Adsorption-desorption Characteristics Of Sediment And Remediation Of Contaminated Sediment

Sediment particles widely exist in natural waters such as rivers,lakes and reservoirs,and have an important impact on complex physico-chemical processes.The electrochemical properties of sediment lead to significant adsorption between sediment and pollutants such as nutrients,heavy metals and organic/inorganic pollutants,thus affecting the migration and transformation of pollutants.Sediment is a complex assemblage of various minerals,including quartz,feldspar,oxide,and clay minerals.In this study,we take phosphorus as an example to analyze the interaction between sediment and phosphorus considering the main constituent minerals,and then the remediation methods of contaminated sediment are further explored.The phosphorus adsorption and desorption experiments of natural sediment and its main constituent minerals are conducted,including quartz,hematite,potassium feldspar,calcite,kaolin,illite and montmorillonite,and the contributions of these minerals to the adsorption and desorption properties of natural sediment are analyzed.The results show that different kinds of minerals have great differences in the adsorption capacity and desorption rate of phosphorus.In addition,a formula of phosphorus adsorption is proposed comprehensively considering the intrinsic properties of sediment(e.g.,mineral composition,particle size)and the external environmental factors such as initial aqueous phosphorus concentration,p H,ionic strength,sediment concentration,and organic matter,which can accurately predict the adsorption of phosphorus under different aqueous environments,and provide a basis for phosphorus dynamics prediction.Based on the above adsorption and desorption studies,we further explore the application of n ZVI in the remediation of contaminated sediment.The solidification experiments of the adsorbed phosphorus by n ZVI are conducted to analyze the solidification effects of n ZVI from the view of mineral composition.The results show that the phosphorus solidification rate gradually increases with the increasing amount of n ZVI,which corresponds to a decreasing risk of phosphorus release into the surrounding water.When the amount added is more than 0.30 g,solidification rate tends to be stable(about 86%).It indicating that the risk of phosphorus adsorbed on particles being released into water decreases gradually.It provides a new method for remediation of contaminated sediment.Moreover,a sediment remediation method of Contaminated Sediment Backfill Technology(CSBT)is proposed based on the idea of reducing the contaminated sediment incipient and not causing secondary pollution sources.That is,the dredged sediment is calcined into ceramsite after pretreatment(e.g.dewatering,detoxification),and then backfilled to the dredged area as a sediment cap,which combines the advantages of sediment dredging and in-situ capping.The potential effects and feasibility of sediment remediation by CSBT are also explored through flume experiments.The results show that this method can effectively solve the problem of internal pollution.It uses the dredged sediment from the original area as the capping material,thus avoiding the introduction of foreign materials.Meanwhile,there is no need to occupy a large scale of land,which effectively solves the problem in the treatment of dredged sediment.Overall,the proposed CSBT provides a new method for the remediation of contaminated sediment.