Research On Preparation,Characterization And Application Of Pyrite Tailings Unburned Ceramsite

In the presented research,pyrite tailings were employed as the basic material for preparation of Pyrite Tailings Unburned Ceramsite(PTUC)through extruding granulation,steam curing and natural air drying.Response Surface Methodology(RSM)was used to optimize the preparation conditions,and the surface morphology as well as the pore structure of PTUC were characterized with XRD,BET and SEM.The adsorption performance of PTUC on total phosphorus was investigated,and a dynamic adsorption-biodenitrification coupling system was constructed to evaluated the application potential of PTUC in the treatment of municipal sewage tail water.The main conclusions are as follows:(1)The optimized preparation process of PTUC is as follows:84.5 g pyrite tailings,10 g cement,1 g quicklime,1 g gypsum,3 g dry sludge and 0.5 g sodium bicarbonate per 100g raw material;After the raw materials was mixed evenly,water was added to granulate materials into spherical particles,then the particles were naturally air-dryed for 12h,subsequently maintained with steam curing at 100℃ for 10h and sprinkling water for 2d.The porosity of obtained PTUC is 60.61%which also presented an 88.55%removal rate of total phosphorus.(2)The apparent density of PTUC is 3.22 kg/m3,bulk density is 1.38 kg/m3,cylinder compression strength is 1.80 MPa,water absorption rate is 25.08%,mud content is 0.54%,void rate is 53.9%,breakage and wear rate is 2.08%,specific surface area is 7.21 m2/g.The original PTUC is mainly composed of FeS2,CaSO4 and SiO2,while cobalt phosphide sulfide(CoPS)crystal was observed in the phosphorus loaded PTUC.PTUC is a mesoporous material with a pore size of 1.7-10.4 nm.(3)The adsorption of total phosphorus by PTUC was preferred in weak acid aqueous,and the optimal pH is 6,and the optimal dosage is 17 g/mgP;the pseudo-first-order kinetic model fitted the removal process of total phosphorus by PTUC well,which indicating the mainly contribution of chemical adsorption.The thermodynamic study indicated the adsorption process was an endothermic process and the well description by Langmuir model indicated the adsorption is monolayer adsorption process.Anions such as Cl-,NO3-and SO42-have no significant effect on the adsorption of total phosphorus by PTUC;the saturated PTUC can be regenerated by 0.5 mol/L sodium hydroxide.(4)In the dynamic adsorption process,the effluent concentration of PTUC was stable at about 0.20 mg/L when HRT was set as 3 h.The optimal HRT of deep bed denitrification filter is 8 h.When the average concentrations of TN and NO3-N in influent are 9.84 mg/L and 7.35 mg/L respecitvely,the average removal rates of TN and NO3--N are 72.40%and 94.59%as the HRT was 8 h.(5)The calculated production cost of PTUC is about 493.92 yuan/ton and the net income is 306.08 yuan/ton(800 yuan/ton according to the market price),which indicating the considerable economic benefits for application of PTUC.