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

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.

Features and mechanism for coagulation－flocculation processes of polyaluminum chloride

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The effect of coupling coagulation and flocculation with membrane filtration in water treatment:A review

Water supply and sanitation demands are foreseen to face enormous challenges over the coming decades to meet the fast growing needs in a global perspective. Significant growth in the industry is predicted and membrane separation technologies have been identified as one of the possible solutions to meet future demands. Application and implementation of membrane technology is expected both in production of potable water as well as in treatment of wastewater. In potable water production membranes are substituting conventional separation technologies due to the superior performance, potential for less chemical use and sludge production, as well as the potential to fulfill hygienic barrier requirements. Membrane bio-reactor （MBR） technology is probably the membrane process which has had most success and has the best prospects for the future in wastewater treatment. Trends and developments indicate that this technology is becoming accepted and is rapidly becoming the best available technology for many wastewater treatment applications. A major drawback of MBR systems is membrane fouling. Studies have shown that fouling mitigation in MBR systems can potentially be done by coupling coagulation and flocculation to the process.

Synthesis and Flocculation Property of Chitosan-Acrylamide Graft Copolymer

Chitosan, as a kind of natural polymer, has many advantages, such as abundant sources, biological degradation, no secondary contamination and facile modification. In this work, we prepared modified chitosan flocculants with double electrical behavior via polymerizing chitosan, acrylamide and sodium carboxymethyl cellulose together by using ammonium persulfate as the indicator in water. The product is a comb-type of chitosan copolymer and a polymeric ampholyte. And then we studied the product by FTIR, UV-Vis, TG, DSC spectrometeries and viscometry, etc. We also performed CACM′s water treat experiment. The effects of pH values, reaction time and dose of the new floccalant on treating various of waste water have been investigated, too.

Improving the sulfidation-flotation of fine cuprite by hydrophobic flocculation pretreatment

Hydrophobic flocculation pretreatment was performed to assess its effect on the recovery of fine cuprite in sulfidation-flotation. The results of the micro-flotation experiment showed that cuprite recovery is related to the particle size, and that an excessive content of fine particles(<18 μm) impacted the recovery of coarse particles. When hydrophobic flocculation pretreatment was used, the recovery of fine cuprite in sulfidation-flotation increased from 60.3% to 86.3% under optimum conditions(pH 9.5; sodium oleate concentration, 2 × 10^(-4) mol×L^(-1); stirring time, 6 min; stirring speed, 1600 r×min^(-1)). The laser particle size analysis and optical microscopy results indicate that hydrophobic flocculation pretreatment effectively reduces the content of fine cuprite, and augments the apparent particle size in the pulp. We performed the Derjaguin–Landau–Verwey–Overbeek(DLVO) theory and extended DLVO theory calculations to further support the interpretation of the results.

Flocculation performance of a novel synthesized flocculant with low ecological risk

Combined flocculants with low ecological risk are urgently required in water supply and wastewater treatment in China. A novel flocculant was thus developed under the condition of low ecological risk(noted as CAS). The experiments to examine wastewater treatment performance of the new product showed that there was favourable performance in the flocculation process in contrast to commercial flocculants in treating kaolin suspensions, municipal effluent and domestic wastewater. Flocculation performance included the turbidity removal rate, sediment character and a decrease in COD(chemical oxygen demand). The sediment time of flocculation is short and the removal rate of turbidity treated by CAS is high compared with PAC(polyaluminum chloride), PAM(polyacrylamide) and the combined addition of PAC and PAM. The optimal concentration required to affect flocculation processes is dependent on kaolin concentration and the character of the wastewater within the range examined. It also showed that CAS is effective to treat wastewater with high turbidity.

Chemical and biological flocculation process to treat municipal sewage and analysis of biological function

The pilot scale experimental apparatus and the procedure of the chemical and biological flocculation process to verify the feasibility in treating Shanghai municipal sewage were introduced in this paper. In addition, the biological function of the process was discussed. The results of optimal running showed that in the reaction tank, the concentration of mixed liquor suspended solid(MLSS) was 2 g/L, hydraulic retention time(HRT) was 35 min, dosage of liquid polyaluminium chloride(PAC) was 60 mg/L, and the concentration of polyacrylamide(PAM) was 0 5 mg/L. The effluent average concentrations of COD Cr , TP, SS and BOD 5 were 50 mg/L, 0 62 mg/L, 18 mg/L, and 17 mg/L, respectively. These were better than the designed demand. In addition, the existence of biological degradation in this system was proven by several methods. The removal efficiencies of the chemical and biological flocculation process were 20% higher than that of the chemical flocculation process above at the same coagulant dosage. The treatment process under different situations was evaluated on a pilot scale experiment, and the results provided magnificent parameters and optimal condition for future operation of the plant.

