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Density functional theory and volume-based thermodynamics calculations were performed to study the effects of different substituents and linkages on the densities, heats of formation (HOFs), energetic properties, and thermodynamics of formation for a series of energetic nitrogen-rich salts composed of triaminoguanidinium cation and 5-nitroiminotetrazolate anions. The results show that the -NO(2), -NF(2), or -N(3) group is an effective substituent for increasing the densities of the 5-nitroiminotetrazolate salts, whereas the effects of the bridge groups on the density are coupled with those of the substituents. The substitution of the group -NH(2), -NO(2), -NF(2), -N(3), or the nitrogen bridge is helpful for increasing the HOFs of the salts. The calculated energetic properties indicate that the -NO(2), -NF(2), -N(3), or -N=N- group is an effective structural unit for improving the detonation performance for salts. The thermodynamics of formation of the salts show that all the salts may be synthesized easily by the proposed reactions. The structure-property relationships provide basic information for the molecular design of novel high-energy salts.

Nitrate pollution of groundwater constitutes an important and rapid increasing environmental problem 1. One of the most common causes of nitrate pollution is the excessive use of fertilizers in intensive agriculture and irrigation with ammoniarich effluents discharged by wastewater treatment plants 2. Conventional physico-chemical methods used to remove nitrate from water contain ion exchange, reverse osmosis and electrochemical reduction and bioremediation 3. Among the techniques available for the removal of nitrate from groundwater, microbial denitrification stands out because of its economical environmental protection and being easy to a large-scale application 4. Denitrification is carried out by facultative aerobic bacteria which acts as a terminal electron acceptor in respiration under the conditional absence of oxygen 5,6. Microbial fuel cells (MFCs) represent an innovative remediation technology for waste and wastewater treatment, because they have the potential for simultaneous electricity generation and removal of organic pollutants. The cathodic compartments of microbial fuel cells are less studied and in most microbial fuel cells the cathodic reaction is abiotic, typically the reduction of oxygen or ferricyanide 7. In this study,