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Homogenous advanced oxidation processes (AOPs) based on transition metal catalysts toward the activation of H2O2 to hydroxyl radical (•OH) have been widely applied to organic pollutants removal, such as Fenton and Fenton-like processes. These transition metal catalysts mostly flocculate as the pH increases. It's worth noting that the formed transition metal flocs are complex heterogeneous aggregations with active substances, providing diverse reaction spaces and interfaces. However, it is a challenge to distinguish the roles of transition metal flocs in the organic pollutants removal from homogeneous catalytic reactions. Herein, we unveiled a pathway for the long-lasting removal of organic pollutants via Cr flocs adsorbed with •OH (HO•-Cr flocs) using a stepwise method. First, adsorbed •OH (•OHads) within the HO•-Cr flocs was proved to be the active site forming hydrogen bond (H-bond) and van der Waals force with organic pollutants. Then, the presence of switchable electron transfer between Cr and OH groups within the HO•-Cr flocs was revealed, contributing to the persistent existence of •OHads and consequently ensuring the long-lasting organics removal. Further, this removal pathway of organic pollutants was confirmed during the leather wastewater treatment. These findings will complement a different pathway for organic pollutants removal via transition metal flocs and extend the lifetime of homogeneous AOPs based on transition metal catalysts, providing significant implications for their design and optimization. [ABSTRACT FROM AUTHOR]

This paper presents the results of a selective flocculation/magnetic separation study performed with a sample of iron ore slime from the desliming stage of the industrial flotation circuit of a mine in the southern region in the Quadrilátero Ferrífero-Brazil that was discarded in a tailings dam. Zeta potential measurements of pure minerals previously identified in the sample (goethite = 52.4%, hematite = 26.2%, quartz = 12.3%, kaolinite = 8.2%, and others = 0. 9%) were evaluated to assess the influence of the reagents used (sodium hexametaphosphate – SHMP (dispersant)) and flocculants (corn starch, nonionic polyacrylamide – P2500 and cationic polyacrylamide – P806)) on their surface properties and consequently on the stability of suspensions of the slime and of the pure minerals individually, aiming to establish conditions for selective separation between Fe-bearing minerals (goethite and hematite) and gangue minerals (quartz and kaolinite) in the subsequent magnetic separation step. At pH 10 and a 25 mg/L dosage of SHMP, a higher Fe recovery was verified with starch (2000 g/t) in relation to nonionic and cationic polyacrylamides, and similar Fe contents in all dosages tested of the flocculants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Particle size and concentration determine the flow behavior of suspensions. • A Cross flow model extension offers a better way to model rheological behavior. • Unlike conventional models, this model introduces a variable number of particles. A number of viscosity and flow curve models can be used to numerically investigate the non-Newtonian behavior of fluids. Although particle size, grain size distribution and concentration play a crucial role in determining the viscosity and flow behavior of suspensions and colloidal systems, they are either ignored or considered indirectly in almost all models. We present a mathematical extension of the widely used Cross flow curve model to account for the effect of concentration and particle size in modeling viscosity and flow curves. In particular, this study takes into account a variable total number of individual particles in unit volume, which is assumed to be constant in other models. The proposed extension allows the flow curve to model suspensions that are typically shear-thinning but can also be Newtonian, or shear-thickening for at different shear rates and concentrations. These considerations provide insight into studying and designing suspensions, colloidal systems, and other complex fluid–solid interactions. [ABSTRACT FROM AUTHOR]

The solids in sewage sludge are primarily composed of organic matter and offer new possibilities for sustainable sludge management, if considered as a stable biomass source in terms of quantity and quality. Reducing the volume of sludge with an extremely high moisture content is challenging, and enhanced dewatering through mechanical treatment is crucial from an environmental and sustainability perspective because it alleviates the reliance on thermal treatment. This study employed ultrasonication to enhance the dewatering efficiency of activated sludge. The disruption of sludge induced by ultrasonication notably facilitated the elimination of intracellular water during mechanical expression. Additionally, the ultrasonicated sludge was verified to be re-flocculated by introducing inorganic electrolytes such as Ca2+ (divalent cations), Al3+ (trivalent cations), and polyferric sulfate. Conversely, no re-flocculation of disrupted sludge was observed upon applying organic polymer flocculant. Under optimized conditions, the sludge re-flocculation progressed to form large flocs, leading to a decreased suspended solids (SS) value from 1423 to 73 mg/L and reduction in capillary suction time (CST) from over 2000 to 18 s. Following pretreatment, the moisture content of the mechanically expressed cake at 500 kPa decreased significantly from 76 wt% (untreated sludge) to less than 60 wt% (treated sludge) due to the elimination of intracellular water. [ABSTRACT FROM AUTHOR]

This study evaluated the coagulation/flocculation process using chitosan as a natural coagulant to concentrate suspensions of the cyanobacterium Synechococcus subsalsus and enable biogas production from concentrated biomass. The chitosan performance was tested and compared with the inorganic ferric chloride (FeCl3) coagulant. Using the liquid fraction of the coagulation/flocculation process in subsequent biomass cultivations proved viable, with similar growths in culture media with up to 80% of the liquid fraction. At pH 6 and 400 mg/L FeCl3, the biomass concentrated almost seven times, increasing the total suspended solids (TSS) of the suspension from 0.4–0.6 g/L to 2.6–4.0 g/L. With 80 mg/L chitosan and pH 7, the TSS concentration attained values in the range of 7.0–9.7 g/L, an increase of more than 30 times, clearly showing that chitosan has a much higher capacity for biomass concentration at a lower concentration. A ratio of 0.3 g chitosan/g dry mass of the biomass was established to reach the maximum densification. The production of methane from chitosan-densified biomass proved to be feasible. Chitosan-densified biomass showed a two-phase cumulative methane production when digested, with slower methane production and 23% lower methane yield after 30 days of digestion (207 NmL CH4/g CODi) compared to the biomass from cultivation (non-densified, 270 NmL CH4/g CODi). However, optimizing the digestion conditions of the densified biomass should increase the methane yield and reduce process time. [ABSTRACT FROM AUTHOR]

