Adsorption Characteristics Of Nitrogen Research Articles

Biochar as a water protection tool in peatland forestry – nutrient recovery from runoff water

Water quality is significantly affected by the forest logging activities that are carried out in drained peatlands, which causes a notable enhancement in sediment loading and nutrient export to water bodies. Furthermore, the seasonal fluctuations in nutrient concentrations in the runoff further underscore the need for efficient water protection tools in peatland forestry. To address these issues, biochar-based adsorption methods can potentially offer an effective alternative for water protection in peatland forestry. The current thesis investigates the potential for adsorption-based nutrient recovery from clear-cut peatland runoff water using Norway spruce and Silver birch biochars. In particular, the aim is to i) study the adsorption characteristics in relation to biochar properties and nutrient compounds in runoff waters in a small-scale laboratory experiment (Paper I); ii) investigate the adsorption characteristics of nitrogen (N) compounds from runoff water in a meso-scale laboratory experiment that utilises biochar reactors (Paper II); and iii) investigate the dynamics of biochar adsorption and desorption under fluctuating total nitrogen (TN) concentrations in runoff water (Paper III). Biochar made from birch and spruce were shown to efficiently adsorb N compounds from the water. Across all experiments, the TN content declined significantly, irrespective of the scale, or whether the runoff volume ranged from litres (I and III) to hundreds of litres (II). Furthermore, the TN content at the beginning of the experiment declined at the fastest rate. The results indicate that cases of relatively low adsorption capacity were attributed to the low initial TN concentrations in the water. In addition, TN adsorption occurs above a threshold concentration in natural runoff water. The spruce did not adsorb TN when the concentrations in the runoff water fell below 0.4 mg L-1. In this thesis, biochar emerges as a compelling water protection solution, particularly in regions where clear-cut peatlands release substantial quantities of nutrients.

Biochar as a water protection tool in peatland forestry – nutrient recovery from runoff water

Water quality is significantly affected by the forest logging activities that are carried out in drained peatlands, which causes a notable enhancement in sediment loading and nutrient export to water bodies. Furthermore, the seasonal fluctuations in nutrient concentrations in the runoff further underscore the need for efficient water protection tools in peatland forestry. To address these issues, biochar-based adsorption methods can potentially offer an effective alternative for water protection in peatland forestry. The current thesis investigates the potential for adsorption-based nutrient recovery from clear-cut peatland runoff water using Norway spruce and Silver birch biochars. In particular, the aim is to i) study the adsorption characteristics in relation to biochar properties and nutrient compounds in runoff waters in a small-scale laboratory experiment (Paper I); ii) investigate the adsorption characteristics of nitrogen (N) compounds from runoff water in a meso-scale laboratory experiment that utilises biochar reactors (Paper II); and iii) investigate the dynamics of biochar adsorption and desorption under fluctuating total nitrogen (TN) concentrations in runoff water (Paper III). Biochar made from birch and spruce were shown to efficiently adsorb N compounds from the water. Across all experiments, the TN content declined significantly, irrespective of the scale, or whether the runoff volume ranged from litres (I and III) to hundreds of litres (II). Furthermore, the TN content at the beginning of the experiment declined at the fastest rate. The results indicate that cases of relatively low adsorption capacity were attributed to the low initial TN concentrations in the water. In addition, TN adsorption occurs above a threshold concentration in natural runoff water. The spruce did not adsorb TN when the concentrations in the runoff water fell below 0.4 mg L-1. In this thesis, biochar emerges as a compelling water protection solution, particularly in regions where clear-cut peatlands release substantial quantities of nutrients.

