Qiongfen Yu

Adsorption equilibrium and kinetics for SO2, NO, CO2 on zeolites FAU and LTA

In order to develop a single-step process for removing SO(2), NO, CO(2) in flue gas simultaneously by co-adsorption method. Pure component adsorption equilibrium and kinetics of SO(2), NO, and CO(2) on zeolite NaY, NaX, CaA were obtained respectively. Equilibrium data were analyzed by equilibrium model and Henrys law constant. The results suggest that Adsorption affinity follows the trend SO(2)>CO(2)>NO for the same adsorbent. Zeolite with stronger polar surface is a more promising adsorbent candidate. Kinetics behavior was investigated using the breakthrough curve method. The overall mass transfer coefficient and diffusivity factor were determined by a linear driving force model. The results are indicative of micropore diffusion controlling mechanism. NaY zeolite has the minimum resistance of mass transfer duo to the wide pore distribution and large pore amount. CaA zeolite exhibits the highest spatial hindered effect. Finally, co-adsorption effect of SO(2), NO, and CO(2) were investigated by multi-components breakthrough method. SO(2) and NO may form new adsorbed species, however, CO(2) presents a fast breakthrough. Chemical adsorption causes SO(2) transforms to SO(4)(2-), however, element N and C are not detected in adsorbed zeolites.

Effect of Preparation Conditions on the Property Cu/AC Adsorbents for Phosphine Adsorption

Copper-based activated carbon adsorbents (Cu/AC) were prepared and used to investigate the effects of various copper precursors, impregnation solution concentration, and calcination temperature on phosphine (PH3) adsorption removal from yellow phosphorus tail gas. N2 adsorption isotherm and X-ray Diffraction (XRD) were used for characterizing the Cu/AC adsorbents. It can be seen that the Cu(N)/AC adsorbent prepared from the Cu(NO3)2 precursor has higher PH3 breakthrough adsorption capacity than other three adsorbent because the surface copper status of it is mainly CuO. Fresh activated carbon requires an optimal impregnation solution concentration (0.05 mol/L) to reach this optimal PH3 breakthrough adsorption capacity (78.62 mg/g). The result shows that the surface chemical characteristics (Cu content) of activated carbon is more important than the physical ones (specific surface or pore volume) for the PH3 adsorption performance. When the calcination temperature is 350°C, the Cu(N)/AC adsorbent has the biggest PH3 breakthrough adsorbed amount of 112.38 mg/g. The present study confirmed that the Cu/AC adsorbents would be one of the candidates for PH3 adsorption removal from yellow phosphorus tail gas.

Preparation and Phosphine Adsorption of Activated Carbon Prepared from Walnut Shells by KOH Chemical Activation

Walnut-shell activated carbons (WSACs) with high surface area and predominant micropore development were prepared by KOH chemical activation. The effects of carbonization temperature, activation temperature, and ratio of KOH to chars on the pore development of WSACs and PH3 adsorption performance of the modified walnut-shell activated carbons (MWSACs) were studied. Criteria for determining the optimum preparation conditions were pore development of WSACs and PH3 breakthrough adsorption capacity of MWSAC adsorbents. The result shows that the optimum preparation conditions are a carbonization temperature of 700°C, an activation temperature of 700°C, and a mass ratio of 3. The BET surface area and the micropore volume of the optimal WASC are 1636m2/g and 0.641cm3/g, respectively. The micropore volume percentage of WSAC plays an important role in PH3 adsorption when there is a slight difference in BET surface areas. High-surface-area WSACs with predominant micropores are suitable for PH3 adsorption removal. The MWSAC adsorbent owns the biggest PH3 breakthrough adsorption capacity (284.12mg/g) due to the biggest specific surface area, total pore volume, and micropore volume percentage. The MWSAC adsorbent will be a potential adsorbent for PH3 adsorption removal from yellow phosphorus tail gas.

Preparation of Activated Carbons from Tobacco Stems by Potassium Hydroxide Activation and Phosphine Adsorption

Activated carbon preparation from tobacco stems by KOH activation at different activation temperatures and KOH/char mass ratios were investigated in this study. The effects of preparation parameters on activated carbon pore structure, morphometrics, microcrystallinities, and surface functional groups were characterized by N2 adsorption, SEM, XRD, and FTIR technologies, respectively. The optimum preparation condition of activated carbon was activation temperature of 850°C, and KOH/char mass ratio of 2. Under this condition, the BET surface area of 2215 m2/g, and the pore volume of 1.343 cm3/g can be obtained. Prepared activated carbon showed clearly honeycomb holes, and a predominated amorphous structure. With increase of activation temperature and KOH/char mass ratio, decrease of surface oxygen functional group, and aromatization of the carbon structure was found. The activated carbon was subject to PH3 purification, and the maximum PH3 adsorption capacity of 253 mg/g can be realized based on well prepared KOH-AC with modification of 2.5% Cu. It seems that the activated carbon produced from chemical activation of tobacco stem would be an effective and alternative adsorbent for PH3 adsorption because of its high surface area, adsorption capacity, and low cost.

Adsorption of Phosphine in Yellow Phosphorus Tail Gas by Impregnated Activated Carbon

Phosphine (PH 3 ) is one of highly toxic air pollutants, commonly produced in phosphorous chemical industry. In order to utilize high concentration CO in yellow phosphorus tail gas, metals (Cu, Fe and Ce) loaded activated carbon adsorbents were prepared for the adsorption of PH 3 in this study. The operating conditions, such as oxygen content, adsorption temperature and space velocity, which influenced the PH 3 adsorption capacity were analyzed. The results showed that over 99% PH 3 adsorption efficiency was achieved on impregnated activated carbon. In addition, oxygen content, adsorption temperature and space velocity were important factors that influenced PH 3 adsorption removal onto impregnated activated carbon. The result showed that the maximum PH 3 adsorption capacity was 134 mg of PH 3 /g of adsorbent during the optimal operating conditions, which were 3% of oxygen content, 70°C of adsorption temperature, and 3000 h -1 of space velocity.

Study of PH3 Adsorption and Regeneration over CuO-ZnO-La2O3/Activated Carbon Adsorbents

CuO-ZnO-La 2 O 3 /activated carbon (AC) adsorbent was prepared and used for efficient adsorption removal of PH 3 at various temperatures in the presence of O 2 . The feasibility of water and thermal regeneration of a spent CuO-ZnO-La 2 O 3 /AC adsorbent was also investigated. The influences of regeneration temperature, water concentration and calcination time were done on the spent CuO-ZnO-La 2 O 3 /AC adsorbent in order to optimize the regeneration processes. It be can be concluded that the CuO-ZnO-La 2 O 3 /AC adsorbent was an efficient adsorbent for PH 3 removal at various temperatures. The adsorbed amount of the MAC adsorbents increased with increasing adsorption temperature. The maximum PH 3 capacity (95~98 mg/g) was obtained on the CuO-ZnO-La 2 O 3 /AC at 70°C and 80°C. The optimal regeneration conditions in this research were steam regeneration at 400°C for 120 min and calcination in an oven with an air atmosphere at 350°C for 120 min. The present study confirmed that the CuO-ZnO-La 2 O 3 /AC would be one of candidates for PH 3 adsorption removal from yellow phosphorous tail gas.