Electrolytic Manganese Slag Pretreatment And Its Application In Light Aggregates

Electrolytic manganese residue(EMR)is acid leaching residue produced by leaching manganese metal from manganese carbonate ore powder with sulfuric acid,and 10?12 t of EMR are produced for every 1 t of electrolytic manganese metal.Electrolytic manganese residue is a small black solid with a certain viscosity and a high moistur.Electrolytic manganese residue mainly contains dihydrate gypsum,silica,and a lot of soluble pullutants.At present,the application rate of electrolytic manganese residue is low,because it contains high soluble manganese and ammonia nitrogen.Therefore,in the paper,the pretreatment of electrolytic manganese residue and its mechanism were systematically studied,and the application of electrolytic manganese residue in firing light aggregate was discussed.(1)In the study,calcium oxide as the treating agent,it was put forward a method about immobilization Mn²⁺and removal NH₄⁺-N by adding CaO,and the mechanism of the immobilization manganese and removal ammonia was also studied.The results show that the precipitation rate of Mn²⁺and the removal efficiency of NH₄⁺-N were99.72%and 91.26%,respectively,when the mass ratio of CaO and EMR was 6:100,liquid-solid was 4:1,55?and reacting for 150 min.The results of scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),and X-ray photoelectron spectroscopy(XPS)display that the Mn²⁺was solidified as groutite(MnOOH),ramsdellite(MnO₂)and ammonia nitrogen escapes by forming NH₃.Kinetic analysis was carried out with manganese curing rate and ammonia nitrogen removal rate as independent variables.The results showed that the process of calcium oxide treatment of electrolytic manganese residue was controlled by the chemical reaction and diffusion mixing of the residual solid film,and apparent activation energy were 11.7135 k J/mol and-7.4473 k J/mol,respectively.(2)In this study,an experimental study of burning phosphorus tailings(BPT)for the immobilization of Mn²⁺and removal of NH₄⁺-N from electrolytic manganese residue was carried out,and the experimental results were further determined by combining with thermodynamic theory calculation.The precipitation rate of Mn²⁺,the removal efficiency of NH₄⁺-N and p H vaule were 99.73%,93.21%and 9.18,respectively,when the BPT to EMR mass ratio 12:100,liquid-solid 6:1,45?and reacting for 180 min.The phase transition,valence,morphology and structure of electrolytic manganese residue before and after treatment were characterized by XRD,XPS,SEM and FT-IR.It was determined that NH₄⁺-N escaped in the form of ammonia,and Mn²⁺was cured in the form of MnO OH and MnO₂.The results of thermodynamic calculation show that the Gibbs free energy of hydration reaction of calcium oxide and magnesium oxide increases gradually with the increase of temperature.The Gibbs free energy of manganese solidification reaction and ammonia nitrogen removal reaction decreases.The Gibbs free energy of magnesium metasilicate is less than that of manganese metasilicate and calcium metasilicate.(3)Electrolytic manganese residue or pretreated electrolytic manganese residue as the main raw material,diatomite as additive and distiller's grains as pore-forming material has carried out the experimental study of lightweight aggregate.The properties of light aggregate are as follows:when raw EMR to diatomite mass ratio of10:7,soaking time of 12 min,sintering temperature of 1160?and preheating temperature of 450?,the cylinder compressive strength,1h water absorption,bulk density and apparent density of lightweight aggregate are 7.17 MPa,6.08%,968kg/m³ and 1659 kg/m³,respectively;When treated EMR to diatomite mass ratio of10:7,soaking time of 12 min,sintering temperature of 1165?and preheating temperature of 450?,the cylinder compressive strength,1h water absorption,bulk density and apparent density of lightweight aggregate are 7.02 MPa,8.38%,891kg/m³ and 1654 kg/m³,respectively.The phase transition and functional group of lightweight aggregate fired by treated EMR or reated EMR,it can be seen that the main phases are:quartzite(SiO₂),quartz(SiO₂),diopside(Ca Mg Si₂O₆),feldspar(Ca(Al Si₂O₈)),mullite(Al₅SiO_9.5),albite(Na Al Si₃O₈)and anhydrite(Ca SO₄);The SEM results shows that the higher the strength of the lightweight aggregate,the less and smaller the pore size,the more crystals in the pore and less liquid phase.