Effect of aging on Phosphorus removal of metallurgical slag and heat reactivation of aged slag

In order to examine the effect of ageing on P removal capacity, the phosphorus (P) removal capacity of three types of slag, argon oxygen decarburisation slag (AOD), blast furnace slag (BFS) and electric arc furnace slag (EAF), was examined after 0, 10, 13 and 19 months in batch experiments. The results showed that ageing reduced P removal capacity, e.g. by 78.4% for 19-month-old AOD slag. For BFS, the P removal rate decreased from 57.4% to 13.8% in 13 months; while EAF slag was found to be less affected by ageing. The decline in P removal capacity with age was probably caused by hydration and carbonation of alkaline minerals on the surface of the slag material during storage. In an attempt to restore the P removal capacity of aged slag, 10-month-old slag samples were heated to an end temperature of 600-1000 °C. It was found that heating at 600 °C for 1 hour increased the P removal capacity of BFS to 97.8% in experiments with 20 mg P L synthetic solution, while heating at 1000 °C for 15 min completely restored the P removal capacity of AOD and EAF.