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Synthesis and flocculation of Polyacrylamide with Low Water Absorption for Non-dispersible Underwater Concrete

Journal of Wuhan University of Technology(Materials Science) 2023年第6期38卷 1404-1413页

作者： LI Hongling YAN Na SUN Guowen ZHENG Haorui YANG Xinyu Depantment of Chemistry and Miaterials Engineering Xinxiang Normal CollegeXinxiang 453003China School of Materials Science and Engineering Shijiazhuang Tiedao UniversityShijiazhuang 050043China Hebei Key Laboratory of Advanced Materials for Transportation Engineering and Environment Shijiazhuang 050043China

The polyacrylamide which is directly added into concrete shows strong water absorption property.Thus the construction of underwater constructure would demand high amount of water,resulting in poor workability of concrete and strength shrinkage after hardening.Herein,a kind of anionic polyacrylamide(APAM)grafted with water reducing functional group(-COOH)was synthesized at low temperatures by partial factor design and response surface design.The structure and morphology of APAM were characterized by UV,FTIR and SEM methods.The experimental results show that the molecular weight of the synthesized APAM could reach 11 million,under the condition that the temperature was 35℃,the pH value was 8,the monomer concentration was 27wt%,the initiator dosage was 0.6wt%,and the monomer ratio(n(AM):n(AA))was 3.When the APAM was applied into the underwater slurry,it presented good flocculation and low water demand.When the dosage was 1%of the mass of the cement,the water demand increased by 12%,which could meet the self-leveling and anti-dispersity of the underwater slurry at the same time.This technology provides technical guidance for the large-scale industrial production of polyacrylamide for underwater concrete construction while achieving environmental protection during production.

关键词： non-dispersible underwater concrete anionic polyacrylamide partial factor design response surfacedesign flocculation

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Experimental study on the effect of hydrodynamic conditions on flocculation and settling properties of fine-grain sediment

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International Journal of Sediment Research 2023年第6期38卷 821-833页

作者： Bismark Odum Chunyang Xu Yongping Chen Yinpeng Yao Yan Zhou The National Key Laboratory of Water Disaster Prevention Hohai University College of Harbor Coastal and Offshore Engineering Hohai University School of Engineering University of Liverpool

The flocculation of cohesive sediment particles is a function of the collision efficiency of sediment particles,which is mainly influenced by local flow hydrodynamics.A detailed study on local hydrodynamic characteristics in a novel stirred tank was done to measure the flow field of a turbulent flow.Instantaneous flow velocity fields were obtained and processed,and the average flow field was computed.Particle image velocimetry(PIV) results measuring the hydrodynamic characteristics(expressed as turbulent kinetic energy(TKE),local dissipation rate of TKE,velocity gradient or shear rate,turbulent shear stress,etc.) were analyzed and discussed.Particle tracking and automated image processing techniques were utilized to analyze the impact of the hydrodynamic conditions on the floc and settling properties.The differences in floc properties under the two turbulent shear states(i.e.,steady-state(SS)and unsteady-state(US)) hydrodynamic conditions were examined.The results show that floc size and floc size distribution(FSD) of pure kaolin clay flocs are significantly influenced by the local dissipation rate of TKE and the turbulent intensity states.The floc size,df,84,at local dissipation rate of TKE of11×10-4,29 × 10-4,44 × 10-4,83 × 10-4,and 142 × 10-4m2/s3is 97,108,107,124,and 150 μm.respectively.It was found that by increasing the local dissipation rate of TKE,the FSD was skewed left.The US shear condition generated larger flocs(and in higher proportions) relative to the SS condition.The settling velocity and flux settling velocities of flocs formed under SS conditions are higher than those formed under US conditions.The fractal dimension of SS flocs also is higher than the fractal dimension of US flocs.These results highlight a significant impact of the states of hydrodynamics on floc properties such as floc size and FSD as well as the settling and morphological properties of flocs.

关键词： Floc size flocculation Settling velocity Turbulent kinetic energy Turbulent shear rate

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flocculation and magnetically-assisted sedimentation of size-sorted beidellite platelets mixed with maghemite nanoparticles

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Nano Research 2020年第11期13卷 3001-3011页

作者： Sofia Housni Sébastien Abramson Jean-Michel Guigner Pierre Levitz Laurent Michot Laboratoire de PHysico-chimie des Electrolytes et Nanosystèmes InterfaciauX(PHENIX UMR 8234 Sorbonne Université-CNRS)Sorbonne UniversitéParis75252France Institut de Minéralogie de Physique des Matériaux et de Cosmochimie(IMPMC UMR 7590Sorbonne Université-IRD-CNRS-MNHN)Sorbonne UniversitéParis75252France

