Authors:R. Sawant, G. Rizvi, N. Chaudhuri and S. Patil
Fluoride complexing of Np(V) has been studied using fluoride ion selective electrode (F-ISE). Free fluoride ion concentrations in the presence of Np(V) were measured at 0.1 and 1.0M ionic strength. The data were used to calculate the stability constant of the fluoride complex of Np(V) and the values obtained are reported here.
Authors:R. Sawant, N. Chaudhuri, G. Rizvi and S. Patil
Complex formation between actinide(VI) and fluoride ions in aqueous solutions has been investigated using a fluoride ion selective electrode (F-ISE). As fairly high acidity was used to suppress hydrolysis of the actinide(VI) ions, significant liquid junction potentials (Ej) existed in the systems. An iterative procedure was developed for computing free hydrogen ion concentration [H+], as it could not be measured directly, using data obtained with F-ISE. Ej values were estimated from known [H+] and the stability constants of fluoride complexes of actinide(VI) ions were calculated following KING and GALLAGHER's method using a computer program. The stability constants were found to follow the order U(VI)>Np(VI)>Pu(VI).
Authors:G. Rizvi, N. Chaudhuri, R. Rastogi and S. Patil
A procedure has been developed for quantitative separation of yttrium from uranium by anion exchange from nearly saturated
NH4Cl solution in 0–2N HCl medium. Apparently no organic matter is leached out during the separation as yttrium could be determined
by EDTA titration without resorting to fuming with perchloric acid before titration. The precision obtained in the analysis
of yttrium in a mixture containing about 12 mg of yttrium and about 300 mg of uranium was ±0.3% (27 determinations).
With contemporary emphasis on sustainability and ecosystem-oriented natural resources management, ecological mapping at landscape scales is becoming increasingly important as a framework for environmental planning, monitoring and assessment. This is especially so when the terrain has substantial variability in elevation and steep slopes. Recognizing the importance of hydrology in landscape dynamics, we base an ecological mapping approach on topological features of terrain from a hydrologic and habitat perspective. This approach emphasizes convexities and concavities of topography as caplands and confluent cuplands, respectively. A concept of coherent convex contours provides an operational basis for determining capland components, with cupland components being predominantly concave contributing areas for higher-order streams. Scaling sequences of subdivisions give progressive partitioning down to sizes of units that serve practical purposes of natural resource management. An innovation of dome domains and terrain tiers is introduced for more detailed topological treatment of land forms.
Authors:F. Benaskar, A. Ben-Abdelmoumen, N. G. Patil, E. V. Rebrov, J. Meuldijk, L. A. Hulshof, V. Hessel, U. Krtschil and J. C. Schouten
An extended cost study consisting of 14 process scenarios was carried out to envisage the cost impact of microprocessing and microwaves separately or in combination for two liquid-phase model reactions in fine-chemicals synthesis: (1) Ullmann C–O cross-coupling reaction and (2) the aspirin synthesis. The former, a Cu-catalyzed substitution reaction, was based on an experimental investigation, whereas the latter, a noncatalyzed aromatic esterification reaction, was based on literature data. The cost of 4-phenoxypyridine production, as a pharmaceutical intermediate in the synthesis of vancomycin or vancocin, was compared with that of the synthesis of aspirin, a key example of large-scale fine-chemical production plants. The operating costs in the Ullmann synthesis were found to be related to material-based process (reactant excess, pretreatment, and catalyst synthesis), whereas those in the aspirin synthesis appeared to be related to downstream-based process (workup, waste treatment). The impact of an integrated microwave heating and microprocessing system on profitability was demonstrated with respect to operational cost and chemical productivity. Different modes of microwave heating and catalyst supply were studied and compared with conventional oil-bath-heated systems in batch and continuous processes. The overall costs including profitability breakthrough for a competitive market price of product were obtained from various combinations of heating and processing. In case of the Ullmann synthesis, the CAPEX (capital expenditure) was negligible compared to the OPEX (operational expenditure), whereas in the aspirin synthesis, the CAPEX was found around 40%, both at a production scales of 1–10 kg/day using proposed upscale methods. The source of the catalyst strongly determined the profitability of a continuously operated Ullmann process due to its effect on the chemical performance. Higher energy efficiencies could be attained using single-mode microwave irradiation; however, the energy contribution to the overall cost was found to be negligible. Different scenarios provided a cost-feasible and profitable process; nevertheless, an integrated microwave heating and microflow processing led to a cost-efficient system using a micropacked-bed reactor in comparison to wall-coated microreactor, showing a profit margin of 20%.