Chemical behavior of sand alternatives in the marine environment

Effect of chemical composition of coal ash used to prepare granulated coal ash on the removal of hydrogen sulfide from water

“…Such a high pH of the GCA1 was attributed to the higher magnesium (1.33 wt.%) and calcium (7.17 wt.%) contents compared with the other GCAs (0.405–0.498 wt.% for magnesium and 4.81–5.31 wt.% for calcium; Table 2). It is supported by the fact that the calcium was eluted from the 0–2.50 mm depth from the surface of the GCA (Okuda et al, 2014) and the hydrolysis of calcium hydroxide might increase the surface pH of the GCAs. In contrast, the pH of GCA2 and GCA3 was pH 6.0–6.2 although those GCAs was prepared from acidic coal fly ashes (pH 4.2–4.5; Tables 1 and 2), indicating that the calcium hydroxide derived from the blast furnace cement might scavenge proton from the coal fly ashes.…”

Environmental behaviour of iron and steel slags in coastal settings

“…Furthermore, disposal of legacy wastes from an era of lax environmental regulation may be providing a range of potential broader benefits in terms of habitat creation and coastal defence provision that warrant further study, although there appear to be physical stability issues at some sites situated on high-energy coastlines. The use of modern iron and steelmaking slags for coastal land reclamation and restoration is already commonly practised internationally, for example in Japan (Nishijima et al 2015 ; Okuda et al 2014 ) and South Korea (Park et al 2022 ), with examples of dumped slag deposits in coastal areas of Spain (Elorza and Recio 2023 ). Therefore, the assessment of their environmental behaviour in coastal settings presented here allows insight into potential leaching behaviours in global settings which can feed into future coastal regeneration efforts and better understanding of potential environmental risks.…”

“…Iron and steel by-products have been disposed of in large quantities in coastal margins given the coastal location of many steel mills (for water use, raw material import and product export), and for land reclamation purposes in jurisdictions with land scarcity pressures (Ding et al 2019 ). Furthermore, there are a range of established and emerging environmental applications for slags in coastal restoration schemes, such as a substrate for coral rehabilitation and seagrass restoration in Egypt (Mohammed et al 2012 ), South Korea (Park et al 2022 ) and Japan (Nishijima et al 2015 ; Okuda et al 2014 ); use of slag in aquaculture or as a broader marine fertiliser in areas of Fe deficiency (Sakurai et al 2020 ), and long-standing uses in coastal defence structures (Lee 1974 ; Foekema et al 2021 ).…”