Recovery of silicon carbide whiskers from coked, converted rice hulls by froth flotation

Claim 1

A method for separating silicon carbide whiskers produced from a high temperature conversion of rice hulls and containing a mixture of silicon carbide whiskers with carbonaceous silicon carbide particles, consisting: (i) shredding the mixture in a controlled manner down to a specified particle size of approximately -10 mesh in order to liberate the silicon carbide whiskers from the carbonaceous silicon carbide particles without removing the carbonaceous material coating from said carbonaceous silicon carbide particles; (ii) dispersing the shredded mixture in water so as to contain about 1 to 15% by weight of solids to form an aqueous mixture of hydrophilic silicon carbide whiskers and hydrophobic carbonaceous silicon carbide particles; (iii) agitating the aqueous mixture to further liberate said hydrophilic silicon carbide whiskers from said hydrophobic carbonaceous silicon carbide particles; (iv) adding surface active reagents to the aqueous mixture, which surface active reagents wet the carbon surface of said carbonaceous silicon carbide particles; (v) agitating the resulting water-reagent mixture; (vi) subjecting the water-reagent mixture to froth flotation having at least three stages; (vii) removing tailings therefrom containing water and silicon carbide whiskers and removing float therefrom containing reagents and carbonaceous silicon carbide particles; and (viii) performing a solid-liquid separation on the tailings, thereby obtaining silicon carbide whiskers from the aqueous mixture tailings.

Claim 2

A method for separating silicon carbide whiskers produced from a high temperature conversion of rice hulls and containing a mixture of silicon carbide whiskers with carbonaceous silicon carbide particles, consisting: (i) shredding the mixture in a controlled manner down to a specified particle size of approximately -10 mesh in order to liberate the silicon carbide whiskers from the carbonaceous silicon carbide particles without removing the carbonaceous material coating from said carbonaceous silicon carbide particles; (ii) dispersing the shredded mixture in water so as to contain about 1 to 15% by weight of solids to form an aqueous mixture of hydrophilic silicon carbide whiskers and hydrophobic carbonaceous silicon carbide particles; (iii) agitating the aqueous mixture to further liberate said hydrophilic silicon carbide whiskers from said hydrophobic carbonaceous silicon carbide particles; (iv) adding surface active reagents to the aqueous mixture, which surface active reagents wet the carbon surface of said carbonaceous silicon carbide particles; (v) agitating the resulting water-reagent mixture; (vi) subjecting the water-reagent mixture to froth flotation having at least three stages; (vii) removing tailings therefrom containing water and silicon carbide whiskers and removing float therefrom containing reagents and carbonaceous silicon carbide particles; and (viii) performing a solid-liquid separation on the tailings, thereby obtaining silicon carbide whiskers from the aqueous mixture tailings.