| How to deal with waste steel slag has been a difficult problem of the iron and steel enterprises.The current use of steel slag waste is mainly concentrated in the construction field,but not widely applied in the water treatment area,due to the fact that the ability of pollution removal is severely limited by the of radius of the steel slag.In this study,combined with requirements of the heavy metal pollution in situ remediation of the groundwater Permeable Reactive Barrier(PRB)material,we investigate steel slag,and develop a PRB material that has the ability of heavy metal removal and can overcome the disadvantages of the steel slag,which pro vides a new idea for the utilization of steel slag and for the in situ remediation of groundwater with heavy metal pollution.In this paper,we studythe steel slag systematically,characterizing its surface morphology and its main components,investigating the possibility of leaching of slag in different conditions,and testing the performance of Cu and Pb removalby its ability of adsorption.The results show the following facts: the steel slag used has a large specific surface area and is alkaline in the water;the slag exudes a small amount of chromiumunder acidic conditions,and a large amount of chromium enters the water from the steel slag under strong alkaline conditions;the steel slog has a strong ability of C u and Pb adsorption in water,with fast absorption reaction and high absorption capacity,and the adsorption reaction is endothermic reaction,but the adsorption capacity is obviously reduced with the increase of steel particle size.Because steel slag has the possibility of leaching chromium under extreme conditions and smaller particle size slag has a high adsorption capacity but difficult to be applied in PRB practical engineering,this study will use steel slag fired ceramsite adsorbent as the research target.At the same time,in order to increase the content of effective metal in the ceramsite and enhance the effect of pore.creating,we introduce the sedimentification sludge from a water.supply plant in Jilin C ity as the ceramic material.By orthogonal test,the optimum conditions for the preparation of ceramsite were as follows: the ratio of controlled steel slag,water sludge and clay was 4: 4: 2 by mass;the preheating temperature was 300 ?,the preheating time was 20min;The calcination temperature was controlled at 800 ° C for 25 minutes.The surface of the prepared ceramsite was rough and porous,and the pore volume was large.The feasibility of the adsorbent was determined by toxic leaching experiment.The static and dynamic experiments show thattheceramsite has strong adsorption capacity of C u and Pb.Especially,the maximum adsorption capacity of C u and Pb is 1.2mg/g(C u)and 14.9mg/g(Pb)in static experiment;the adsorption reaction occurred as endothermic reaction,slightly affected by temperature,but affected by the initial p H value.The dynamic adsorption is affectedby the reaction column height,flow rate,the initial concentration of liquid.As effective heightof the reaction column is slowed down,the initial concentration of the feed solution is reduced,the break.through time and the exhaustion time of the reaction column are both delayed,but the maximum removal ability is slightly increased.In the static synchronous adsorption,the ceramsite has stronger affinity to Pb,and there is adsorption competition phenomenon.The total amount of synchronous adsorption is less than that of the adsorption of Pb alone,which is greater than the adsorption capacity of Cu alone.In the dynamic synchronous adsorption,the break.through time of both C u and Pb is earlier than that in the individual dynamic experiments;and the penetration time for C u is earlier than Pb.In the early stage,flow of Cu concentration exceeds the initial concentration of the inflow,and this is due to Pb replacement of Cu.In dynamic experiments,there is still Pb replacement of C u,but it confirms that there exists a small amount of C u adsorption point on the ceramsite.Bythe extraction of ceramsite after the individual adsorption and the synchronous adsorption experiments,we found that the main adsorption points of C u and Pb were different,and the degree of affinity of C u and Pb was different.The adsorption of C u and Pb by steel slag and ceramsite can be described by Langmuir model and Freundlich model.It can be seen that the adsorption of Cu and Pb by ceramsite is more stable than that of pollutant.The results verified the linear expression used by Langmuir fitting in differentconcentration range of the initial solution.The quasi.first.order kinetics and quasi.second.order kinetics of Cu and Pb adsorption by steel and ceramsite have a high precision.The adsorption of C u by steel slag is controlled by chemical adsorption and the adsorption by ceramsite is controlled by physical adsorption.The adsorption of Pb is more consistent with the mechanism of chemical adso rption.The inner diffusion model of steel slag and ceramsite adsorption on both C u and Pb can be fitted into the third order linear equation without passing through the origin,indicating that the adsorption process is affected by the diffusion Rate,but the control conditions are not limited to this.The dynamic adsorption model describesaccurately the dynamic adsorption of Cu and Pb by the ceramsite,and it confirms that the adsorption rate,adsorption capacity and half of the ceramsite permeation time are all controlled bythe influent flow rate,the effective height of the reaction column,and the initial concentration of the solution.It is important to note that simply increasing the thickness of the adsorbent can extend the penetration time,but it cannot take full advantage of the adsorption capacity of the ceramsite.Therefore,using steel slag as a raw material and supplemented with water sludge and clay can make a strong adsorbent material of C u and Pb,and this satisfies the engineering requirement of PRB applications.It benefits relevant enterprises in the making.harmless tasks of the solid waste,also producing economic profits,and thus has a significant practical value. |
PDF Full Text Request