Polymer particles having the same chemical makeup but different sizes would have their own special contributions to the generation of static charges,owing to the differences in catalyst residue and surface properties ...Polymer particles having the same chemical makeup but different sizes would have their own special contributions to the generation of static charges,owing to the differences in catalyst residue and surface properties among them.Experiments were performed in a gas-solid fluidized bed to determine the changes in the electrostatic charges with addition of various fine polyethylene particles,which were the same material as the coarse polyethylene particles,to better understand their role in influencing electrostatic charge generation/dissipation.By measuring the electrostatic potential at different bed axial heights,it was found that the electric field inside the bed was significantly influenced by the size of added fine polyethylene particles,mass fractions and catalyst residue.Consequently,an impact factor of fine particles(Fb) was proposed,which was the sum of particle diameter term and catalyst residue term.Within the experimental limits in this paper,after three kinds of fines with Fb all less than 1 were added in the fluidized bed,the electrostatic potential in the bed was just influenced slightly.However,the bed electrostatic potential changed significantly following the addition of the fines with the smallest particle diameter and highest residual catalyst content.While Fb of this kind of fines was less than 1,the static potential did not change much but even decreased slightly with the addition of fines.Once Fb of the fourth kind of fines was more than 1,the electrostatic potential in the bed increased greatly.With Fb of the fourth kind of fines increasing further,the electrostatic potential fell a little,and meanwhile it was found that a large amount of fine particles adhered to the column wall.展开更多
In this study, biochars from rice straw （Oryza sativa L.） were prepared at 200-600 ℃ by oxygen-limited pyrolysis to investigate the changes in properties of rice straw biochars produced at different temperatures, a...In this study, biochars from rice straw （Oryza sativa L.） were prepared at 200-600 ℃ by oxygen-limited pyrolysis to investigate the changes in properties of rice straw biochars produced at different temperatures, and to examine the adsorption capacities of the biochars for a heavy metal, copper（II） （Cu（II））, and an organic insecticide of cyromazine, as well as to further reveal the adsorption mechanisms. The results obtained with batch experiments showed that the amount of Cu（II） adsorbed varied with the pyrolysis temperatures of rice straw biochar. The biochar produced at 400 ~C had the largest adsorption capacity for Cu（II） （0.37 mol kg-1） among the biochars, with the non-electrostatic adsorption as the main adsorption mechanism. The highest adsorption capacity for cyromazine （156.42 g kg-1） was found in the rice straw biochar produced at 600 ℃, and cyromazine adsorption was exclusively predominated by surface adsorption. An obvious competitive adsorption was found between 5 mmol L-1 Cu（II） and 2 g L-1 cyromazine when they were in the binary solute system. Biochar may be used to remediate heavy metal- and organic insecticide-contaminated water, while the pyrolysis temperature of feedstocks for producing biochar should be considered for the restoration of multi-contamination.展开更多
文摘Polymer particles having the same chemical makeup but different sizes would have their own special contributions to the generation of static charges,owing to the differences in catalyst residue and surface properties among them.Experiments were performed in a gas-solid fluidized bed to determine the changes in the electrostatic charges with addition of various fine polyethylene particles,which were the same material as the coarse polyethylene particles,to better understand their role in influencing electrostatic charge generation/dissipation.By measuring the electrostatic potential at different bed axial heights,it was found that the electric field inside the bed was significantly influenced by the size of added fine polyethylene particles,mass fractions and catalyst residue.Consequently,an impact factor of fine particles(Fb) was proposed,which was the sum of particle diameter term and catalyst residue term.Within the experimental limits in this paper,after three kinds of fines with Fb all less than 1 were added in the fluidized bed,the electrostatic potential in the bed was just influenced slightly.However,the bed electrostatic potential changed significantly following the addition of the fines with the smallest particle diameter and highest residual catalyst content.While Fb of this kind of fines was less than 1,the static potential did not change much but even decreased slightly with the addition of fines.Once Fb of the fourth kind of fines was more than 1,the electrostatic potential in the bed increased greatly.With Fb of the fourth kind of fines increasing further,the electrostatic potential fell a little,and meanwhile it was found that a large amount of fine particles adhered to the column wall.
基金supported by the National Natural Science Foundation of China (Nos.41371245 and 41230855)the National Key Technology R&D Program of China (No.2012BAJ24B06)
文摘In this study, biochars from rice straw （Oryza sativa L.） were prepared at 200-600 ℃ by oxygen-limited pyrolysis to investigate the changes in properties of rice straw biochars produced at different temperatures, and to examine the adsorption capacities of the biochars for a heavy metal, copper（II） （Cu（II））, and an organic insecticide of cyromazine, as well as to further reveal the adsorption mechanisms. The results obtained with batch experiments showed that the amount of Cu（II） adsorbed varied with the pyrolysis temperatures of rice straw biochar. The biochar produced at 400 ~C had the largest adsorption capacity for Cu（II） （0.37 mol kg-1） among the biochars, with the non-electrostatic adsorption as the main adsorption mechanism. The highest adsorption capacity for cyromazine （156.42 g kg-1） was found in the rice straw biochar produced at 600 ℃, and cyromazine adsorption was exclusively predominated by surface adsorption. An obvious competitive adsorption was found between 5 mmol L-1 Cu（II） and 2 g L-1 cyromazine when they were in the binary solute system. Biochar may be used to remediate heavy metal- and organic insecticide-contaminated water, while the pyrolysis temperature of feedstocks for producing biochar should be considered for the restoration of multi-contamination.
