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[en] A great quantity of industries are responsible for contaminating the environment with the heavy metals which are containing in their wastewaters. The recovery of these metals is both from an environmental and economical points of view of the upmost interest. A study is made of the use of mill scale-originating in the hot rolling of steel-as an adsorbent for the removal of heavy metals from liquid effluents. The adsorption of Zn''2+, Cd''2+ y Pb''2+ on the rolling mill scale was investigated by determination of adsorption isotherms. The effect of time, equilibrium temperature and concentration of metal solution on mill scale adsorption efficiency was evaluated. The adsorption process was analysed using the theories of Langmuir and Freundlich. Desorption process of metals from loaded mill scales was also studied using several doser bent at different experimental conditions. It has been proved that the mill scale is an effective adsorbent for the cations studies in aqueous solutions within the range of the working concentrations. (Author) 32 refs
[en] In the present work, hematite iron oxide nano-particles are synthesized through a facile wet chemical precipitation route. The phase formation behavior and microstructure evolution of the synthesized nano-particles are studied using infrared spectroscopy in conjunction with x-ray diffraction analyses and electron microscopy. Chemi-resistive type hydrogen sensing characteristics (e.g. response %, response time, recovery time) of hematite iron oxide nano-particulate sensing element are evaluated using an automated, dynamic flow gas sensing measurement set-up. The sensing characteristics are measured by varying the operating temperature (275–350 °C) of the sensor and concentration of hydrogen (250–1660 ppm). From the operating temperature dependence of response and recovery times, we have estimated the respective activation energies for response and recovery processes. (paper)
[en] Management and recovery of waste are activities with multiple impacts: technologically (by using waste on current production flows, thus replacing poor raw materials), economically (can substantially reduce manufacturing costs by recycling waste), social (by creating new jobs where it is necessary to process the waste in a form more suited to technological flows) and ecologically (by removing waste that is currently produced or already stored - but poses a threat to the health of the population and / or to the environment). This is also the case for medical waste, for example radiographs, which are currently produced in large quantities, for which replacement solutions are sought, but are currently stored by archiving in hospital units. The paper presents two methods used for this kind of waste management, the result being the recovery of silver, material with applications and with increasing price, but also the proper disposal of the polymeric support. This analysis aims at developing a more efficient recycling technology for medical radiographs. (paper)
[en] Characterization and beneficiation studies have been carried out on Brahmagiri placer deposits of Puri, Dist., Odisha. The studies show that this deposit contains potential amount of heavy minerals. The dune sands contain higher heavy minerals than that of beach sand. One of the dune sand samples collected from this deposit shows heavy mineral content of about 29 % also. A composite sand sample is prepared and heavy mineral recovery is studied from this by using gravity table. During recovery of heavy minerals both fresh and sea water are used to see their effect on grade and recovery of concentrate. Sea water rougher gravity table data shows better results than fresh water rougher gravity table. The gravity table study of composite sample shows a yield of 14.8% with a grade of 91.2 % and 93.2 % recovery. (paper)
[en] The objective of this project was to move the testing of uranium adsorbents from the laboratory to the field. We were successfully able to test fibers in both a flume and ocean environment under varying conditions to quantify the adsorptive properties and uranium uptake of adsorbents under coastal ocean conditions. Through this testing we have identified numerous challenges to be overcome prior to large-scale deployment of these fibers This project began in Phase I with laboratory experiments examining the effects of flow rates and water filtration on the absorption of uranium to fibers in flow-through columns. In this experiment we found that fibers adsorb most efficiently at a flow rate of 250 ml/min, on a per liter basis. However faster flow rates increase exposure volume and allowed for slightly greater total U absorption. Therefore a balance between current speeds that are too fast and potentially break down fibers and those that are slower will be important to consider, alongside bio-fouling and exposure time, when deciding which current regimes are best to place fibers in the ocean. Phase II examined