AbstractThis study addresses the challenge of the reverse effect observed in the dewatering process of waste slurry as poly-aluminum chloride (PAC) dosages increase. It investigates the flocculation mechanism of PAC at varying dosages in a high-water-content slurry using molecular dynamics simulation methods. The results indicate that PAC molecules primarily adsorb montmorillonite particles while exerting negligible influence on quartz. Dewatering efficiency is influenced by the adsorption-repulsion interaction at the PAC-montmorillonite interface. Efficiency increases with PAC dosage up to an optimum level due to enhanced adsorption but decreases thereafter due to increasing repulsion. Within this optimal range, montmorillonite interfaces exhibit a higher negative charge, facilitating stable PAC adsorption and leading to increased aggregation of montmorillonite particles, thereby forming flocs. The adsorption capacity of PAC on montmorillonite particles escalates with dosage until achieving the optimal flocculation effect. However, surpassing this optimal dosage prompts repulsion among outer PAC molecules, gradually causing montmorillonite particles to separate due to repulsion, thereby weakening the flocculation effect. This research provides theoretical support for the flocculation and dewatering of PAC in high-water-content waste slurry, emphasizing the rational and cost-effective addition of PAC in practical applications. [ABSTRACT FROM AUTHOR]

It is undeniable that removal efficiency is the main factor in coagulation-flocculation (C-F) process for wastewater treatment. However, as far as environmental safety is concerned, the ecotoxicological aspect of the C-F process needs to be examined further. In this study, a systematic review was performed based on publications related to the toxicity research in C-F technology for wastewater treatment. Through a series of screening steps, available toxicity studies were categorized into four themes, namely acute toxicity, phytotoxicity, cytotoxicity, and genotoxicity, which comprised 48 articles. A compilation of the methodologies executed for each theme was also outlined. The findings show that conventional metallic coagulants (e.g., alum, iron chloride, and iron sulfate) were less toxic when tested on test species such as Daphnia magna (water flea), Lattuca sativa (lettuce), and animal cells compared to synthetic polymers. Natural coagulants such as chitosan or Moringa oleifera were less toxic compared to metallic coagulants; however, inconsistent results were observed. Moreover, an advanced C-F (electrocoagulation) as well as integration between C-F and Fenton, adsorption, and photocatalytic does not significantly change the toxicological profile of the system. It was found that diverse coagulants and flocculants, species sensitivity, complexity in toxicity testing, and dynamic environmental conditions were some key challenges faced in this field. Finally, it was expected that advances in technology, interdisciplinary collaboration, and a growing awareness of environmental sustainability will drive efforts to develop more effective and eco-friendly coagulants and flocculants, improve toxicity testing methodologies, and enhance the overall efficiency and safety of water and wastewater treatment processes. [ABSTRACT FROM AUTHOR]

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Low-cost and high-performance materials or techniques that could synergistically remove phenanthrene (PHE) in a simple manner were highly desired. Herein, we reported an alkali-activated slag (AAS) that proved applicable in both construction and environmental protection efforts. AAS was synthesized by mixing ground granulated blast furnace slag (GGBFS) and an alkaline solution. The prepared AAS mortar achieved the highest mechanical strength when using an alkaline activator with a Na2O concentration of 8% by slag weight. Moreover, AAS exhibited excellent sorption performance towards PHE, with the highest sorption performance reaching 44.0 mg/g, which was much higher than that of GGBFS. Sorption of PHE reached equilibrium within approximately 120 h and fit well with the pseudo-second-order model. Furthermore, the primary sorption mechanisms for PHE on AAS were attributed to cation-π interactions, hydrogen bonding, and flocculation. The strategy of using AAS not only met the requirements for high-performance and low-cost materials but also addressed the challenging issues of developing an all-in-one treatment for PHE pollutants, which was of great significance to wastewater purification. [ABSTRACT FROM AUTHOR]

In this paper, the flocculation effect of single flocculants and compound flocculants on emulsified wastewater under different conditions was studied. The effect of flocculant type, dose, settling time and composite ratio of flocculant on the treatment of emulsified wastewater were investigated through single-factor condition tests, and then the optimal conditions of flocculants for treating emulsified wastewater were obtained. The results showed that the single inorganic flocculant could break the stable state of the emulsion when the pH was adjusted to 7 and formed tiny flocs, but it took a long time to settle down. The single organic flocculant had no flocculation effect. The inorganic–organic composite flocculants could effectively solve the problem of emulsion breaking and flocculation, and could form large flocs and alum flower formations at the same time, with mud and water effectively separated. The best conditions for the composite flocculants were as follows: under the condition of room temperature and pH 7, the dose of PFC was 2250 mg/L and APAM was 5 mg, the homogeneous stirring time was 10 min, and the settling time was 0.5 h. The removal rate of COD and turbidity reached 84.75% and 99.86%. The study could provide a new treatment idea and method for the pretreatment of stabilized high-turbidity wastewater. [ABSTRACT FROM AUTHOR]

In this paper, the three inorganic flocculants polymeric chloride PAC, FeCl3, and Al2(SO4)3 and two organic flocculants anionic polyacrylamide APAM and cationic polyacrylamide CPAM were screened to determine the most efficient flocculants and the optimal dosage, optimizing the flocculation operating conditions through the orthogonal test and then proving the experimental effect according to a comparison study of the high-concentration method and the traditional activated sludge method. The results show that the addition of CPAM achieves the best flocculation for high-concentration activated sludge suspension, and that the sludge interface descent rate, sludge volume index, and sludge settling ratio are better than those of other flocculants. The orthogonal test was used on the sludge volume index to perform evaluations and analyses: mixing section mixing intensity > Flocculation Stage 1 section mixing intensity > Flocculation Stage 2 section mixing intensity > mixing section residence time > flocculation section hydraulic residence time. In the comparison test, the settling performance of the high-concentration method was higher than that of the traditional activated sludge method. In terms of pollutant removal, the removal rates of COD, ammonia nitrogen, and total nitrogen of the traditional activated sludge method were 90.85%, 95.74%, and 71.6%, respectively. The average removal rates of COD, ammonia nitrogen, and total nitrogen of high-concentration activated sludge method were 92.24%, 97.28%, and 80.97%—higher than that of the traditional activated sludge method. [ABSTRACT FROM AUTHOR]

