| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程研究所 === 83 === A study was conducted on the leaching toxicity and the reuse
feasibility of the residual oil cracking(ROC) spent catalysts.
In assessing the leaching behavior of nickel and vanadium, an
automatic pH/ORP control system was utilized. At pH=5, the
equilibrium nickel solubility did not change with the redox
potential. Compared with result from sequential extraction,
the amount of nickel dissolved was equal to the exchangeable
fraction of spent catalyst. At pH=8, the dissolved nickel
concentration increased with decreasing ORP, and is portional
to the dissolved iron concentration. The dissolved
concentration of vanadium increased with decreasing ORP at both
pH=5 and pH=8. Thisbehavior could be explained by the reducing
reaction of vanadium. Second, we used batch reactor to study
the effect of pH, surface loading and temperature on the
adsorption of fluoride by spent catalysts. Both equilibrium
and kinetics of adsorption were investigated. Result show that
the ROC spent catalyst is a good adsorbent. The adsorption of
fluoride could be modeled with the linear adsorption isotherm.
The adsorption capacity increased with temperature and surface
loading. The adsorption reactionas a first order reaction. At
low pH, the fluoride adsorptionuld be attributed to the silica
portion in spent catalysts; whereas, fluoride adsorption could
be attributed to the alumina portion under acidic to slightly
basic conditions. Judging from the activated energy, the
adsorption reaction is proposed to be a physical adsorption,
and is mainly driven by the electrostatic force.
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