Composition and method for making silicon-containing products

A method for making carbon-silica products comprising the steps of:

• providing plant matter comprising at least about 3 weight percent of silica, non-silica minerals and metals;
• contacting the plant matter with an aqueous solution of sulfuric acid having an acid concentration ranging from about 0.01 weight percent to about 30 weight percent to produce a mixture of plant matter and acid solution;
• reacting the mixture at a temperature ranging from about 10° C. to about 250° C. for a reaction period ranging from about six seconds to about 48 hours, thereby leaching minerals out of the plant matter to produce a carbon-silica product having an adjusted mole ratio of fixed carbon to silica of at least about 1.0:1;
• and
• thereafter removing the acid solution from the carbon-silica product.