In this study,the flocculation and the subsequent decantation step of mixed suspensions of 10 nm-sizedγ-Fe_(2)O_(3) magnetic nanoparticles and 500 nm-sized beidellite clay platelets was investigated.This work may find application in the field of water treatment,specifically the flocculation processes with magnetically assisted sedimentation.After a short description of the preparation and characterization of the raw materials(nanoparticles and clays),the influence of several parameters(pH,concentrations of nanoparticles and clays etc.)on the amount of flocculated materials was examined,which gave information on the concentration ranges allowing a complete flocculation,together with a better understanding on the interactions between nanoparticles and clays responsible for flocculation.The optimal conditions for magnetically assisted settling were then determined by comparing for each sample sedimentation velocities under gravity and in the presence of a Nd-Fe-B magnet.Finally,the complex multiscale structure of the flocs in water was explored,through the measurement of several bulk properties(zeta-potential and volume measurements,laser granulometry),while the organization of the materials at a microscopic scale was investigated by cryo-transmission electron microscopy(cryo-TEM)and small-angle X-ray scattering(SAXS).

关键词： magnetic separation nanoparticles clay flocculation decantation characterization

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Novel synthesis of aluminum hydroxide gel-coated nano zero-valent iron and studies of its activity in flocculation-enhanced removal of tetracycline

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Journal of Environmental Sciences 2020年第3期32卷 194-205页

作者： Xiangyu Wang Binbin Zhang Jun Ma Ping Ning Faculty of Environmental Science and Engineering Kunming University of Science and TechnologyKunming 650500China School of Environment Harbin Institute of TechnologyHarbin 150090China

A newly designed aluminum hydroxide gel-coated nanoscale zero-valent iron(AHG@NZVI)with enhanced activity and dispersibility of NZVI was successfully synthesized.The AHG@NZVI composite was synthesized via control of the surface AHG content.AHG@NZVI-1,AHG@NZVI-2 and AHG@NZVI-3 were prepared under centrifugal mixing speeds of 1000,2000 and 4000 r/min,respectively.The activity of AHG@NZVI was evaluated by its tetracycline(TC) removal efficiency.The effects of AHG content,pH value,reaction temperature,and presence of competitive anions on TC removal were investigated.TC could be removed by both adsorption and chemical reduction on AHG@NZVI-2(centrifugal speed 2000 r/min) in a short time with high removal efficiency(≥98.1%) at the optimal conditions.Such excellent performance can be attributed to a synergistic interaction between aluminum hydroxide gel and NZVI:(1) AHG could enhance the stability and dispersity of NZVI;(2) aluminum hydroxide gel could absorb a certain amount of TC and Fe^2+/Fe^3+,which facilitated the mass transfer of TC onto the NZVI surface,resulting in acceleration of the reduction rate of TC by the AHG@NZVI composite;and(3) AHG-Fe^2+/Fe^3+could absorb a certain amount of TC by flocculation.The kinetics of TC removal by AHG@NZVI composite was found to follow a two-parameter pseudo-first-order model.The presence of competitive anions slightly inhibited the activity of AHG@NZVI systems for TC removal.Overall,this study provides a promising alternative material and environmental pollution management option for antibiotic wastewater treatment.

关键词： Nanoscale zerovalent iron Aluminum hydroxide gel Synergistic effect Tetracycline flocculation

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Analysis of floc morphology in a continuous-flow flocculation and sedimentation reactor

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Journal of Environmental Sciences 2017年第2期29卷 268-275页

作者： Pengfei Ren Jun Nan Xinran Zhang Kai Zheng School of Municipal and Environmental Engineering Harbin Institute of TechnologyHarbin 150090China State Key Laboratory of Urban Water Resource and Environment Harbin Institute of TechnologyHarbin 150090China

The floc morphology was investigated in a continuous-flow reactor, in order to understand the evolution of flocs in practical flocculation and sedimentation processes in water utilities. Kaolin-humic acid suspension was used as the test water, and polyaluminum chloride was chosen as the coagulant. An in-situ recognition system was applied to analyze the floc size, boundary fractal dimension, and eccentricity ratios. Particle numbers and turbidity were also determined in the sedimentation stage. At a coagulant dose of 1 mg/L as Al, the average floc size increased from 62 to 78 μm and the boundary fractal dimension was around 1.14, suggesting that flocs were compact and continuously grew during the entire flocculation process. However, with the dose increased to 5 mg/L, the average floc size decreased and stabilized at around 65 μm, with the fractal dimension of 1.20. It can be concluded that the excess coagulant doses resulted in the formation of chain-shaped, lower density, and more branched structure flocs, thereby restricting flocs’ further growth in the subsequent flocculation. Floc morphology analysis suggested that charge neutralization dominated in the initial flocculation stage, then the bridge and sweep mechanisms were dominant in the subsequent flocculation. In addition, compared with the traditional inclined plate settler, a novel V-shaped plate settler introduced in this study had an advantage in small size floc（less than 5 μm） removal. The V-shaped region could promote aggregate restructuring and re-flocculation; therefore, the V-shaped plate settler provides an alternative method for sedimentation.

