Thermal treatment for recovery of manganese and zinc from zinc-carbon and alkaline spent batteries

The aim of this paper is the recovery of manganese and zinc from a mixture of zinc-carbon and alkaline spent batteries, containing 40.9% of Mn and 30.1% of Zn, after preliminary physical treatment followed by removal of mercury. Separation of the metals has been carried out on the basis of their different boiling points, being 357°C and 906°C the boiling point of mercury and zinc and 1564°C the melting point of Mn(2)O(3). Characterization by chemical analysis, TGA/DTA and X-ray powder diffraction of the mixture has been carried out after comminution sieving and shaking table treatment to remove the anodic collectors and most of chlorides contained in the mixture. The mixture has been roasted at various temperatures and resident times in a flow of air to set the best conditions to remove mercury that were 400°C and 10 min. After that, the flow of air has been turned into a nitrogen one (inert atmosphere) and the temperatures raised, thus permitting the zinc oxide to be reduced to metallic zinc by the carbon present in the original mixture and recovered after volatilization as a high grade concentrate, while manganese was left in the residue. The recovery and the grade of the two metals, at 1000°C and 30 min residence time, were 84% and 100% for zinc and 85% and 63% for manganese, respectively. The recovery of zinc increased to 99% with a grade of 97% at 1200°C and 30 min residence time, while the recovery and grade of manganese were 86% and 87%, respectively, at that temperature. Moreover, the chlorinated compounds that could form by the combustion of the plastics contained in the spent batteries, are destroyed at the temperature required by the process.

The 'real' woman with heart failure. Impact of sex on current in-hospital management of heart failure by cardiologists and internists

AIM

To identify differences between sexes in the clinical profile, use of resources, management and outcome in a large population of 'real world' patients with heart failure (HF).

METHODS

A prospective cross-sectional survey was conducted on 2127 consecutive patients (47% women) admitted with HF to 167 cardiology and 250 internal medicine departments between February 14 and 25, 2000.

RESULTS

Women were older, had a higher prevalence of atrial fibrillation, and more frequently a hypertensive or valvular aetiology. Females were admitted more frequently in Medical than in Cardiology Departments. The rate of invasive and non-invasive procedures was lower in women than in men, slightly higher if managed by cardiologists. Women were less frequently prescribed ACE-inhibitors, amiodarone, and spironolactone, and more frequently prescribed digoxin. In-hospital mortality was similar, without difference between health-care providers. A 6-month follow-up was performed in 56.4% of the cases in both setting, but less frequently in women. Event rates were similar with nearly half of patients re-hospitalised at least once.

CONCLUSION

The 'real' HF woman has generally a more severe disease; she is an old lady who is more frequently hospitalised in a medical unit, receives few diagnostic, and cardiovascular procedures and pharmacological therapy, has a relatively low probability of dying in hospital, but a high likelihood of requiring readmission.

Enzymatic extraction of carotenoids from plant material using two immiscible liquid phases

The kinetics of extraction of carotenoids from orange flavedo was investigated. Extraction was carried out using a mixture of degrading enzymes and an edible oil as the solvent. More than 70 microg of carotenoids per g of wet flavedo were extracted within the first 3-4 hours. The results obtained were interpreted by a simple kinetic model considering the unsteady mass transfer of carotenoids in the two-phase system.

Effect of polyols and sugars on heat-induced flavin dissociation in glucose oxidase

A thermodynamic investigation was carried out on heat-induced flavin dissociation in Aspergillus niger glucose oxidase. Experimental measurements performed by difference spectroscopy showed that the dissociation of the FAD cofactors is a highly cooperative process and is probably related to the extended conformational changes resulting from protein unfolding. Microenvironmental modifications attained by the addition of polyhydric compounds (glycerol, fructose, sucrose and sorbitol) from 10 to 30% by weight were found to hinder the dissociation. The stabilizing effect provided by these substances was interpreted as a consequence of preferential exclusion phenomena, which are likely to be determined by the perturbation of the surface tension of water, in the case of sugars, or by the solvophobic effect, in the case of glycerol.

Thermal denaturation of erythrocyte carbonic anhydrase

An experimental study on the thermal behaviour of erythrocyte carbonic anhydrase was carried out with the main aim to estimate the thermodynamic parameters that control the stability of the enzyme. The effects of thermal denaturation on the catalytic properties of the enzyme were also investigated. Below 60 degrees C the enzyme was found to be very stable, whereas between 60 and 65 degrees C a drastic decrease in the biological activity was observed. From the obtained results some considerations were made about the stabilization of the active form of the protein.