High pressure adsorption isotherms of nitrogen onto granular activated carbon for a single bed pressure swing adsorption refrigeration system

Adsorption characteristics of nitrogen onto granular activated carbon for the wide range of temperature (303–323 K) and pressure (0.2027–2.0265 MPa) have been reported for a single bed pressure swing adsorption refrigeration system. The experimental data were fitted to Langmuir, Dubinin-Astakhov and Dubinin-Radushkevich (D-R) isotherms. The Langmuir and D-R isotherm models were found appropriate in correlating experimental adsorption data with an average relative error of ±2.0541% and ±0.6659% respectively. The isosteric heat of adsorption data were estimated as a function of surface coverage of nitrogen and temperature using D-R isotherm. The heat of adsorption was observed to decrease from 12.65 to 6.98 kJ.mol−1 with an increase in surface concentration at 303 K and it followed the same pattern for other temperatures. It was found that an increase in temperature enhances the magnitude of the heat of adsorption.

INVESTIGATION OF IMPREGNATED ACTIVATED CARBON PROPERTIES USED IN HYDROGEN SULFIDE FINE REMOVAL

Abstract - The effects of relative humidity (RH), carbon dioxide (CO 2 ), methane (CH 4 ), oxygen (O 2 ) presence and gas hourly space velocity (GHSV) on H 2 S adsorption dynamics of KOH/CaO impregnated activated carbon are investigated in this study. X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray detector (SEM-EDX), thermogravimetric analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) techniques are applied and nitrogen adsorption characteristics are determined for characterization. The presence of water, O 2 and lower GHSV has beneficial effects on the activated carbon performance. CO 2 decreases the adsorption capacity due to its acidic characteristics. Best adsorption capacity is obtained as 13 wt % in KOH/CaO impregnated activated carbon, in a CH 4 (60%)/CO 2 (38%)/O 2 (2%) gas atmosphere, at ambient temperature, RH 90 and 5000 h -1 GHSV. Sulphur species formation was verified with the help of SEM-EDX, XRD, TGA, FTIR and nitrogen adsorption analysis on the exhausted samples.

Adsorption Characteristic Research of Sediments of Lake Baiyangdian

This paper regarded the sediments of Lake Baiyangdian as the object of study, researched and analyzed ammonia nitrogen adsorption characteristics of sediment samples. The results showed that: the sediments adsorption to ammonia nitrogen reached a state of equilibrium after 2.5h, The ammonia nitrogen adsorption rate was maximum in 0~10min. Sediment adsorption of ammonia nitrogen was higher as ammonia nitrogen liquid balance concentration increased. The adsorption isotherm curve of ammonia nitreogen can be fitted well by the Langmuir adsorption isotherm model. The total maximum adsorption quantity of ammonia nitrogen by the sediments of Lake Baiyangdian is between 54.12mg/kg to 240.12mg/kg.

Adsorption, dissociation, penetration, and diffusion of N2 on and in bcc Fe: first-principles calculations

We report first-principles calculations of adsorption, dissociation, penetration, and diffusion for the complete nitridation mechanism of nitrogen molecules on a pure Fe surface (bcc, ferrite phase). The mechanism of the definite reaction path was calculated by dividing the process into four steps. We investigated various reaction paths for each step including the energy barrier based on the climb image nudged elastic band (CI-NEB) method, and the complete reaction pathway was computed as the minimum energy path (MEP). The adsorption characteristics of nitrogen (N) and molecular nitrogen (N2) indicate that nitrogen atoms and molecules are energetically favorable at the hollow sites on pure Fe(100) and (110). The dissociation of the nitrogen molecule (N2) was theoretically supported by electronic structure calculations. The penetration of nitrogen from the surface to the sub-surface has a large energy barrier compared with the other steps. The activation energy calculated for nitrogen diffusion in pure bcc Fe was in good agreement with the experimental results. Finally, we confirmed the rate-determining step for the full nitridation reaction pathway. This study provides fundamental insight into the nitridation mechanism for nitrogen molecules in pure bcc Fe.

