binary mixtures of propiophenone (PPH) with aniline, N-Methylaniline, N,N-dimethylaniline and N,N-diethylaniline were measured over the entire composition range from 303.15 K to 318.15 K and at atmospheric pressure 0.1 MPa. Experimental data of ultrasonic sound were compared and discussed with the computed values of ‘u’ from various velocity theories like Nomoto’s relation (U_NOM), impedance relation (U_IMP), Van Dael and Vangeel’s ideal mix relation (U_VDV), Rao’s specific velocity relation (U_RAO), Junjie’s theory (U_JUN) and Jouyban-Acree’s (U_JOE) relation for the above binary mixtures over the entire mole fraction range at the studied temperatures. The results are satisfactory and are in agreement between the theoretical and the experimental values. Further, the molecular interaction parameter (α), average percentage error and Chi-square test values were computed by using the values of experimental and theoretical ultrasonic velocities. The Δu values were correlated with Redlich-Kister polynomial equation to compute the coefficients and the standard deviations of the binary mixtures. The results were analyzed in terms of intermolecular interactions.     

Amphiphilic ABA‐type triblock copolymers for the development of high‐performance poly(vinylidene fluoride)/poly(vinyl pyrrolidone) blend ultrafiltration membranes for oil separation

ABA‐type amphiphilic triblock copolymers (TBCs) were synthesized by a reversible addition fragmentation chain transfer (RAFT) process with a telechelic polystyrene macro‐RAFT agent and 4‐[n‐(acryloyloxy)alkyloxy]benzoic acid monomers. Ultrafiltration (UF) membranes were fabricated by a phase‐inversion process with blends of the TBC, poly(vinylidene fluoride) (PVDF), and poly(vinyl pyrrolidone) (PVP) in dimethylformamide. The UF‐fabricated membranes were characterized by scanning electron microscopy, atomic force microscopy, water contact angle measurement, thermogravimetric analysis, and differential scanning calorimetry. Pure water permeation, molecular weight cutoff values obtained by the permeation of different molecular weight polymers as probe solutes, bovine serum albumin (BSA) solution permeate flux, and oil–water emulsion filtration tests were used to evaluate the separation characteristics of the fabricated membranes. The tripolymer blend membranes exhibited a higher flux recovery ratio (FRR) after the membrane was washed with sodium lauryl sulfate (0.05 wt %) solution for a BSA solution (FRR = 88%) and oil–water emulsion (FRR = 95%) feeds when than the PVDF–PVP blend membrane (57 and 80% FRR values for the BSA solution and oil–water emulsion, respectively). The pendant carboxylic acid functional moieties in this ABA‐type TBC have potential advantages in the fabrication of high‐performance membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45132.     

Steady-state and dynamic performance analysis of PV supplied DC motors fed from intermediate power converter

The steady-state and transient performance of PM and series motors coupled to centrifugal pump supplied from Photovoltaic source through intermediate buck-boost converter is analyzed. The effect of duty ratio selection based on maximum power operation of PV source and maximum daily gross mechanical power is investigated on the solar cell array operating point, motor armature voltage, armature current and motor efficiency variation. Studies are carried out by formulating the mathematical models for photovoltaic source, DC motors, power converter and load. Starting torque variation, Torque magnification factors expressions are derived and their variations plotted for the above two cases. Simulation software is developed for the transient and steady-state analysis of PV supplied DC motors for different duty ratios of power converter and solar insolations. Steady-state and transient performance characteristics are presented. The performance of PM DC motor is compared with the series motor operating under identical conditions.     

Tool steel and copper coatings by friction surfacing - A thermography study

Infrared thermography was used to record thermal profiles during friction surfacing. Thermal profiles for different sets of consumable rod/substrates (tool steel/steel; copper/steel and copper/copper) were recorded and analyzed. The thermal profiles showed distinct stages of plastic deformation with respect to temperature. The mechanism of bonding or no-bonding was discussed based on thermal profile data. It was found that a metallurgically bonded coating can be obtained if the flow stress of the plasticized material is comparable with the localized stress developed due to axial loading.     

