Sorptive properties of polycaproamide fibres containing antistats

Conclusions Modification of polycaproamide fibres with ethoxylated amines increases free volume and the combinatorial entropy of the polymer.The indicated changes in fibre structure cause an increase in their hygroscopicity.Bulgaria. Translated from Khimicheskie Volokna, No. 4, pp. 55–56, July–August, 1984.     

Catalytic oxidation of anisole over titanium silicalite-1

The reaction of anisole hydroxylation with hydrogen peroxide to form methoxyphenols over TS-1 was studied. Four C1-C3 alcohols and the two aprotonic solvents acetone and acetonitrile were used. Product conversion was almost proportional to the titanium content of the catalyst sample. The highest conversion and p-selectivity were observed in ethanol. Some speculations, based on the formation of substrate-solvent or titanium-solvent-oxidant complexes, about the role of the solvent are presented. It was found that in all the solvents studied the p/o ratio increased with time.     

Thermal storage: Nucleation of melts of inorganic salt hydrates

This paper reviews the heterogeneous nucleation of melts of some inorganic salt hydrates. Five salt hydrates were tested as materials for heat storage.     

Hollow-Fiber Membrane Extraction of Copper from Aqueous Nitrate Media by LIX® Reagents: Comparison of Extraction Efficiency and Fractional Resistances

Abstract

Extraction of copper from nitrate/nitric acid aqueous solutions was studied using a HF Membrane Module and four LIX reagents (LIX® 860N-I, LIX® 984N, LIX® 84-I, and LIX® 65N) containing different active compounds (ketoximes and/or salicylaldoximes). Kinetic experiments varying the flow rates of both phases, aqueous and organic, and the extractant concentration were carried out to compare the extraction rate and efficiency from nitrate-aqueous media. A mathematical model based on the “aqueous extraction mechanism” in which the chemical reaction takes place in an aqueous-reaction zone was applied to determine the individual resistances of the copper mass-transfer process. It was found that the fractional resistance due to chemical reaction in the aqueous reaction zone, which varied from 92.5% to 95.8% in the order LIX® 860N-I < LIX® 984N < LIX® 84-I < LIX® 65N, controlled the total rate of the hollow-fiber copper extraction from nitrate aqueous media.     

Kinetic Aspects of Copper‐LIX ® Extraction from Nitrate/Nitric Acid Aqueous Solutions

Abstract

A comparative kinetic study of the extraction of copper from nitrate/nitric acid aqueous solutions by different classes of LIX ^® reagents (LIX 984N, LIX 860N‐I, LIX 84‐I, LIX 65N) was performed. Using a Rotating Diffusion Cell, the rate constants of the chemical reactions (forward and reverse) were estimated and compared. In the case of the mixed extractant LIX 984N, a synergistic effect was observed. The values of the forward reaction constants of all the extractants were found to be an order of magnitude higher than those of the reverse reaction. The relatively low E _a ‐values prove the substantial influence of the diffusion on the extraction kinetics under the experimental conditions studied.     

Mathematical Modeling of Theoretical Cryptosporidium Inactivation in Full-Scale Ozonation Reactors

Conditions for theoretical inactivation of Cryptosporidium by ozone could be achieved at full-scale facilities if their design is appropriate. To perform this task correctly the chemical engineer's approach for process design must be applied. This paper discusses the basic equations the estimation of the disinfection efficiency of different ozone reacting systems. Available kinetic data have been integrated in a global model accounting for the hydrodynamics and mass transfer performances of the ozonation reactor. Thus the proposed method allows one to predict Cryptosporidium inactivation level in a given ozonation system. However, if a specified disinfection goal is to be achieved for Cryptosporidium with the developed model it is also possible to choose and optimize the design of the ozone reactor.     

Influence of Geometrical Characteristics and Operating Conditions on the Effectiveness of Ozone Contacting in Fine-Bubbles Conventional Diffusion Reactors

Ozone contactor hydrodynamics are strongly dependent on the geometry and the operating conditions of the system. In this paper results obtained on a pilot scale reactor showing the relationship between the geometrical characteristics of an ozonation reactor and its hydrodynamic behavior are presented. The validity of the proposed models has been checked on several full-scale reactors for which data were available in the literature.     

Electrochemical investigation of the adsorption behaviour of anhydrides and imides on iron in acid medium

The capacitance method was applied to the study of the adsorption of anhydrides and imides with different size of the anhydride and imide ring on iron electrodes in acid medium. It was found that the addition of anhydrides and imides to sulphuric acid solution leads to a decrease in the electrode double layer capacitance. The latter is determined by the adsorption of the compounds investigated. Verifying the validity of Frumkin's isotherm adsorption parameters which characterize the interaction forces between the species in the adsorbed layer, their maximum surface excess, as well as the area occupied by a single adsorbate, were determined. The data obtained, and those provided by quantum-chemical calculations of the partial electron charges and the geometric area of the organic molecules studied, form the basis of a discussion on the orientation of the species adsorbed. The inhibiting effect observed is explained in relation to the adsorption behaviour.     

Problems of operation and main reasons for failure of membranes in tertiary treatment systems.

This paper presents the results of the long-term operation and monitoring of membrane fouling at several full-scale MF/RO water recycling facilities operated by Agbar in Spain. It was demonstrated that membranes give very reliable treatment enabling the production of high-grade recycled water, well disinfected and with the removal of all priority substances. The high organic and salt concentrations of raw wastewater combined to extremely high variations justified the implementation of sand filtration to protect MF/RO membranes. Membrane autopsy was used to better understand the predominant fouling mechanisms and optimise down-stream operation and membrane cleaning strategy. The main membrane pathologies are described with recommendation of an adequate cleaning strategy.