biofouling, comparing exposure of fibers in filtered flume water to that in a coastal ocean environment. Results from the dock and flume parallel experiment indicate a strong effect of biofouling on the capacity of the adsorbent fibers to adsorb uranium towards the very end of the experiment. Dock and flume samples showed comparable adsorption rates with the flume maximum achieved at day 49 with an adsorbance of 3.4 g U/kg-ads while the dock maximum was reached at day 42 with an adsorbance of 2.7 g U/kg-ads. Biofouling mitigation techniques were also examined. A comparison of 5 m and 12 m samples showed less growth at 12 meters where there is less light as well as less growth on the copper cages, which are toxic to many marine organisms. Overall despite biofouling, particles and other elements present, the fibers adsorbed uranium up to 2.7 g U/kg-ads in our open water dock experiments. This is lower than the maximum achieved in the flume of 3.4 g U/kg-ads and much lower than rates observed with synthetic seawater in laboratory experiments. Phase III involved two parts: working at Woods Hole Oceanographic Institution (WHOI) we examined the feasibility of reusing fibers after ocean deployment. Fiber reuse is an important consideration for operational costs associated with deployment. At present our data implies that reuse after open ocean exposure may not be significantly more effective than a single long deployment of fibers. The second part of Phase III involved collaboration with A. Slocum and M. Haji at MIT to examine the effects of various enclosures for fibers. This also involved testing a rotating system, designed to be deployed as part of an offshore wind turbine.
[en] In this paper we are concerned with the contact process with random recovery rates and edge weights on the complete graph with n vertices. We show that the model has a critical value which is inversely proportional to the product of the mean of the edge weight and the mean of the inverse of the recovery rate. In the subcritical case, the process dies out before an amount of time with order with high probability as . In the supercritical case, the process survives for an amount of time with order with high probability as .
[en] Topics covered in this Nuclear Technology and Research Development (NTRD) monthly update include: Advanced Fuels Campaign, Material Recovery and Waste Forms Development, MPACT Campaign, Fuel Cycle Options Campaign, Joint Fuel Cycle Study Activities, and AFCI-HQ Program Support.
[en] An evidence-based methodology was adopted in this research to establish strategies to increase lead recovery and recycling via a systematic review and critical appraisal of the published literature. In particular, the research examines pollution prevention and waste minimization practices and technologies that meet the following criteria: (a) reduce/recover/recycle the largest quantities of lead currently being disposed of as waste, (b) technically and economically viable, that is, ready to be diffused and easily transferable, and (c) strong industry interest (i.e., industry would consider implementing projects with higher payback periods). The following specific aims are designed to achieve the study objectives: Aim 1 - To describe the recycling process of recovering refined lead from scrap; Aim 2 - To document pollution prevention and waste management technologies and practices adopted by US stakeholders along the trajectory of LAB and lead product life cycle; Aim 3 - To explore improved practices and technologies which are employed by other organizations with an emphasis on the aforementioned criteria; Aim 4 - To demonstrate the economic and environmental costs and benefits of applying improved technologies and practices to existing US smelting operations; and Aim 5 - To evaluate improved environmental technologies and practices using an algorithm that integrates quantitative and qualitative criteria. The process of identifying relevant articles and reports was documented. The description of evidence was presented for current practices and technologies used by US smelters as well as improved practices and technologies. Options for integrated environmental solutions for secondary smelters were introduced and rank ordered on the basis of costs (i.e., capital investment) and benefits (i.e., production increases, energy and flux savings, and reduction of SO2 and slag). An example was provided to demonstrate the utility of the algorithm by detailing the costs and benefits associated with different combinations of practices and technologies. The evidence-based methodology documented in this research reveals that it is technically and economically feasible to implement integrated environmental solutions to increase lead recovery and recycling among US smelters. The working example presented in this research can be confirmed with US stakeholders and form the basis for implementable solutions in the lead smelter and product industries to help reverse the overall trend of declining life-cycle recycling rates.