Chitosan was used to change the surface charge of alum sludge into negative charge so as to realize the flocculation removal of algae. The effects of pH, ratio of chitosan and alum sludge, dosage of chitosan and algae density on algal removal performance of modified alum sludge were evaluated by response surface method, and a mathematical model was established. Using the optimization function of response surface software, the parameters of pH, the ratio of alum sludge to chitosan, chitosan dosage, algal density were 7.51, 53.28, 4.51 mg/L and 4.36 x 106 cells/mL, respectively. The removal rate of algae density measured under the optimal conditions was 100. 0%, which was consistent with the predicted results of the model. The flocculation mechanism was mainly that algae cells and modified alum sludge formed floes through electrostatic adsorption, revealed by Zeta potential and SEM. [ABSTRACT FROM AUTHOR]

In order to investigate the mechanism of alkali-free ternary oil-displacing agents in stabilizing the emulsification of produced fluids and to provide a basis for the treatment of these fluids, a study was conducted. This study focused on the oil content in free water, the dynamic interfacial tension between oil and water, the lifetime of droplet interfaces, and the distribution state and size variation of oil droplets as influenced by the concentration of the displacement agent. It was found that upon the addition of a low concentration of surfactant (100 mg/L), a significant reduction in dynamic interfacial tension, interface lifetime, and oil droplet size was observed, along with a significant increase in the oil content in water. As the concentration of the surfactant increased, changes in dynamic interfacial tension, interface lifetime, particle size, and oil content became less noticeable. With an increase in NaCl concentration, there were insignificant changes in dynamic interfacial tension and interface lifetime, but an increase in oil droplet size and the oil content in water was observed. Furthermore, an increase in polymer concentration led to insignificant changes in dynamic interfacial tension and interface lifetime, but exerted a dual effect on oil droplet size and oil content. These findings indicate that surfactants and NaCl contribute to the stabilization of emulsions, with the effect of surfactants being substantially greater than that of NaCl. Low polymer concentrations are not conducive to emulsion stability, but as their concentration increases, they become beneficial for emulsion stabilization. [ABSTRACT FROM AUTHOR]

A new integrated method, i.e., vacuum preloading–flocculation–solidification combined method (VP-FSCM), has been developed for treatment and recycling of slurry-like mud (MS). However, due to the insufficient solidification caused by the decay of vacuum pressure among other factors, the superiority of VP-FSCM under various mixing conditions and the distribution of engineering properties of VP-FSCM-treated MS are not well understood especially at the field pilot scale. In this study, a series of laboratory experiments are performed first to identify the influence of equivalent initial water content (wei) and binder content (wc) on the superiority of VP-FSCM over the conventional pure cement solidification method (PCSM), and some field pilot experiments are then conducted to further demonstrate the solidification efficiency of VP-FSCM and characterize the spatial distribution of strength of VP-FSCM-treated MS. The results indicate that VP-FSCM outperforms PCSM in treatment and utilization of MS, with the strength of VP-FSCM-treated MS being approximately 2.24 times larger than that of PCSM treated MS under the equivalent circumstance at the field pilot scale. In addition, the strength of VP-FSCM-treated MS increases substantially with the decrease in distance away from the central axis of a prefabricated horizontal drain and tends to show higher spatial variability than that of PCSM treated MS. [ABSTRACT FROM AUTHOR]

In this study, facile construction engineering of Pr6O11@C with efficient photocatalytic activity was established. Taking advantage of the flocculation of Pr3+ in the base medium, acid red 14 (AR14) was flocculated together with Pr(OH)3 precipitate, in which Pr(OH)3 and AR14 mixed highly uniformly. Calcinated at high temperature in N2, a novel Pr6O11@C was successfully synthesized. The resulting materials were characterized by XRD, SEM, FT-IR, Raman, and XPS techniques. The results show that the cubic Pr6O11@C with Fm3m space group, similar to that of Pr6O11, was obtained. From the results of the photodegradation of AR14, it is found that the photocatalytic efficiency of Pr6O11@C is higher than that of pure Pr6O11 due to the formation of abundant carbon bonds and oxygen vacancies. Compared with pure Pr6O11 and other carbon-based composites, the acid resistance of Pr6O11@C is greatly improved due to the highly uniform dispersion of Pr6O11 and C, which lays a solid foundation for the practical application of Pr6O11@C. Moreover, the role of NH3·H2O and NaOH used as precipitants for the photocatalytic efficiency of Pr6O11 was investigated in detail. [ABSTRACT FROM AUTHOR]

This work investigated the flocculation of sub-micron titanium dioxide (TiO2) by polyacrylic acids (PAAs), with a focus on studying the correlation between the PAAs adsorption conformation and the flocculation efficiency/floc property. The adsorption analysis of PAAs on the TiO2 surface was studied by attenuated total reflection Fourier transform infrared, Raman, X-ray photoelectron spectroscopy, CHNS elemental analyzer coupled with quartz crystal microbalance with dissipation monitoring. Adsorption densities were fitted using Langmuir and Freundlich isotherm models. The flocculation process of TiO2 by PAAs of different molecular weights (MWs) was monitored in real-time by a photometric dispersion analyser, and the floc structure was studied by scanning electron microscope. The results showed that the adsorption of PAAs followed the Langmuir isotherm, and formed monolayer adsorption on the TiO2 surface regardless of MWs through hydrogen and bidentate chelating chemical bonds. The thickness of adsorption layer increased with increasing MW, which could promote floc size by providing molecular "bridges"; but impeded the flocculation rate. For sub-micron particles, polyacrylic acid with a medium MW (512 kDa) was the optimum polymer owing to obtaining the fastest flocculation rate and relatively dense flocs in this work. PAA with high MW resulted in larger flocs with greater porosity, whereas the low MW PAA can only generate smaller flocs with a slower flocculation rate. [ABSTRACT FROM AUTHOR]

