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.     

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.     

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.     

Synthesis of N-heteroaryl retinals and their artificial bacteriorhodopsins

N-Heteroaryl retinals derived from indole, 1-indolizine and 3-indolizine (10 a-c) have been synthesized after their UV/Vis red-shifted absorption properties had been predicted by time-dependent density functional theory (TD-DFT) computations. The three new analogues form artificial pigments upon recombination with bacterioopsin: indolyl retinal 10 a undergoes fast and efficient reconstitution to form a species with a UV/Vis absorbance maximum similar to that of wild-type bacteriorhodopsin, whilst the indolizinyl retinals 10 b and 10 c also reconstitute in significant proportion to give noticeably red-shifted, although unstable, pigments. Significant changes in the pK(a) values of these artificial bacteriorhodopsins are interpreted as arising from nonoptimal binding-site occupancy by the chromophore due to steric constraints.     

Treatment of phenol-containing aqueous solutions by membrane-based solvent extraction in coupled ultrafiltration modules

Extractive treatment of phenol-containing aqueous streams by two coupled hollow fiber modules (for simultaneous extraction and stripping) is experimentally and theoretically studied. The effects of hydrodynamic conditions (linear velocities of all three liquids) and concentrations (initial phenol concentrations) are explored and an optimal combination of these process parameters is found for maximisation of the phenol fluxes in both modules. The extraction/stripping performance of the coupled HF modules was compared when using different organic solvent (alcohols and alkanes). Analysis of the mass-transfer resistances of the different liquid layers in both modules is presented based on mathematical model and experimental data from equilibrium measurements and kinetic experiments. It is found that an important part of the overall resistance is located in the aqueous phase’s boundary layers. A substantial improvement of the stripping yield is reached by using a series of stripping modules.