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Meng J.,Key Laboratory of Marine Chemistry Theory and Technology | Meng J.,Ocean University of China | Yao Q.,Key Laboratory of Marine Chemistry Theory and Technology | Yu Z.,Key Laboratory of Marine Chemistry Theory and Technology
Ecological Engineering | Year: 2014

Phosphorus (P) speciation in size-fractionated sediments was studied, and the phosphate adsorption characteristics associated with grain size were investigated in the laboratory. Detrital P (De-P) was the most abundant form and had the highest proportion of total P (TP), followed by organic P (Or-P). Bioavailable P (BAP) was much more concentrated in fine sediments than sandy sediments, which meant that fine sediments played a dominant role in P transfer from sediments to overlying water and/or ambient pore water. Native adsorbed phosphorus (NAP) was close to the exchangeable P (Ex-P) concentrations in sediments. The adsorption capacity was 116.0, 84.8, 73.6 and 50.0μgg-1 for fine silt, medium silt, coarse silt and sand, respectively. The zero equilibrium phosphate concentration (EPC0) values obtained from the adsorption isotherms of size-fractionated sediments from the same sampling site were very close in value (55.0, 54.9, 51.7 and 49.0μgL-1 for fine silt, medium silt, coarse silt and sand, respectively), revealing a potential method for predicting the phosphate concentrations of overlying water and/or ambient pore water, which were also considered to be the equilibrium concentrations of phosphate through long-term adsorption and desorption processes by sediments. The adsorption capacity, adsorption rate and NAP were all largely controlled by sediment grain size. Based on our data, the maximum total phosphate adsorption amount (TQmax) of fine sediments (<32μm) was almost six times as large as that of sediments larger than 32μm. Due to the much higher phosphate adsorption capacity of fine sediments, compared to the sandy sediments, the mud belt in the East China Sea (ECS) inner shelf should play a key role in controlling the phosphate concentration in the overlying water and/or ambient pore water and may act as an efficient "trapper" for the overloaded phosphate discharged by the Changjiang, greatly reducing the risk of eutrophication on the outer shelf of the ECS. © 2014 Elsevier B.V. Source


Xu Y.,Key Laboratory of Marine Chemistry Theory and Technology | Wang M.,Key Laboratory of Marine Chemistry Theory and Technology | Ma Z.,Ocean University of China | Gao C.,Ocean University of China
Desalination | Year: 2011

In this study, the surface charged and structural information of sulfonated polyethersulfone nanofiltration membrane are acquired through the analysis on the relevant electrochemical impedance spectroscopies (EIS) expressed in terms of dispersions of the impedance with frequency (1KHz-1MHz). The measurements are performed in the different electrolyte solutions (NaCl, MgCl2, LaCl3, KCl, K2SO4, and K3PO4) with different concentrations ranging from 1×10-4mol/L to 6×10-3mol/L. After that, the corresponding equivalent circuit as a theoretical model is set up. Experimental results indicate that the resistance of active layer is influenced by the concentration and ion species of electrolytes, while the capacitance is independent of them. For different cations and anions the corresponding resistances of the active layer take on a sequence of SO4 2->Cl->PO4 3- and Na+>La3+>Mg2+ respectively, which is in well agreement with the variation trend of ion retention, especially for monovalent and divalent ions. Furthermore, the thickness of the active layer in the working state is estimated from the capacitance values and compared with the result obtained by SEM. On the basis of the above, it is reasonable to think that EIS can be used for online analysis in membrane process. © 2010 Elsevier B.V. Source


Xu J.,Key Laboratory of Marine Chemistry Theory and Technology | Ruan G.,Institute of Seawater Desalination And Multipurpose Utilization | Zou L.,University of South Australia | Gao C.,Key Laboratory of Marine Chemistry Theory and Technology
Desalination | Year: 2010

