Application of steelmaking slag on the recovery of degraded paddy field

In Japan and some East Asian countries, due to the gradual depreciation of rice, the application of fertilizer is decreasing, which leads to soil acidic, silicate lack, etc.. This makes the degradation of paddy soil and finally leads the drop of rice production. Therefore, it is important to search a material which could efficiently supply calcium and silicate to paddy soil with lower cost. On the other hand, steelmaking slag is an inevitable by-product of iron and steel industry, which has a very large annual production. Most importantly, lime and silicate always exist in the steelmaking slag. Thus, there is a high chance that the steelmaking slag could be utilized as a soil amendment. However, due to the differences on the refining purposes and the cooling methods, both the chemical and the mineral compositions of steelmaking slag vary in a wide range. This leads unstable dissolution behaviors of elements and causes the difficulties on the actual application of steelmaking slag on soil amending. Therefore, the purpose of this study is to develop an innovative soil amendment based on steelmaking slag, which can serve the demands of both the recovery of degraded paddy field and maintaining good high temperature refining ability. To achieve this purpose, the primary thing is to understand the formation condition of every mineral phase and the distribution behaviors of elements among them in steelmaking slag. By studying several kinds of steelmaking slags, the lime and silicate rich phases were specified, and their formation condition were discussed. Then, by using leaching experimental method, the dissolution behavior of Ca and Si were studied.