Synergistic effects between nitrogen functionalities and metals content on the removal of phosphate ions

The release of phosphate ions in the runoff is today a major threat to the environment and humans. Therefore, it is vital to develop effective technologies to remove phosphate ions from aqueous solutions before they are discharged into runoff and natural water bodies. This study aims to evaluate and proposed a mechanism of phosphate adsorption by using nitrogen and metals-functionalized chars. In order to isolate the contribution of individual components of lignocellulosic biomass, simple cellulose was used for the char production. Five samples of nitrogen-doped chars were produced via annealing cellulose under ammonia gas at different temperatures (500, 600, 700, 800, 850 and 900 ℃). Some of the analytical techniques used for the chars characterization were: Elemental and proximate analysis, gas physisorption analysis, Scanning Electron Microscopy and X-ray photoelectron spectroscopy analysis. These samples were subsequently used for phosphate adsorption. Characterization of the resulting chars shows an increase of the nitrogen content in the samples, where the greater percentage of it appears at a temperature of 800 ℃ (12.5 wt%) and the maximum surface area was for char produced at 900 ℃ (1314 m2/g). To evaluate the effect of nitrogen and metals in char to adsorb phosphate ions, three sets of chars were produced at 800 ℃; char with magnesium and nitrogen (Mg_N_char); char with nitrogen (N_char) and char with magnesium (Mg_N_char). The results show that Mg_N_char sample exhibits a maximum adsorption capacity of 340 mg/g, whereas the Mg_char and N_char samples give an adsorption capacity of 7.8 mg/g and 21.4 mg/g respectively. These results demonstrate that the presence of magnesium and nitrogen in chars is very effective in the retention of phosphate ions. Other metals such as Fe and Ca combined with nitrogen will also be tested, details of the results will be presented at the conference

Core level binding energy for nitrogen doped char: XPS deconvolution analysis from first principles

Amorphous carbon produced from lignocellulosic materials has received much attention in recent years because of its applications in environmental and agricultural management with potential to sequester carbon, serve as a soil amendment, and improve soil aggregation. Modern engineered amorphous carbons with promising properties, such as porous structure, surface functionalities (O, N, P, S) and layers with large number of defects, are used in the field of adsorption and catalysis. There is a growing interest in the production of nitrogen-doped carbonaceous materials because of their excellent properties in a variety of applications such carbon electrodes, heterogenous catalysis adsorption and batteries. However, quantifying the surface nitrogen and oxygen content in amorphous nitrogen doped carbons via deconvolution of C 1s x-ray photoelectron (XPS) spectra remains difficult due to limited information in the literature. No suitable method exists to accurately correlate both the nitrogen and oxygen content to the carbon (C 1s) XPS spectrum in the literature. To improve the interpretation of spectra, the C 1s, N 1s and O 1s core level energy shifts have been calculated for various nitrogenated carbon structures from first principles by performing density functional theory (DFT) based calculations. Furthermore, we propose a new method to improve the self-consistency of the XPS interpretation based on a seven-peak C 1s deconvolution (3 C-C peaks, 3 C-N/-O peaks, and π-π* transition peaks). With the DFT calculations, spectral components arising from surface-defect carbons could be distinguished from aromatic sp2 carbon. The deconvolution method proposed provides C/(N+O) ratios in very good agreement (error less than 5%) with those obtained from total C 1s, N 1s and O 1s peaks. Our deconvolution strategy provides a simple guideline for obtaining high-quality fits to experimental data on the basis of a careful evaluation of experimental conditions and resul

Chars from wood gasification for removing H2S from biogas

Biomass gasification is a mature thermochemical process used to produce a gaseous fuel to run burners, engines, and gas turbines. One of the byproducts of biomass gasification is char, which is a residue with low value and sometimes this material is even considered waste. Therefore, options for using gasification chars are required. On the other hand, there is a necessity of making biogas production and use more attractive by employing cheap materials for the biogas cleaning process. One of the promising options for using gasification chars is for cleaning biogas produced via anaerobic digestion (AD). The objective of this work was to assess the use of residual gasification chars from fast growing wood species (Eucalyptus Grandis-EG and Pinus Patula-PP) to remove hydrogen sulfide (H2S) from biogas produced via AD. Gasification chars were produced employing a laboratory scale downdraft gasifier. EG char (EG-C30) was produced by gasification of EG using a 30 L min−1 airflow, whereas the PP chars (PP–C20 and PP-C40) were produced from PP using 20 and 40 L min−1 airflow. Results show that these three chars offer potential for biogas cleaning, although PP-derived chars produced at higher airflow rates are more effective. The H2S removal capacity of the chars is ascribed to their large apparent surface area (up to 517 m2 g−1) and the presence of minerals and metals (e.g., Ca, K, and Fe) in the chars’ ash

