1,721,009 research outputs found
Cr(III)/A1(III)/Fe(III) ion binding on mixed bed ion exchangers. Synergistic effects of the resins behaviour
No full textIon exchange, as a conservative technology, allows for removal and recycling of metals from liquid effluents. Chelating exchangers may be used to the purpose due to their specificity toward metal species. The specificity, related to the metal-functional group affinity and thus the high stability of the complexes formed, is paid in terms of regeneration levels necessary to reverse the exchange reaction by mass action. Moreover, the liquid-phase speciation of the metals with organic and inorganic ligands, commonly present in industrial effluents, determines the active metal concentrations at the binding sites and thus the removal efficiency of the chelating resins which is, in general, more affected by stereochemical factors during the interaction of the active species at the functional groups.
In this context, we investigated the behaviour of a mixed bed weak electrolyte anion (amino) and cation (carboxylate) conventional ion-exchangers as an alternative to chelating resins. The synergistic effects of the two functional groups to selectively remove, separate and recover Cr(III), Al(III), Fe(III) from segregated industrial effluents are discussed. The exhaustion behaviour of the carboxylate resin toward chromic and aluminum species is synergized by the cooperative presence of the anion resin, this latter being able to selectively retain ferric species. Difficult regeneration behaviour of the metal-form carboxylate resin is also favored by the presence of the weak base amino functional groups in the free base form
Pretreatment of tannery wastewaters by an ion exchange process for Cr(III) removal and recovery
No full textConventional treatment of tannery wastewaters includes the physico-chemical treatment in order tb precipitate metals (mostly Cr(III). The landfilling disposal of mixed physico-chemical and biological tannery sludges is an economical and environmental problem, due to the saturation of possible sites.
A new process, namely, IERECHROM(R) (Ion Exchange REcovery of CHROMium), has been developed for removal, recovery and reuse of Cr(III) ionic complex from segregated tannery wastewaters. The process is based on the use of a weak electrolyte macroporous carboxylate resin, retaining the metal of reference together with other trace metals, including aluminum and iron.
A 10 m(3)/d fully automated pilot plant was assembled and a demonstration campaign was carried out at a medium size Italian tannery by using the IERECHROM process; The adoption of the IERECHROM process simplified the tannery wastewater treatment lay-out as the physico-chemical treatment was not necessary. A considerable decrease in the use of chemical compounds, a sludge production reduced by 80% with respect to the traditional treatment, and lower costs for sludge treatment and disposal were demonstrated
Sulphite ion chromatography determination in aqueous media. Evaluation of interferences and column fouling
No full textCoagulants removal and recovery from water clarifier sludge
No full textSeveral million tons per year of water clarifier sludge are produced in Europe, with forecasts of the figure doubling by the next decade. End disposal of reference sludge is mainly based on controlled landfilling, after conditioning to minimise the volume of solids. The conditioning operation is carried-out in acidic or alkaline media, thus also allowing for coagulants recovery (AI, Fe species). The quality of the chemicals recovered may not be sufficient to justify their reuse, e.g., to water clarification operations.
With the aim of improving the purity of coagulants recovered, a new ion exchange process for selective removal, separation and recovery of Al(III) and Fe(III) species from the clarifier sludge is presented. The IERAL (Ion Exchange Recovery of Aluminium) process is based on the use of a commercial weak electrolyte carboxylate resin (Purolite C106, from Purolite Co., UK), allowing for the removal of metals from the clarifier sludge acidic leachate (pH 3.5), followed by selective separation and recovery of the aluminium and ferric species during the resin regeneration step.
Together with the performance of a fully automated 50 L/d pilot plant, this paper reports the basic principles of the process
Anion Exchange Kinetics in Resins of High Selectivity. Part II†. The Case of Chloride/Sulphate Exchange
No full textFive kinetic models potentially applicable to ion exchange with ions of high selectivity, discussed in Part I of this study, are systematically applied to experimental data on chloride/sulfate forward and reverse exchange and sulfate isotopic exchange with three different types of resins (quaternary ammonium, tertiary amine, and secondary amine groups) and highly dilute solutions (< 0.006 N). Interpretation of these data shows conceivably that the system is controlled by film diffusion, with a small contribution from intraparticle diffusion in forward and isotopic exchange and especially for the resin of highest sulfate selectivity
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