Effects of calcination on the environmental behavior of sediments by phosphorus speciation and interface characterization

Potential of water sediments in construction materials: Current approaches and critical consideration of future challenges

Human activities result in sediment accumulation, so the reservoirs gradually lose their functionality, impacting their ability to manage large flood inflows, supply water, and generate hydroelectric power. Therefore, periodic removal of sediments from water reservoirs is essential to maintain functionality. Notwithstanding, the management of dredged sediments is a multifaceted process that involves careful consideration of environmental, regulatory, and economic factors to ensure their responsibility and sustainable handling. In this regard, the search for synergies represents an important development factor in the current industrial world, which can bring several benefits, especially in the construction industry. By reusing sediments, the environmental externalities typically associated with building materials production can be reduced by transforming sediments from waste material into valuable resources. The consolidated knowledge in this review emphasizes the advances in the upcycling of dredged sediments into building materials in various ways, including aggregate production, brick manufacturing, traditional binder replacement, and alkaline activation. The provided summary of benefits, disadvantages, challenges, and future potential of freshwater dredged sediments (FDS) use can stimulate the rationalization of material flows, reduce the dependence on primary raw materials in the construction industry, and at the same time contribute to maintaining the functionality of water reservoirs.

Simultaneous immobilization of ammonia and phosphorous by thermally treated sediment co-modified with hydrophilic organic matter and zeolite

The use of calcined sediments (CS) for thin-layer capping is an environment-friendly technology for controlling nitrogen (N) or phosphorus (P) release. However, the effects of CS derived materials and efficiency in controlling the sedimentary N/P ratio have not been thoroughly investigated. While zeolite-based materials have been proven efficient to remove ammonia, it is limited by the low adsorption capacity of PO₄^3-. Herein, CS co-modified with zeolite and hydrophilic organic matter (HIM) was synthesized to simultaneously immobilize ammonium-N (NH₄⁺-N) and remove P, due to the superior ecological security of natural HIM. Studies on the influences of calcination temperature and composition ratio indicated that 600 °C and 40% zeolite were the optimal parameters leading to the highest adsorption capacity and lowest equilibrium concentration. Compared with doping with polyaluminum chloride, doping with HIM not only enhanced P removal but also achieved higher NH₄⁺-N immobilization efficacy. The efficiency of zeolite/CS/HIM capping and amendment in prohibiting the discharge of N/P from sediments was assessed via simulation experiments, and the relevant control mechanism was studied at the molecular level. The results indicated that zeolite/CS/HIM can reduce 49.98% and 72.27% of the N flux and 32.10% and 76.47% of the P flux in slightly and highly polluted sediments, respectively. Capping and incubation with zeolite/CS/HIM simultaneously resulted in substantial reductions in NH₄⁺-N and dissolved total P in overlying water and pore water. Chemical state analysis indicated that HIM enhanced the NH₄⁺-N adsorption ability of CS owing to its abundant carbonyl groups and indirectly increased P adsorption by protonating mineral surface groups. This research provides a novel strategy to control sedimentary nutrient release by adopting an efficient and ecologically secure remediation method to rehabilitate eutrophic lake systems.

Comparison of magnetite, hematite and goethite amendment and capping in control of phosphorus release from sediment

The characteristics and mechanism of phosphate adsorption onto magnetite, hematite and goethite were comparatively studied, and the effects of magnetite, hematite and goethite amendment and capping on endogenous phosphorus (P) liberation from sediment into overlying water (OW) were comparatively investigated. The adsorption of phosphate onto magnetite, hematite and goethite mainly obeyed the inner-sphere complexation mechanism, and the phosphate adsorption capacity decreased in the order of magnetite > goethite > hematite. The magnetite, hematite and goethite amendment all can decrease the risk of endogenous Prelease into OW under anoxic conditions, and the inactivation of diffusion gradients in thin films-labile P in sediment made a great contribution to the restraint of endogenous P release into OW by the magnetite, hematite and goethite amendment. The efficiency of endogenous P release restraint by the iron oxide addition decreased in the order of magnetite > goethite > hematite. The magnetite, hematite and goethite capping all can be effective for the suppression of endogenous P release from sediment into OW under anoxic conditions, and most of P immobilized by the magnetite, hematite and goethite capping layers is relatively or very stable. The results obtained from this work suggest that magnetite is more suitably used a capping/amendment material to prevent P release from sediment than hematite and goethite, and magnetite capping is a promising approach for hindering sedimentary P release into OW.