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Wang S.,Zhejiang University | Xu H.,Environmental Science Research and Design Institute of Zhejiang Province | Yao P.,Zhejiang Test Academy of Quality and Technical Supervision | Chen X.,Zhejiang University
Electrochemistry | Year: 2012

Seawater can be used as an electrolyte for Cl 2 evolution, and proper selection of electrode materials is of great importance. In this paper, a new type of dimensionally stable anodes, Ti/RuO 2-IrO 2-Sb 2O 5-SnO 2, was investigated for Cl 2 evolution from seawater. The physicochemical and electrochemical properties were examined, and the electrocatalytic activity for Cl 2 evolution was measured under different conditions. It was shown that the RuO 2-IrO 2Sb 2O 5-SnO 2 coating was compact in microstructure. The current efficiency was 71.2-86.7%, depending on the operational conditions. The anodes were predicted to be able to work effectively for over 6 years at a current density of 1500Am -2 for seawater electrolysis. © The Electrochemical Society of Japan All rights reserved.

Lin H.,Zhejiang Normal University | Zhang M.,Zhejiang Normal University | Mei R.,Environmental Science Research and Design Institute of Zhejiang Province | Chen J.,Zhejiang Normal University | Hong H.,Zhejiang Normal University
Bioresource Technology | Year: 2014

This study proposed a novel approach for quantitative evaluation of the physicochemical interactions between a particle and rough surface. The approach adopts the composite Simpson's rule to numerically calculate the double integrals in the surface element integration of these physicochemical interactions. The calculation could be achieved by a MATLAB program based on this approach. This approach was then applied to assess the physicochemical interactions between rough membrane surface and sludge foulants in a submerged membrane bioreactor (MBR). The results showed that, as compared with smooth membrane surface, rough membrane surface had a much lower strength of interactions with sludge foulants. Meanwhile, membrane surface morphology significantly affected the strength and properties of the interactions. This study showed that the newly developed approach was feasible, and could serve as a primary tool for investigating membrane fouling in MBRs. © 2014 Elsevier Ltd.

Gong M.,Hohai University | Zhu W.,Hohai University | Xu Z.R.,Hohai University | Xu Z.R.,Environmental Science Research and Design Institute of Zhejiang Province | And 2 more authors.
Renewable Energy | Year: 2014

In the present study, ten different types of dewatered sewage sludges were treated in supercritical water in a high-pressure autoclave under a given condition (at 400°C, 60min and 23MPa). The feasibility of direct gasification and the effect of sludge properties on the gasification of dewatered sewage sludge with various properties in supercritical water were investigated. The results showed that dewatered sewage sludge with various water contents (73.48-88.51wt%), organic matter contents (29.25-73.02wt%, on dry basis) and inorganics can be directly gasified in supercritical water. The total gas and phenol production increased linearly with the increment of organic matter content in dewatered sewage sludge. The difference in hydrogen content in the gaseous product may be related to the content of water and inorganic as well as pH value of the sludge. The char/coke formed in the solid residue increased with decrement of water content, which inhibited the gasification reaction and resulted in the carbonization reaction. © 2014 Elsevier Ltd.

Xu Z.R.,Hohai University | Xu Z.R.,Environmental Science Research and Design Institute of Zhejiang Province | Zhu W.,Hohai University | Li M.,Hohai University | And 2 more authors.
Applied Energy | Year: 2013

Hydrogen gas has been successfully produced from sewage sludge by supercritical water gasification. Therefore, whether toxic compounds are synthesized in the supercritical water gasification of sewage sludge should be clarified because of the complex pollutants in sludge. In the current study, the content and forms of polycyclic aromatic hydrocarbons (PAHs) in the solid residue from the supercritical water gasification of wet sludge was investigated using a high-pressure autoclave. The process parameters, such as reaction temperature (400-455 °C), reaction time (0-60. min), dry matter content (5.6-23.8. wt%) in the feedstock, and heating period, were varied to investigate their effects on the PAH content and forms. The results showed that PAHs are generated during supercritical water gasification and that high reaction temperature, long reaction time, and low dry matter content favor the formation of PAHs in the solid residue, mainly involving 4-ring PAHs. Moreover, the amount of total PAHs in the solid residue did not exceed the allowable limits of soil quality assessment for exhibition (B class) in China and meets the Canadian soil quality for commercial land use. In addition, the mechanism of PAH formation during supercritical water gasification was discussed in this paper. © 2012.

Xu Z.R.,Environmental Science Research and Design Institute of Zhejiang Province | Xu Z.R.,Hohai University | Zhu W.,Hohai University | Gong M.,Hohai University | Zhang H.W.,Hohai University
International Journal of Hydrogen Energy | Year: 2013

In the present study, the catalytic effects of alkali salts [NaOH, KOH, K2CO3, Na2CO3 and Ca(OH) 2] on the direct gasification of dewatered sludge in supercritical water were investigated by using a high-pressure autoclave at a constant temperature of 450 °C and a residence time of 30 min. The hydrogen yield increased in the presence of the alkali salts, except for Ca(OH)2. Specifically, the hydrogen yield increased from 0.68 to 3.45 mol/(kg OM) as the K2CO3 concentration increased from 0 to 8 wt%. Although Ca(OH)2 did not significantly impact the catalytic effect on the hydrogen yield, it did impact the CO2 yield. Generally, the addition of alkali salts did not affect the organic matter or total phenol concentrations in the liquid residue. Moreover, char formation was considerably suppressed by the alkaline catalyzed hydrolysis of the dewatered sludge [except in the case of Ca(OH)2]. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Li L.,Hohai University | Xu Z.R.,Hohai University | Xu Z.R.,Environmental Science Research and Design Institute of Zhejiang Province | Zhang C.,Hohai University | And 2 more authors.
Bioresource Technology | Year: 2012

Solid residues (SRs) are important byproducts of sub- and super-critical water gasification of sewage sludge (SS). In this study, the quantitative evaluation of heavy metals (HMs) in SRs, compared with SS, is applied in terms of potential ecological risks, pollution levels, and both bioavailability and eco-toxicity. The results show the bioavailability and eco-toxicity of HMs in SRs decrease, although the total concentration of HMs increased, particularly in the bioavailable fraction of Cu, which decreased nearly 97%. The geo-accumulation and potential ecological risk index indicated that the gasification process increased contamination by two levels (to the maximum), while the overall risk was in keeping with SS. However, based on the risk assessment code, each tested HM exhibited lower environmental risk after gasification, especially for Cd, which drastically dropped from 66.67 (very high risk) in SS to 0.71 (no risk) in SRs, with a reaction temperature of 375. °C for 60. min. © 2012.

Bai J.,Environmental Science Research and Design Institute of Zhejiang Province | Xu H.,Environmental Science Research and Design Institute of Zhejiang Province | Zhang Y.,Environmental Science Research and Design Institute of Zhejiang Province | Peng Z.,Environmental Science Research and Design Institute of Zhejiang Province | Xu G.,Environmental Science Research and Design Institute of Zhejiang Province
Biochemical Engineering Journal | Year: 2013

A pilot-scale hybrid hydrolysis acidification reactor (HHAR) with periodic water allocation mode operation followed by sequencing batch reactor (SBR) in anoxic and aerobic metabolic function was evaluated for the treatment of low-biodegradable combined industrial and domestic wastewater. The HHAR combines the advantages of both the UASB reactor and AF, omitting the three-phase separator. Furthermore, it has lower average up-flow velocity (0.38-0.92m/h) and higher periodic up-flow velocity (6m/h), which made the reactor keep higher MLSS concentration (more than 10,000mg/L) and sludge-bed is in periodic " expansion-sedimentation-expansion" state. When HRT less than 10h, the B/C variation was positive and reached the maximum value of 0.07 at 8h. SBR with a total cycle period of 4.5h was applied as the post-treatment process to remove residual COD, NH3-N and TN. At steady stage, the pilot-scale SBR effluent COD, NH3-N and TN concentration was 65, 0.75 and 17.71mg/L, corresponding in this case to full-scale SBR plant effluent was 93, 16.4 and 34mg/L. Comparison results indicated that the application of HHAR-SBR system to treat combined industrial and domestic wastewater can improve effluent quality significantly. © 2012 Elsevier B.V.

Ling Y.,Zhejiang University | Xu H.,Environmental Science Research and Design Institute of Zhejiang Province | Chen X.,Zhejiang University
Chemical Engineering Science | Year: 2015

Degradation of organic pollutants using electrochemical method has obtained great attentions in recent years. Up to now, most works have focused on electrode property improving and pollutant degradation efficacy examining, but very few efforts have been paid to the electrochemical reactor investigation. This article presents a novel continuous multi-cell electrochemical reactor, which consists of ten serially connected cells using PbO2/Ti anode and stainless steel cathode with a short electrode gap of only 2mm. Hydraulic characteristics of the reactor were investigated using the residence time distribution (RTD) studies. The low dispersion number, 0.06, and Morrill dispersion index (MDI), 1.91, indicate that the reactor is close to a plug-flow reactor (PFR). Electrolysis of 50mg/L synthetic phenol wastewater was conducted using the multi-cell reactor at a current density of 10mA/cm2, a retention time of 100min and an electrolyte conductivity of 2.5mS/cm, and the chemical oxygen demand (COD) of the effluent was only 16mg/L. During the electrolysis process, the applied voltage in each cell kept stable at a low value of 3.4V. A comparison between the multi-cell reactor and the conventional single cell reactor for wastewater treatment under the same operating conditions showed that the multi-cell reactor performed much better than the single-cell reactor. For treating 500mg/L phenol wastewater, the effluent COD of the single-cell reactor was 534mg/L, with a current efficiency of only 19.9%. On the contrary, the effluent COD of the multi-cell reactor was 242mg/L and the current efficiency could reach 71.8%. © 2014 Elsevier Ltd.

Zhang M.,Zhejiang University | Wei Y.,Environmental Science Research and Design Institute of Zhejiang Province | Huang M.,Zhejiang University
Advanced Materials Research | Year: 2012

Degradation of dye wastewater was studied by using nano-ferrous modified bentonite as the heterogeneous catalyst for a Fenton-like oxidation. By comparing the effect of homogeneous Fenton reactions as well as heterogeneous Fenton-like process for nano-modified bentonite, it is found that the advanced oxidation processes assisted by nano-ferrous/bentonite complexes exhibit the stronger degradation capacity. And the removal rate of Fenton-like reaction increased from 23.6% to 75.5% when the ferrous concentration increasing from 20 to 100mmol/L. Being compared with homogeneous Fenton reactions, 20% increased degradation efficiencies is obtained by Fenton-like oxidation process for nano-modified bentonite under 6g nano-ferrous/bentonite complexes in 100mL dye wastewater. © (2012) Trans Tech Publications, Switzerland.

Liang D.,Zhejiang University | Gao J.,Zhejiang University | Wang J.,Zhejiang University | Chen P.,Zhejiang University | And 2 more authors.
Catalysis Communications | Year: 2011

A series of carbon supported bimetallic Pt - Cu catalysts were prepared and used for glycerol oxidation with oxygen in a base-free aqueous solution. It was found that bimetallic Pt - Cu/C was more active than monometallic Pt/C towards selective oxidation of glycerol to glyceric acid. The selectivity of free glyceric acid reached 70.8% at an 86.2% conversion of glycerol over 5Pt - Cu/C. Highly dispersed bimetallic Pt - Cu nanoparticles with small particle size in dominant alloyed phase of PtCu3 were confirmed by XRD and TEM in the bimetallic Pt - Cu/C catalyst, which is proposed to contribute to the improved performance. © 2011 Elsevier B.V. All rights reserved.

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