Contribution Of Amino Group Research Articles

Volatile-char interactions during biomass pyrolysis: Contribution of amino group on graphitized carbon nanotube to xylose evolution based on experimental and theoretical studies

Char surface functional group has been shown to play an important role in volatile-char interactions during biomass pyrolysis, which are known to be effective for the modification of the pyrolysis products. Using xylose and amino-modified graphitized carbon nanotube (CNT-NH2) as model compounds, the contribution of the designated surface functional group to the evolution of pyrolysis volatile was investigated in this paper by combined theoretical and experimental approaches. The results showed that the interactions between xylose and CNT-NH2 significantly prevented the ring-opening reaction of xylose to form the most typical anhydrosugar, xylosan, while the ring-contraction reaction of xylose was facilitated to yield furfural. The Density Functional Theory (DFT) calculations demonstrated that two medium hydrogen bonds were formed between the amino group and two hydroxyl groups (1-OH and 3-OH) of xylose with a binding energy of −11.67 kcal/mol, leading to diverse changes in the Mayer bond orders of xylose and thus varying pyrolysis pathways.

Synthesis of amino-functionalized graphene as metal-free catalyst and exploration of the roles of various nitrogen states in oxygen reduction reaction

Nitrogen-containing graphene is a promising candidate for oxygen reduction reaction (ORR) in fuel cells. However, there are still some challenges in further application and modification of N-graphene and in understanding the roles of various nitrogen states on electrocatalysis. Herein, we design a simple and effective solvothermal method to synthesize amino-functionalized graphene (AG) from graphite oxide (GO) only in the presence of ammonia solution. Having a significant amount of amino species with the total nitrogen content of up to 10.6% (atom%), the resultant product can act as an efficient metal-free catalyst, exhibiting enhanced electrocatalytic properties for ORR. Furthermore, a combination of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements was used to investigate the roles of various nitrogen states in ORR, and the contribution of amino group has been demonstrated for the first time. Our experiments show that the graphitic- and amino-type of nitrogen components determine the onset potential and electron transfer number, while the total content of graphitic and pyridinic nitrogen atoms is the key factor to enhance the current density in the electrocatalytic activity for ORR. This work could lead to economical synthesis of AG as efficient ORR electrocatalyst in fuel cells, and help to understand the catalytic mechanism of various nitrogen states towards ORR.

Biosorption of chromium from aqueous solutions by pretreated Aspergillus niger: Batch and column studies

This study involved the investigation of enhancement of chromium biosorption capacity of dead Aspergillus niger fungal biomass by pretreatment and its use in a column mode. Cetyl trimethyl ammonium bromide (CTAB) pretreatment exhibited maximum chromium removal. An initial factorial design of experiments showed that factors such as pH of the solution, temperature and biomass mass were important. The kinetics of biosorption of chromium was found to follow Ho pseudo-second order reaction. Isotherm studies conducted at 5 ± 2, 15 ± 2, 22 ± 2, and 30 ± 2 °C provided maximum biosorption capacities of 14.5, 15.2, 10.6, and 11.6 mg/g, respectively. The Freundlich isotherm model was found to describe biosorption. Thermodynamic studies indicated that the biosorption reaction was spontaneous and exothermic in nature. Reusability of biomass was examined by the desorption studies, in which NaOH eluted 90% chromium. Data from a column study using CTAB pretreated biomass immobilized in polysulfone matrix followed Yan's model and the adsorption capacity of the biomass was found to be less than the adsorption capacity obtained in the batch study. Fourier transform infrared spectroscopy analysis indicated that in addition to various functional groups present on the cell wall, the contribution of amino groups towards the biosorption process was evident.