Study On The Preparation And Planting Performance Of Eco-concrete Based On Electrolytic Manganese Slag

Electrolytic manganese slag is the acidic filter slag produced in the process of smelting and producing metal manganese.China mainly disposes of electrolytic manganese slag in slag warehouses.A large number of easily mobile manganese ions and ammonia nitrogen in the stored electrolytic manganese slag have caused many environmental problems and severely restricted the development of the electrolytic manganese industry.The resource utilization of electrolytic manganese slag can not only absorb a large amount of piled electrolytic manganese slag,but also create a certain economic value while having environmental benefits.In this thesis,based on the basic characteristics of electrolytic manganese slag,the manganese and ammonia nitrogen in the electrolytic manganese slag are stabilized,and the research on the preparation of cementitious materials from electrolytic manganese slag is carried out.At the same time,using this composite cementitious material as a binder and adding lightweight aggregates to prepare vegetation-type ecological concrete,the preparation process and vegetation performance are studied,and the main conclusions are as follows(1)Physicochemical properties of EMR were analyzed by XRD?XRF?DTA-TGA and BET.The results show that the electrolytic manganese slag mainly contains Si O₂and Ca SO₄·2H₂O,while manganese ions and ammonia nitrogen are mainly in the form of Mn SO₄·2H₂O,(NH₄)₂SO₄,(NH₄)₂(Mg,Mn,Fe)(SO₄)₂·6H₂O Exist,the migration and transformation ability is strong,and its content far exceeds the national safety discharge standard.(2)For the manganese and ammonia nitrogen in the electrolytic manganese slag,first use Ca O to pre-treat the electrolytic manganese slag(EMR)to remove the ammonia nitrogen and stabilize the heavy metals in it.The results showed that the residual rate of NH₄⁺-N was 0.95%under the addition of 6%Ca O,and the Mn concentration was below the detection limit,and the best pretreatment effect was obtained.With 4%Ca O addition,the residual rate of NH₄⁺-N is 1.62%,and the curing rate of Mn reaches 99.98%,achieving a good pretreatment effect.(3)Cementitious materials are prepared from electrolytic manganese slag,phosphogypsum,slag powder,and cement.Under the condition of fixed slag and cement content,the influence of different sulfate content on the mechanical properties of composite cementitious materials was studied.Through XRD,FTIR,TG-DSC,SEM-EDS and other characterization methods,the structure and reaction mechanism of the hydration product of the gelling material were analyzed.The results show that the solidified body under the optimal ratio of composite cementitious materials has a14-day compressive strength of 20.62 MPa and a softening coefficient of 0.80.The main hydration products are ettringite,C-S-H,and C-A-S-H.The hardened toxicity leaching experiment shows that the pollutants in the leaching solution meet the standard limit of"Surface Water Environmental Quality Standard"(GB 3838-2002),and heavy metals such as Cr,Cu,Zn,As,Cd,Sb can even reach the?Environmental Quality Standard for Surface Water?(GB 3838-2002)standard limit of Class I standard,has good environmental stability.(4)A composite cementitious material was used as a binder and ceramsite was used as aggregate to prepared a clay ceramsite ecological concrete with good water permeability and high strength.At the same time,the improved electrolytic manganese slag and phosphogypsum were used as the nutrient matrix of ecological concrete.It can basically meet the needs of plant growth.