Dissolution Mechanisms of Steelmaking Slag–Dredged Soil Mixture into Seawater

Abstract

A steelmaking slag-dredged soil mixture has been applied to develop or recover the sea coast. In recent years, the side effect of its utilization has been reported, in which the coastal environment has been rehabilitated from sea desertification. It is considered that the mixture can provide various nutrient elements essential for the growth of seaweeds which are lacking in the natural seawater. In the present research, the dissolution behaviors of steelmaking slag-dredged soil mixture into seawater were investigated at laboratory-scale experiments, and the mechanisms were discussed. Variation of pH and the dissolution of Ca were significantly dependent on the CaO/ SiO 2 ratio of the slag, and simultaneously, a slight buffering action on the pH of seawater was provided by the dredged soil. When the pH of seawater increased to a certain extent, Mg contained in seawater precipitated and hindered the further increase of the pH. After the complete precipitation of Mg, pH started to increase again. Dissolution of Si and P greatly depended on the CaO/SiO 2 ratio of the slag and also slightly depended on the ratio of steelmaking slag to dredged soil. According to the CaO/ SiO 2 ratio of the slag, the existing forms of Si were considered to change, while those of P were considered to be the HPO 4 2ion in the whole range. A reasonable dissolution mechanism of Fe from steelmaking slag-dredged soil mixture was estimated based on the variation of ORP value, dissolved Fe concentration and its solubility diagram in seawater condition.

Dissolution mechanisms of steelmaking slags in sea water

“…The authors in this study have clarified the dissolution mechanisms of steelmaking slag under various conditions (Zhang et al 2012, 2014, 2015, 2016). It was demonstrated that the use of steelmaking slag with organic acid or the blending of steelmaking slag with dredged soil is effective for the promotion of efficient elution of nutrient elements compared to the application of steelmaking slag alone.…”

“…In the present paper, the dissolution behaviour of steelmaking slags in sea water elucidated by authors is reviewed. In the previous researches, the dissolution behaviour of steelmaking slag was first measured (Zhang et al 2012) and the effect of blending of steelmaking slag with dredged soil on its dissolution behaviour was studied (Zhang et al 2016). In order to understand the role of organic acid contained in dredged soil, the effect of gluconic acid addition in sea water on the slag dissolution was studied in detail (Zhang et al 2014(Zhang et al , 2015.…”

“…3. Dissolution behaviour of steelmaking slag mixed with dredged soil into sea water (Zhang et al 2016) Generation of soil dredged from the sea bottom is inevitable during the periodical cleaning of harbour or the decontamination of coast. The disposal of dredged soil can cause various issues because it often contains heavy metals, toxic inorganic and organic substances, various bacillus, and also a lot of water.…”

Alkali Elution Behavior of Steelmaking Slag Packed in an Open Channel Vessel in Seawater

“…Steelmaking slag has been utilized in ocean area as sea-grass beds due to its rich source of minerals such as iron oxide and silicon oxide [1][2][3][4][5][6][7][8][9][10][11], a usable material to prevent seawater contamination caused by sulfide contained in the bottom soil matter of the sea [12][13][14][15], and materials to increase soil strength by mixing with dredged soil or bottom materials of the sea [16,17]. However, a part of CaO in steelmaking slag exists as isolated free CaO and is decomposed into Ca 2+ and OHions in seawater.…”

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

“…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.…”