Influence of coarse tailings on flocculation settlement

The composition of tailings particles in mines plays a key role in the flocculation settlement of slurries.To study the influence of coarse particle tailings(CPTs)on the flocculation settlement of tailings slurries(TSs),static flocculent settling tests,scanning electron microscopy observations,and laser particle size analyses were conducted using the tailings obtained from a copper mine.The results demonstrate that(i)in the accelerated and free settling process,CPTs did not directly settle at the bottom of graduated cylinders;instead,they were netted by the flocculent structures(FSs)and settled together more quickly.The CPTs accelerate the rapid settlement of TSs;the acceleration effect is more obvious when the CPTs content is greater than 50 wt%.(ii)The most appropriate flocculant unit consumption(FUC)is 20 g·t-1,and no substantial increase is observed in the flocculant settling velocity with an increase in the flocculant because the effective FSs did not substantially change and thus did not lead to a notable increase in the settling velocity of the solid–liquid interface(SLI).(iii)In the effective settling space of the thickening facility,free water quickly flowed from the pores of FSs,which is reflected in the period from 0 to 1 min.

Impact of dynamic distribution of floc particles on flocculation effect

Polyaluminum chloride （PAC） was used as coagulant and suspended particles in kaolin water. Online instruments including turbidimeter and particle counter were used to monitor the flocculation process. An evaluation model for demonstrating the impact on the flocculation effect was established based on the multiple linear regression analysis method. The parameter of the index weight of channels quantitatively described how the variation of floc particle population in different size ranges cause the decrement of turbidity. The study showed that the floc particles in different size ranges contributed differently to the decrease of turbidity and that the index weight of channel could excellently indicate the impact degree of floc particles dynamic distribution on flocculation effect. Therefore, the parameter may significantly benefit the development of coagulation and sedimentation techniques as well as the optimal coagulant selection.

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

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.

Particle size distribution and removal by a chemical-biological flocculation process

The particle characterization from the influent and effluent of a chemical-biological flocculation （CBF） process was studied with a laser diffraction device. Water samples from a chemically enhanced primary treatment （CEPT） process and a primary sediment tank process were also analyzed for comparison. The results showed that CBF process was not only effective for both the big size particles and small size particles removal, but also the best particle removal process in the three processes. The results also indicated that CBF process was superior to CEPT process in the heavy metals removal. The high and non-selective removal for heavy metals might be closely related to its strong ability to eliminate small particles. Samples from different locations in CBF reactors showed that small particles were easier to aggregate into big ones and those disrupted flocs could properly flocculate again along CBF reactor because of the biological flocculation.

Selective flocculation of fines

A number of factors that affect selective flocculation of fines have been identified and the effect of some of parameters on process behavior has been explained with the help of a few case studies. Experiments with francolite montmorillonite and francolite palygorskite mixtures indicated that francolite recovery depends on pH and the type of dispersant. The results showed that removal of multivalent ionic species on clay mineral surfaces seems to enhance flocculation, and separation efficiency increases as Ca 2+ ions are removed from the surface. When chalcopyrite and quartz are present together, it is however necessary to clean the flocs obtained to remove entrapped quartz.

Flocculation control study based on fractal theory

A study on flocculation control based on fractal theory was carried out. Optimization test of chemical coagulant dosage confirmed that the fractal dimension could reflect the flocculation degree and settling characteristics of aggregates and the good correlation with the turbidity of settled effluent. So that the fractal dimension can be used as the major parameter for floc-culation system control and achieve self-acting adjustment of chemical coagulant dosage. The fractal dimension flocculation control system was used for further study carried out on the effects of various flocculation parameters, among which are the dependency relationship among aggregates fractal dimension, chemical coagulant dosage, and turbidity of settled effluent under the conditions of variable water quality and quantity. And basic experimental data were obtained for establishing the chemical coagulant dosage control model mainly based on aggregates fractal dimension.

Temperature variation characteristics in flocculation settlement of tailings and its mechanism

Rapid flocculation and settlement(FS)of mine tailings is significant for the improvement and development of the filling process,whereas the settlement velocity(SV)of tailings in FS has been recognized as a key parameter to evaluate the settlement effect.However,the influence of temperature on the SV and its mechanism have not been studied.FS experiments on tailings with various ambient temperatures were carried out.The SVs of tailings with a solid waste content of 10wt%and an anionic polyacrylamide content of 20 g·t^−1 were measured at different temperatures.The SV presented an“N”-shaped variation curve as the temperature changed from 5 to 40℃.The mechanism of these results can be explained from the perspective of the electric double-layer repulsive force,molecular dynamics,and the polymer flocculation principle,as revealed from the scanning electron microscopy of floc particles.The findings will be beneficial in the design of tailings dewatering processes and save costs in the production of cemented paste backfill.

