Electrochemical aspects of grinding media-mineral interaction on sulphide flotation

Galvanic interaction between electrically conducting minerals may affect the mineral surface and influence their flotabilities. The metallographic examinations as well as hardness measurements have been made with grinding media. Rest potential, combination potential, galvanic current and polarization studies were made to understand the probable electrochemical interaction between grinding media and chalcopyrite. The galvanic contact lowered the flotability of chalcopyrite. AES and ESCA indicated that galvanic coupling of chalcopyrite with grinding media resulted in the formation of oxy-hydroxide species of iron on the chalcopyrite surface. Scanning electron microscopy was used to study the surface morphological changes on the grinding media due to galvanic interaction with chalcopyrite.     

Interfacial energies in crystal structure transformations

Turnbull's theory of heterogeneous nucleation has been extended to obtain approximate values of interfacial energies in solids which exhibit reversible phase transformations. DTA curves of reversible transformations can be analysed in terms of the nucleation theory and with some reasonable assumptions, an estimate of can be obtained. A knowledge of the crystal structures of the two phases, along with the enthalpy of the transformation also affords a method of estimating -values theoretically. These three approaches have been applied to quartz, K₂SO₄, CsCl, NH₄Cl, and NH₄Br; the results have been compared.Taken in part from PhD thesis of M. Natarajan, to be submitted to the Indian Institute of Technology, Kanpur.     

Photoluminescence ofF-aggregate centres in thermal neutron irradiated LiF TLD-100 single crystals

In LiF, the photoluminescence emission ofF ₂ andF ₃ ⁺ centres are produced on irradiation peaks in the red (660 nm) and green (520 nm) region respectively. In this work, their relative sensitivities for thermal neutrons and gamma rays are compared.     

Investigation of Pesticidal and Anti-biofilm Potential of Calotropis gigantea Latex Encapsulated Zeolitic Imidazole Nanoframeworks

Journal of Inorganic and Organometallic Polymers and Materials - Zeolitic imidazole frameworks (ZIFs) are multifunctional and biocompatible material for biomedical applications. Herein we report...     

A review on nanodispersed lead-free solders in electronics: synthesis,microstructure and intermetallic growth characteristics

Journal of Materials Science - Lead-free solder research has witnessed a great jump in the past decades due to the increased restrictions over the use of toxic lead-bearing solder alloys. Among the...     

Microbial quality of domestic and imported brands of bottled water in Trinidad

A cross-sectional study was conducted to determine the microbial quality of domestic and imported brands of bottled water available in Trinidad, purchased from six geographical regions in Trinidad, and representing the whole island. A sample size of 344 bottles of water was determined by using a precision rate of 2% and a Type 1 error of 5%. The membrane filter technique was used with cultures grown on m-Endo agar and m-FC agar for total coliforms and thermotolerant coliforms, respectively. Aerobic plate count (APC) was determined on nutrient agar; Pseudomonas aeruginosa was detected on MacConkey agar, Escherichia coli was isolated on eosin methylene blue (EMB) and Salmonella spp. was assayed by using standard methods.Of the 344 water samples tested, 262 (76.2%) and 82 (23.8%) were domestic and imported brands, respectively. Eighteen (5.2%) of the 344 samples contained coliforms with a mean count of 0.88+/-6.38 coliforms per 100 ml, while 5 (1.5%) samples contained E. coli. The prevalence of total coliforms in domestic brands of bottled water was 6.9% (18 of 262) as compared with 0.0% (0 of 82) detected in imported brands. The difference was statistically significant (p=0.004). Similarly, the prevalence of aerobic bacteria in domestic brands of bottled water (33.6%) was significantly higher (p=0.001) than was found in imported brands (14.8%). Twenty-six (7.6%) of the total samples of water contained Pseudomonas species, but all were negative for thermotolerant coliforms and Salmonella spp.It was concluded that based on the recommended zero tolerance for coliforms in potable water, 5% of bottled water sold in Trinidad could be considered unfit for human consumption.     

Single cell protein production from digested and undigested poultry litter by Candida utilis: optimization of process parameters using response surface methodology

In this study, production of single cell protein (SCP) was carried out using Candida utilis from undigested poultry litter (UPL) and digested poultry litter (DPL). UPL and DPL were hydrolyzed by acid hydrolysis initially and the resulting crude hydrolysates were used for SCP production. Fermentation variables of the production medium were optimized by single variables optimization methodology. By this conventional approach, SCP production from UPL and DPL has increased to 25 and 20 %, respectively. The proportional analysis of these results revealed that UPL was the suitable substrate than DPL for the production of SCP by C. utilis. Further, 2³ central composite design was applied to determine the optimal process parameters for SCP production using UPL as substrate. The analysis of treatment combinations showed that a second-order polynomial regression model was in good agreement with experimental results at R ² value ?0.98 (P < 0.05). These results suggest that UPL concentration was the most influential factor affecting the SCP production with a P value of 2.22E-09 followed by yeast extract and pH at 0.0339 and 0.0439, respectively. Based on contour plots, the optimum conditions for SCP production were found to be the UPL concentration—5.6 % w/v, yeast extract concentration—2.3 % w/v, and pH—7. After statistical optimization, SCP production by C. utilis strain has increased 29 %. It is understood from this study that UPL could be used effectively as substrate for the production of animal feed supplement with benefit of reducing feed cost as well as mitigating environmental problems associated with poultry litter.