Cellulose in the nano regime, defined as nanocellulose, has been intensively used for water treatment. Nanocellulose can be produced in various forms, including colloidal, water redispersible powders, films, membranes, papers, hydrogels/aerogels, and three-dimensional (3D) objects. They were reported for the removal of water contaminants, e.g., heavy metals, dyes, drugs, pesticides, pharmaceuticals, microbial cells, and other pollutants from water systems. This review summarized the recent technologies for water treatment using nanocellulose-based materials. A scientometric analysis of the topic was also included. Cellulose-based materials enable the removal of water contaminants, and salts offer advanced technologies for water desalination. They are widely used as substrates, adsorbents, and catalysts. They were applied for pollutant removal via several methods such as adsorption, filtration, disinfection, coagulation/flocculation, chemical precipitation, sedimentation, filtration (e.g., ultrafiltration (UF), nanofiltration (NF)), electrofiltration (electrodialysis), ion-exchange, chelation, catalysis, and photocatalysis. Processing cellulose into commercial products enables the wide use of nanocellulose-based materials as adsorbents and catalysts. [ABSTRACT FROM AUTHOR]

Star-shaped SBRs with alkoxy silyl groups in the center of the molecule and amine groups at the polymer chain ends were prepared. The number of arms were varied, and its influence on the silica/silane-filled compound properties was investigated. The polymer–filler interactions and the filler–filler interactions were evaluated from the viscoelastic properties. The flocculation, tensile properties and tanδ at 60 °C, an indicator of rolling resistance, were investigated as well. The polymer–filler interactions were increased in the SBR with a higher number of arms due to the higher amount of amine groups in these SBRs. The Payne effect was slightly increased with a higher number of arms. This indicates a deteriorated micro-dispersion of the silica caused by too many interactions generated by the higher amount of amine groups in SBR. These high interactions due to the amine groups lead to higher tensile moduli. The combination of the higher polymer–filler interactions and the higher Payne effect in SBR with a high number of arms results in the same tanδ compared to the SBR with a low number of arms. [ABSTRACT FROM AUTHOR]

The production of municipal sludge is increasing with the development of urbanization in these years. The municipal sludge usually has a high moisture content and contains large number of organic pollutants. Inappropriate treatment methods will lead to secondary pollution. Conventional mechanical dehydration can hardly meet the moisture content requirements for subsequent disposal. Flocculation is widely used in the sludge dewaterability enhancement for its economic efficiency and reliability. This paper provides a comprehensive review of flocculation-based techniques for municipal sludge dewatering. Firstly, the advantages and disadvantages of pretreatment techniques is elaborated. Even though flocculation is widely applied in sludge dewatering, deep dehydration always faces bottleneck in area such as removing cell bound water and changing the structure of EPS, etc. when using individual flocculation. Limited understanding of mechanisms and behaviors of joint technology of flocculation and physical/chemical/biological methods, have been highlighted as knowledge gaps in sludge dewatering. Some specific cases, mechanisms of action, practical considerations, dewatering effects and economic analyses of flocculation-coupled multiple technologies for deep sludge dewatering are analyzed in detail, Finally, the limitations, challenges and outlook of flocculants applied in sludge dewatering are comprehensively discussed. [ABSTRACT FROM AUTHOR]

The present study aims to remove chromium (Cr) from a synthetic solution using Ziziphus jujube seed (ZJS)‐activated biochar (ZJSAB) as an adsorbent. Physicochemical characterization was carried out to understand the properties of ZJSAB samples. Adsorption characteristics of ZJSAB were determined using batch experiments for various temperatures, pH, dosage, concentration, and duration. The study reveals ZJSAB has 93 % efficiency in the removal of Cr for an initial concentration of 60 mg L−1 at 30 °C and 2 pH with 0.6 g L−1 dosage and 120 min duration. Freundlich isotherm and pseudo‐second‐order models were best fit with maximum removal efficiency for ZJSAB. When 0.3 N hydrochloric acid was introduced to a desorption study, Cr desorption was 93.47 %. The study reveals that activated biochar from ZJS was efficient for Cr removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

As people's material quality of life continues to improve, water resources become subjected to varying degrees of contamination. As one of the most commonly utilised agents in water treatment, a flocculant exhibits a diverse range of forms and a vast scope of applications. However, the application of flocculants gives rise to a series of issues, including the use of large doses, the formation of sludge, the difficulty of recycling flocculants, and other concerns. The development of new flocculation technology has become a crucial step in enhancing the purification of wastewater and reducing environmental pollution. Magnetic flocculation can be classified into two main categories: magnetic seeds flocculation and magnetic flocculation. This paper presents an overview of the factors influencing magnetic flocculation, including the type of magnetic seeds, magnetic seeds particle size, and other pertinent considerations. Furthermore, the classification of magnetic flocculants in the process of magnetic flocculation is discussed. This includes the types of magnetic flocculant, namely, inorganic composite magnetic flocculants, organic composite magnetic flocculants, and biological composite magnetic flocculants. Inorganic composite magnetic flocculants are inexpensive and simple to produce; however, their dosage is considerable, and the resulting floc is not tightly formed, which impairs the efficacy of flocculation. The use of organic composite magnetic flocculants requires a smaller dosage and exhibits a strong flocculating ability; however, it may possess toxic properties and potentially cause harm to the water body. The biological composite magnetic flocculant exhibits high efficiency and no pollution, yet it is subject to stringent environmental conditions, displays poor stability, and is applicable to a relatively limited range of treatment scenarios. Furthermore, the integration of magnetic flocculation technology with other techniques is classified and summarised in diverse contexts, and the prospective research focus and direction of magnetic flocculants are proposed. [ABSTRACT FROM AUTHOR]

The settling velocity (ws) in estuarine environments can impact whether a region is eroding or accreting sediment on the bed, yet determining this rate can be an indirect process requiring a number of assumptions. Accurate determination of ws is especially needed for numerical models to reproduce observed sediment concentrations at the appropriate timescale. We collected information on suspended sediment flocculation at a channel site (13 m deep) and a shallows site (4 m deep) within South San Francisco Estuary, alongside timeseries of flow, wave statistics, turbulent shear, and bottle samples analyzed for both ws and particle size. Using the measurements of floc size and settling velocity, we performed a sensitivity analysis on the unknown parameters in the general explicit formula for settling velocity. The collected particle size distribution data show that multiple classes of flocs are present; these are characterized as flocculi, microflocs, and macroflocs. We show that ws of flocculi is closest to ws for the full distribution. The determined parameter values lead to near‐bed mass‐weighted settling velocities (standard deviation) of 1.18 (0.55) and 0.22 (0.15) mm/s at the channel and shallows sites, respectively. Modeling efforts can use this work to help select an appropriate sediment model and parameter values. Plain Language Summary: Tides and waves pick up mud on the bottom of estuaries and transport it between the river and ocean or between the shallows and the deep channel. One important control on this transport of mud is how fast it settles out of the water column. Larger things typically settle faster, and as small particles stick together into larger aggregates, or "flocs", the flocs settle faster than the original small particles. We collected data in the channel and shallows of San Francisco Estuary, and compute settling velocity using a range of tuning parameters. We use the observations to narrow the values of these parameters, and we show how the choice of some parameter values can be more important than others in determining settling velocity. In locations where sediment flocculates, this work will help modelers select appropriate models and parameter values. Key Points: The parameters needed to compute settling velocity are constrained using settling column dataMultiple floc classes are common, suggesting a multiple class model is necessaryThe characteristic size of particles in San Francisco Estuary is smaller than the size commonly observed with camera setups [ABSTRACT FROM AUTHOR]

