Preparation Of Copper Slag Based Oxalate Chemically Bonded Ceramics And Study Of Solidified Heavy Metals

Copper slag is the waste residue produced in the copper smelting process.With the increasing demand for copper,a large amount of copper slag will be produced each year.So many scholars have studied how to use copper slag,but the current technology for achieving large-scale utilization of copper slag is not yet mature.In this paper,copper chemical bond oxalate ceramics(F-CBOC)were prepared by using copper slag and oxalic acid,which has the characteristics of high early strength,fast solidification and good durability.It provides a new method for the utilization of copper slag.Because F-CBOC contains FeC2O4·2H2O gel,Fe3+ and C2O42-,it can be used for solidification/stabilization of high arsenic slag and heavy metals.(1)The effects of CS/C ratio on the properties of the solidified body were studied.The results showed that CS/C had a significant effect on the compressive strength and the initial setting time of the solidified body.When the CS/C was equal to 100/27.5,the strength of the solidified body reached the maximum value,and the strength of solidified body reached 53.25MPa after natural curing 28d,which exceeded the national requirement for the strength of building materials.The effect of borax on F-CBOC was studied,it was found that the effect of borax on the mechanical properties of F-CBOC was not obvious,but it had a good retardation effect.XRD、FT-IR、TG-DSC and SEM were used to analyse the solidified body,the result showed the main component of F-CBOC was FeC2O4·2H2O in wireless chain structure.Furthermore,FeC2O4·2H2O was insoluble in water,so FeC2O4·2H2O played a strength supporting role in F-CBOC.(2)By examining the high temperature resistance of F-CBOC,the following results could be obtained.When the temperature reached 200℃,the color of the solidified body remained unchanged and the compressive strength was almost unchanged.When the temperature reached 250℃,the color of the solidified block was reddish-brown color,and the compressive strength of the solidified body was remarkably decreased.When the temperature increased to 1000℃,the solidified body did not produce significant cracks.From the above studies,it was known that the compressive strength of F-CBOC was not affected before 200℃.(3)By analyzing the high arsenic slag,it is received that the main compositions are pharmacosiderite and amorphous arsenic compound,and arsenic leaching concentration is as high as 558.8mg/L.The solidification of high arsenic slag has been studied by the traditional cement solidification method,and the results show the maximum capacity of cement is less than 30%.From the study on high arsenic slag by using F-CBOC,it is obtained that the ceramic has good solidification effect on high arsenic slag,the solidified body has higher compressive strength,and the arsenic leaching concentration is far below the national standard.The maximum capacity of F-CBOC is higher than 52%.Firstly,the solidification of high arsenic slag is physical inclusion by FeC2O4·2H2O gel.Secondly,amorphous arsenic compounds was convert Fe4(OH)4(AsO4)3H·5H2O by Fe3+ in F-CBOC,so as to achieve the effect of solidification.(4)The results showed that F-CBOC had good solidification effect on heavy metals Pb and Cu,but the solidification effect on Cd was general.By researching the compressive strength of the solidified body and the solubility of heavy metal oxalate,it could be concluded that the mechanism of heavy metal solidification by F-CBOC was the formation of heavy metal oxalate salt precipitation,followed by physical inclusion using F-CBOC to achieve the purpose of heavy metal solidification.(5)Through the cost analysis,it is reached that the cost of F-CBOC is low,its main significance is energy-saving and environmental protection,aiming to achieve the purpose of using waste to treat waste.So the material has a broad application prospect.