Production and characterization of H2S and PO4 3− carbonaceous adsorbents from anaerobic digested fibers

La digestión anaerobia (EA) es una tecnología importante para producir biogás a partir de estiércol. Si bien el AD del estiércol lácteo resulta en el aprovechamiento de la energía contenida en el estiércol, la mayoría de los nutrientes (fósforo y nitrógeno) permanecen en el efluente líquido, lo que representa una fuente importante de contaminación. Además, el biogás producido contiene H 2 S y CO 2 , lo que limita su uso práctico como combustible. En este artículo, informamos la producción y el uso de un adsorbente carbonoso de fibras AD para la eliminación de sulfuro de hidrógeno (H 2 S) del biogás y fosfato (PO 4 3− ) de los efluentes líquidos acuosos. Los adsorbentes estudiados se produjeron mediante pirólisis lenta entre 350 y 800 ° C seguido de CO 2activación. Se informan los análisis elementales y próximos, el área de superficie y la distribución del tamaño de poro de cada uno de los adsorbentes estudiados. Sus capacidades de adsorción se evaluaron utilizando H 2 S PO avance y 4 3- pruebas por lotes de equilibrio. La capacidad de sorción varió entre 21.9 y 51.2 mg g −1 para H 2 S y entre 4.9 mg g −1 y 37.4 mg g −1 para PO 4 3− . Comercialmente disponible carbón activado estudió adsorbido 23,1 mg g -1 H 2 S y 15,7 mg g -1 PO 4 3- . Los resultados muestran que la retención de H 2Los compuestos de S y PO 4 3 se regían por el contenido de cenizas, el área superficial y el pH. Se proponen mecanismos de adsorción para sorción de H 2 S y PO 4 3− . © 2018Anaerobic digestion (AD) is an important technology to produce biogas from dairy manure. Although the AD of dairy manure results in the harnessing of the energy contained in manure, most of the nutrients (phosphorous and nitrogen) remain in the liquid effluent, representing an important source of pollution. Additionally, the biogas produced contains H2S and CO2, limiting its practical use as fuel. In this paper, we report the production and use of a carbonaceous adsorbent from AD fibers for the removal of hydrogen sulfide (H2S) from biogas and phosphate (PO4 3−) from aqueous liquid effluents. The adsorbents studied were produced via slow pyrolysis between 350 and 800 °C followed by CO2 activation. The elemental and proximate analyses, surface area and pore size distribution of each of the adsorbents studied are reported. Their adsorption capacities were assessed using H2S breakthrough and PO4 3− batch equilibrium tests. The sorption capacity varied between 21.9 and 51.2 mg g−1 for H2S and between 4.9 mg g−1 and 37.4 mg g−1 for PO4 3−. Commercially available activated carbon studied adsorbed 23.1 mg g−1 H2S and 15.7 mg g−1 PO4 3−. The results show that the retention of H2S and PO4 3− compounds were governed by the ash content, surface area and pH. Adsorption mechanisms for H2S and PO4 3− sorption are proposed. © 201

Bioenergy potential of millet chaff via thermogravimetric analysis and combustion process simulation using Aspen Plus.

Millet chaff constitutes one of the most abundant agro-residues in the sub-Saharan Africa and its utilisation as a feedstock in developing sustainable bioenergy solutions is very sketchy. This study presents the first comprehensive physicochemical and combustion characteristics of millet chaff via thermogravimetric analysis and process simulation using Aspen Plus. The millet chaff sample was collected and assessed as received for proximate and ultimate analyses. The results showed the biomass has 71.25 wt%, 15.35 wt%, 13.40 wt% and 13.15 MJ/kg for volatile matter, fixed-carbon, ash content and higher heating value respectively. The material consists of low nitrogen and sulphur content with potassium, aluminium, magnesium, calcium, iron and sodium as the inorganic components. Kinetic study using distributed activation energy model (DAEM) revealed an average frequency factor and activation energy of 1.41 × 1018(s−1) and 149.39 kJ/mol. Ignition and burnout temperature in the range of 232-244°C and 430-489°C were recorded. The average combustion thermodynamic parameters; ΔH, ΔG and ΔS were found to be 144.75 kJ/mol, 167.12 kJ/mol and -40.08 J/mol. The combustion process analysis coupled with steam turbine cycle via process simulation revealed an excellent combustion efficiency at air-fuel ratio of 5.14. (stoichiometric air). The power generation and electric efficiency of 0.7kWh/kg and 21.07% respectively were recorded at 24% excess air with minimal environmental impacts. This suggests that millet chaff is a good biomass feedstock suitable for clean bioenergy production