Jorge Manuel Rodrigues De Carvalho

Recovery of zinc from an industrial effluent by emulsion liquid membranes

Abstract A zinc plant effluent was treated with the emulsion liquid membrane (ELM) separation technique. The effluent contrained 335 ppm of Zn, 21.6 ppm of Cd and 3.9 ppm of Cu. A study was made of the effects of the membrane composition and operating parameters for two selective ion -exchangers (thioDEHPA and dithioDEHPA) in relation to the level of zinc in the permeate and the final zinc concentration in the effluent. It is shown that kinetic studies are essential to establish the adequate permeation time. A useful way of representing the concentrations of the feed and the receiving aqueous phase is proposed, in such a way that the occurrence of break-up and/or osmosis can be easily detected. It was noticed that measuring the dynamic interfacial tension is a very helpful technique to follow the degradation of reagents in permeation and to interpret some kinetic data.

Removal of phenols from aqueous solutions by emulsion liquid membranes

The present study deals with the extraction of phenols from aqueous solutions by using the emulsion liquid membranes technique. Besides phenol, two derivatives of phenol, i.e., tyrosol (2-(4-hydroxyphenyl)ethanol) and p-coumaric acid (4-hydroxycinnamic acid), which are typical components of the effluents produced in olive oil plants, were selected as the target solutes. The effect of the composition of the organic phase on the removal of solutes was examined. The influence of pH of feed phase on the extraction of tyrosol and p-coumaric was tested for the membrane with Cyanex 923 as an extractant. The use of 2% Cyanex 923 allowed obtaining a very high extraction of phenols (97-99%) in 5-6 min of contact time for either single solute solutions or for their mixtures. The removal efficiency of phenol and p-coumaric acid attained equivalent values by using the system with 2% isodecanol, but the removal rate of tyrosol was found greatly reduced. The extraction of tyrosol and p-coumaric acid from their binary mixture was also analysed for different operating conditions like the volume ratio of feed phase to stripping phase (sodium hydroxide), the temperature and the initial concentration of solute in the feed phase.

Modeling of the Extraction Equilibrium of Copper from Sulfate Solutions with Acorga M5640

The extraction equilibrium of copper from sulfate media with the aldoxime Acorga M5640 in ShellSol D70 has been investigated. The distribution results were interpreted by taking into account the nonideality of the aqueous phase. The activity of copper and hydrogen ions in the target systems CuSO4/H2SO4/Na2SO4 and CuSO4/H2SO4/Fe2(SO4)3/ZnSO4 were calculated through the speciation of the aqueous solutions and by applying the Pitzer model. The experimental pH values were found in good agreement with the predicted pH values. A model considering the dimerization of the aldoxime extractant was proposed to predict the distribution ratio and the copper loading isotherms. The extraction constant at infinite dilution and the apparent dimerization constant were evaluated from the experimental data and were found to be 103.06 ± 0.07 and 51 ± 9 M−1, respectively, at 25°C.

Mercury removal from process sludges via hypochlorite leaching

Abstract Hypochlorite leaching of two types of chlorine‐alkali sludges was studied. Experiments were carried out to determine the relevant variables affecting mercury extraction. Ninety seven percent of mercury extraction was achieved with experimental conditions of 150 g 1 ‐1 NaCl, 35°C temperature, 0.26% (w/w) active chlorine, a solid/liquid ratio (w/w) of 0.30 and a stirring speed of 1050 rpm. The effects of reactor geometry, type of agitator and consumption of acid and chlorine during leaching were analysed. A relationship was established between the mercury in the leaching solution and in the solid under equilibrium conditions.

Treatment of Toxic Wastes Using an Hydrometallurgical Process

A hydrometallurgical process, which consists of a hypochlorite leaching of chlorine-alkali sludge followed by a solid liquid separation with cake washing is presented. The effect of temperature, level of agitation, amount of chlorine in the leaching solution and its consumption in the behaviour of the leaching process was analysed. The results showed that to achieve higher leaching kinetics, there is not any advantage of temperature higher than 25°C, and that there is no need for very strong agitation. It was noted that the chlorine consumption is higher than stoichiometrically necessary. Some flowsheets are proposed with the corresponding computer worksheets. One of them was checked and confirmed by a continuous experiment on laboratory scale. Recirculation of the leaching solution and of the filtration cake washing water diminished the necessary reagent consumption. However the percentage of mercury extraction is slightly decreased due to the increase of mercury concentration in the initial leaching sol...