关键词： flocculation Sedimentation Continuous-flow reactor In-situ recognition system V-shaped plate settler tank

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What have we known so far about microplastics in drinking water treatment?A timely review

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Frontiers of Environmental Science & Engineering 2022年第5期16卷 39-56页

作者： Jinkai Xue Seyed Hesam-Aldin Samaei Jianfei Chen Ariana Doucet Kelvin Tsun Wai Ng Environmental Systems Engineering Faculty of Engineering&Applied ScienceUniversity of Regina3737 Wascana ParkwayRegina SK S4S 0A2Canada

Microplastics(MPs)have been widely detected in drinking water sources and tap water,raising the concern of the effectiveness of drinking water treatment plants(DWTPs)in protecting the public from exposure to MPs through drinking water.We collected and analyzed the available research articles up to August 2021 on MPs in drinking water treatment(DWT),including laboratory-and full-scale studies.This article summarizes the major MP compositions(materials,sizes,shapes,and concentrations)in drinking water sources,and critically reviews the removal efficiency and impacts of MPs in various drinking water treatment processes.The discussed drinking water treatment processes include coagulation-flocculation(CF),membrane filtration,sand filtration,and granular activated carbon(GAC)filtration.Current DWT processes that are purposed for particle removal are generally effective in reducing MPs in water.Various influential factors to MP removal are discussed,such as coagulant type and dose,MP material,shape and size,and water quality.It is anticipated that better MP removal can be achieved by optimizing the treatment conditions.Moreover,the article framed the major challenges and future research directions on MPs and nanoplastics(NPs)in DWT.

关键词： Microplastics Drinking water treatment Coagulation flocculation Membrane Filtration

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Effect of Mn^(2+)on the phosphorus removal and bioflocculation under anoxic condition

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Journal of Environmental Sciences 2022年第5期34卷 37-46页

作者： Xiaohui Xu Lanhe Zhang Xiangdong Zhang Xiaohui Guan Dezhou Wei School of Resources&Civil Engineering Northeastern UniversityShenyang 110819China School of Chemical Engineering Northeast Electric Power UniversityJilin 132012China

Manganese ion(Mn^(2+))generated from metallurgical,steel making and chemical industries enters sewage treatment plants and affects the sludge activity and flocculation.The effect of Mn^(2+)on the removal of chemical oxygen demand(COD)and total phosphorus(TP)and sludge activity were investigated in anoxic zone of an anaerobic/anoxic/oxic(A2O)process.The compositions and structures of extracellular polymeric substances(EPS)were charac-terized using three-dimensional excitation emission matrix fluorescence spectroscopy(3D-EEM),X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FTIR)to reveal the relationship among Mn^(2+),EPS and sludge flocculation.The results showed thatlow concentration of Mn^(2+)(flocculation.However,high concentration of Mn^(2+)(>10 mg/L)hindered microbial flocculation and reduced removal efficiencies of the pollutants.When Mn^(2+)was 5 mg/L,removal efficiencies of COD and TP reached 65%and 90%,respectively.Sludge flocculation was the best and SVI was 70.56 mL//g.The changes of Mn^(2+)concentration caused deviation of groups'compositions in LB-EPS and TB-EPS,where the main components were always protein(PN)and polysaccharide(PS).The addition of Mn^(2+)resulted in the degradation of humic acids.However,it did not give rise to significant morphology changes of EPS.

关键词： Mn^(2+) Wastewater Anoxic sludge Extracellular polymeric substances (EPS) flocculation

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Synthesis and evaluation of cationic flocculant P(DAC-PAPTAC-AM) for flocculation of coal chemical wastewater

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Journal of Environmental Sciences 2021年第1期33卷 239-248页

作者： Wenquan Sun Shengbao Zhou Yongjun Sun Yanhua Xu College of Urban Construction Nanjing Tech UniversityNanjing 211800China School of Environmental Sciences and Engineering Nanjing Tech UniversityNanjing 211816China

