The importance of pre-treatment of spent hydrotreating catalysts on metals recovery

This work describes a three-step pre-treatment route for processing spent commercial NiMo/Al2O3 catalysts. Extraction of soluble coke with n-hexane and/or leaching of foulant elements with oxalic acid were performed before burning insoluble coke under air. Oxidized catalysts were leached with 9 mol L-1 sulfuric acid. Iron was the only foulant element partially leached by oxalic acid. The amount of insoluble matter in sulfuric acid was drastically reduced when iron and/or soluble coke were previously removed. Losses of active phase metals (Ni, Mo) during leaching with oxalic acid were compensated by the increase of their recovery in the sulfuric acid leachate.

Recuperação de metais de catalisadores usados de hidrotratamento (NiMo E CoMo/AL2O3)

This work presents a detailed study of the leaching behavior of deactivated hydrotreating catalysts (CoMo, NiMo/Al2O3) in presence of oxalate and NH4+ ions in various media. The yield of metals recovery may be optimized by adjusting several experimental parameters (time, temperature, etc). Leaching is limited by physical factors (diffusional effects caused by coke) and by the existence of silicate/spinel-like species which are poorly soluble in leaching solutions. Coke may be eliminated by an oxidation step at temperatures between 300-400ºC. Above 400ºC, solubilization of Ni and Co is drastically reduced. 50-90% wt of sulphate species and 15-30% wt of phosphate ions are solubilized during leaching. Silicon (as SiO2) is not solubilized. The best Ni-Co-Mo recoveries are in the 70-90% wt range; Fe recovery may be quantitative, whereas Al leaching may be lower than 5% wt.

Gerenciamento de resíduos laboratoriais: recuperação de elementos e preparo para descarte final

This work shows some laboratory waste management developed in order to recover some elements or to prepare the waste for a correct final disposal. The 25 elements chosen cover basically all chemical behaviors found for the metals in the Periodic Table. The treatments adopted were based on the classical behavior in aqueous solution (wet chemistry) but an important condition for a full success was the previous knowledge of the qualitative composition of the wastes treated. Some general trends were found: the final liquid waste was always saline and normally presented a higher volume than the original waste; most original wastes were acid in nature; steps such as solid-liquid separation, washing, evaporating and calcining were currently performed. This work was also a very good experience in chemistry in solution for students and showed them the need of treating wastes for a better environment.

Recuperação de metais de catalisadores mássicos e monometálicos

This work presents a study on the dissolution of some commercial monometallic and non-supported deactivated catalysts in HF + H2O2 mixtures (and, eventually, other media) under mild experimental conditions, after a previous oxidation step. The samples were neither crushed nor grinded. The best experimental conditions were dependent on the nature of the support and of the active phase. For example, the Pt/Al2O3 catalyst was dissolved in about 10 minutes, without agitation and heating; however, dissolution of the Pd/Al2O3, Ni/Al2O3, Ni/SiO2, Cu/Al2O3 and V2O5 samples required a temperature of 60 ºC and an agitation of 400 rpm. A careful addition of a NaOH solution allowed a quantitative precipitation of aluminium as criolite (Na3AlF6) or precipitation of Si as Na2SiF6; NaF was obtained as a by-product. As expected, processing of Pd/C, V2O5 and CuO.Cr2O3 samples was relatively simple. Metals recovery from catalysts reached a quantitative level in all samples studied; it is particularly interesting that platinum and palladium could be easily recovered in a single step process, thus separing them from aluminium.

Processamento de pilhas Li/MnO2 usadas

This work presents two recycling processes for spent Li/MnO2 batteries. After removal of the solvent under vacuum the cathode + anode + electrolyte was submitted to one of the following procedures: (a) it was calcined (500 ºC, 5 h) and the calcined solid was submitted to solvent extraction with water in order to recover lithium salts. The residual solid was treated with sulfuric acid containing hydrogen peroxide. Manganese was recovered as sulfate; (b) the solid was treated with potassium hydrogeno sulfate (500 ºC, 5 h). The solid was dissolved in water and the resulting solution was added dropwise to sodium hydroxide. Manganese was recovered as dioxide. The residual solution was treated with potassium fluoride in order to precipitate lithium fluoride.

Recuperação de chumbo, mercúrio e elementos dos grupos 4 a 7 da tabela periódica de seus resíduos

This work shows routes to recover some elements from their laboratory wastes and broken apparatus (thermometers and densimeters). Most elements chosen present a chemical behavior in aqueous solution which is not currently studied in the ordinary experimental classes. The routes were based on the previous knowledge of the qualitative composition of the wastes treated. Wastes containing chromium were the most difficult to treat. The elements were recovered in good yields and can be reused in new experiments. This work was a very good experience in chemistry for students and shows the need of managing wastes for a better environment.

