Abstract: Such system can include, in the first plane, a first optical device for producing converging radiation from incident, substantially parallel radiation passing through the first optical device and, in a second plane, substantially parallel to the first plane, a second optical device for receiving, as incident radiation, converging radiation from the first optical device and for recollimating or reducing the degree of convergence of this incident, converging radiation as it passes through the second optical device.

Abstract: A method for separating and recovering substantially pure aluminum, iron and silica from fly ash, a by-product of coal combustion, includes reacting the fly ash with aqueous fluosilicic acid and aqueous hydrogen fluoride at temperatures sufficiently high to form aqueous silicon fluoride vapor and fluorides and fluosilicate of aluminum and iron, separating the aluminum and iron fluorides and fluorosilicates from the aqueous silicon fluoride vapor, hydrolizing the silicon fluoride vapor to form silicon dioxide in substantially pure form and hydrogen fluoride, recovering and recycling the hydrogen fluoride for reuse in the process, and separating the aluminum and iron fluorides and fluosilicates from one another, and recovering substantially pure aluminum fluoride, substantially pure iron and other substantially pure metals, by electroplating or otherwise.

Abstract: A method for treating water or waste water to remove pollutants therefrom includes treating fly ash comprising aluminum, iron and silica with an aqueous base, recovering a base-treated, solid fly ash, washing the base-treated solid fly ash with water, recovering a rinsed, base-treated fly ash solid, reacting the rinsed, base-treated fly ash solid with mineral acid, and recovering an aqueous, solubilized acidic fly ash leachate, then mixing the aqueous, acidic solubilized fly ash leachate with water or waste water to remove pollutants therefrom, or with sludge to reduce its resistant to dewatering.