Aiming at the problems such as low settling speed and poor solid-liquid separation effect of a uranium ore high-calcium slurry, static flocculation method was used to settle high-calcium pulp of a uranium ore, and the effects of flocculant type, dosage, mixed flocculant ratio and adding method on the settling effect were investigated. The results show that the settling rate of high calcium pulp can be significantly increased by the mixed flocculant prepared by WZ944 flocculant and 5330 flocculant. The optimal mass ratio of the two flocculants is 1:1, and the minimum dosage of the mixed flocculant is 35 g/t. The research results can provide reference for the optimization design of the uranium ore solid-liquid separation process. [ABSTRACT FROM AUTHOR]

Using the high-speed motion acquisition system, we studied the settling process of the coal flocs under different addition interval time. The gray value and zeta potential of supernatant generally increased as the interval time increased, proving the effect of interval time on coal slime sedimentation. Furthermore, the interval time 25 s presented the smallest floc amount. The floc size and zeta potential were measured via the inverted fluorescence microscope and the micro electrophoresis, respectively. The interval time 25 s presented the fastest settling velocity. The floc amount in supernatant roughly decreased as the zeta potential increased. The settling velocity decreased with the settling time. The results can provide valuable insight into the development of technology for coal slime sedimentation. [ABSTRACT FROM AUTHOR]

To achieve long-term and efficient photobiological hydrogen production by green algal aggregates remains a challenge. Herein, we demonstrated that mixotrophic cultivation of green algal aggregates can greatly increase the hydrogen production of Chlorella pyrenoidosa by 37 times, and the period of the hydrogen production was up to 21 days with a hydrogen yield of 14.97 mmol L−1. We found that glucose enabled the green algal culture flocculated by cationic etherified starch anaerobic overall, while the algal cells remained highly active. Therefore, long-term effective hydrogen production by green algae was realized. The simplicity and low cost of the method, which requires only cationic etherified starch and glucose, gives it a good potential for scale-up applications and a positive impact on the energy and environment fields. [Display omitted] • A new strategy of mixotrophic cultivation increased the H 2 production by 37 times. • H 2 production was prolonged to 21 days by supplementation with 50 mM glucose. • Large green algal aggregates up to 1000 μm were formed. • Algal aggregates were wholly anaerobic while maintaining high cellular activity. [ABSTRACT FROM AUTHOR]

Living organisms are frequently exposed to multiple biotic and abiotic stress forms during their lifetime. Organisms cope with stress conditions by regulating their gene expression programs. In response to different environmental stress conditions, yeast cells activate different tolerance mechanisms, many of which share common signaling pathways. Flocculation is one of the key mechanisms underlying yeast survival under unfavorable environmental conditions, and the Tup1‐Cyc8 corepressor complex is a major regulator of this process. Additionally, yeast cells can utilize different mitogen‐activated protein kinase (MAPK) pathways to modulate gene expression during stress conditions. Here, we show that the high osmolarity glycerol (HOG) MAPK pathway is involved in the regulation of yeast flocculation. We observed that the HOG MAPK pathway was constitutively activated in flocculating cells, and found that the interaction between phosphorylated Hog1 and the FLO genes promoter region increased significantly upon sodium chloride exposure. We found that treatment of cells with cantharidin decreased Hog1 phosphorylation, causing a sharp reduction in the expression of FLO genes and the flocculation phenotype. Similarly, deletion of HOG1 in yeast cells reduced flocculation. Altogether, our results suggest a role for HOG MAPK signaling in the regulation of FLO genes and yeast flocculation. [ABSTRACT FROM AUTHOR]

AbstractA novel inorganic-organic composite flocculant polyferric titanium silicate/chitosan (PFTS/CTS) was successfully synthesized in this study. The optimal preparation parameters of flocculant were optimized by orthogonal experiment with organic polymer polyacrylamide (PAM) removal rate as the evaluation index. The results shows that the examined preparation parameters are in the order of aging time > m(Fe + Ti):m(CTS) > n(Fe + Ti):n(Si), and the best experimental formula is that aging time = 2 days, m(Fe + Ti):m(CTS)=5 and n(Fe + Ti):n(Si)=0.5. The obtained PAM (50 mg/L) removal rate is 78.7% under the selected suitable wastewater treatment condition. Compared with the single CTS, PFTS and polyferric silicate (PFS), PFTS/CTS exhibits superior flocculation performance. The reason for the improvement of flocculation performance of PFTS/CTS can be attributed to its good crystallinity, special scaly accumulation structure and high positive charge, as well as the synergistic effect of inorganic flocculant and organic flocculant in the PFTS/CTS flocculant, which is successfully composited through coordination bond between titanium ions of PFTS and hydroxyl or amino groups of CTS. The main mechanism of treating PAM by PFTS/CTS is physical and chemical effect including micro-flocs are formed through chelate, charge neutralization and adsorption in the first process, and then the larger particles are formed by bridging, wrapping and sweeping. In addition, the flocs of treating PAM using PFTS/CTS are dense and large, its formation and the sedimentation are fast. The prepared flocculant exhibits eminent application prospects in the field of PAM wastewater. [ABSTRACT FROM AUTHOR]

