| Because of the increasing public awareness of pollution and environmental protection, gaseous pollutants control technology as a hot topic, has been widely studied. Although control technologies of volatile organic compounds (VOCs) and sulfur dioxide (SO2) have been conducted, researches on the mechanism as well as micro structure-function of activated carbons (ACs) are still in exploration. In this thesis, commerial ACs were selected as a adsorbent for acetone and SO2adsorption, the relationship between gaseous pollutants and micro structure-function material surface physicochemical properties was systematically and quantificationally analyzed. The inherent correlation between acetone and SO2adsorption activity and the AC's surface physicochemical properties and complex interaction mechanism was studied from the micro/macro point of view. The primary contents and conclusions are listed as follows:(1) Series of analysis methods such as elemental analysis, scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET) surface area analyser, fourier transformed infrared (FTIR) were used to study the surface physicochemical properties and structure of ACs. And these gaseous pollutant adsorption performance by AC in association with basic physical property data, adsorption performance data and thermodynamic test data were systematically and quantificationally investigated. The relationship between physicochemical properties of ACs and adsorption behavior was set up. The effect of microstructure of ACs on organic and inorganic gaseous pollutants adsroption performance was also analysed. The coupled effects of heat and mass transfer in gaseous pollutants adsorption process by AC was theoretically studied. The received findings were that the Langmuir adsorption isotherm model described the adsorption of acetone onto ACs very well. Adsorption of acetone increased positively-linearly with the increases of micropore volume. Acetone surface coverage in the ACs increased obviously with the increase of acetone concentration. Smaller acetone surface coverage resulted in higher ACs adsorption energy for acetone. Heat transfer coefficients exhibited insignificant effect on mass transfer. In contrast, mass transfer coefficients exhibited more impact on heat transfer. The mass transfer effects caused by a temperature gradient were more obvious than heat transfer effects caused by a concentration gradient.For SO2adsorption on ACs, the linear correlation coefficient of specific surface area and micropore specific surface area and SO2adsorption capacity increased with the increasing of SO2inlet concentration. In the higher inlet concentration and lower adsorption temperature, total pore volume and micropore volume of ACs have both a well linear fitting with the SO2adsorption capacity. With the same adsorption temperature and inlet concentration, the impact of textural properties of ACs on SO2adsorption were in order as narrow pore volume> micropore volume> micropore surface area> BET surface area> total pore volume. When the adsorption at a certain temperature, the maximum adsorption capacity of micropore volume performed as AC-SX> AC-NX> AC-HN> AC-GZ, the order of adsorption energy were AC-GZ> AC-NX> AC-HN> AC-SX, it was explained that the larger the maximum adsorption capacity of micropore volume, the lower the adsorption energy, so absorption of AC-SX was occurred easily.(2)Commerial ACs were modified with microwave thermal treatment, inorganic and organic chemical reagents. The structure characteristics parameters such as physicochemical properties of modified ACs were obtained by the characterizations of Boehm titration, transmission electron microscope (TEM), BET and FTIR to investigate the adsorption performance of acetone by modified ACs. The research shows that the Langmuir adsorption isotherm model described the adsorption of acetone onto modified ACs. The specific surface area and total pore volume of modified ACs decreased slight, but the micropore specific surface area increased remarkably. With an increase of temperature, large number of surface acidic functional groups resolve and surface basic functional groups were formed gradually in thermal treatment. After alkaline solutions modification, with an increase of alkaline of solutions, surface basic functional groups increased remarkably and surface acidic functional groups were removed completely, which resulted in a dercease of acetone adsorption capacity. Esters modification could directional modified pore structure of ACs. It decreased the mesopore specific surface area, prompted micropore specific surface area, and improved the ability of the modified ACs capture adsorbate molecule. In early stage of adsorption of acetone on modified ACs, a small amount of ester reagents was replaced by acetone. The modified AC-ethy has a good performance on the treatment of high humidity and low density of acetone. Compared with the AC-NX, the acetone adsorption capacity of AC-ethy was not affected by water vapor.(3) The heat and mass transfer in a fix bed of AC and the variation of the ratio of desorption gas condensability was investigated on a double bed five steps pressure swing adsorption (PSA) for the first time. The results show that the pressure inside the adsorption bed was changed periodically, the temperature curve of different height was changed according to the changing periodicity, the mass transfer area was mainly in0.08-0.15m. The concentration of gas phase composition was decreased gradually with the increase of adsorption column height. It begin into a stability stage after400cycles. No SO2was detected when the bed height was higher than0.6m. During the purge desorption and vacuum desorption stage, the ratio of desorption gas condensability was increased, then tends to stable, finally bring down with desorption time increasing. In our experiment conditions, the best operation time for each stage were adsorption with170s, purge desorption with15s, vaccum desorption with180s, balance pressure with3s. The avarge condensability of SO2in desorption gas can achieved2.0.(4) Self-made AC was prepared by a chemical activation method using an tobacco industry waste. Experiments were conducted to study the influence of AC properity, The pore distribution of different ACs by using the pore structure parameter and the different of AC on acetone adsorption efficiency were investigated. The results show that the AC pore structure and adsorption properties were determined by the activation agent types and dosage. AC prepared by ZnCl2exhibited the highest specific surface area. Nitrogen adsorption isotherm for the three ACs in line with type I adsorption isotherm. Micropore distribution of ACs was illustrated by D-A equation and H-K equation, respectively. ACs exhibited the most wide pore distribution was prepared by ZnCl2, which appeared muti-peak distribution. Meso and macropore distribution of ACs was displayed by BJH equation. Most abundant meso and macropore structure were formed on the AC treated by KOH. Higher dosage of activation agent resulted in more meso and macropore when the same activation agent was used. The solid surface fractal dimensions of ACs was calculated. AC with K2CO3as a activation agent is the most rough, it was illustrated that the content of tiny micropore (<0.6nm) was the maximum. Adsorption of acetone has been measured for AC with two times dosage of K2CO3as a activation agent. The result shows that the Langmuir and Temkin model fitted experimental data well.This research provides a reasonable basis in industrial application of purification of gaseous pollutants by adsorption of AC, and also a new comprehensive utilization method by rural waste biomass resources. |
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