Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Reexamination Certificate
2007-11-20
2007-11-20
Lorengo, J. A. (Department: 1755)
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
C423S328100, C423S328200, C423S331000, C423S332000, C423S335000, C588S315000, C588S412000
Reexamination Certificate
active
11282059
ABSTRACT:
Methods for the removal of lead from a metal silicate during the process of manufacturing of such a material are provided. With the reliance upon lower cost starting silicon dioxide starting materials that are known to exhibit elevated amounts of heavy metal therein for the purpose of producing metal silicates (such as sodium silicate, as one example), it has been realized that removal of significant amounts of such heavy metals is necessary to comply with certain regulatory requirements in order to provide a finished material that exhibits the same low level of heavy metal contamination as compared with finished materials that are made from more expensive, purer starting silicon dioxides. Two general methods may be followed for such decontamination purposes. One entails the introduction of a calcium phosphate material, such as dicalcium phosphate, tricalcium phosphate, and/or hydroxyapatite, to a formed metal silicate solution but prior to filtering. The other requires the introduction of calcium phosphate material (again, hydroxyapatite, tricalcium phosphate, and/or dicalcium phosphate) in a silicon dioxide, caustic, and water slurry with said dicalcium phosphate thus present throughout the overall reaction steps of metal silicate formation and is removed by filtering. In each situation, the hydroxyapatite, tricalcium phosphate, or dicalcium phosphate actually aids in rendering immobile the heavy metals therein, such as lead, cadmium, and the like, thereby preventing release of high amounts of bioavailable amounts of such heavy metals from products for which the target metal silicates are considered reactants. Thus, the heavy metal-containing metal silicates may then be utilized to produce precipitated silicas, as one example, that exhibit much lower levels of bioavailable heavy metals as compared with the original silicon dioxide source.
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Huang Yung-Hui
Offidani John V.
Abu-Ali Shuangyi
J.M. Huber Corporation
Lorengo J. A.
Nieves Carlos
Parks William
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