Abstract
Sediment phosphorus (P) removal is crucial for the control of eutrophication, and the in-situ adsorption is an essential technique. In this study, modified maifanite (MMF) prepared by acidification, alkalization, salinization, calcination and combined modifications, respectively, were first applied to treat sediment P. The morphology and microstructure of MMF samples were characterized by X-ray fluorescence (XRF), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET). Various adsorption parameters were tested, such as dosage of maifanite, time, operation pH and temperature. The adsorption mechanisms were also investigated and discussed. Results showed that CMMF-H2.5-400 (2.5 mol/L H2SO4 and calcined at 400 °C) exhibited the highest P adsorption capacity. Thus, it was selected as the in-situ adsorbent material to control the internal P loading. Under the optimal conditions of dynamic experiments, the adsorption rates of TP, IP, OP, Fe/Al-P and Ca-P by CMMF-H2.5-400 were 37.22%, 44.41%, 25.54%, 26.09% and 60.34%, respectively. The adsorption mechanisms analysis revealed that the adsorption of P onto CMMF-H2.5-400 mainly by ligand exchange. Results of this work indicated that the modification treatment could improve the adsorption capacity of maifanite, and CMMF-H2.5-400 could be further applied to eutrophication treatment.
Highlights
Eutrophication has become a worldwide water quality issue[1,2]
modified maifanite (MMF) samples were prepared by various modification methods and applied to adsorb sediment P in all fractions for the first time
The results revealed that the modification treatment could improve the adsorption capacity of maifanite and CMMF-H2.5-400 was selected as the optimal in-suit adsorption material
Summary
Eutrophication has become a worldwide water quality issue[1,2]. Phosphorus (P) is an essential element that can trigger severe eutrophication[3,4]. The sediment plays a great role in the overall P dynamics of water bodies-it may either act as a sink to adsorb P or an internal source to release P on the base of concentration gradients[19]. Reducing internal P loading in sediments has been proposed as an essential technique for eutrophication control[20,21]. Some natural or modified clay minerals selected as P adsorbent materials have been applied to reduce the sediment internal P loading. Maifanite has great surface area and strong adsorption capacity due to the vesicular pores and sponge shaped morphological structure[34,35] It could adsorb P via chemisorption due to the aluminum (Al) and iron (Fe), etc. There is a need to modify RMF to enhance its confined capacity of adsorption
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