Preparation Of Sustained-release Fertilizer For Soil Remediation Based On Titanium-bearing Blast Furnace Slag

With the rapid development of society,people’s life quality improving,metal products increasingly popular,metal smelting industry also developed rapidly,but the metallurgical process will produce by-products slag,if allowed to pile up will cause the occupation of land,environmental secondary pollution caused,in turn,the rise in the cost of governance,therefore uphold the sustainable environmental protection,high value-added use of byproduct slag.Slag pollution belongs to solid waste pollution.In the past,the state invested huge capital and material resources in solid waste control,but the overall situation is not optimistic.For example,a large amount of titanium blast furnace slag produced by Pan Gang Group’s in smelting vanadium titanium magnetite in blast furnace will produce a large amount of harmful waste water and waste gas without effective treatment,which will cause a serious impact on the environment.This topic adhering to the idea of"waste utilization,waste treatment",using titanium blast furnace slag of Pan Gang Group’s titanium blast furnace slag as raw materials,adopting high-temperature co-melting one-step method to doping Mn and Fe transition metal elements and KOH modification to rebuild a kind of slow release fertilizer with soil repair function.The main research methods and results are as follows:（1）Ti-bearing blast furnace slag in-situ doped with Mn O₂was respectively tested for XRD at different temperatures of 500,700,900,1000,1100,1200,1300,1400and 1500℃for holding for 1h.It can be known that with the temperature rise peak position basically unchanged,but with the temperature rise peak intensity gradually increased.The main peak（2Theta=33.24°）shifted first to the right and then to the left,mainly due to the enrichment of perovskite at low temperature and doping of transition metal ions at high temperature.（2）The reconstituted slag with 10%Mn O₂in situ doping alone or 30%KOH base thermal modification alone did not change the main mineral phases and the peak intensity and position did not change significantly after calcination to 1500℃and holding for 1h.（3）The reconstituted slag with Mn O₂/Fe₂O₃in situ doping and KOH base thermal modification is calcined at high temperature to 1500℃and held for 1h,the main mineral phase is perovskite phase,meanwhile,the new potassium-aluminosilicate phase and manganese and magnesium oxide phase are generated,and the diopside phase decreases.（4）After thermal modification by doping Mn O₂of different mass and adding KOH base of different mass,metal ions are doped into the perovskite phase.Among them,Mn⁴⁺in the perovskite phase of reconstruction slag modified by 5%Mn O₂and20%KOH is at most 5.04wt%.Mn⁴⁺in the perovskite phase of the reconstituted slag modified by 10%Mn O₂and 30%KOH is 3.03wt%.（5）Using methylene blue and tetracycline hydrochloride as target pollutants and reconstructed residue as photocatalyst,the degradation of organic pollutants in simulated full spectrum was investigated.The results showed that the degradation efficiency of methylene blue and tetracycline was the highest in Mn/Fe system reconstruction with 10%transition metal doping and 30%KOH addition,which were42.67%,68.74%,46.84%and 39.36%,respectively.However,the degradation efficiency was slightly lower than that of titanium-containing furnace slag.The results show that the content of total organic carbon in photocatalytic degradation solution of reconstructed slag is lower than that of titanium blast furnace slag,indicating that the reconstructed slag is more complete and better in degradation of organic pollutants.（6）The plant planting experiment was carried out with chives of four seasons as experimental plants.The comparison of the results showed that the plants in the fertilizer group prepared with reconstructed residue had the best growth state and nutritional quality,followed by the blank control group and the commercial fertilizer group.（7）Adding 100 m L（10 mg/L）methylene blue solution into the soil to simulate the contaminated soil planting experiment,the planting results showed that the plant growth in the reconstructed residue preparation group was the best,followed by the blank control group,and finally the plant growth in the commercial fertilizer group.Meanwhile plant after picking for 60 days under natural light,respectively for 30 days and 60 days of light soil samples to extract the total organic carbon of soil test,the results show that preparation of fertilizer applied to reconstruct slag with longer duration of lighting in the soil,further degradation of organic pollutants in the soil,while commodity fertilizer may appear the phenomenon of environmental pollution.（8）The sustained-release fertilizer constructed by simple high-temperature solid solution method with titanium-bearing blast furnace slag as raw material can degrade organic pollutants and repair soil,which meets the requirements of green and sustainable development and opens a new idea for the resource utilization of titanium-bearing blast furnace slag.