AbstractThe widespread use of polymer flooding has resulted in a large number of produced liquids consisting of crude oil emulsions and oily wastewater. Efficient flocculants are required to treat these produced liquids till the oily wastewater satisfies the requirements for reinjection formation in order to maintain the regular manufacturing process. In this work, an unsaturated polyether macromonomer (PEP-30) was prepared by ring-opening polymerization using isobutenol as a starting material. Subsequently, a novel flocculant (PMAP) was obtained by copolymerization of dimethylamino propylmethacrylamide (DMAPMA) and PEP-30. For the produced liquids with different crude oil emulsion content, the oil removal rate of PMAP at a dosage of 150 mg/L was more than 75%, and the oil removal rate and versatility were better than those of conventional cationic flocculants. Furthermore, the findings of the flocculation mechanism investigation demonstrated that PMAP had a low interfacial elastic modulus and a large interfacial adsorption mass. Specifically, the optical tweezers were used to detect the interaction force between oil droplets. PMAP effectively strengthened the attraction between oil droplets, extending their duration in contact during flocculation and promoting their coalescence. [ABSTRACT FROM AUTHOR]

Graft modification can effectively improve the flocculation performance of chitosan. In this work, molecular dynamics simulations were employed to investigate the water solubility of chitosan-grafted polyacrylamide (CTS-g-PAM) and its adsorption mechanism with kaolinite, focusing on the effects of branched-chain length and distribution. The solubility parameters obtained from the simulations align better with those calculated using the group contribution method. The radius of gyration (Rg), solvation free energy (∆GSFE), mean square displacement and diffusion coefficient were utilized to analyze changes in solubility of these CTS-g-PAM in aqueous solution. The adsorption interaction between CTS-g-PAM and kaolinite was investigated using interaction energy and diffusion coefficients. The water solubility of CTS-g-PAM initially increased, followed by a subsequent decrease as the length of branched-chain increased along with a decrease in their number. Similarly, the adsorption interaction between CTS-g-PAM and kaolinite increased firstly followed by a decrease with increasing branched-chain length. The magnitude of interaction energy with kaolinite (0 0 1) followed the order of CA10-12 (−826.227 kcal/mol) >CA8-15 (−744.583 kcal/mol) >CA6-20 (−637.366 kcal/mol) >CA12-10 (−598.109 kcal/mol). These trends align with the findings of flocculation tests. Our work provides a theoretical basis for designing chitosan-based flocculants with enhanced water solubility and improved flocculation efficiency. [ABSTRACT FROM AUTHOR]

An important aspect of water treatment is removing fine-grain materials from water. Due to the properties of fine-grain materials, they are difficult to remove from water. During the sedimentation process, which takes place in settling tanks, such materials are removed. The sedimentation process is often accompanied by coagulation and flocculation processes, which form aggregates of particles (flocs) from the fine-grained material particles in a suspension (non-grainy suspension). This kind of suspension (consisting of aggregates of particles or flocs) shows a different behaviour when falling compared with classic grainy suspensions. The main goal and novelty of this article are to propose (and test) a modification of the often used Stokes' formula with the addition of fractal geometry into the calculation of the terminal velocity of free-falling particles in order to overcome Stokes' formula's limitation, thus obtaining the sedimentation process efficiency. Because of this fractal modification, it is possible to use the simple and elegant Stokes' formula in order to calculate better the terminal velocity of non-grainy particles—aggregates or flocs—and thus obtain the sedimentation efficiency for the whole range of suspensions, both non-grainy and grainy. The results obtained in this article show that the sedimentation process efficiency calculated by using the modified formula based on the fractal geometry morphology of particles (the proposed fractal method) describes and agrees more with the data from the experiment than the sedimentation efficiency calculated only based on particle size (classic method). [ABSTRACT FROM AUTHOR]

Currently, the application of natural materials is a good alternative to prevent secondary damage to humans and the environment. Therefore, in recent years, much attention has been paid to the use of these degradable and environmentally friendly materials to reduce toxicity and treatment costs. As a natural material, starch offers advantages of low cost, flexible modification, abundant presence of hydroxyl functional groups, and eco‐friendly. These configurations make it to a suitable material for remediation purposes, as it has received a great attention for removal of pollutants from water and wastewater, including but not limited to the heavy metals, pharmaceutical, dyes, and even inorganic contaminants. This work, therefore, aims to systematically evaluate starch‐based materials applications in remediation of water and wastewater media using the appropriate search terms from international databases including PubMed, Science Direct and Google Scholar, and through PRISMA checklist. For this, the publications from 1973 to 2021 are searched. In the initial search, 980 articles are found of which 49 articles are included in the study. Then, the performance of the starch‐based materials for every single study as the pollutant(s) involved is summarized and discussed. The advantages and disadvantages of such application are extracted and a perspective is presented accordingly. This comprehensive review shows that the starch‐based derivatives' can be potential options in water and wastewater treatment purposes, especially those modified. However, some limitations should be overcoming before scaling of the results. [ABSTRACT FROM AUTHOR]

Microalgae are a valuable source of lipids, proteins, and pigments, but there are challenges in large-scale production, especially in harvesting. Existing methods lack proven efficacy and cost-effectiveness. However, flocculation, an energy-efficient technique, is emerging as a promising solution. Integrating surfactants enhances microalgal harvesting and disruption simultaneously, reducing processing costs. This study investigated cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and sodium dodecyl sulphate (SDS) for harvesting Tetraselmis sp. strains (75LG and 46NLG). CTAB exhibits superior results, with 88% harvesting efficiency at 1500 and 2000 mg L−1 for 75LG and 46NLG, respectively, for 60 min of sedimentation—thus being able to reduce the operating time. Beyond evaluating harvesting efficiency, our study explored the kinetics of the process; the modified Gompertz model led to the best fit. Furthermore, the largest kinetic constants were observed with CTAB, thus highlighting its efficacy in optimising the microalgal harvesting process. With the incorporation of the suggested enhancements, which should be addressed in future work, CTAB could hold the potential to optimise microalgal harvesting for cost-effective and sustainable large-scale production, eventually unlocking the commercial potential of microalgae for biodiesel production. [ABSTRACT FROM AUTHOR]

