1,721,181 research outputs found
Adsorbimento di composti organici volatili (VOCs) in soluzione acquosa su materiali sorbeniti granulari
No full textSolubility of benzene in copolymer aqueous solutions for the design of gas absorption unit operations
No full textIn this work, an amphiphilic block copolymer (ABC) aqueous solution is proposed as innovative green liquid for benzene recovery from polluted gas. This ABC has been selected among four commercially available copolymers, two thermosensitive ABC containing poly-ethylene oxide and poly-propylene oxide blocks-Pluronic (R) L62 and Pluronic (R) P123 - one non-thermosensitive ABC - poly(vinyl pyrrolidone)-polystyrene (PVP-PS) and one non-ionic surfactant - polyoxyethylene sorbitol monooleate (Tween 80 (R)). For each copolymer aqueous solution, benzene Henry's constant (H) has been experimentally calculated and the effects of temperature (4-90 degrees C) and copolymer concentration (4-20%) have been investigated. Experimental results at 20 degrees C and 4% copolymer concentration showed that the H values are in the range 50-280 atm, with a ranking PVP-PS 1100 atm) has been measured in P123 aqueous solution at 90 degrees C, corresponding to its critical point (i.e. phase separation and no micelles presence). As a result of its benzene H values, the P123 aqueous solution was found to be the most promising liquid for benzene recovery among those investigated, being effective for both operations of gas absorption (at low temperature) and solvent regeneration by thermal stripping (at high temperature)
Calcium bisulfite oxidation rate in the wet limestone-gypsum flue gas desulfurization process
No full textIn this paper oxidation of calcium bisulfite in aqueous solutions was studied, in connection with the limestone-gypsum flue gas desulfurization process. Experimental measurements of the oxidation rate were carried out in a laboratory scale stirred reactor with continuous feeding of both gas and liquid phase. A calcium bisulfite clear solution was used as liquid phase, and pure oxygen or mixtures of oxygen and nitrogen were used as gas phase. Experiments were carried out at T = 45 degrees C varying the composition of the liquid phase and the oxygen partial pressure. Manganous sulfate was used as catalyst. The analysis of the experimental results showed that the kinetics of bisulfite oxidation in the presence of MnSO4 follow a parallel reaction mechanism, in which the overall reaction rate can be calculated as the sum between the uncatalyzed rate (3/2 order in bisulfite ion) and the catalyzed reaction rate (first order in manganous ion)
Ottimizzazione del processo di cristalizzazione della DesB-MS: caratterizzazione delle condizioni di equilibrio al variare della temperatura
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Recovery of tungstate from aqueous solutions by ion exchange
No full textA commercial anionic resin has been tested to evaluate its suitability for tungsten recovery from aqueous solutions. Equilibrium runs at fixed temperature have been carried out at different pH levels, showing a higher exchange capacity at acid pH. Kinetics studies consist of the analysis of the breakthrough curves at different tungsten concentrations, flow rates, pHs, and bed depths. At basic pH, the breakpoint and the saturation times of the system are almost constant with pH whatever the flow rates and the tungsten concentrations are. Moreover, the length of the mass transfer zone remains almost unchanged with bed depth, feed flow rate and concentration. At acid pH a critical working condition appears, as the breakpoint time progressively decreases and the saturation time strongly increases. The different behaviors of the exchange resin at acid and basic pHs can be connected to the different forms of tungsten present in solution
Mass transfer between a fixed bed of limestone particles and acid solutions
No full textLimestone dissolution in acid solutions was experimentally studied by means of a fixed-bed reactor. A diffusive model was proposed to describe experimental results. The model, based on the film theory, takes into account the effect of the electric potential of diffusion on the dissolution rate. In order to validate the model, experiments were carried out to study the effect of both particle size and liquid-solid relative velocity on the dissolution rate. Furthermore, the limestone dissolution rate in aqueous solutions of SO2(aq), HCl, and H2SO4 was measured at different acid concentrations. The results showed that the diffusive model, associated with the correlation proposed by Chu et al. [Chu, J. C.; Kalil, J.; Wetteroth, W. A. Chem. Eng. Prog. 1953, 49 (3), 141] for the evaluation of the liquid-solid mass-transfer coefficient, is capable of describing the dependence of the dissolution rate on both the size of the limestone particles and the liquid-solid relative velocity. In addition, it was found that, in agreement with the physical meaning of the film theory, the thickness of the liquid film is not dependent on the kind of acid present in the solution nor on its concentration but only on the fluid dynamic conditions of the liquid-solid system
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