A study of factors influencing the kinetics of copper cementation during atmospheric leaching of converter matte
The kinetics of copper cementation during atmosphere leaching of a Ni-Cu matte in CuSO4-H2SO4 solution was studied as a function of initial copper ion concentration, initial acid concentration, temperature, stirring rate, particle size distribution and pulp density. It was found that all these process variables influenced the rate of cementation. A two-stage rate of reaction was observed in most of the experiments, with the rate of cementation in the initial stage being slower than that of the subsequent second stage. The increased rate of cementation in the second stage was attributed to the enhancing effect of the surface deposit. The cementation process was found to take place by two different rate-controlling mechanisms. At a temperature range of 50i?½70i?½C, an activation energy of 74.6 kJ/mol was obtained, indicating a surface reaction controlled process. At higher temperatures (70i?½80i?½C) a lower value of activation energy was observed (18.2 kJ/mol), indicative of a process controlled by diffusion through surface layers. The structural characteristics of the cemented deposit could not be determined in the investigated system where the deposit was mixed with the leach solid residue.
Selective leaching of nickel from low-sulfur Ni-Cu matte at atmospheric pressure
Abstract A process of the selective leaching of nickel from low-sulfur Ni-Cu matte at atmospheric pressure was described. This matte was obtained from high grade Ni-Cu matte by magnetic separation, which mainly contained Ni-Cu alloy and a small quantity of sulfides. Firstly, the acid-oxygen (CuSO 4 -H 2 SO 4 -O 2 ) leaching of the matte was conducted at atmospheric pressure. When the solution pH value reached 1.0–2.0, the oxygen flow was ceased. Then, the aqueous copper was rejected by cementation reaction with Ni in the alloy. The mineralogical characteristics of the matte in the process were analyzed by X-ray diffractometry, optical microscopy and scanning electron microscopy. And the effects of variations in temperature, particle size distribution, oxygen flow rate, pulp density, initial acid concentration and initial concentration of copper ion were investigated.
Data Driven Policy: The Case for Certification Research
This article describes the program of research being implemented to investigate the outcomes of certification in the U.S. and Canadian workforce and its relevance to the goal of providing policy makers with pragmatic, action-oriented recommendations. Such recommendations encompass policy issues of workforce production, regulation, distribution, financing, and oversight of credentialing organizations. Few studies exist to substantiate the association between certification credentialing and practice outcomes, thereby leaving policy makers, consumers, and nurses in a vacuum when pushed to protect the public through the credentialing vehicles. The Nursing Credentialing Research Coalition (NCRC) has embarked on a research program that will reveal the relationship between certification and its influence on a nurse’s personal, professional, and practice characteristics as well as those judged by consumers and employers. Selected findings and implications for policy are described. Certified nurses’ reports of early interventions for complications are important quality measures for policy.