WTP Rozgrund, which was used to treat to the water from Rozgrund reservoir, must have been set out of operation due to the deteriorated quality of the water and its smell. The aAim of this work was to perform the pilot-plant tests, with the goal ofaiming to treating water from the reservoir to achieveand get the compliantying water quality of the water. Conventional water treatment concerning coagulation, flocculation, and filtration with two different filtration fillings – Filtralite Mono-MultiFine and filter sand with black-coal material Carboziar – was compared with conventional treatments with filter sand and Carboziar complemented with filtration through granulated active coal (Norit 830), the ultrafilration using fully automated equipment with membrane module UA-640 (Microdyn-Nadir), and ultrafiltration combined with active granulated carbon. Monitored wereas the pH, turbidity, color, alkalinity, CODMn, TOC, aluminum, number and size of particles, and hydrobiology in the samples of raw and treated water. Obtained results provided that the two most suitable treatment technologies were the filtration with double layer filling consisting of sand and antracite combined with filtration via GAU (removal efficiency of CODMn and turbidity was 90.5% and 85%, respectively) and the ultrafiltration combined with GAU (82.6% for CODMn and 89% for turbidity removal). Biological activation after the treatment was not found. [ABSTRACT FROM AUTHOR]

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In this study, cashew nut husk was used to prepare agro-based coagulant (Tanhusk). The agro-based coagulant was compared with aluminum sulfate (alum) in the treatment of paint industry effluent (PIE). The effects of parameters such as pH (4–12), contact time (0–60 min), and coagulant dosage (100–500 mg/L) on the effluent decontamination were investigated. Coagulation/flocculation efficiency using Tanhusk was found to increase with contact time and decreasing pH, while alum performed better at alkaline conditions. A comparison of the results gave an efficiency of alum at 91% and Tanhusk at 73.18%. The kinetics of the coagulation and flocculation treatment of PIE using alum and Tanhusk by the integral and particle aggregation were studied. The reaction order kinetics for alum and Tanhusk were second order. The rate constants were 0.00008 L/mg and 0.00005 L/mg min for alum and Tanhusk, respectively. The kinetics of particle aggregation based on Tanhusk bio-coagulant dosage and effluent pH showed that the destabilization of monomers facilitated the forming of dimers and trimers. The study affirmed that the plant-based coagulant Tanhusk can be a potential replacement for alum for the treatment of paint effluent. [ABSTRACT FROM AUTHOR]

This study aimed to optimize the removal of tannic acid (TA) from simulated wastewater by applying the electrocoagulation (EC) process and the alum nanoparticles (Al NPs) generated during the EC process, using the response surface method (RSM) methodology based on the central composite design (CCD). The structure and state of Al NPs were studied by X-ray diffraction analysis, field emission scanning electron microscopy, X-ray fluorescence (XRF), and Brunauer–Emmett–Teller analyses. We used four independent factors: current–voltage (20.83, 41.66, 62.49, 83.32, and 104.16 A/m2)/Al NPs dosage (0.1, 0.325, 0.55, 0.775, and 1 g/L), initial pH (5, 6, 7, 8, and 9/ 3, 5, 7, 9, and 11), initial TA concentration (10, 35, 60, 85, and 110 mg/L), and treatment time (10, 20, 30, 40, and 50 min). In addition, the total TA removal percentage was taken as a response variable. The analysis of the responses was performed using analysis of variance (ANOVA) as a statistical method. The quadratic model was proposed, and the ANOVA and model fitness were produced through RSM, with the coefficient of determination (R2) above 0.94 and 0.96 for all two responses representing the high importance of the suggested model. The EC process and the Al NPs removed TA with a maximum efficiency of 89.79% and 96.33%, respectively, in the optimal condition. The results indicated that the EC process and the Al NPs were effective and readily available methods for TA removal from aquatic environments. [ABSTRACT FROM AUTHOR]

This study delves into assessing the effectiveness of modified magnetic seeds in treating oily wastewater through magnetic flocculation. Initially, the research focuses on characterizing the magnetic seeds' properties and evaluating their oil adsorption capabilities pre- and post-modification. The investigation identifies a correlation between the adsorption process and the second-stage kinetic magnetic seed model as well as the Langmuir model, both before and after modification. Moreover, the study highlights the enhanced adsorption capacity of modified magnetic seeds for chemical oxygen demand in comparison with conventional ones. Interestingly, both types of seeds display a closer conformity with the Freundlich adsorption isotherm model concerning their oil adsorption behaviors. In the magnetic flocculation process, polymerized aluminum chloride serves as the flocculant at a specific concentration in conjunction with magnetic seeds. Optimal treatment conditions involve maintaining a particular water temperature and pH level. These conditions facilitate a chemical oxygen demand removal rate of 75.5% and an impressive 93.2% efficiency in removing oil content. As a result, utilizing modified magnetic seeds exhibits substantial potential in degrading pollutants within oily wastewater treatment. This approach not only enhances adsorption capabilities when combined with magnetic flocculation but also provides valuable theoretical insights into treating oily wastewater via magnetic flocculation. [ABSTRACT FROM AUTHOR]

In the aim of textile printing and dyeing wastewater efficient and environmental friendly treatment, a cross-linked grafted cationic starch flocculant (CGSt) was prepared to study its removal performance of textile dyes. Here in, corn starch (St) was used as raw material, methacryloyloxyethyl trimethyl ammonium chloride and N.N′-methylenebisacrylamide were used as cationization grafting monomer and crosslinking monomer, respectively, and an environmentally friendly Fenton initiation system was adopted. The chemical structure and physicochemical properties of CGSt were characterized FTIR, NMR, XPS, EDS, XRD and SEM. The flocculation performance of CGSt on acid light yellow G, direct lake blue 5B and reactive brilliant blue KE-GN was investigated. The removal rate (RR) of CGSt to acid light yellow G, reactive brilliant blue KE-GN and direct lake blue 5B reaches 97.2%, 96.3% and 97.2%, respectively. CGSt has a wide flocculation window from 5 g/L to 12 g/L. It maintains good flocculation performance in a wide pH range from 4 to 9, and the RR was the highest when pH was 9, which is beneficial for the treatment of textile printing and dyeing wastewater with high alkalinity, complex composition and variable water quality by CGSt. [ABSTRACT FROM AUTHOR]