Removal of arsenic (III) and arsenic (V) from aqueous medium using chitosan-coated biosorbent

A biosorbent was prepared by coating ceramic alumina with the natural biopolymer, chitosan, using a dip-coating process. Removal of arsenic (III) (As(III)) and arsenic (V) (As(V)) was studied through adsorption on the biosorbent at pH 4.0 under equilibrium and dynamic conditions. The equilibrium adsorption data were fitted to Langmuir, Freundlich, and Redlich-Peterson adsorption models, and the model parameters were evaluated. All three models represented the experimental data well. The monolayer adsorption capacity of the sorbent, as obtained from the Langmuir isotherm, is 56.50 and 96.46 mg/g of chitosan for As(III) and As(V), respectively. The difference in adsorption capacity for As(III) and As(V) was explained on the basis of speciation of arsenic at pH 4.0. Column adsorption results indicated that no arsenic was found in the effluent solution up to about 40 and 120 bed volumes of As(III) and As(V), respectively. Sodium hydroxide solution (0.1M) was found to be capable of regenerating the column bed.     

Multi‐scale modeling of moving interface problems with flux and field jumps: Application to oxidative degradation of ceramic matrix composites

Problems involving reaction and species diffusion involve field and flux jumps at a moving reaction front. In multi‐scale problems such as carbon fiber composite oxidation, these effects need to be tracked at the microscopic scale of individual carbon fibers. A multi‐scale model is derived in this paper for predicting species distribution in such problems using a fully coupled multi‐scale homogenization approach. The homogenized fluxes from the micro‐scale are derived using Hill's macro‐homogeneity condition accounting for both flux jumps and species density field jumps at the reacting interface in the micro‐scale unit cell. At the macro‐scale, the competition between the transport of reacting species (oxygen) and the reaction product (carbon dioxide) is modeled using homogenized mass conservation equations. The moving reaction front in carbon fibers at the micro‐scale is tracked using level set method and an adaptive meshing strategy. The macroscopic weight loss of the composite when exposed to oxygen is simulated as a function of time using a coupled finite element methodology at various locations in a validated macroscopic model. Copyright © 2010 John Wiley & Sons, Ltd.     

A decision support system for production planning and bid preparation for a small job shop manufacturer

With the advent of the inexpensive micro-computer, small manufacturers have been able to automate many applications in their day-to-day operations. Under the auspices of the State of Missouri “Productivity Improvement Program” - a program to aid small manufacturing businesses in improving their productivity, a Decision Support System (DSS) was developed to assist a small metals manufacturing company in production planning and bid preparation.

The DSS was developed at UMR by a graduate student as part of his master's thesis; the work was funded by both the Productivity Improvement Program and the small manufacturer. After development of the DSS, the graduate student was hired full time for one year to assist the manufacturer in implementing the DSS and to train on site personnel in its operation.

This paper discusses the development of the DSS, its implementation, and its utilization.     

Competitive adsorption of Cu (II), Co (II) and Ni (II) from their binary and tertiary aqueous solutions using chitosan-coated perlite beads as biosorbent

A new composite chitosan-coated biosorbent was prepared and was used for the removal and recovery of heavy metals from aqueous solution. In the present investigation, equilibrium adsorption characteristics of Cu (II), Ni (II), and Co (II) from their binary and tertiary solution on newly developed biosorbent chitosan-coated perlite beads were evaluated through batch and column studies. These beads were characterized by using FTIR, EDXRF and surface area analysis techniques. The effect of various biosorption parameters like effect of pH, agitation time, concentration of adsorbate and amount of adsorbent on extent of adsorption was investigated. The adsorption follows Lagergren first order kinetic model. The equilibrium adsorption data were fitted to Freundlich and Langmuir adsorption isotherm models and the model parameters were evaluated. Both the models represent the experimental data satisfactorily. The sorbent loaded with metal was regenerated with 0.1N NaOH solution. Furthermore the column dynamic studies indicate the re-usage of the biosorbent.