This study was performed to investigate the removal of phosphate from domestic wastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water,and thermal modification were i...This study was performed to investigate the removal of phosphate from domestic wastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water,and thermal modification were investigated. The results showed that thermal activation at 800℃ for 1 hr was the optimum operation to improve the adsorption capacity. The adsorption process of the thermally modified slag was well described by the Elovich kinetic model and the Langmuir isotherm model. The maximum adsorption capacity calculated from the Langmuir model reached 13.62 mg/g. Scanning electron microscopy indicated that the surface of the modified slag was cracked and that the texture became loose after heating. The surface area and pore volume did not change after thermal modification. In the treatment of domestic wastewater, the modified slag bed（35.5 kg） removed phosphate effectively and operated for 158 days until the effluent P rose above the limit concentration of 0.5 mg/L. The phosphate fractionation method, which is often applied in soil research, was used to analyze the phosphate adsorption behavior in the slag bed. The analysis revealed that the total contents of various Ca-P forms accounted for 81.4%-91.1%, i.e., Ca10-P 50.6%-65.1%, Ca8-P 17.8%-25.0%,and Ca2-P 4.66%-9.20%. The forms of Al-P, Fe-P, and O-P accounted for only 8.9%-18.6%. The formation of Ca10-P precipitates was considered to be the main mechanism of phosphate removal in the thermally modified slag bed.展开更多
The production of heavy and extra-heavy oil is challenging because of the rheological properties that crude oil presents due to its high asphaltene content.The upgrading and recovery processes of these unconventional ...The production of heavy and extra-heavy oil is challenging because of the rheological properties that crude oil presents due to its high asphaltene content.The upgrading and recovery processes of these unconventional oils are typically water and energy intensive,which makes such processes costly and environmentally unfriendly.Nanoparticle catalysts could be used to enhance the upgrading and recovery of heavy oil under both in situ and ex situ conditions.In this study,the effect of the Ni-Pd nanocatalysts supported on fumed silica nanoparticles on post-adsorption catalytic thermal cracking of n-C_7 asphaltenes was investigated using a thermogravimetric analyzer coupled with FTIR.The performance of catalytic thermal cracking of n-C_7asphaltenes in the presence of NiO and PdO supported on fumed silica nanoparticles was better than on the fumed silica support alone.For a fixed amount of adsorbed n-C_7asphaltenes（0.2 mg/m～2）,bimetallic nanoparticles showed better catalytic behavior than monometallic nanoparticles,confirming their synergistic effects.The corrected OzawaFlynn-Wall equation（OFW） was used to estimate the effective activation energies of the catalytic process.The mechanism function,kinetic parameters,and transition state thermodynamic functions for the thermal cracking process of n-C_7 asphaltenes in the presence and absence of nanoparticles are investigated.展开更多
基金supported by the Mega-projects of Science Research for Water Environment Improvement of China (Nos. 2013ZX07209-001-003, 2012ZX07307-001-006)
文摘This study was performed to investigate the removal of phosphate from domestic wastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water,and thermal modification were investigated. The results showed that thermal activation at 800℃ for 1 hr was the optimum operation to improve the adsorption capacity. The adsorption process of the thermally modified slag was well described by the Elovich kinetic model and the Langmuir isotherm model. The maximum adsorption capacity calculated from the Langmuir model reached 13.62 mg/g. Scanning electron microscopy indicated that the surface of the modified slag was cracked and that the texture became loose after heating. The surface area and pore volume did not change after thermal modification. In the treatment of domestic wastewater, the modified slag bed（35.5 kg） removed phosphate effectively and operated for 158 days until the effluent P rose above the limit concentration of 0.5 mg/L. The phosphate fractionation method, which is often applied in soil research, was used to analyze the phosphate adsorption behavior in the slag bed. The analysis revealed that the total contents of various Ca-P forms accounted for 81.4%-91.1%, i.e., Ca10-P 50.6%-65.1%, Ca8-P 17.8%-25.0%,and Ca2-P 4.66%-9.20%. The forms of Al-P, Fe-P, and O-P accounted for only 8.9%-18.6%. The formation of Ca10-P precipitates was considered to be the main mechanism of phosphate removal in the thermally modified slag bed.
基金the Natural Sciences and Engineering Research Council of Canada (NSERC)the Department of Chemical and Petroleum Engineering at the Schulich School of Engineering at the University of Calgary
文摘The production of heavy and extra-heavy oil is challenging because of the rheological properties that crude oil presents due to its high asphaltene content.The upgrading and recovery processes of these unconventional oils are typically water and energy intensive,which makes such processes costly and environmentally unfriendly.Nanoparticle catalysts could be used to enhance the upgrading and recovery of heavy oil under both in situ and ex situ conditions.In this study,the effect of the Ni-Pd nanocatalysts supported on fumed silica nanoparticles on post-adsorption catalytic thermal cracking of n-C_7 asphaltenes was investigated using a thermogravimetric analyzer coupled with FTIR.The performance of catalytic thermal cracking of n-C_7asphaltenes in the presence of NiO and PdO supported on fumed silica nanoparticles was better than on the fumed silica support alone.For a fixed amount of adsorbed n-C_7asphaltenes（0.2 mg/m～2）,bimetallic nanoparticles showed better catalytic behavior than monometallic nanoparticles,confirming their synergistic effects.The corrected OzawaFlynn-Wall equation（OFW） was used to estimate the effective activation energies of the catalytic process.The mechanism function,kinetic parameters,and transition state thermodynamic functions for the thermal cracking process of n-C_7 asphaltenes in the presence and absence of nanoparticles are investigated.
