Bioleaching of metal ions from low grade sulphide ore: Process optimization by using orthogonal experimental array design

The present work was aimed at studying the bioleachability of metal ions from low grade sulphide ore containing high amount of carbonaceous materials by selected moderately thermophilic strain of acidophilic chemolothotrophic bacteria, Sulfobacilllus thermosulfidooxidans. The bioleaching process was optimized by constructing L25 Taguchi orthogonal experimental array design and optimization of variable proportions of process parameters. Five factors were investigated and twenty five batchbioleaching tests were run under lower, medium and higher levels of these factors. The parameters considered for shake flask leaching experiments were initial pH (1.8, 2, 2.5, 3, 3.5), particle size, (50, 100, 120, 200, 270 m), pulp density (1, 5, 10, 15, 25%), temperature (40, 45, 47, 52, 57oC) and agitation (100, 120, 180, 220, 280 rpm). Statistical analysis (ANOVA) was also employed to determine significant relationship between experimental conditions and yield levels. The experimental results for selective leaching showed that under engineered leaching conditions; pH 1.8, particle size 120 m, pulp density 10%, temperature 47°C and agitation 180 rpm, the percent bioleachabilities of metals were Zn 72%, Co68%, Cu 78%, Ni 81% and Fe 70% with an inoculum size of 1.0 ×107 /mL

Process optimization and mechanistic studies of lead (II): Aspergillus caespitosus interaction for industrial effluent treatment

The lead (II) accumulation potential of various biosorbent had been widely studied in the last few years, but an outstanding Pb(II) accumulating biomass still seems crucial for bringing the process to a successful application stage. This investigation describes the use of non-living biomass of Aspergillus caespitosus for removal of Pb from Pb(NO3)2 solution in a batch system under different experimental conditions. The highest Pb(II) sorption (351.7 ± 5.7 mg/g biomass) was observed at 600 µg/ml initial Pb concentration. Biosorption data were well defined by pseudo-second order, saturation mixed order and Langmuir isotherm models. The thermodynamic parameters: G (303 K), H and S were determined to be 4.64 kJ/mol, 75.4 kJ/mol and 26.2 J/mol-K respectively. The Pb uptake from binary solution was inhibited in the order of copper > nickel > zinc > manganese. Fourier transform infrared spectroscopy (FT-IR) characterization of Pb biosorption revealed the involvement of –SO3 and –CN groups along with other groups. The biosorbed Pb was stripped out (85.5%) using 0.01 M HCl and about 12% loss in Pb(II) sorption capacity was observed after five sorption-desorption cycles. High Pb (II) uptake (351.7 ± 5.7 mg/g biomass) by A. caespitosus proved it to be an outstanding biomaterial until now reported in literature for accumulating from solutions.Key words: Aspergillus caespitosus, Pb, Langmuir isotherm, pseudo-second-order kinetic model, FTIR, SEM, EDAX

The state of ambient air quality in Pakistan—a review

Background and purpose: Pakistan, during the last decade, has seen an extensive escalation in population growth, urbanization, and industrialization, together with a great increase in motorization and energy use. As a result, a substantial rise has taken place in the types and number of emission sources of various air pollutants. However, due to the lack of air quality management capabilities, the country is suffering from deterioration of air quality. Evidence from various governmental organizations and international bodies has indicated that air pollution is a significant risk to the environment, quality of life, and health of the population. The Government has taken positive steps toward air quality management in the form of the Pakistan Clean Air Program and has recently established a small number of continuous monitoring stations. However, ambient air quality standards have not yet been established. This paper reviews the data being available on the criteria air pollutants: particulate matter (PM), sulfur dioxide, ozone, carbon monoxide, nitrogen dioxide, and lead. Methods: Air pollution studies in Pakistan published in both scientific journals and by the Government have been reviewed and the reported concentrations of PM, SO2, O3, CO, NO2, and Pb collated. A comparison of the levels of these air pollutants with the World Health Organization air quality guidelines was carried out. Results: Particulate matter was the most serious air pollutant in the country. NO2 has emerged as the second high-risk pollutant. The reported levels of PM, SO2, CO, NO2, and Pb were many times higher than the World Health Organization air quality guidelines. Only O3 concentrations were below the guidelines. Conclusions: The current state of air quality calls for immediate action to tackle the poor air quality. The establishment of ambient air quality standards, an extension of the continuous monitoring sites, and the development of emission control strategies are essential. © Springer-Verlag 2009

Interpretation and Visualization of Non-Linear Data Fusion in Kernel Space: Study on Metabolomic Characterization of Progression of Multiple Sclerosis

Contains fulltext : 93904.pdf (publisher's version ) (Open Access

Institutional distance and knowledge acquisition in international buyer–supplier relationships::the moderating role of trust

Institutional distance can generate expanded opportunities for multinational firms to facilitate learning and responsiveness. However, such distance can also create obstacles regarding knowledge transfer and integration. A theoretical puzzle concerns the mechanisms and conditions in which international buyers and suppliers can overcome institutional distance and acquire new knowledge. We develop an integrative moderated-mediation model in which institutional distance prevents parties from accessing knowledge but, when knowledge is obtained and mutual trust is developed, it promotes cross-border knowledge acquisition in international buyer-supplier exchange, particularly between international firms and firms from the Asia Pacific region. These findings indicate that firms can overcome the challenges of regulative and cognitive distance and facilitate access to knowledge and knowledge acquisition when they are able to develop and cultivate relationships of mutual trust with foreign partners. While normative distance may create learning incentives and opportunities in international buyer-supplier relationships, its impacts on knowledge accessibility and acquisition are insignificant.fi=vertaisarvioitu|en=peerReviewed

A Biological Model for Resource Allocation and User Dynamics in Virtualized HetNet

Virtualization technology is considered an effective measure to enhance resource utilization and interference management via radio resource abstraction in heterogeneous networks (HetNet). The critical challenge in wireless virtualization is virtual resource allocation on which substantial works have been done. However, most existing researches on virtual resource allocation focus on improving total utility. Different from the existing works, we investigate the dynamic-aware virtual radio resource allocation in virtualization based HetNet considering utility and fairness. A virtual radio resource management framework is proposed, where the radio resources of different physical networks are virtualized into a virtual resource pool and mobile virtual network operators (MVNOs) compete for virtual resources from the pool to provide service to users. A virtual radio resource allocation algorithm based on biological model is developed, considering system utility, fairness, and dynamics. Simulation results are provided to verify that the proposed virtual resource allocation algorithm not only converges within a few iterations, but also achieves a better trade-off between total utility and fairness than existing algorithm. Besides, it can also be utilized to analyze the population dynamics of system