Influence of outside environmental variations on ammonia nitrogen adsorption characteristics of HVMT/PC/EPDM composite

A new kind of ammonia nitrogen (AN) sewage water treatment composite was prepared by melt blending, with synthetic rubber ethylene propylene diene monomer (EPDM) and polycarbonate (PC) as the matrix, the natural vermiculite (VMT) powder modified by hydrochloric acid solution (HVMT) as the filler. By Fourier transform infrared (FTIR) measurement and XRD measurement, it was confirmed that the HVMT was more suitable as filler than VMT. By considering the influence of pH, temperature, adsorption composite content and initial mass concentration on removal rate and adsorption capacity, it can be concluded that the removal rate increased first and then decreased with the increasing pH. “Room temperature” was the optimum temperature for the composite. The removal rate of AN increased with the increasing adsorption composite content. When the adsorption reached equilibrium, the removal rate remained unchanged; the adsorption capacity of AN increased with increasing initial concentration. The removal rate increased gradually with lower initial concentration of AN. When the initial concentration increased to a certain level, the removal rate started to decline. When the initial concentration and composite content showed adsorption equilibrium, the adsorption capacity remained unchanged. The composite can be recycled to be reused after regeneration for nine cycles; the AN adsorption capacity of composite was decreased by only 4.5 %. If the composite can be prepared in large-scale production lines, the costs of HVMT/PC/EPDM porous composite can be controlled at less than USD 16/kg.

Systematic Simulation of Disordered Cylindrical Nanoporous Materials

This paper describes a simple method, based on the Dual Site–Bond Model, for constructing disordered cylindrical porous substrata. Heterogeneity is accounted for by allowing the presence of variable cross-sectional areas along the length of the pore tubes forming the solid. The degree of heterogeneity is easily controlled with overlapping between the pore-size distributions of pore cavities and pore necks. Some simulated materials with different textural properties are presented. An analysis of the texture of the generated structures, together with their nitrogen adsorption characteristics, has been carried out and is discussed.

Adsorption Characteristics of Nitrogen and Oxygen onto Ion-Exchanged X-Type Zeolite

Adsorption characteristics of nitrogen and oxygen onto the ion-exchanged X-type zeolites through pressure swing adsorption (PSA) process were investigated. On the basis of Na-X zeolite, a series of ion-exchanged X-type zeolites containing Ag, Li, Ca, Sr, Br, and K were prepared and investigated in this work. It was revealed that the ion-exchanged X-type zeolites showed a remarkably improved and selective adsorption capability for nitrogen. At equilibrium pressure under 0.5 atm, adsorption capability for nitrogen was decreased in the order of Ag-X > Li-X > Sr-X > Ca-X > Na-X > Ba-X > K-X. At equilibrium pressure over 1 atm, however, the capability was decreased in the order of Li-X > Ag-X > Sr-X > Ca-X > Na-X > Ba-X > K-X. The Li-X zeolite exhibited the selective adsorption capability for nitrogen in the air separation process at high pressure. The separation factor for nitrogen/oxygen (= N2/O2) in the Li-X zeolite was ca. 13.

Effect of precursor composition on the activation of pitchbased carbon fibers

Pure and silver-containing carbon fibers were prepared from isotropic pitch precursors supplied by Conoco, Inc., and a Korean research team and activated in carbon dioxide to varying degrees of burn-off. The specific activation rates for the carbon fibers were measured as well as the nitrogen adsorption characteristics of the activated carbon fibers. Scanning electron microscopy was used to investigate the surface morphology and the behavior of silver particles during the activation process. Molecular composition of the two pitch precursors was determined using a gas chromatograph mass spectrometer and a MALDI TOF mass spectrometer. Results showed that specific surface area increased with the burn-off, and the trends were similar for the pure and silver-containing fibers formed from both isotropic pitch precursors. However, the catalytic behavior of silver during activation, the activation rate, and even the pore characteristics of the activated fiber were found to be dependent on the molecular composition of the precursor pitch.

Adsorption dynamics of gases and vapors on the nanoporous metal organic framework material Ni2(4,4'-bipyridine)3(NO3)4: guest modification of host sorption behavior.

