Fractionation of Phosphorus in Steelmaking Slags and Aquatic Particulate Materials Using a Sequential Extraction Technique

Abstract

We measured the concentrations and chemical forms of phosphorus (P), an essential nutrient in marine ecosystems, in steelmaking slag (Slag) to determine whether use of Slags as a basal medium for artificial tidal flats and seagrass beds was an environmentally acceptable option for the reuse and recycling of Slags. We tested six Slag samples, including dephosphorization slags and converter slags. The total P concentrations were one order of magnitude higher in the Slags than in the aquatic particulate materials. We used a sequential extraction technique in which the strength of the extractants was increased stepwise in order to separate the P pools in the Slags into four fractions; exchangeable P, Fe (III)-bound P, authigenic P-like component, and detrital P-like component. We considered P contained in the first two fractions to be easily mobilized under the conditions found in some marine environments, such as the highly reduced zones of subsurface sediments. The mobile P accounted for 55-660 μmol P g -1 and for 56-81% of the total P in the Slags. The results strongly suggested that Slags have substantial potential to function as a P source that could sustain biological productivity in artificial tidal flat and seagrass bed ecosystems. On the other hand, Slags also have the potential to mitigate intense and rapid release of P from basal media, because mechanisms exist for adsorption and co-precipitation of phosphate with major components of Slags, including iron, calcium, and magnesium.

Nutrient dynamics in core sediments of an artificial basal medium prepared with steelmaking slag and dredged materials

“…Steelmaking slags contain a considerable amount of calcium oxide (Kourounis et al 2007;Tsukasaki et al 2015). As a result, the possibility of an increase in the pH of the pore water and the overlying seawater due to dissolution of calcium from slags is a matter of concern (Asaoka et al 2013).…”

“…However, it is important to note that not all the phosphorus in slag is biologically available; a considerable part is tightly bound to or entrapped in slag particles. By using a sequential extraction technique for chemical fractionation of various forms of phosphorus, Tsukasaki et al (2015) showed that the amount of phosphorus mobilized under natural marine conditions (mobile P) varied widely, depending on the type of slag. In the slag and DM used in this core experiment, 30.4 and 45.2 % of TP, respectively, was mobile P. We therefore recalculated the integrated phosphate loss by diffusion using these values and concluded that a large amount of mobile P (>99 %) remained in the slag-based sediments after 379 days.…”

“…Laboratory experiments have examined reactions and characteristics of slag in marine environments (Futatsuka et al 2004;Asaoka et al 2013;Yamamoto and Liu 2013;Tsukasaki et al 2015;Zhang et al 2015). The data could provide precise information useful to simulate the potential and kinetics of the dissolution of nutrients and iron as well as various chemicals from slag, especially in sediment pore water environments.…”

Enhanced phosphorus removal from wastewater by growing deep-sea bacterium combined with basic oxygen furnace slag

“…As one kind of mass industrial solid waste, open dumping of steel slag not only occupies land but causes potential pollution by dust as well as the alkalinity to air, soil and groundwater (Asuman Korkusuz et al, 2007). Attentions has been attracted to the use of steel slags as potential adsorbents in regulating the phosphorus cycle through uptake from and slowly release to the water as well as alternatives to the basal medium for construction of artificial wetland, tidal flats and seagrass beds recently (Claveau-Mallet et al, 2014;Hayashi et al, 2011;Hussain et al, 2015;Tsukasaki et al, 2015;Yamamoto and Liu, 2013). Among variety slags generated from different steelmaking processes, slag from the basic oxygen furnace (BOFS) presents the highest phosphorus adsorption capacity (Barca et al, 2012;Oguz, 2004).…”

Effect of Temperature on Desulphurization of Liquid Iron Using Basic Oxygen Furnace Slag

“…Additionally, FeO and P2O5 in the slag could be utilized, that could be one of the main burden to produce iron and phosphorus compounds [2]. Besides, the slag was able to be recycled to make constructive materials as indicated in the research of Tsukasaki and co-workers [3]. The application of the slag have been explored in term of the agglomeration of iron ore or pretreatment processes as well [4][5][6].…”