Abstract: Material such as an oil slick floating on a body of liquid, ordinarily water, is collected by a mechanism comprising an impeller beneath the liquid surface and a rotatable tubular element which together form a free vortex as the surface of the body of liquid that draws the material into a vortex pocket from which it can be pumped.

Abstract: In the disclosed process, the winning of noble or relatively electronegative metals (e.g. Au, Ag, Cu, Ni, etc.) from substantially aqueous solutions containing ions of the metal through the use of relatively electropositive precipitant metals (e.g. Fe, Zn, Al, etc.) is carried out along with recovery or utilization of some of the energy which can be produced by chemical or electrochemical action. In this process, an electrochemical primary cell-like arrangement with a one-fluid or two-fluid electrolyte (wherein the precipitant metal can be an anode) can also provide improvements in the character (orderliness, efficiency, purity of product, etc.) and control of the cementation reactions. For example, bright (high purity) copper can be obtained in a cathode compartment in a two-fluid cell using a scrap iron anode, a pregnant hydrometallurgical cuprous or cupric leach solution as the catholyte, and an external circuit connecting the cathode to the anode.