Process for enhanced metal recovery from, for example, metal-containing feedstock using liquid and/or supercritical fluid carbon dioxide and a source of oxidation. The oxidation agent can be free of complexing agent. The metal-containing feedstock can be a mineral such as a refractory mineral. The mineral can be an ore with high sulfide content or an ore rich in carbonaceous material. Waste can also be used as the metal-containing feedstock. The metal-containing feedstock can be used which is not subjected to ultrafine grinding. Relatively low temperatures and pressures can be used. The metal-containing feedstock can be fed into the reactor at a temperature below the critical temperature of the carbon dioxide, and an exotherm from the oxidation reaction can provide the supercritical temperature. The oxidant can be added to the reactor at a rate to maintain isothermal conditions in the reactor. Minimal amounts of water can be used as an extractive medium.

A method for desulfurization and dezincification of tailings includes the step of passing tap water into a high oxidation reduction electrocatalytic water equipment to reduce the pH value of tap water to 1-2, mixing a specific ratio of the pH value 1-2 acid electrocatalytic water with low-quality high-sulfur iron in the tailings, heating the mixture to let H.sup.+ in the acid electrocatalytic water be reacted with sulfur and zinc in the low-quality high-sulfur iron and to further cause generation of an ion state of hydrogen sulfide gas where the volatilization of water vapor effectively removes the sulfur and zinc elements in the low-quality high-sulfur iron and the hydrogen sulfide gas thus generated is collected.

A method for desulfurization and dezincification of tailings includes the step of passing tap water into a high oxidation reduction electrocatalytic water equipment to reduce the pH value of tap water to 1-2, mixing a specific ratio of the pH value 1-2 acid electrocatalytic water with low-quality high-sulfur iron in the tailings, heating the mixture to let H.sup.+ in the acid electrocatalytic water be reacted with sulfur and zinc in the low-quality high-sulfur iron and to further cause generation of an ion state of hydrogen sulfide gas where the volatilization of water vapor effectively removes the sulfur and zinc elements in the low-quality high-sulfur iron and the hydrogen sulfide gas thus generated is collected.

Present invention describes a biotechnological procedure to remove magnetic sulfur impurities from iron concentrate, wherein includes: to bioleach iron concentrate ores agglomerated in heaps under temperature condition between 5 and 35° C., inoculating the iron concentrate ores with Acidithiobacillus thiooxidans cultures, with an inoculum concentration 10.sup.4 and 10.sup.6 cel/g and addition of water supplemented with nitrogen and phosphorous source (0.01 to 0.5 g (NH.sub.4).sub.2HPO.sub.4/L), without potassium addition, adjusting pH between 1.0 and 9.0, and a feeding rate between 5 and 15 L/h/m.sup.2; this procedure allows a removal efficiency above 80% in 21 days, with a maximum iron loss of 3%.

Present invention describes a biotechnological procedure to remove magnetic sulfur impurities from iron concentrate, wherein includes: to bioleach iron concentrate ores agglomerated in heaps under temperature condition between 5 and 35° C., inoculating the iron concentrate ores with Acidithiobacillus thiooxidans cultures, with an inoculum concentration 10.sup.4 and 10.sup.6 cel/g and addition of water supplemented with nitrogen and phosphorous source (0.01 to 0.5 g (NH.sub.4).sub.2HPO.sub.4/L), without potassium addition, adjusting pH between 1.0 and 9.0, and a feeding rate between 5 and 15 L/h/m.sup.2; this procedure allows a removal efficiency above 80% in 21 days, with a maximum iron loss of 3%.

A method of recovering gold from gold-containing sulphide minerals in an ore that has a recovery-oxidation curve in a graph of % recovery of gold versus % oxidation of the minerals that has a slope of less than 1:1 in a higher % oxidation part of the curve, includes operating at least one oxidation unit to achieve a target % oxidation for sulphur in the ore that is in a higher oxidation part of the curve and producing an output having liberated gold as a consequence of sulphur oxidation in the oxidation unit and allowing variations of the % oxidation in the oxidation unit during the method.

A method of recovering gold from gold-containing sulphide minerals in an ore that has a recovery-oxidation curve in a graph of % recovery of gold versus % oxidation of the minerals that has a slope of less than 1:1 in a higher % oxidation part of the curve, includes operating at least one oxidation unit to achieve a target % oxidation for sulphur in the ore that is in a higher oxidation part of the curve and producing an output having liberated gold as a consequence of sulphur oxidation in the oxidation unit and allowing variations of the % oxidation in the oxidation unit during the method.

A process for the depression of iron sulphides and other disposable elements in the mineral concentration by flotation and electrochemical reactor. The proposed invention represents a method based on the action of electrodes on the mineral, which can replace, compliment or minimise the consumption of chemical reagents, as well as improving the effect thereof.

A process for the depression of iron sulphides and other disposable elements in the mineral concentration by flotation and electrochemical reactor. The proposed invention represents a method based on the action of electrodes on the mineral, which can replace, compliment or minimise the consumption of chemical reagents, as well as improving the effect thereof.

Lead is recovered from lead paste of a lead acid battery in a continuous and electrochemical lead recovery process. In especially preferred aspects, lead paste is processed to remove residual sulfates, and the so treated lead paste is subjected to a thermal treatment step that removes residual moisture and reduces lead dioxide to lead oxide. Advantageously, such pretreatment will avoid lead dioxide accumulation and electrolyte dilution.