Cactus cladodes have been emerged as one of the most popular plant-based flocculants. They have been listed as a promising natural alternative to the noxious synthetic flocculants. However, practical application of this bio-flocculant is still hampered by some questions concerning their formulations' stability, active agents therein and their flocculating performance. Thus, in this study, three cactus formulations, namely, cactus juice (CJ), cactus lyophilized powder (CLP) and oven-dried powder (CDP) were subjected to a physicochemical characterization to provide an in-depth understanding of the main flocculation active agents and distinguish the suitable preparation method promoting bio-flocculants' stability and effectiveness. Therefore, their flocculating activity was evaluated in treating a model-colored effluent, a crystal violet (CV) dye solution. The obtained results show that the three cactus formulations exhibit a significant sugars content with considerable calcium amounts. The highest sugars content was registered for CLP thanks to the efficacy of lyophilization method to maintain their stability. Furthermore, the main flocculating active compound was identified as an arabinogalactan composed of long polygalacturonic acid chain backbones with branches of neutral sugar residues involving mostly the arabinose. As for the color removal performance, an outstanding CV removal exceeding 99% was found using CLP under alkaline pH. It was occurred through charge neutralization and bridging mechanisms. Hence, based on these groundbreaking results, the application of cactus formulation-based flocculants, especially the lyophilized one is highly recommended to ensure a clean, eco-friendly and sustainable wastewater treatment approach. [ABSTRACT FROM AUTHOR]

The main purpose of this paper was to reveal the effect of aluminum (Al)-based coagulants on enhanced coagulation for the removal of algae and the synergistic optimization mechanism among different Al species. The formation, breakage, and regrowth processes of algal coagulation flocs formed by a series of monomeric Al-based coagulants (Al2(SO4)3, Al13, and Al30), Al13/Al30 composite coagulant and poly(diallyldimethylammonium chloride)/Al13 (PDADMAC/Al13) composite coagulant were studied. Results indicated that Al13 mainly employed a charge neutralization mechanism, which was conducive to the destabilization of algae and the regeneration of flocs, while Al30 mainly employed a sweep flocculation mechanism, which was conducive to the formation of algae and the strength of flocs. Meanwhile, the charge neutralization was the main mechanism during the algae coagulation process because it could effectively remove the soluble microbial products (SMP) component in the extracellular organic matter (EOM). Therefore, Al13 could achieve a higher coagulation performance than other monomeric Al-based coagulants. The Al13/Al30 composite coagulant could make up for the deficiency of the sweep flocculation mechanism in Al13 and charge neutralization mechanism in Al30, and achieve the best synergistic optimization performance at Al13:Al30-7:3. Additionally, PDADMAC, as a polymer, could further enhance the charge neutralization ability of Al13 at low dosages and the sweep flocculation ability of Al13 at high dosages, respectively. However, an excessive dosage would lead to charge reversal and thus reduce the coagulation effect. Therefore, controlling the dosage was key when using Al-composite coagulants. The findings of our research could offer a certain theoretical foundation for the development of inorganic polymer flocculants. [ABSTRACT FROM AUTHOR]

Cassia fistula (C. fistula) seed-derived coagulants have demonstrated substantial potential for treating dye-based wastewater. Such coagulants exhibit notable coagulating-flocculating activity and are environmentally friendly. However, recovering these natural coagulants from aqueous media poses challenges. In this study, we introduce a novel plant-derived magnetic coagulant that is a combination of C. fistula seed gum with magnetic spinel ferrite. This research includes a pilot-scale study to simulate full-scale textile wastewater treatment using this composite. Material characterisations revealed that spherical CoFe2O4 particles could be effectively coated with the active coagulant, C. fistula gum. The saturation magnetisation of the composite, measured at 54.11 emu/g, facilitates its convenient separation from aqueous solutions using an external magnetic field. Bench-scale studies showed that initial pH and coagulant dosage substantially affect the removal efficiency of colour and chemical oxygen demand (COD). In the pilot-scale study, the C. fistula-CoFe2O4 composite demonstrated promising coagulant properties. It achieved a colour removal percentage of 94.0 % with a volume of 30 L and a coagulant dosage of 12.3 g L-1 . Using this coagulation-flocculation process as a primary treatment step, possibly followed by biological or membrane methods, can help meet Vietnamese environmental standards. [ABSTRACT FROM AUTHOR]

Abstract In this study, the effect of presence and concentration of two synthetic polymeric flocculants with different charging mechanisms (anionic and cationic) on surface quality and abrasive tool wear in polishing process of building stones was investigated. The polishing tests were performed in laboratory scale on two stone samples (granite and marble). An index, entitled improvement index (I) was defined for evaluating the effectiveness of flocculants on surface quality and abrasive tool wear. The results revealed that flocculation process had a noticeable effect on enhancement of surface quality and reduction of abrasive tool wear for both stone samples. The cationic flocculant was more effective for granite sample and anionic flocculant was more effective for marble sample. The granite particles mainly exhibit negative surface charge while the marble particles have positive surface charge in the pH range of wastewater used for polishing tests. Therefore, charge neutralization mechanism plays a major role in flocculation process of granite and marble samples. It was found that the use of flocculation process for treatment of wastewater in stone processing plants leads to increase of abrasive tool lifespan and more high-quality products.

The wastewater treatment process for middle rank coal employed coagulation-flocculation technology with bio coagulants to efficiently reduce the concentration of contaminants. This method utilized Moringa oleifera L. seed powder as the main bio coagulant, in addition to papaya seeds (Carica papaya Linn) and Ambon banana peel waste (Musa paradisiaca var) as secondary bio coagulants, which are combined with the main bio coagulant. The aim of this study was to determine the characteristics and effectiveness of bio coagulant compounds obtained from plants and waste materials. The study objective was also to investigate the effectiveness of combining bio-coagulants derived from Moringa oleifera L., Carica papaya, and Musa paradisiaca var in treating coal effluent. Biocoagulant is a natural alternative to chemicals like Aluminum Sulfate (Alum) that are detrimental to the environment. It is present in the ecosystem and serves as a substitute for these hazardous substances. The results revealed that the optimal dosage for combining bio coagulants was 1 gram per liter, with a composition ratio of 2 parts primary bio coagulant to 1 part auxiliary bio coagulant. The analysis of water pollutants showed a reduction in turbidity and Total Suspended Solid (TSS) by 99.26% and 99.11% respectively. Additionally, there was a decrease in the levels of heavy metals Iron (Fe) and Manganese (Mn) by 98.71% and 99.88% respectively.