A reevaluation of the correlation between the synthesis parameters and structure and properties of nitrogen-doped carbon nanotubes

Nitrogen-doped carbon nanotubes（NCNTs） were synthesized by chemical vapor deposition using cobaltbased oxides as catalyst and ethylenediamine（EDA） as carbon/nitrogen precursor. The influence of growth time,EDA concentration and growth temperature on the morphology,yield,composition,graphitization and oxidation resistance of the NCNTs was systematically investigated by using Raman spectroscopy,temperature-programmed oxidation and other techniques. The NCNT growth from ethylenediamine with a high N/C ratio involves several processes including mainly（1） catalytic growth of NCNTs,（2） homogeneous gas-phase decomposition of EDA,（3） non-catalytic deposition of pyrolytic carbon/nitrogen species and（4）surface etching of amorphous carbon or carbon at defect sites through gasification. At a later growth stage the etching process appears to be dominating,leading to the thinning of nanotubes and the decrease of yield.Moreover,the surface etching through carbon gasification strongly influences the structure and degree of graphitization of NCNTs.

Role of carbon matrix heteroatoms at synthesis of carbons for catalysis and energy applications

The conceptual ideas about the positive effects of N- and O-heteroatoms on the reactivity of carbons in gasification processes, their catalytic activity in electron transfer reactions, as well as the performance of the electrode double-layer supercapacitors due to their electron-donating influence on the 7r-conjugated system of graphene layers have been developed. This influence decreases both work function and band gap of carbons, and also significantly affects their electron-donating properties. As a result of our investigations based on quantum chemical calculations of model graphene clusters with N- and O-heteroatoms in different positions, prognostic data have been obtained. These data have been confirmed by our experimental results of catalytic activity of corresponding carbons in H202 decomposition reaction, their reactivity in gasification processes, and also their performance as electrodes in supercapacitors.

Nitrogen removal from coal gasification wastewater by activated carbon technologies combined with short-cut nitrogen removal process

A system combining granular activated carbon and powdered activated carbon technologies along with shortcut biological nitrogen removal （GAC-PACT-SBNR） was developed to enhance total nitrogen （TN） removal for anaerobically treated coal gasification wastewater with less need for external carbon resources. The TN removal efficiency in SBNR was significantly improved by introducing the effluent from the GAC process into SBNR during the anoxic stage, with removal percentage increasing from 43.8%49.6% to 68.8%-75.8%. However, the TN removal rate decreased with the progressive deterioration of GAC adsorption. After adding activated sludge to the GAG compartment, the granular carbon had a longer service-life and the demand for external carbon resources became lower. Eventually, the TN removal rate in SBNR was almost constant at approx. 43.3%, as compared to approx. 20.0% before seeding with sludge. In addition, the production of some alkalinity during the denitrification resulted in a net savings in alkalinity requirements for the nitrification reaction and refractory chemical oxygen demand （COD） degradation by autotrophic bacteria in SBNR under oxic conditions. PACT showed excellent resilience to increasing organic loadings. The microbial community analysis revealed that the PACT had a greater variety of bacterial taxons and the dominant species associated with the three compartments were in good agreement with the removal of typical pollutants. The study demonstrated that pre-adsorption by the GAC-sludge process could be a technically and economically feasible method to enhance TN removal in coal gasification wastewater （CGW）.