The critical role of surfactants towards CdS nanoparticles: synthesis, stability, optical and PL emission properties

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Cadmium sulfide (CdS) nanoparticles (NPs), prepared by a convenient chemical precipitation method, have been characterized using techniques such as TEM, XRD, zeta potential, absorption and photoluminescence (PL) emission spectroscopy to establish the structure directing role of different cationic and anionic surfactants and their impact on the nanoparticles stabilization. In the synthesis of the CdS NPs, cadmium acetate and sodium sulfide, employed as starting reagents, were dissolved in aqueous solutions of different surfactants to study the effect of their structures on the nucleation, growth, optical and PL emission properties of the NPs. By varying the surfactant species, the CdS NPs have significantly different optical and PL emission properties despite being produced under similar reaction conditions. Depending on the surfactant structure, the growing CdS NPs were stabilized by the surfactants to different extents. For example, in the surfactant with the longest chain length (e.g. cetyltrimethylammonium bromide; CTAB), the CdS NPs were most stable, whereas using a surfactant with a smaller chain length i.e. DTAB, the NPs were unstable for even 1 h. On the other hand, anionic surfactants of even smaller chain lengths were able to stabilize the CdS NPs for quite long times. The generalized study of growth of spherical CdS NPs involves monitoring the kinetics during the progress of the reaction. Additionally, an interesting prominent effect of surfactant structure on the PL emission properties of the NPs has been established under identical reaction conditions

MLTE Algorithm for Multicast Service Delivery in OFDMA Networks

Dispensing and overseeing radio resources to the multi-cast transmissions in OFDMA (orthogonal-frequency division-multiple-access) systems is testing exploration issue tended to by this paper. A sub-grouping technique, which separates the subscribers into subgroups as indicated by the accomplished channel quality, is considered to defeat the throughput confinements of conventional multicast data conveyance schemes. A low complexity algorithm intended to work with diverse resource allocation strategies, is additionally proposed to diminish the computational complexity of the subgroup development issue. Reproduction results, did by considering the long term evolution system taking into account OFDMA, affirm the adequacy of the proposed arrangement, which accomplishes a close ideal execution with a restricted computational load for the system. In this paper we are introducing the MLTE for improve the MBPS speed for fix network coverage at uniform and sparse. DOI: 10.17762/ijritcc2321-8169.150713

Bio-hydrometallurgical approach in processing of low grade Indian uranium ore in Column Reactor

In order to augment the supply of uranium for electricity generation, bioleaching is being considered for exploiting a low-grade uranium ore (with 0.024% U3O8 of Turamdih Mines, Jharkhand, India). This ore contains silicate and magnetite as the main minerals and uraninite and hematite as minor minerals. At NML, efforts have been made to use Acidithiobacillus ferrooxidans (Ac.Tf) initially on bench scale in shake flask and then in column to recover uranium. In shake flasks, ~98% uranium dissolution was achieved in 30days at 1.7pH, 35oC temperature and 20% (w/v) pulp density. In a laboratory scale column containing 2.5kg ore, uranium bio-recovery of 55.48% was obtained in 30 days at 1.7pH. To scale up the process, the bio-leaching experiments carried out on 80kg ore showed uranium recovery of 69.8% as against a recovery of 55.12% in control set at 1.7 pH in 50 days. Bio-recovery of uranium has been correlated with the change in redox potential (Eh) and ferric ion concentration

Biosorption of trivalent chromium from a model tanning solution by adapted aspergillus niger

Industrial effluents containing metallic species are responsible for environmental degradation which have been prioritised as major inorganic contaminants. Conventional methods are quite expensive resulting in need for cost-effective process for removing heavy metals from discharging effluents. The use of microbial biomass for removal of heavy metals from aqueous solutions (biosorption) is one such approach gaining increasing attention. Trivalent chromium ion present in tannery effluents has been the targeted ionic species for removal due to its exceeding limits in industrial discharges (<--0.3 ppm as per WHO). At NML, efforts were made for biosorption of trivalent chromium from tannery effluents with Cr (III) concentration in the range 1500-5000ppm. Aspergillus niger, obtained from a culture bank has been used in biosorption of trivalent chromium of tannery effluents. The fungal species grown in Czapek Dox Medium and adapted on Cr(III) ions ranging from 10-2000ppm at 2.5 pH and 35°C, was used for biosorption of chromium from a model tanning solution. A.niger was used in forms such as live, adapted and pre-treated (autoclaved, alkali-treated) for biosorption at pH 2.5 and 35°C. At Cr(IlI) conc. of 2000ppm in the aqueous solution, the adsorption efficiency followed the order: alkali treated (52%)>live(38%)>autoclaved dead mass(27%). The varying biosorption capacities may be attributed to exposed metal binding sites in alkali treated fungus causing high biosorption efficiency which also obeyed the sorption isotherm

Bioleaching - an alternate uranium ore processing technology for India

Meeting the feed supply of uranium fuel in the present and planned nuclear reactors calls for huge demand of uranium, which at the current rate of production, shows a mismatch. The processing methods at UCIL (DAE) needs to be modified/ changed or re-looked into because of its very suitability in near future for low-index raw materials which are either unmined or stacked around if mined. There is practically no way to process tailings with still some values. Efforts were made to utilize such resources (low-index ore of Turamdih mines, containing 0.03% U3O8) by NML in association with UCIL as a national endeavor. In this area, the R&D work showed the successful development of a bioleaching process from bench scale to lab scale columns and then finally to the India’s first ever large scale column, from the view point of harnessing such a processing technology as an alternative for the uranium industry and nuclear sector in the country. The efforts culminated into the successful operation of large scale trials at the 2ton level column uranium bioleaching that was carried out at the site of UCIL, Jaduguda yielding a maximum recovery of 69% in 60 days. This achievement is expected to pave the way for scaling up the activity to a 100T or even more heap bioleaching trials for realization of this technology, which needs to be carried out with the support of the nuclear sector in the country keeping in mind the national interest