Preparation Of Cobalt Slag Based Porous Ceramsite Filter Material And Study On Water Treatment Performance

In recent years,with the rapid development of manganese in lithium electricity industry,the amount of cobalt slag was increasing sharply,and cobalt slag recycling method and ability was very limited.How to make full use of these cobalt slag is of great significance to further promote the sustainable and efficient development of cobalt smelting industry in china.ceramsite was one of the fastest developing new materials in recent years,especially its porous interior and shape,and had a certain strength and firmness,because of its excellent performance was widely used in the water treatment industry.At present,it had become a hot topic in domestic and international research that the solid waste was used as biological aerated filter material for wastewater treatment.In this paper,the cobalt slag was analyzed by XRD and XRF.It was found that the cobalt slag contains SiO₂?Al₂O₃ and MgO,which were in line with elements needs by Reily ternary phase diagram to prepare ceramsite,In this study,cobalt slag was used to prepare cobalt slag based porous ceramsite and used as filter material in aerated biofilter,It had found new utilization ways for the cobalt smelting waste which had been difficult to be utilized,and can also achieve the multiple effects of Treating Waste by Waste and reducing the preparation cost of the filter material for water treatment with environmental and economic dual effects.This article is divided into two parts,preparation of sintering-expanded ceramsite and application study in waste water treatment.In the first part,the porous ceramsite was made by using cobalt slag as raw material.A study was conducted on the mass ratio of reaction materials which have been prepared by calcination with cobalt slag,sand,sawdust,NaHCO₃ and Ca?OH?₂.Furthermore,in various tests for the ceramsite,strength was the principal factor to determine the mechanical properties of ceramsite.To choose the most suitable product,porosity,calcination temperature and time were introduced as factors in orthogonal experiment design to determine the preparation of cobalt slag-based porous ceramsite.XRD and SEM were used for the characterization of porous ceramic characteristics.The results showed that the optimized raw materials ratios were the ratio of cobalt residue to sand was 3:1,the weight ratios of NaHCO₃,Ca?OH?₂ and sawdust additions were 6.25%,10%and 25%,respectively.Under the optimum sintering conditions of sintering temperature being 1125^oC,holding time 1 h.Performance indices of ceramsite produced under the best technological condition were as follows:grain diameter was 4⁹ mm,silt carrying capacity was 0.165%,sum of braking and ware rate was 0.057%,solubility in hydrochloric acid was 0.204%,void fraction was53.348%,piled density was 0.691 g/cm³,apparent density was 1.514 g/cm³.All the indexes are satisfied with nation standard Artifical Ceramsite Filter Material for Water Treatment?CJ/T 299-2008?.Analysis by SEM showed that cobalt residue ceramsite had large number of well-distributed,three-dimensional connected pores,which was very suitable for the survival of micro-organnisms.In the second part,cobalt slag-based ceramsites prepared under the best technological condition were used as filter material of Biological Aerated Filter?BAF?to treat domestic sewage.Inculation of biofilm was used as the method of start-up of reactor,which need only 6 days and steady-state operation of BAF for 21 consecutive days.The removal efficiency of pollutants such as NH₄⁺-N,TN and TP were studied under different HRT and C/N ratio.The backwash mode and backwash cycle of BAF were also explored.The results show that BAF has good decontamination effect under the operating conditions of C/N ratio of 4/1 and HRT of 3.22 h.The BAF process is continuously operated for 24 d under optimal operating conditions,Gas-water combined backwash of BAF process at 13 d,the removal rate of NH₄⁺-N,TN and TP in wastewater?NH4+-N is 100 mg/L,TP is 5 mg/L?during the stable operation of the reactor is 96%,61%,95%.respectively,the effluent quality of NH₄⁺-N and TP reached Criteria A of Level?of the Discharge Standard of Pollutants for Municipal Wastewater Treatmentplant?GB 18918-2002?.It is expected to provide a new idea for the advanced treatment of wastewater with low concentration of nitrogen and phosphorus.