This study combines measurements of the thermodynamics and kinetics of guest sorption with powder X-ray diffraction measurements of the nanoporous metal organic framework adsorbent (host) at different adsorptive (guest) loadings. The adsorption characteristics of nitrogen, argon, carbon dioxide, nitrous oxide and ethanol and methanol vapors on Ni2(4,4'-bipyridine)3(NO3)4 were studied over a range of temperatures as a function of pressure. Isotherm steps were observed for both carbon dioxide and nitrous oxide adsorption at approximately 10-20% of the total pore volume and at approximately 70% of total pore volume for methanol adsorption. The adsorption kinetics obey a linear driving force (LDF) mass transfer model for adsorption at low surface coverage. At high surface coverage, both methanol and ethanol adsorption follow a combined barrier resistance/diffusion model. The rates of adsorption in the region of both the carbon dioxide and methanol isotherm steps were significantly slower than those observed either before or after the step. X-ray diffraction studies at various methanol loadings showed that the host structure disordered initially but underwent a structural change in the region of the isotherm step. These isotherm steps are ascribed to discrete structural changes in the host adsorbent that are induced by adsorption on different sites. Isotherm steps were not observed for ethanol adsorption, which followed a Langmuir isotherm. Previous X-ray crystallography studies have shown that all the sites are equivalent for ethanol adsorption on Ni2(4,4'-bipyridine)3(NO3)4, with the host structure undergoing a scissoring motion and the space group remaining unchanged during adsorption. The activation energies and preexponential factors for methanol and ethanol adsorption were calculated for each pressure increment at which the linear driving force model was obeyed. There was a good correlation between activation energy and ln(preexponential factor), indicating a compensation effect. The results are discussed in terms of reversible adsorbate/adsorbent (guest/host) structural changes and interactions and the adsorption mechanism. The paper contains the first evidence of specific interactions between guests and functional groups leading to structural change in flexible porous coordination polymer frameworks.

Scaling Dimensions of Nitrogen Adsorption Characteristics in Modulated Mesoporous Aluminophosphates

Mesoporous alumina-aluminophosphates (MAAP) of the general formula Al100PXM20(M= Al, Fe, Cr, and Ni andX= 0, 4.5, 9, 18, 36, 72, and 144) were tested for their pore size distribution by nitrogen adsorption. The distribution of pore size can be modified by the addition of phosphorus. The scaling or fractal dimensions (DS) of the adsorption characteristics in the pores, calculated from the plots of the log of the corresponding cumulative BJH desorption pores surface area versus the log of the corresponding pore size, indicate that for low values ofP/P0, the adsorption proceeds in a two-dimensional manner, independently of the pore size distribution (p.s.d.). However, at highP/P0values and narrow p.s.d.DS≥ 3, while at wide p.s.d.DS> 3. At mediumP/P0values theDSvalues obtained were found as high as 10 for narrow pore size distribution and decrease as the p.s.d. becomes wide by the addition of phosphorus. These phenomena are related to the supercritical condensation of nitrogen in the pores of MAAP.

Evaluation of the External Surface Area of Carbon Black by Nitrogen Adsorption

Abstract Specific surface area is an important property for carbon black grade classification, production control, and prediction of rubber reinforcement characteristics. Total surface area alone is insufficient for estimating the reinforcing properties of a microporous carbon black because the internal area of the micropores is inaccessible to rubber molecules. The CTAB surface area test, based on adsorption of a molecule too large to enter the micropore, measures the surface area available to rubber. Although widely used, the CTAB method has failed to gain wide popularity due to its labor-intensive nature and poor testing precision. In the present paper, the extent of microporosity on the surface of carbon blacks is investigated. The external surface area derived from the nitrogen adsorption characteristics is compared to CTAB surface area for a number of standard rubber carbon blacks. This study reports the optimum testing conditions to achieve precise external surface area measurements and the ability of this method to overcome the disadvantages of the CTAB method. Other advantages of this technique are discussed.