Atmospheric leaching of enargite in iron sulfate solutions catalyzed by activated carbon

Traditionally, smelting has been the primary method of treatment for copper sulfide concentrates. In modern smelters the environmental problem of sulfur dioxide emission has been addressed effectively, but pyrometallurgical treatment of concentrates containing elevated levels of arsenic is still difficult and costly. Therefore, arsenic is considered a penalty element for smelters. However, the depletion of “clean” (non-arsenical) copper deposits and the increasing demand for copper will make the treatment of copper-arsenic sulfides such as enargite and tennantite unavoidable. Thereby a viable processing method is required. Hydrometallurgical treatment of enargite using atmospheric leaching promises a comparatively simple method for managing arsenic by co-precipitating it with iron in the form of scorodite. The major challenge involved with this option is the slow rate of enargite leaching. A novel treatment for enargite-rich copper concentrates through atmospheric ferric leaching catalyzed by activated carbon is presented in this study. Enargite concentrates from three different sources in Chile and Peru and one enargite mineral sample from the United States were used in the leaching experiments. Batch leaching tests were conducted in sealed, jacketed, glass stirred-tank reactors. The results showed that enargite leaching was up to 6 times faster in the presence of activated carbon, making it possible to achieve virtually complete copper extraction within 24 hours. SEM studies revealed changes in the morphology of the passive layer on enargite particles which is formed as a product of leaching. The laboratory-scale tests indicated that desirable leaching kinetics could be maintained after recycling activated carbon particles multiple times to new leaching tests and also at a carbon:enargite concentrate mass ratio as low as 0.25. Activated carbon loss was reduced from 26 % to 5 % of the initial carbon mass by decreasing the impeller speed from 1200 rpm to 800 rpm, while the leaching performance remained similar. The effects of concentrate grind size, solution redox potential and initial total iron concentration on copper extraction have also been studied. The presented method promises a commercially attractive route to treat enargite concentrates.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat

Human Otopathologic Findings in Cases of Folded Cochlear Implant Electrodes

HYPOTHESIS: We hypothesize that human cases of cochlear implantation (CI) with folding of the electrode array will demonstrate greater degrees of intracochlear ossification, lower spiral ganglion neuron (SGN) counts, and poorer audiometric outcomes. BACKGROUND: CI electrode array folding, such folding of the proximal array, is a relatively common surgical complication that can occur with forceful electrode insertion and may be an important and avoidable factor affecting implant outcomes. However, otopathologic findings and audiologic outcomes of human cases where folding of the implant electrode array is observed remain undefined. METHODS: Specimens from a human temporal bone repository having undergone CI during life were evaluated. Specimens with folding of the electrode array on histological analysis constituted study cases. Electrode-matched specimens without array folding constituted controls. All specimens were examined by light microscopy and histopathologically described. Intracochlear fibrosis and osseous tissue, and SGN counts were measured. Pre- and postoperative word recognition scores were also compared. RESULTS: Cases with folded electrodes showed greater volumes of intracochlear osseous tissue than controls, which was most prominent in areas adjacent to array folding. Both cases and controls demonstrated similar amounts of fibrous tissue. Folded cases showed decreased SGNs when compared with the contralateral ear, whereas controls showed stable SGN populations between ears. In this small cohort, postoperative hearing outcomes were similar between groups. CONCLUSION: Atypical fibro-osseous changes and lower SGN counts are observed in cases of CI electrode folding. Future studies are necessary to determine if recognition and correction of folding can prevent long-term intracochlear changes

Precurved Cochlear Implants and Tip Foldover: A Cadaveric Imaging Study

Objective: This study aims to define a reliable protocol for radiographic identification of placement and tip foldover of newly designed precurved and straight electrodes. Study Design: Prospective imaging study. Setting: Academic institution. Methods: Three models of cochlear implants (Cochlear, MED-EL, and Advanced Bionics) were inserted into fresh cadaveric specimens (n = 2) in 3 configurations (normal positioning in the scala tympani, intracochlear tip foldover, and placement into the vestibular system) for a total of 9 implant scenarios. Specimens were imaged with plain radiography in Stenvers projection, as well as by high-resolution computed tomography. Results: Electrode placement and presence or absence of electrode tip foldover were easily identified in all 9 scenarios on plain radiography based on the described technique. Each was confirmed with high-resolution computed tomography. Plain film temporal bone images of new electrode designs with proper and improper placement are provided for reference. Conclusion: A defined protocol for intraoperative plain film radiography allowed for reliable imaging of 3 newly designed cochlear implant electrodes and immediate identification of extracochlear placement and tip foldover. Findings may be used for intraoperative confirmation of electrode array placement