In this study,a high-efficiency cationic flocculant,P(DAC-MAPTAC-AM),was successfully prepared using UV-induced polymerization technology.The monomer Acrylamide(AM):Acryloxyethyl Trimethyl ammonium chloride(DAC):methacrylamido propyl trimethyl ammonium chloride(MAPTAC)ratio,monomer concentration,photoinitiator concentration,urea content,and cationic monomer DAC:MAPTAC ratio,light time,and power of highpressure mercury lamp were studied.The characteristic groups,characteristic diffraction peaks,and characteristic proton peaks of P(DAC-MAPTAC-AM)were confirmed by fourier transform infrared spectroscopy(FTIR),X-Ray diffraction(XRD),1H nuclear magnetic resonance spectrometer(1H NMR),and scanning electron microscopy(SEM).The effects of dosage,pH value,and velocity gradient(G)value on the removal efficiencies of turbidity,COD,ammonia nitrogen,and total phenol by poly aluminum ferric chloride(PAFC),P(DACMAPTAC-AM),and PAFC/P(DAC-MAPTAC-AM)in the flocculation treatment of coal chemical wastewater were investigated.Results showed that the optimal conditions for the flocculation of coal chemical wastewater using P(DAC-MAPTAC-AM)alone are as follows:dosage of 8-12 mg/L,G value of 100-250 s^-1,and pH value of 4-8.The optimal dosage of PAFC is 90-150 mg/L with a pH of 2-12.The optimal dosage for PAFC/P(DAC-MAPTAC-AM)is as follows:PAFC dosage of 90-150 mg/L,P(DAC-MAPTAC-AM)dosage of 8-12 mg/L,and pH range of 2-6.When P(DAC-MAPTAC-AM)was used alone,the optimal removal efficiencies of turbidity,COD,ammonia nitrogen,and total phenol were 81.0%,35.0%,75.0%,and 80.3%,respectively.PAFC has good tolerance to wastewater pH and good pH buffering.Thus,the flocculation treatment of coal chemical wastewater using the PAFC/P(DAC-MAPTAC-AM)compound also exhibits excellent resistance and buffering capacity.

关键词： Coal chemical wastewater Cationic flocculant flocculation Coagulation Pretreatment

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Influence of zeta potential on the flocculation of cyanobacteria cells using chitosan modified soil

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Journal of Environmental Sciences 2015年第2期27卷 47-53页

作者： Liang Li Honggang Zhang Gang Pan Research Center for Eco-Environmental Sciences Chinese Academy of Sciences

Using chitosan modified soil to flocculate and sediment algal cells has been considered as a promising strategy to combat cyanobacteria blooms in natural waters. However, the flocculation efficiency often varies with algal cells with different zeta potential（ZP） attributed to different growth phases or water conditions. This article investigated the relationship between ZP of Microcystis aeruginosa and its influence to the flocculation efficiency using chitosan modified soil. Results suggested that the optimal removal efficiency was obtained when the ZP was between- 20.7 and- 6.7 m V with a removal efficiency of more than 80% in 30 min and large floc size of 〉 350 μm. When the algal cells were more negatively charged than- 20.7 m V, the effect of chitosan modified soil was depressed（〈 60%） due to the insufficient charge density of chitosan to neutralize and destabilize the algal suspension. When the algal cells were less negative than- 6.7 m V or even positively charged, a small floc size（〈 120 μm） was formed, which may be difficult to sink under natural water conditions. Therefore, manipulation of ZP provided a viable tool to improve the flocculation efficiency of chitosan modified soil and an important guidance for practical engineering of cyanobacteria bloom control.

关键词： Cyanobacteria blooms flocculation Chitosan Modified soil Zeta potential

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Evaluation of flocculation characteristics of kaolinite dispersion system using guar gum:A green flocculant

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International Journal of Mining Science and Technology 2019年第5期29卷 745-755页

作者： R.K.Dwari B.K.Mishra Mineral Processing Department CSIR-Institute of Minerals and Materials TechnologyBhubaneswar 751013India Indian Institute of Technology Goa 403401India

This paper reports the systematic investigation on the flocculation,sedimentation and consolidation characteristics of kaolinite using guar gum as a green flocculant.In-situ flocculation behavior of kaolinite at various pH,guar gum dosages,and ionic strength were studied using a light scattering technique.The effect of these parameters on the settling rate,solid consolidation,and supernatant liquid clarity was recorded.The morphology of kaolinite and flocculated kaolinite aggregates were analyzed using FESEM.The morphology studies suggest that it is poorly crystalline with multiple steps on edge,broken edge;laminar with high aspect ratio and have rough basal surface.The complex irregularity on the basal surface and the presence of multiple steps in the edges,broken edges(hydroxyl groups)have facilitated the guar gum adsorption.The isoelectric point of kaolinite is pH 3.96.The pH,ionic strength and flocculant dosage have a significant effect on the kaolinite settling rate.The guar gum has exhibited excellent turbidity removal efficiency at pH 5.The turbidity removal is inefficient at pH 10.However,guar gum has shown high turbidity removal with 80%transmission at pH 10 in the presence of a KNO3 electrolyte.

关键词： Guar gum Dewatering Kaolinite Light scattering Morphology flocculation

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