Sulfatação seletiva de minério de níquel laterítico / Selective sulfation of nickel laterite ore

A explotação do níquel a partir de reservas de minério laterítico tem ganhado força devido à redução das reservas de níquel na forma de sulfeto com teor elevado deste metal. Um processo híbrido hidro-pirometalúrgico foi aplicado em uma amostra de minério laterítico brasileiro com a finalidade de recuperar seletivamente o níquel, visando sempre ao baixo consumo de reagentes. O processo consistiu na adição de ácido sulfúrico, tratamento térmico entre 100 e 260 °C, pirólise em torno de 690 °C seguida de lixiviação com água. Os parâmetros operacionais estudados foram: pH inicial de lixiviação, quantidade de H2SO4 adicionado, adição de sais e tamanho de partícula. Sob condições favoráveis, recuperações de níquel da ordem de 86% foram obtidas. Estas recuperações são fortemente dependentes do tamanho de partícula da amostra e da quantidade do ácido sulfúrico adicionado, devido à grande quantidade de magnésia presente no minério

Kinetic study and thermodynamic equilibrium modeling of the Co(II) and Mn(II) bioadsorption using the Rhodococcus opacus strain

Microbial biomass is considered a renewable and environmentally friendly resource. Thus, the research conducted a kinetic study and thermodynamic equilibrium modeling of the cobalt (Co) and manganese (Mn) bioadsorption process using the Rhodococcus opacus (RO) strain as a biosorbent. The inactive biomass subjected to 0.1 M NaOH pretreatment was brought into contact with synthetic solutions of Co and Mn. The experimental data for the Co(II) and Mn(II) bioadsorption process were fit to the Langmuir model with kads of 0.65 and 0.11 L.mg-1, respectively. A better statistical fit was also obtained for the pseudo-second order kinetic model (R2Co(II) = 0.994 and R2Mn(II) = 0.995), with 72.3% Co(II) and 80% Mn(II) removals during the first 10 min. In addition, a higher affinity of RO for the Co(II) ion was observed, with maximum uptake values of 13.42 mg.g-1; however, a higher adsorption rate was observed for Mn(II) ion (k = 0.21 g.mg-1.min-1 at 318 K). The bioadsorption process was spontaneous and dependent on temperature, being endothermic and irreversible for the Co(II) ion (∆H = 2951.91 J.mol-1) and exothermic and reversible for the Mn(II) ion (∆H = -2974.8 J.mol-1). The kinetic and thermodynamic equilibrium modeling allowed to identify the main mechanisms involved in the biosorption process of both metals.Campus San Juan de Luriganch

Copper and metals concentration from printed circuit boards using a zig-zag classifier

The consumption of electronic products has grown considerably in the last decades. These products become obsolete in a short period of time, generating electronic waste, which presents loads of materials harmful to health and metals of great value to industries. In this work, an innovative metal concentration technique for PCBs was applied aiming at the valuable metals recovery from ground printed circuit boards (PCBs) of computers that would be discarded. The PCBs were comminuted, classified by sieving and the metallic materials were processed in a zig-zag classifier type. The Schytil's phase diagram was developed to estimate the air flow rate to be used in the classifier. The product of each step was characterized. The copper content rose from 13.8% (w/w) to 48.8% (w/w) after the passage of the PCBs powder through the classifier. Its recovery and Newton's efficiency were above 89.4% and 0.91, respectively. The total content of metals was increased from 39.5% (w/w) to 89% (w/w) with a recovery of more than 82% and Newton's efficiency of 0.67 for the particle size in the range from 0.2 to 0.1 mm. The gold content has increased from 200 ppm to more than 8000 ppm after segregation by a simple manual concentration. Results shown that the use of zig-zag classifier to separate and concentrate metals was fairly effective, do not generate liquid and gaseous effluents and eliminates a number of pyrometallurgical or hydrometallurgical steps for metals obtaining. Keywords: Printed circuit boards, Recycling, Copper, Zig-zag classifier, Schytil's phase diagra

Preparation and characterization of Ti/SnO2-Sb electrode by Pechini's method for phenol oxidation

In this paper the influence of calcination temperature on the corrosion resistance of a Ti/SnO2-Sb electrode prepared according to Pechini's method and its efficiency for phenol oxidation in chloride medium were investigated. When calcination was performed at 600 °C tin distribution throughout the film was more uniform, providing a more homogeneous film structure. Electrolysis of a 0.34 mol.L-1 NaCl solution containing 100 mg.L-1 phenol at 10 mA.cm-2 for 30 minutes lead to corrosion of the electrodes calcined at 400 and 500 °C, whereas the one calcined at 600 °C remained practically unchanged, indicating that the coating structure, which is dependent of calcination temperature, plays an important role on the structural integrity of electrode material. Phenol concentration was reduced in 90% with the Ti/SnO2-Sb electrode calcined at 600 °C after 60 minutes of electrolysis at 10 mA.cm-2