摘要:

An extensive experimental investigation was conducted with activated carbons to establish the adsorption capacities of heavy metals (Cd2+, Ni2+, Cu2+, and Zn2+) in the presence of complexing agents (EDTA, triethylenetetramine (TRIEN), citrate, etc.). Adsorption equilibria are explained by species charges and carbon surface charge characteristics. In the pH range 7.5−8.0, the active sites are positively charged. The adsorption capacities of Cd2+(and other heavy metals), free ligands, and cadmium-ligands are also a function of feed metal concentration, types of ligands, molar ratio of ligand/metal, and pH. Complete metal-ligand species distributions are calculated by computer solutions of multiple reaction equilibria. For an equilibrium cadmium concentration of 0.1 mM (pH 7.5−8.0), the sequence in adsorption capacity for cadmium chelates isQCd−EDTA>QCd−citrate>QCd−TRIEN>QCd−tartrate. A relationship between the adsorption capacity, surface charge of activated carbon, and the average species charge for various cadmium ligands systems is presented.

ISSN:0098-6445    

DOI:10.1080/00986448308940474

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Continuous production of ethanol by fermentation with immobilized yeasts gives a better yield and capacity and can be better controlled than conventional processes with batch reactors and a suspended biomass. This paper (the first of three) examines the operative conditions for immobilizingSaccharomyces Cerevisiaeon beech wood cubes. After preliminary evaluation of the non-influence of mass transfer phenomena and the extent of alcoholic inhibition, an experimental investigation of the kinetics for a metabolic reaction in a continuous recycle reactor was carried out. The kinetic equation was found to be a Michaelis-Menten type with uncompetitive inhibition by substrate, and linear inhibition by product.

ISSN:0098-6445    

DOI:10.1080/00986448308940475

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The biochemical production of ethanol has been studied in a packed tubular reactor withSaccharomyces Cerevisiaeimmobilized on wooden cubes.

ISSN:0098-6445    

DOI:10.1080/00986448308940476

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

By way of comparison with the kinetic investigation of the continuous production of ethanol in a tubular reactor with immobilized yeasts, a study was carried out of continuous fermentation in a stirred reactor, with final separation and recycling of the microorganisms. Flocculation with potassium ferrocyanide and zinc sulphate was used to separate the biomass. The maintenance of the metabolic activity was assessed. Next, discontinuous fermentation at various substrate and biomass concentrations was performed to determine the kinetics of glucose-ethanol transformation by flocculated and reinoculatedSaccharomyces Cerevisiae.

ISSN:0098-6445    

DOI:10.1080/00986448308940477

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Preparation is made of a group of four new chemically improved limestones (SO2-sorbents) from reactants of 65% limestone, 25% fly ash, and 10% binder of either a ball clay or mixture of the clay with a small quantity of colloidal silica. Fabrication is by pan granulation followed by varying extents of calcination. Potential products in the sorbents are inferred from the phase diagram of the CaO(base)-SiO2(acid)-Al2O3(acid) system. The sorbents show SO2-sorbency up to 2.8−3.0 times that of limestone during coal combustions, evaluations by both thermogravimetry (TG) using the Rapid TG Method and a 6-inch fluidized bed combustion (FBC) unit. Linear correlation with nearly perfect fit of data points is obtained between a parameter for SO2-sorption by evaluations from the Rapid TG Method and SO2-decrease in emissions by evaluations via the FBC method. Other linear correlations indicate a trend of direct proportionality between SO2-decrease and carbon-decrease in FBC emissions. A chemical mechanism is suggested in order to describe this simultaneous occurrence of SO2-decrease and carbon-decrease in emissions from coal combustion.

ISSN:0098-6445    

DOI:10.1080/00986448308940478

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The effect of coil pitch and the cross-sectional ellipticity on residence time distribution (RTD) for diffusion-free laminar flow in helically coiled tubes has been studied. The numerically computed RTDs reveal that the increase in the coil pitch broadens the RTD while the increase in the cross-sectional ellipticity narrows the RTD. The condition under which the effect of coil pitch on RTD can be ignored has been reported.

ISSN:0098-6445    

DOI:10.1080/00986448308940479

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A data acquisition system has been developed to collect, analyze and store large volumes of rapid kinetic data measured from a stopped-flow spectrophotometer. A digital minicomputer, with an A/D converter, tape drive unit and formatter, analog recorder, oscilloscope, and input/output terminal interfaced to the stopped-flow spectrophotometer provides the complete system. Timing for actual data collection is generated through internal computer software with inclusion of A/D conversion time. After a simple initialization from the computer console, software programming provides complete interaction between a user and the terminal. The user is directed through the initialization by a series of decision steps. The first step is to choose a data file, either existing or new. Once the desired file is selected, several options including data collection, analysis, storage, and printing are selectable.

ISSN:0098-6445    

DOI:10.1080/00986448308940480

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A flocculation model of filtration was applied to estimate flocculation conditions in filter beds. The model was derived on the basis of hydraulic parameters and defined in terms of the mean velocity gradient in filter beds. The velocity gradient allows us to establish the effect of filter media density, which has not been yet described quantitatively. Presented are also relations between media density and the optimal filtration rate and filter bed depth. It was found that floes compressibility together with some other hydraulic parameters should be considered important when determining the filtration capacity of the beds. Development of the flocculation effects in filtration theory leads to the optimization of filter designing.

ISSN:0098-6445    

DOI:10.1080/00986448308940481

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Generalized criteria are developed for identifying the various reaction-mass transfer regimes that might be encountered in the analysis of gas-liquid reactions in continuous stirred-tank reactors. These criteria are based on approximations to the governing differential equations (boundary value problem). The approximate criteria are shown to be in good agreement with the exact criteria obtained by solving the boundary value problem. It is not necessary to solve the boundary value problem to evaluate the approximate criteria, so numerical work can usually be avoided. Calculation of the utilization factor in the various reaction-mass transfer modes is discussed. The approximation of van Krevelen and Hoftijzer3is applicable in all regimes.

ISSN:0098-6445    

DOI:10.1080/00986448308940482

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

We report results of Monte Carlo investigations of dispersion in one- and two-phase flow through disordered porous media represented by square and simple cubic networks of pores of random radii. Dispersion results from the different flow paths and consequent different transit limes available to tracer particles crossing from one plane to another in a porous medium. Dispersion is found to be diffusive for the process simulated, i.e., a concentration front of solute particles can be described macroscopically by a convective diffusion equation. Dispersivity in the direction of mean flow, i.e., longitudinal dispersivity, is found to be an order of magnitude larger than dispersivity transverse to the direction of mean flow. In two-phase flow, longitudinal dispersivity in a given phase increases greatly as the saturation of that phase approaches its percolation threshold; transverse dispersivity also increases, but more slowly. As the percolation threshold is neared, the backbone of the sublatlice occupied by the phase becomes increasingly tortuous, with numerous subloops which provide alternate particle paths that are evidently highly effective in dispersing a concentration front of tracer particles.

ISSN:0098-6445    

DOI:10.1080/00986448308940483

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor