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| 1 | Optimized coagulation pretreatment alleviates ultrafiltration membrane fouling: The role of floc properties and slow-mixing speed on mechanisms of chitosan-assisted coagulation显示文摘To alleviate ultrafiltration(UF) membrane fouling, the pre-coagulation of poly-aluminum chloride(PACl) with the aid of chitosan(CTS) was conducted for synthetic humic acid–kaolin water treatment. Pre-coagulation of three molecular weights(MW) CTSs(50–190 kDa(CTSL), 190–310 kDa(CTSM) and 310–375 kDa(CTSH)) was optimized with slow-mixing speeds of 30, 60 and 90 r/min, respectively. The removal efficiency and floc properties as well as membrane fouling were analyzed, and were compared to results obtained by conventional coagulation with PACl. Results showed that variations in floc properties could be ascribed to the coagulation mechanisms of CTS_L/CTS_M/CTS_H at different slow-mixing speeds, resulting in reduced UF membrane fouling. Specifically, at the low speed of 30 r/min, all three CTS types produced flocs with similar properties, while CTSLresulted in the lowest removal efficiency and aggravated irreversible fouling. At the appropriate speed of 60 r/min, CTSMgenerated the most compact flocs with the combined effects of bridging and path mechanisms. The compact cake layer formed could alleviate irreversible fouling,which was beneficial for prolonging the operation of the UF membrane. At the high speed of90 r/min, CTSHformed fragile flocs and aggravated irreversible membrane fouling. We considered membrane fouling to be affected by floc properties and the resultant removal efficiency, which was governed by the MW of the CTS used and the slow-mixing speed applied as well. | Peng Du Xing Li Yanling Yang Zhaoyang Su Hang Li Nan Wang Tingting Guo Tingting Zhang Zhiwei Zhou | 2019 | Journal of Environmental Sciences2019，31，8： | 3 |
| 2 | Floc structure and membrane fouling affected by sodium alginate interaction with Al species as model organic pollutants显示文摘Membrane filtration combined with pre-coagulation has advantages in advanced wastewater treatment. As a model of a microbial polysaccharide, research on the effect of sodium alginate(SA) on alum hydrolysis has been rare; therefore, it is necessary to gain insight into the interface interaction between SA molecules and Al species, and the role SA plays during floc formation. In this study, the interaction mechanism between SA and Al species has been investigated, by evaluating the effect of SA on floc characteristics and membrane fouling during coagulation–ultrafiltration with different Al species coagulants(AlCl3 and preformed Al13). Al 2 p X-ray photoelectron spectroscopy(XPS) confirmed that the complexation of ligands and Al species strongly affects the reaction pathways for Al hydrolysis and the final nature of the flocs, as Al13 can be decomposed into octahedral precipitates when SA is added. The presence of SA can affect floc properties, which have important impacts on the characteristics of the cake layer and membrane fouling. Due to the bridging ability of SA, the floc strength increased by about 50% using Ala, which was much better than preformed Al13, with a percentage increase of only about 6%. Moreover,the recovery factor of HA-flocs was decreased from 96% to 43% with SA addition of 0.5 mg/L.It was concluded that SA can affect the characteristics of the cake layer and membrane fouling through participating in the formation of primary flocs and altering the Al hydrolysis pathway. | Xuejun Xiong Hui Xu Beiping Zhang Xiaohui Wu Hongyan Sun Dongsheng Wang Zhengyang Wang | 2019 | Journal of Environmental Sciences2019，31，8： | 3 |
| 3 | Analysis of influencing factors on fine sediment flocculation in the Changjiang Estuary显示文摘-- Based on the test data in dynamic water and static water, the main factors, which influence the fine sediment flocculation, are analyzed with a gray model method of correlation theory. It is shown that the main influencing factors are water temperature, settling time, salinity, grain size, sediment concentration and current velocity according to the correlation coefficients. Among them, the salinity and the sediment grain size are critical type influencing factors (CrTIF); the settling time, the sediment concentration and the velocity are continuous type influencing factors (CoTIF); and the water temperature has the characteristics of both. When the critical values of CrTIF are reached or exceeded,the fine sediments will be flocculated, but values of CrTIF will not influence the settlement strength of flocs. The influence of CoTIF is continuous. The values of the CoTIF will not only influence the occurrence of flocculation but also the settlement strength of the flocs. | 蒋国俊 姚言明 唐子文 | 2002 | Acta Oceanologica Sinica2002，21，3： | 2 |
| 4 | Coagulation effect and floc properties of polyferric silicate sulphate and polyferric sulphate in the Yellow River water treatment显示文摘Two inorganic polymer coagulants,polyferric silicate sulphate(PFSS) and polyferric sulphate(PFS),were comparatively evaluated in the Yellow River water treatment.The removal efficiency of turbidity and UV254 were investigated,and the zeta potential was measured.An online laser scatter instrument was used to determine the size distribution of flocs formed in the coagulation processes.Compared with PFS,PFSS forms flocs with higher growth rates and larger sizes.The formed flocs were exposed to a series of shear forces,and the floc strength was measured from the relationship between the applied shear speed and the resulting floc size.The flocs formed by PFSS had a higher strength.The floc breakage(expressed as breakage factor,Bf) and re-growth ability(expressed as breakage factor,Rf) under different shear forces and different shear periods were investigated,and it was found that larger Bf and Rf appeared after exposure to stronger shear force and longer shear period.Under the same shear condition,the flocs formed by PFSS showed a larger Bf while the flocs formed by PFS had better re-growth ability. | Cao, Bai Chuan Gao, Bao Yu Yue, Qin Yan Fu, Ying Xu, Chun Hua | 2010 | Science China Chemistry2010，53，3： | 1 |
| 5 | Pretreatment of polyvinyl alcohol by electrocoagulation coupling with catalytic oxidation:Performance,mechanism and pathway显示文摘In this study,various conditions for the removal of polyvinyl alcohol(PVA)by electrocoagulation(EC)coupled catalytic oxidation are systematically studied.The direct oxidation of the anode,the reduction of the cathode,the oxidation of·OH and·Cl,and the synergistic effect of flocculation on the degradation of polyvinyl alcohol are investigated.It is observed that the optimum experimental conditions obtained are as follows:Cell voltage 9 V,natural pH 7,NaCl concentration 0.02 mol/L,and interelectrode distance3.0 cm.The evolution of iron ions is also discussed in the EC process.By contrast,EC had made an outstanding contribution to the removal of PVA,which removes 71.29%of PVA.Free radicals,especially·OH and·Cl,are equivalent to the contribution of the electrodes in the degradation of PVA.And the contribution of PVA degradation by anode oxidation and cathode reduction are 12.76%and 8.02%,respectively.Characterization of solution and floc,such as Fourier transform infrared spectrometry(FTIR),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),thermogravimetric analysis(TGA),GC-MS and molecular weight,showed that PVA is effectively removed by the EC process,and a possible degradation pathway is proposed. | Zhaoyang Wang Xiaolei Teng Mingzheng Xie Xiuwen Cheng Junfeng Li | 2020 | Chinese Chemical Letters2020，31，10： | 0 |
| 6 | Influence of COM-peptides/proteins on the properties of flocs formed at different shear rates显示文摘Coagulation followed by floc separation is a key process for the removal of algal organic matter(AOM) in water treatment. Besides optimizing coagulation parameters,knowledge of the properties of AOM-flocs is essential to maximizing AOM removal.However, the impact of AOM on the floc properties remains unclear. This study investigated how peptides/proteins derived from the cellular organic matter(COM) of the cyanobacterium Microcystis aeruginosa influenced the size, structure, and shape of flocs formed at different shear rates(G). Flocs formed by kaolinite, COM-peptides/proteins and a mixture of the same were studied, and the effect of intermolecular interactions between floc components on floc properties was assessed. The coagulation experiments were performed in a Taylor–Couette reactor, with aluminum(Al) or ferric sulphate(Fe) utilized as coagulants. Image analysis was performed to gauge floc size and obtain data on fractal dimension. It was found that floc properties were affected by the presence of the COM-peptides/proteins and the coagulant used. COM-peptides/proteins increased floc size and porosity and widened floc size distributions. The Fe coagulant produced larger and less compact flocs than Al coagulant. Moreover, the decrease in floc size that occurred in parallel with increase in shear rate was not smooth in progress. A rapid change for the kaolinite-coagulant suspension and two rapid changes for the suspensions containing COM were observed. These were attributed to various intermolecular interactions between floc components participating in coagulation at different G. Based on the results obtained, shear rates suitable for efficient separation of flocs containing COM were suggested. | Monika Filipenska Petra Vasatova Lenka Pivokonska Lenka Cermakova andrea Gonzalez-Torres Rita K.Henderson Jana Naceradska Martin Pivokonsky | 2019 | Journal of Environmental Sciences2019，31，6： | 0 |
| 7 | CHARACTERS OF SEDIMENTATION OF SUSPENSION FLOCCULATED OR COAGULATED显示文摘CHARACTERSOFSEDIMENTATIONOFSUSPENSIONFLOCCULATEDORCOAGULATED￥KangYong;HuXiaomin;DengChanglie;LuoQian(DepartmentofMineralEngin... | Kang Yong Hu Xiaomin Deng Changlie Luo Qian(Department of Mineral Engineering ,Northeastern University,Shenyang 110006) | 1996 | 中国有色金属学会会刊:英文版1996，6，4： | 0 |
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