Bio-fouling results in deterioration of permeate quality and flux in reverse osmosis (RO) process. Cellulose triacetate hollow fiber membrane used for RO in SWRO has anti-chlorine property that makes technical sense compared to polyamide spiral-wound RO for overcoming bio-fouling. Mode of chlorine injection is the controlling factor of sterilization in SWRO system. This work evaluated the effects of five different modes of chlorine injecting system as well as HCl injection on the performance of HF RO system. In addition, effects of HCl and anti-scalants on anti-scale performance of HF RO system were also investigated, respectively. A brief list of chemical costs under different abovementioned operating conditions was covered in a cost analysis. The results indicated that the injecting mode that employed continuous chlorine with a relatively low concentration of 0.3-0.4 mg/L at pH 5.8-6.2 was preferable in the aspects of total bacterial count (TBC) removal, permeate flow rate, differential pressure, permeability (Pp), performance factor (η) and chemical costs. HCl injection could improve the sterilization and prevent scaling on the membrane surface efficiently. The expense of anti-scalant (MDC220) was higher than HCl. © 2010 Elsevier B.V. All rights reserved. Source


Li J.-B.,Key Laboratory of Marine Chemistry Theory and Technology | Zhang G.-L.,Key Laboratory of Marine Chemistry Theory and Technology | Zhang J.,East China Normal University | Liu S.-M.,Key Laboratory of Marine Chemistry Theory and Technology | Ren J.-L.,Key Laboratory of Marine Chemistry Theory and Technology
Continental Shelf Research | Year: 2010

Matrix bound phosphine (MBP), a kind of chemically reduced phosphorus, has received limited attention in prevailing modeling of the phosphorus biogeochemical cycle. MBP has been found to occur in marine sediments. MBP in the sediments of the Yellow Sea and its coastal areas was measured by gas chromatography from 2004 to 2007. MBP levels in surface sediments were 0.19-38.24 ng kg-1 in the shelf of the Yellow Sea, 0.34-17.15 ng kg-1 in the Jiaozhou Bay, 2.11-71.79 ng kg-1 in the Sanggou Bay and 0.28-319.32 ng kg-1 in the rivers around the Jiaozhou Bay. High levels of MBP occurred in the northern and middle areas of the Yellow Sea. Obvious seasonal variation of MBP was observed in surface sediments of the Sanggou Bay, with the highest MBP level occurring in summer and the lowest in winter. MBP in surface sediments of the inner Jiaozhou Bay was higher than those in the outer region. MBP levels increased with depth in the top 5-10 cm sediments of the Jiaozhou Bay and on the intertidal flats. Environmental factors such as type of sediments, temperature, organic matter and human activity were found to affect the concentrations and distribution of MBP in marine sediments. © 2010 Elsevier Ltd. All rights reserved. Source


Zhou C.,Key Laboratory of Marine Chemistry Theory and Technology | Zhou C.,Ocean University of China | Gao X.-L.,Key Laboratory of Marine Chemistry Theory and Technology | Gao X.-L.,Ocean University of China | And 4 more authors.
Desalination | Year: 2013

A novel composite nanofiltration membrane was prepared from O-carboxymethyl chitosan (O-CMC) and epoxy chloropropane (ECH) through coating and chemical cross-linking reaction on the polyacrylonitrile (PAN) supporting layer. O-CMC was synthesized from chitosan and monochloroacetic acid. Chemical structures and compositions of O-CMC and NF membranes were characterized by infrared spectroscopy, and morphological structures were characterized by atomic force microscopy and field emission scanning electron microscopy. Permeation performance of NF membranes was examined with a cross-flow flat NF membrane device. Preparing conditions of NF membranes were optimized by studying the change of salt rejection and permeation flux, and the optimum conditions were determined as follows: casting solution concentration 3wt.%, ECH concentration; 2wt.%, cross-linking temperature; 50°C and cross-linking time; 12h. Furthermore, properties of the optimal NF membrane were tested in different operating conditions. At 0.5MPa and 25°C, its salt rejection and permeation flux to 1000mg·L-1 Na2SO4 aqueous solution were 94.36% and 16.78L·m-2·h-1, respectively. Rejections of the membrane to different inorganic electrolyte solutions (1000mg·L-1) accorded with the following order: Na2SO4>NaCl>MgSO4>MgCl2. In addition, the MWCO was about 689Da, and the zeta potentials were negative in experimental pH range. At last, good durability and stability were exhibited by the means of long-term operation during 2weeks. © 2013 Elsevier B.V. Source

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