Copper batch experiments

The main features of the copper catalyzed autoxidation of ascorbic acid were summarized in detail in Section III. Recently, Strizhak and coworkers demonstrated that in a continuously stirred tank reactor (CSTR) as well as in a batch reactor, the reaction shows various non-linear phenomena, such as bi-stability, oscillations and stochastic resonance (161). The results from the batch experiments can be suitably illustrated with a two-dimensional parameter diagram shown in Pig. 5. 

At high [Cu(II)] and low [H2A] initial concentrations, the Pt electrode potential, used to follow the chemical process, increased monotonously. When both species were present at high initial concentrations, a monotonous decrease was observed. Various non-monotonic transient regimes were found at approximate initial concentrations of [Cu(II)] 10-4 M and [H2A] 10-4 M. Thus, the batch experiments properly illustrate that the system is sensitive to variations of the initial concentrations of ascorbic acid and copper(II) ion, and the observations can be indicative of a transient bi-stability. 

Analysis of the model For die application of the model, we need the operating equilibrium loading of the resin zyln lx, which is different (lower) that the maximum loading QM evaluated in batch experiments. The equilibrium loading is a function of the maximum inlet concentration of copper, which is 0.308 mol/m3. By using the equilibrium relationship (eq. (4.5)),... 

Using Kirby s data and familiar first order kinetics, the relationship shown in Figure II was derived. This was tested at temperatures up to 280 C (corresponding to 916 Ibs/sq in. equilibrium steam pressure) in 0.25 inch-diameter copper tubing reactors. In these batch experiments. 0.6 g of... 

The experiment is repeated with a new batch of phosphate buffer, the only modification now being addition of 100 jxL of the copper(II) nitrate solution at the beginning of the experiment, that is, together with the addition of the ca. 1 mM sodium sulfite. The oxidation procedure, cat-... 

Flotation has been used for more than 100 years to separate sulphides, oxides and other salts from ores, as well as to obtain phosphates, barite, chromite and other materials. Up to 90% of copper, lead, nickel, zinc are extracted using flotation in the USA [152 - 153]. In Russia, flotation is widely used to additionally obtain apatite, barite and phosphates. Flotation of iron oxides is not used in practise yet, but the number of experiments carried out in this direction is rather large. The main physicochemical principles of flotation have been discussed above [59 -74]. Here, only some practical problems will be discussed. In [153], requirements are pointed out which apply to three-phase flotation foams, and the main components of the process are defined, i.e. surfactant - collector surfactant - frother activator, depressants, colligend, gangue. The peculiarities of flotation and foam separation in batch and continuous modes are outlined as well as the structure and properties of the main types of flotation agents described. As surfaces of the majority of mineral particles are hydrophilic in nature, hydrophobisation of particles is necessary for a selective separation. 

Ghaee et al. [80] studied the adsorption property of copper and nickel on macroporous CS membranes. Batch adsorption experiments were carried out with mono- and bicomponent solutions on CS membrane. In monocomponent adsorption, the copper ion adsorption was 19.87 mg/g, which was higher than those of nickel (i.e., 5.21 mg/g). Maximum adsorptions for copper and nickel were 25.64 and 10.3 mg/g, respectively. Compared to monoadsorption, the amount of adsorption for individual component in bicomponent mixtures showed a decrease. That is due to the competitive adsorption and coordination site limitation. Aliabadi et al. [81] prepared electro-spun nanofiber membrane of PE oxide/CS for the adsorption of nickel, cadmium, lead, and copper ions from aqueous solutions. The maximum adsorption capacity of nickel, copper, cadmium, and lead ions by the PEO/CS nanofiber membrane followed the descending order nickel(II) > copper(II) > cadmium(II) > lead(II). 

Figure 10.5. Experimental setup for investigating the electric field influence experiments on onedimensional pattern formation, (a) batch and (b) flow reactor. Pj, Pj platinum electrodes. R, Rj Reservoirs containing aqueous copper nitrate (0.01 M) and potassium chromate (0.1 M) solutions, respectively. B DC voltage source, M digital multimeter T tubular reactor Sj, S2 magnetic stirrers.

Christl and Kretzschmar (2001) studied the interaction of copper with fulvic acid and hematite, and the results were compared with model calculations based on the linear additivity assumption. The sorption data for the ion-single sorbent systems were modeled with a basic Stem model (BSM) (Section 12.2.2) for hematite and the NICA-Donnan model for fulvic acid. In the second step, pH-dependent sorption of Cu and fulvic acid in systems containing Cu, hematite, and fulvic acid was investigated in batch sorption experiments. Comparison of the experimental data with model calculations shows that Cu sorption in binary hematite-fulvic acid systems is systematically underestimated by up to 30% by using the linear additivity assumption, as shown in Figure 14.4. 

The main classes of catalysts used for heterogeneous WHPCO reaction are clays and anionic clays (hydrotalcites), metal-ion exchanged zeolites and mesoporous silica containing transition metals, and doped metal oxides. Although some other transition metals have been also used (Mn, V), most catalysts contain iron and/or copper as the active elements. Leaching of the active metal is also a significant problem in this case. While different types of catalysts have been reported, only a few of them have been effectively proven to have a stable activity in long-term continuous experiments or at least in several repeated batch tests. Between the stable catalysts, Fe- and Cu-PILC (pillared clays) materials " have the best combination of activity and stability. However, the limited quantity of active elements (around 2% wt. of iron or copper) necessary to achieve stable performances, limits the overall activity. 

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