Experimental Investigation of Phosphorus Release from Haihe River Sediments Capped by Natural Zeolites and Its Modified Ones

Abstract

Due to its economic and environmental benefits, increasing attention is being placed on capping as a relatively new option in managing both contaminated sediments and dredged materials. In this study, three barriers were studied by the use of short-term batch experiments and long-term sediment incubation experiments in order to prevent P release from Haihe River sediments. They are natural zeolite, surfactant-modified zeolite (SMZ) and aluminum modified zeolite. Batch experiments of phosphate adsorption on zeolites showed that Frundlich adsorption isotherm was the best in fitting for experimental data. Both SMZ and the aluminum modified zeolites showed higher adsorption capacity than natural zeolites, and adsorption capacity was in the order of SMZ > aluminum modified zeolites > natural zeolites. A system including sediment, water and capping materials was designed for the incubation experiment to clarify the release of phosphorus from sediments under anaerobic condition. The incubation experiments were performed at the acidity of overlying water pH7, room temperature 25 °C, and lasted for three months. With the same amounts of the three capping materials applied respectively to the system, efficiency of phosphorus inactivation was in the order of SMZ > aluminum modified zeolites > natural zeolites, which was in consistent with the adsorption capacity of the three materials. The inactivation of phosphorus was mainly caused by the covering effect, co-precipitation effect and adsorption effect of the capping materials.