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Interaction between sphalerite and pyrite and its effect on surface oxidation of sphalerite

Yang B., Xie X., Tong X., Lan Z., Cui Y.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 2

311--320

EN

The interaction between sphalerite and pyrite was investigated by dissolution test, X-ray photoelectron spectroscopy (XPS), zeta potential measurement and density functional theory (DFT) calculation. Dissolution tests indicated that sphalerite dissolution was promoted due to the galvanic interaction between sphalerite and pyrite. The Zn2+ ion concentration increased with increasing pyrite content and dissolved time. XPS analysis results demonstrated that a new oxidation product was formed on the sphalerite surface in the presence of pyrite in a pulp. Zeta potential measurements showed that the isoelectric point of sphalerite increased from 3.3 to 5.4 due to galvanic interaction. DFT calculation results suggested that electron transfer from sphalerite to pyrite occurred when they contacted. The Zn 4s and S 3p states of sphalerite lost electrons. The Fe 4p and 4s of pyrite states obtained electrons, and Fe 3d and S 3s states lost a small number of electrons. The surface oxidation of sphalerite was promoted due to the interaction with pyrite, and the collectorless floatability of sphalerite decreased.

2

Interactive effects of nitrogen and water addition on competitive hierarchies between early- and late-successional plant species

Jiang L., Lan Z., Liu G., Kardol P.

Polish Journal of Ecology

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2014

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Vol. 62, nr 4

665--678

EN

Increased nitrogen (N) and water availability, resulting from global changes or ecosystem management, were predicted to promote plant productivity and change community composition through shifts in competition hierarchies. So far, however, it still remains unclear how competitive interactions respond to N and water additions, which will be important to understand how plant community composition changes. To test plant competition ability in different successional stages under N and water addition treatments, a pot experiment under field conditions was performed. Six dominant plant species, three early-successional species, Artemisia lavandulaefolia, Artemisia capillaris, and Pennisetum centrasiaticum versus three late-successional species, Stipa krylovii, Leymus chinensis, and Artemisia frigida, were grown in monocultures and in two-species mixtures under factorial combinations of N and water addition treatments. We found that (1) there were interactive effects of N addition, water addition and interspecific competition on plant biomass; (2) For a given species, competitive abilities were correlated with biomass difference of neighboring species; (3) N and water additions interactively increased competition intensity and shifted species competitive hierarchies; (4) Late- successional species had stronger competitive abilities in the N addition treatment, whereas early-successional species had stronger competitive abilities after water addition or N + water addition. Our results show that N and water additions increased the intensity and impact of interspecific competition on plant growth, which has great implications for community structures. Since interspecific differences in competitive abilities were not well explained by species biomass, species identity, such as plant functional traits, should be included to predict the impact of increased N and water availability on plant communities and ecosystem functions.

3

Evaluations of port performances from a seaborne cargo supply chain perspective

Low J. M. W., Lam S. W., Tang L. C., Lan Z.

Polish Maritime Research

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2013

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S 1

20--31

EN

Previous research on port efficiency focuses primarily on the provider’s perspective and assumes that maximizing the output is always desirable. This paper recognizes that maximizing the final output does not necessarily guarantee an efficient system and the notion of port efficiency and service effectiveness needs to be considered from the perspectives of both the provider and the consumer of the port service. The paper proposes a network-DEA model to evaluate the performances of 30 seaports worldwide. The concurrent consideration of efficiency scores from the network-DEA model and the traditional DEA-CCR model will offer valuable insights to port operators on how to improve port performances as part of a seaborne cargo supply chain.