Processamento de placas de circuito impresso de equipamentos eletroeletrônicos de pequeno porte

A hydrometallurgical process applicable to printed circuit boards of small electrical and electronic devices was developed. This involved three leaching steps (60 ºC, 2 h): 6 mol L-1 NaOH, 6 mol L-1 HCl and aqua regia. NaOH removed the resin and flame retardant that covered the circuit boards. HCl dissolved the most electropositive metals and a small amount of copper (~0.3 wt%). Aqua regia dissolved the noble metals. Silver precipitated as AgCl. Gold and platinum were quantitatively extracted with pure methyl-isobutylketone and Alamine 336 (10 % vol. in kerosene), respectively. Slow evaporation of the raffinate crystallized CuCl2.4H2O (89% yield).

Influence of digestion methods on the recovery of Iron, Zinc, Nickel, Chromium, Cadmium and Lead contents in 11 organic residues

There are currently many devices and techniques to quantify trace elements (TEs) in various matrices, but their efficacy is dependent on the digestion methods (DMs) employed in the opening of such matrices which, although "organic", present inorganic components which are difficult to solubilize. This study was carried out to evaluate the recovery of Fe, Zn, Cr, Ni, Cd and Pb contents in samples of composts and cattle, horse, chicken, quail, and swine manures, as well as in sewage sludges and peat. The DMs employed were acid digestion in microwaves with HNO3 (EPA 3051A); nitric-perchloric digestion with HNO3 + HClO4 in a digestion block (NP); dry ashing in a muffle furnace and solubilization of residual ash in nitric acid (MDA); digestion by using aqua regia solution (HCl:HNO3) in the digestion block (AR); and acid digestion with HCl and HNO3 + H2O2 (EPA 3050). The dry ashing method led to the greatest recovery of Cd in organic residues, but the EPA 3050 protocol can be an alternative method for the same purpose. The dry ashing should not be employed to determine the concentration of Cr, Fe, Ni, Pb and Zn in the residues. Higher Cr and Fe contents are recovered when NP and EPA 3050 are employed in the opening of organic matrices. For most of the residues analyzed, AR is the most effective method for recovering Ni. Microwave-assisted digestion methods (EPA3051 and 3050) led to the highest recovery of Pb. The choice of the DM that provides maximum recovery of Zn depends on the organic residue and trace element analyzed.

Availability of heavy metals in contaminated soil evidenced by chemical extractants

Heavy metals have been accumulating in Brazilian soils, due to natural processes, such as atmospheric deposition, or human industrial activities. For certain heavy metals, when in high concentrations in the soil, there is no specific extractant to determine the availability of these elements in the soil. The objective of the present study was to evaluate the availability of Cd, Cu, Fe, Mn, Pb and Zn for rice and soybeans, using different chemical extractants. In this study we used seven soil samples with different levels of contamination, in completely randomized experimental design with four replications. We determined the available concentrations of Cd, Cu, Fe, Mn, Pb and Zn extracted by Mehlich-1, HCl 0.1 mol L-1, DTPA, and organic acid extractants and the contents in rice and soybeans, which extracts were analyzed by ICP-OES. It was observed that Mehlich-1, HCl 0.1 mol L-1 and DTPA extractants were effective to assess the availability of Cd, Cu, Pb and Zn for rice and soybeans. However, the same was not observed for the organic acid extractant.

Recovery of Trypanosoma forattinii Coutinho and Pattoli from a Trinidadian rodent

Recovery of Trypanosoma forattinii from natural infected Oryzomys capito velutinus from Trinidad, is reported. Negative results were obtained with attempts to infect experimentally, several laboratories animals, silvatyc rodents of the same ecological area and several species of triatomids bugs. Positive results were obtained only by using O. capito velutinus born in laboratory.

Cultural adaptation and psychometric properties of Brazilian Need for Recovery Scale

OBJECTIVE: To translate the Need for Recovery Scale (NFR) into Brazilian Portuguese and culturally adapt it and assess the stability, internal consistency and convergent validity of the Brazilian scale among industrial workers. METHODS: The translation process followed the guidelines for cultural adaptation of questionnaires including the steps of translation, synthesis, back translation, expert committee review, and pre-testing. The Brazilian Portuguese NFR, final version (Br-NFR) was assessed for stability (n=52) and internal consistency (n=192) and for convergent validity through simultaneous assessment with other instruments: the Borg Scale (n=59); the Chalder Fatigue Questionnaire (n=57) and 3 subscales of the SF-36 (n=56). RESULTS: Stability and internal consistency met the criterion for a reliable measure (ICC=0.80 and Cronbach's alpha =0.87, respectively). The convergent validity between Br-NFR and other instruments also showed good results: Borg Scale (r= 0.64); Chalder Questionnaire (r= 0.67); SF-36 subscales: vitality (r= -0.84), physical functioning (r= -0.54), and role-physical (r= -0.47). CONCLUSIONS: The Br-NFR proved to be a reliable instrument to evaluate work-related fatigue symptoms in industrial workers. Furthermore, it showed significant and good correlations with well-established instruments such as the Borg Scale, the Chalder Questionnaire and SF-36 vitality subscale, supporting the validity of the Br-NFR.

