Preparation Of Nickel-iron Slag-based Phosphate Cementitious Materials And Research On Solidification Of Electrolytic Manganese Slag

Ferronickel slag-based phosphate cementitious material(FBPCM)was prepared by using ferronickel slag(FS)to react with phosphoric acid(P1),sodium dihydrogen phosphate(P2)and potassium dihydrogen phosphate(P3)respectively,and used to solidify electrolytic manganese residue(EMR)to realize the safe and environmentally friendly disposal of EMR.In this paper,the effects of three kinds of phosphorus sources and the dosage of EMR on the mechanical properties,reaction p H,soluble manganese ions and curing rate of ammonia nitrogen of the solidified body were discussed.The solidified body was characterized and analyzed by SEM,XRD and FT-IR,and the encapsulation mechanism of soluble manganese ion and ammonia nitrogen in solidified body was discussed.The research results and conclusions were as follows:(1)The optimal raw material ratio for the preparation of FBPCM:when the mass ratio m(FS/P1)was 4:1,the cementitious material PA2 had the best properties and the maximum compressive strength could reach 6.3 MPa;When the mass ratio m(FS/P2)was 5:1,the cementitious material PB3 had the best properties and the maximum compressive strength could reach 22.7 MPa.When the mass ratio m(FS/P3)was 4:1,the cementitious material PC2 had the best properties and the maximum compressive strength could reach 27.5MPa.(2)The encapsulation mechanism of FBPCM:characterization of XRD,SEM,FT-IR analysis showed that the main gelling of cementitious material magnesium were Mg₂(PO₄)(OH)·3H₂O and Mg HPO₄·7H₂O,and part of the unreacted forsterite(Mg₂Si O₄)filled in material internal,which increased the material density and compressive strength.(3)When the mass ratio m(FS/P1)was 6:1,the solidified body SA4 had the best properties and the maximum compressive strength could reach 4.0 MPa.The curing rate of the solidified body SA4 for the manganese ions and ammonia nitrogen were 99.91%and 82.86%,respectively.When the mass ratio of m(FS/P2)was 5:1,the solidified body SB3 had the best properties and the maximum compressive strength could reach 6.5 MPa.The curing rates of manganese ions and ammonia nitrogen were 99.91%and 65.16%,respectively.When the mass ratio m(FS/P2)was 4:1,the solidified body SC2 had the best performance and the maximum compressive strength could reach 6.7MPa.The curing rates of manganese ions and ammonia nitrogen were 99.99%and 91.63%,respectively.The leaching concentrations of manganese ions and ammonia nitrogen were lower than the minimum limits stipulated by the state.(4)The dosage of EMR had a significant effect on the mechanical properties and curing effect of the solidified body.With the increase of the dosage of EMR,the compressive strength of the three solidified bodies all showed a decreasing trend,indicating that the addition of EMR hindered the hydration reaction of the solidified body.With the increase of the content of EMR,the curing rate of manganese ion and ammonia nitrogen decreased gradually,and the leaching concentration and ammonia nitrogen also increased correspondingly.When the content of EMR was20%,the solidified body prepared had the best mechanical properties and the best curing effect.(5)The characterization of XRD,SEM,FT-IR analysis showed that the main gelling of the solidified body were MnPO₄·H₂O?(NH₄)₂HPO₄ and NH₄MgPO₄·6H₂O,which suggested that manganese was enclosed mainly by MnPO₄·H₂O,ammonia nitrogen was enclosed mainly by(NH₄)₂HPO₄ and NH₄MgPO₄·6H₂O.The cementitious material could involved in the solidified body,which increased the density of material structure.In addition,ammonia nitrogen and manganese could be effectively solidified by means of physical encapsulation,physical adsorption and chemical bonding.