104 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
Caratterizzazione chimico-fisica dei fenomeni di ritenzione e rilascio tra inquinanti organici bioresistenti e fasi solide naturali: Quali le indeterminazioni
No full textAccidental Road Spilling of Polychlorobiphenyls – A Case History
No full textApprox. 1,400 kg of Apirolio, an extremely toxic insulating oil mixture, containing polychlorobiphenyls (75.6%) and polychlorobenzenes (24.2%) with traces of dioxins and furans, were accidentally spilled by a truck transporting an electric transformer, along 12 kms of SS 16 bis speedway on Dec. 7th, 1988. After immediate off-limiting of the accident area, a reclamation strategy was adopted that, based on accurate analytical survey of the contaminated environments (asphalt, agricultural soil, trees, produce, groundwater), allowed safe decontamination of the area.</jats:p
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
Recupero di reattivi coagulanti da fanghi di chiarificazione delle acque naturali : processi basati su scambio ionico
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