*5.3.3 BOF and SAF slags*

Basic oxygen furnace (BOF) and submerged arc furnace (SAF) slags have complex physical and chemical characteristics [30]. These materials are composed of oxides of calcium, silicon, phosphorus, sulfur, and manganese produced in steel refining processes. Depending upon the sufficiency of the cleaning cycle, inadequately Fe and entrapped metal droplets during the tapping also incorporate into

*Performance Evaluation of Waste Materials for the Treatment of Acid Mine Drainage… DOI: http://dx.doi.org/10.5772/intechopen.99669*

BOF/SAF slags. Because of the popularity of steel, which is linked to the increase in population results during the production cycle of steel produces more amount of BOF and SAF slags from the production process. Various studies suggested that every year steel industry produced is about 100–200 kg of slag as by-products. After the production, the slags are partially reprocessed but a major part of the slag is used as a landfill material and holds pond and lagoon due to the less demand in the market. This slag raises the pH of AMD and reduces the chemical elements (pollutants) to the desired amount. However, it partially removes the sulphate and also various metals such as Mn, Ni, Co, Zn, Mg. This slag is an ideal candidate for the treatment of AMD and also minimizes the environmental impact with the disposal process of these slags [37].

## *5.3.4 Eggshell waste*

Now a day's egg production rates are higher in various countries so that the waste shell produces from eggs are increasing rapidly [38]. According to the study, the global egg production rate is approaching 86.8 Mtpa globally per year soon. This material is used as alternative treatment material to treat AMD. The primary constituent of ES is CaCO3 is an alkaline material that reacts with acidic water to neutralize it by the process of adsorption and precipitation of metals and also used for the complex, binding, and ion exchange material for various metals ions in the wastewater (Equation 9). This eggshell waste is a very cheap and biodegradable material which are collected, characterized, prepared, and evaluated for the degradation of various anions like aluminum, iron, manganese, and anions like sulphate present in AMD. Due to similar properties like limestone, it can be a good neutralizing agent [39].

$$\text{CaCO}\_3 + \text{H}\_2\text{SO}\_4 \rightarrow \text{CaSO}\_4 + \text{CO}\_2 + \text{H}\_2\text{O} \tag{9}$$