Comparison of selective flocculation of low grade goethitic iron ore fines using natural and synthetic polymers and a graft copolymer

This study aims to beneficiate low grade goethitic iron ore fines using a selective flocculation process. Selective flocculation studies were conducted using different polymers such as starch amylopectin(AP), poly acrylic acid(PAA), and a graft copolymer(AP-g-PAA). The obtained results were analyzed; they indicate the enhancement of the iron ore grade from 58.49% to 67.52% using AP-g-PAA with a recovery of 95.08%. In addition, 64.45% Fe with a recovery of 88.79% was obtained using AP. Similarly, using PAA, the grade increased to 63.46% Fe with a recovery of 82.10%. The findings are also supported by characterizing concentrates using X-ray diffraction(XRD) and electron probe microanalysis(EPMA) techniques.

Relationship between biogeochemical features of biogenic elements and flocculation in the Changjiang Estuary

This paper reports the relationship between the biogeochemical characteristics of C. N. P and flocculation and settling of suspended materials in the Changjiang Estuary. Regional activities of bacteria and the plankton and biogeochemical processes at the water-particle interface under some environmental conditions are quite variable. This leads to the transition of material phase with speciation variation of elements C. N. P. in the transfer processes. Therefore, the composition and reactivity of particle surface and dissolved constituent are modified, affecting the stability of the particulate dispersion system. In summer, the concentration of NO3 and PO4 are positively correlated with turbidity, while the weight percentage of PON, POC and PP are negatively correlated with turbidity. When particles in the river move seaward, two zones can be distinguished: i) zone with maximum flocculation speed, in salinity 0. 1～2. 0 ;ii) zone with huge coagulating particles netting and high turbidity at the bottom, in salinity 2～11.The highest values of C/N in particles (or the low valley of C. E. C.of particle surface) appear in the two zones. These results demonstrate that the biogeochemical action is one of the major factors and mechanisms to dominate the flocculation of particles in the Changjiang Estuary.

Artificial neural network approach to assess selective flocculation on hematite and kaolinite

Because of the current depletion of high grade reserves, beneficiation of low grade ore, tailings produced and tailings stored in tailing ponds is needed to fulfill the market demand. Selective flocculation is one alternative process that could be used for the beneficiation of ultra-fine material. This process has not been extensively used commercially because of its complex dependency on process parameters. In this paper, a selective flocculation process, using synthetic mixtures of hematite and kaolinite in different ratios, was attempted, and the ad-sorption mechanism was investigated by Fourier transform infrared （FTIR） spectroscopy. A three-layer artificial neural network （ANN） model （4？4？3） was used to predict the separation performance of the process in terms of grade, Fe recovery, and separation efficiency. The model values were in good agreement with experimental values.

Study on Production and Flocculation Conditions of Bio-Flocculant

One strain of bacteria which shows very high flocculation characteristics is found. It is identified as a Pseudomonas species. The influence of components of culture medium on the flocculant production by Pseudomonas sp. is studied.The results of our experiments show that the higbest level of bio-flocculant accumulation is obtained and the hioflocculant can efrectively flocculate kaolin clay on condition that this stralu is grown in the medium containing glucose as carbon source, aud (NH4)2SO4 as nitrogen source, with the yend extract being added. In addition, some kinds of cationic ions have some influences on the flocculation rate of kaolin clay with tbe Al3+ions in particular.

FLOCCULATION/COAGULATION OF NATURAL ORGANIC MATTER FOR PRETREATMENT OF WATER ANDWASTE WATER

Characterization of water, waste water and natural organic matter are involved in this paper, and as well as the features of flocculation and coagulation for removing natural organic matter from water and waste water Novel flocculant and coagualant is strongly asked for improving removal efficiency and environment friendly. Enhanced coagulation is introduced to meet the experimental and practical requirement.

Flocculation of Kaolinite Suspensions in Water by Coconut Cream Casein

The flocculation of kaolinite colloidal particles was carried out at pH = 6 in suspension of initial turbidity varying between 24 NTU and 102 NTU by a casein extracted from Cocos nucifera cream. During Jar-test essays, 90% to 99% of colloids were eliminated in the sediments. The optimal doses of casein used depend on the initial colloids concentrations of the suspension and were found to be 60 mg/L and 100 mg/L respectively for suspensions having turbidity of 24 NTU and 102 NTU. The corresponding residual turbidity are respectively 2.80 NTU and 10.22 NTU for clarified water. The structural analysis of the freeze-dried sediments by FTIR shows sharp adsorption bands at 1558 cm–1 and 1653 cm–1, indicating the presence of casein in the sediment. The flocculation process between the particles of kaolinite and the coconut casein is adsorption and bridging.