A method of removing hydrogen sulfide from a subterranean geological formation includes injecting a drilling fluid suspension in the subterranean geological formation. The drilling fluid suspension has a pH of 10 or more and includes a layered triple hydroxide material, including manganese, cobalt, and iron, in an amount of 0.01 to 0.5 precent by weight of the drilling fluid suspension. The method further includes circulating the drilling fluid suspension in the subterranean geological formation and forming a water-based mud and scavenging the hydrogen sulfide from the subterranean geological formation by reacting the hydrogen sulfide with the layered triple hydroxide material in the water-based mud.

FeCo core-shell nanospheres and a method for producing the FeCo core-shell nanospheres are disclosed. Further disclosed is a method of reducing an organic contaminant in a solution by mixing the FeCo core-shell nanospheres with the solution. The FeCo core-shell nanosphere includes a shell made of a material having a formula Co.sub.xFe.sub.yO.sub.(x+1.5y) and a hollow core. The FeCo core-shell nanospheres are produced by mixing cobalt nitrate and iron nitrate in a solvent mixture to form a first mixture and mixing urea with the first mixture to form a second mixture. The solvent mixture is removed from the second mixture to form a powder. The powder is ground to form the FeCo core-shell nanospheres.

FeCo core-shell nanospheres and a method for producing the FeCo core-shell nanospheres are disclosed. Further disclosed is a method of reducing an organic contaminant in a solution by mixing the FeCo core-shell nanospheres with the solution. The FeCo core-shell nanosphere includes a shell made of a material having a formula Co.sub.xFe.sub.yO.sub.(x+1.5y) and a hollow core. The FeCo core-shell nanospheres are produced by mixing cobalt nitrate and iron nitrate in a solvent mixture to form a first mixture and mixing urea with the first mixture to form a second mixture. The solvent mixture is removed from the second mixture to form a powder. The powder is ground to form the FeCo core-shell nanospheres.

Provided are cobalt ferrite particles having a micrometer-order average particle diameter and similar particle diameters. When a cobalt ferrite precursor is treated at a high temperature and a high pressure, an oxidation reaction is caused in the presence of a complexing agent, thereby obtaining intended cobalt ferrite magnetic particles.