Influence of variables on centrifuge-flotation technique for recovery of Toxocara canis eggs from soil

The purpose of this study was to evaluate the influence of variables in a flotation technique for the recovery of Toxocara canis eggs from soil. The trials were done under standardized conditions on one gram of previously sterilized soil samples contaminated with 200 eggs of T. canis. The following variables were evaluated in serial steps: sieving; type of wash; time of stirring; resuspension of sediment; solution flotation. Centrifuge-flotation in sodium nitrate (d = 1.20 g/cm³) was adopted as an initial technique, using Tween 80 (0.2%) and decinormal sodium hydroxide as solutions for washing the samples. Ten tests were done to compare the variables, using counting in triplicate. The sieving of the material reduced significantly the recovery of eggs (p < 0.001) and the number of eggs recovered was higher when the sediment was resuspended (p < 0.05). After standardization, flotation solutions sodium chloride, zinc sulfate, sodium dichromate, magnesium sulfate, and sodium nitrate (d = 1.20g/cm³) were compared. The best results were obtained by using zinc sulfate solution. In conclusion, the chances of recovering T. canis eggs from samples using flotation solutions can be increased by washing of soil twice using distilled water, and resuspension of sediment. On the other hand, the sieving procedure can drastically reduce the number of eggs.

EFFICACY OF NITAZOXANIDE AGAINST Toxocara canis: LARVAL RECOVERY AND HUMORAL IMMUNE RESPONSE IN EXPERIMENTALLY INFECTED MICE

SUMMARY The efficacy of nitazoxanide (NTZ) against toxocariasis was investigated in an experimental murine model and results were compared to those obtained using mebendazole. Sixty male BALB/c mice, aged six to eight weeks-old, were divided into groups of 10 each; fifty were orally infected with 300 larvaed eggs of T. canisand grouped as follows, G I: infected untreated mice; G II: infected mice treated with MBZ (15 mg/kg/day) 10 days postinfection (dpi); G III: infected mice treated with NTZ (20 mg/kg/day) 10 dpi; G IV: infected mice treated with MBZ 60 dpi; G V: infected mice treated with NTZ 60 dpi; GVI: control group comprising uninfected mice. Mice were bled via retro-orbital plexus on four occasions between 30 and 120 dpi. Sera were processed using the ELISA technique to detect IgG anti- Toxocaraantibodies. At 120 dpi, mice were sacrificed for larval recovery in the CNS, liver, lungs, kidneys, eyes and carcass. Results showed similar levels of anti- ToxocaraIgG antibodies among mice infected but not submitted to treatment and groups treated with MBZ or NTZ, 10 and 60 dpi. Larval recovery showed similar values in groups treated with NTZ and MBZ 10 dpi. MBZ showed better efficacy 60 dpi, with a 72.6% reduction in the parasite load compared with NTZ, which showed only 46.5% reduction. We conclude that administration of these anthelmintics did not modify the humoral response in experimental infection by T. canis. No parasitological cure was observed with either drug; however, a greater reduction in parasite load was achieved following treatment with MBZ.

Infarct Size as Predictor of Systolic Functional Recovery after Myocardial Infarction

Background: The effects of modern therapy on functional recovery after acute myocardial infarction (AMI) are unknown.Objectives:To evaluate the predictors of systolic functional recovery after anterior wall AMI in patients undergoing modern therapy (reperfusion, aggressive platelet antiaggregant therapy, angiotensin-converting enzyme inhibitors and beta-blockers).Methods:A total of 94 consecutive patients with AMI with ST-segment elevation were enrolled. Echocardiograms were performed during the in-hospital phase and after 6 months. Systolic dysfunction was defined as ejection fraction value < 50%.Results:In the initial echocardiogram, 64% of patients had systolic dysfunction. Patients with ventricular dysfunction had greater infarct size, assessed by the measurement of total and isoenzyme MB creatine kinase enzymes, than patients without dysfunction. Additionally, 24.5% of patients that initially had systolic dysfunction showed recovery within 6 months after AMI. Patients who recovered ventricular function had smaller infarct sizes, but larger values of ejection fraction and E-wave deceleration time than patients without recovery. At the multivariate analysis, it can be observed that infarct size was the only independent predictor of functional recovery after 6 months of AMI when adjusted for age, gender, ejection fraction and E-wave deceleration time.Conclusion: In spite of aggressive treatment, systolic ventricular dysfunction remains a frequent event after the anterior wall myocardial infarction. Additionally, 25% of patients show functional recovery. Finally, infarct size was the only significant predictor of functional recovery after six months of acute myocardial infarction.

Protein recovery, separation and purification: selection of optimal techniques using an expert system

The paper discusses the utilization of new techniques ot select processes for protein recovery, separation and purification. It describesa rational approach that uses fundamental databases of proteins molecules to simplify the complex problem of choosing high resolution separation methods for multi component mixtures. It examines the role of modern computer techniques to help solving these questions.