Iron Removal

Introduction

Iron is removed from groundwater by creating a strongly oxidizing environment. This is usually achieved by aeration; by the addition of oxidants such as chlorine or by raising the pH of the water using alkaline materials such as limestone.

Iron is one of the most abundant metals of the Earth's crust. It occurs naturally in water in soluble form as the ferrous iron (bivalent iron in dissolved form Fe2+ or Fe(OH)+) or complexed form like the ferric iron (trivalent iron: Fe3+ or precipitated as Fe(OH)3). The occurrence of iron in water can also have an industrial origin ; mining, iron and steel industry, metals corrosion, etc.

Process

In general, iron does not present a danger to human health or the environment, but it brings unpleasantness of an aesthetic and organoleptic nature. Indeed, iron gives a rust color to the water, which can stain linen, sanitary facilities or even food industry products. Iron also gives a metallic taste to water, making it unpleasant for consumption. It can also be at the origin of corrosion in drains sewers, due to the development of microorganisms, the ferro bacteries.

In aerated water, the redox potential of the water is such as it allows an oxidation of the ferrous iron in ferric iron which precipitates then in iron hydroxide, Fe(OH)3, thus allowing a natural removal of dissolved iron.

4 Fe2+ 3 O2 --> 2 Fe2O3

Fe2O3 + 3 H2O --> 2Fe(OH)3

 Various studies have been increasingly performed on the reduction of sulfur content of iron ores and concentrates. The presence of sulfur in these materials causes technical problems in steel and alloys and environmental issues in the sintering of iron ore process. The achievement of higher sulfur removal rates has been an important goal since the development of sulfur removal techniques. In this research, an effort is made to separately introduce the various processes, industrial practices, and fundamental research activities to remove sulfur from iron ores, concentrates, or roasted iron ores. In this way, the optimized condition and latest innovations in sulfur removal using flotation are reviewed and the development of leaching and bio leaching techniques for sulfur reduction is introduced; following the development of thermal decomposition, physical separation methods, and magnetic separation technique are discussed. In each section, a brief introduction of fundamentals for the sulfur removal techniques and their potential advantages for sulfur removal are described and challenges for each technique are presented. Finally, the techniques are compared from technical, economic and environmental viewpoints, and future trends in desulfurization of iron ores are presented.