Application of novel composite materials as sediment capping agents: Column experiments and modelling

The research objective of the study is the estimation of Phoslock™ as a P&N-inactivation agent in the overlying water and sediment cores under oxic and anoxic conditions from a polluted pond. Phoslock™ was compared with ferrihydrite, unmodified bentonite (N-Bentonite), natural Zeolite (N-Zeolite), Alum and commercial Z2G1™. Under oxic conditions, the maximum sorption capacities (qm) calculated from the Langmuir model were 14.1, 12.4, 11.2, 9.1 and 3.7 mg g–1 for ferrihydrite, Phoslock™, alum, Z2G1, and natural bentonite, respectively. However, under anoxic conditions the maximum sorption capacities followed the order: Phoslock™ > alum > Z2G1>ferrihydrite > N-bent onite. Moreover, Phoslock™ as a P-inactivation agent resulted in about ~81% and ~82% reduction of the phosphate flux from oxic and anoxic sediments respectively. Also, the effect of dissolved organic matter (DOM) on phosphate sorption capacity (PAC) of Phoslock™ and Z2G1 was studied experimentally and theoretically, simulating natural eutrophic waters. At both P-sorption agents by increasing the concentration of DOM, the sorption capacity is declined. However, it is noteworthy that in the case of Phoslock™ application the PAC is retarded, whereas in the case of Z2G1 is sharp. Furthermore, the results unveiled that Phoslock™ restrained P release from the sediments, therefore a portion of P-mobile is reduced in sediments and undergone transformation to non-reactive species. Finally, in economic terms the research outcomes of this study were verified by literature, where we reported that the concentration of 20.53 mg mobile P kg–1 can be feasibly treated for $30.53 kg–1 of Phoslock™ applied.