Application of Plant-Based Coagulants and Their Mechanisms in Water Treatment:A Review

This review describes the mechanisms of natural coagulants.It provides a good understanding of the two key processes of coagulation-flocculation:adsorption and charge neutralization,as well as adsorption and bridging.Various factors have influence the coagulation/flocculation process,including the effect of pH,coagulant dosage,coagulant type,temperature,initial turbidity,coagulation speed,flocculation speed,coagulation and flocculation time,settling time,colloidal particles,zeta potential,the effects of humic acids,and extraction density are explained.The bio-coagulants derived from plants are outlined.The impact of organic coagulants on water quality,focusing on their effects on the physicochemical parameters of water,heavy metals removal,and bacteriological water quality,is examined.The methods of extraction and purification of plant-based coagulants,highlighting techniques such as solvent extraction and ultrasonic extraction,are discussed.It also examines the parameters that influence these processes.The methods and principles of purification of coagulating agents,including dialysis,freeze-drying,ion exchange,electrophoresis,filtration,and centrifugation,are listed.Finally,it evaluates the sustainability of natural coagulants,focusing on the environmental,technical,and economic aspects of their use.At the end of this review,the readers should have a comprehensive understanding of the mechanisms,selection,extraction,purification,and sustainability of plant-based natural coagulants in water treatment.

On-line optical determination of floc size of Fe(Ⅲ) coagulants

This study investigated the floc aggregation, average floc size, floc size variance and floc growth velocity when ferric chloride （FeCl3） and polyferric chloride （PFC） were used to treat the simulated water samples. The factors including coagulant dose, ionic strength and solution pH, which affect the floc aggregation, were studied. Experiments were carried out in a bench-scale reactor using photometric dispersion analyzer （ PDA）. Results showed that there were great differences between the floc aggregation of PFC and FeCl3. The average floc size and fioc growth velocity of PFC were much larger than those of FeCl3. Compared with FeCl3, PFC gave a better coagulation performance in wider range of pH, dosage and ionic strength. It was also found that the coagulation efficiency of PFC did not depend on average floc size but on floc growth velocity.

The Effect on Activated Sludge of Chemical Coagulants Applied in Synchronization Dephosphorization

Combined with the practical experience of wastewater treatment plant, the chemical coagulants have inhibition effects on microorganism activity, with the influence degree of PAC (polyaluminium chloride) > AlCl3> Fe2(SO4)3. In synchronization dephosphorization, the inhibition rates of PAC in 10 ppm and 20 ppm are 11.9% and 33% respectively;while the inhibition rates of AlCl3 and Fe2(SO4)3 in 20 ppm are 15.8% and 8.5% respectively, compared with 9.6% and 5.4% in 10 ppm. Backwash wastewater from sand filter after adding coagulants has no direct inhibition effect on microorganism, but it results in inorganic components increase in active sludge. By taking North STP as an example, the VSS/SS ratio reduced from 0.65 after coagulants application to 0.54.

Use of Natural Coagulants in Removing Organic Matter, Turbidity and Fecal Bacteria from Hospital Wastewater by Coagulation-Flocculation Process

Hospital wastewater represents an infectious and toxic risk to human health and the environment due to its contents. Most hospitals in developing countries, including Benin, do not have a wastewater treatment plant. In this study, the wastewater from two hospitals in northern Benin was characterized and then treated with Azadirachta indica leaves, Moringa oleifera and Luffa cylindrica seeds by coagulation/flocculation process. The wastewater characteristics showed that the collected samples are greatly polluted by organic matter and fecal bacteria such as Escherichia coli, Enterococcus fecal and Total coliforms. Jar-test results revealed that 95.74%, 78%, 49.19% of turbidity, 51.35%, 38.32%, 22.19% of COD, 93.16%, 85.26%, 83.30% against Escherichia coli, 92.11%, 90.93%, 94.60% against total Coliforms and 99.37%, 91%, 99%, 55.07% against Enterococcus were removed from hospital wastewater using Moringa oleifera, Luffa cylindrica seed and Azadirachta indica leaves respectively at dose of 100 mg/L. The results highlighted that the natural coagulants could be successfully used for the removal of turbidity and fecal bacteria from hospital wastewater.

Study on coagulation property of metal-polysilicate coagulants in low turbidity water treatment

In order to remove the low turbidity present in surface water, a novel metal-polysilicate coagulant was used to treat the raw water taken from Tanjiang River in Guangdong Province. This study on the effects of Al/Fe molar ratio on the performance of a complex compound formed by polysilicic acid, aluminium and ferric salt (PAFS) showed that PAFS with Al/Fe ratio of 10:3 seemed to have the best coagulation performance in removing turbidity and color. Experimental results showed that under the conditions of polymerization time of 15 d, sedimentation time of 12 min, and pH of 6?8, PAFS with Al/Fe molar ratio of 10:3 had the best coagulation efficiency and lowest residual Al concentration. The turbid- ity decreased from 23.8 NTU to 3.23 NTU and the residual Al concentration was only 0.165 mg/L in the product water. It could be speculated that colloidal impurities and particulate Al were removed by adsorption bridging and electrical neu- tralization of long chain inorganic polymer coagulants.

Treatment of bleaching wastewater from pulp paper plants in China using enzymes and coagulants

The treatment of wastewater from pulp-paper plants in China by horseradish peroxidase was investigated in this study. The effects of horseradish peroxidase and coagulants were discussed in detail. The results indicated that enzymes might improve the removal of AOX, TOC and colour for pulp\|paper wastewater and modified chitosan is far more effective than Al\-2(SO\-4)\-3 to remove AOX, TOC and colour.

Preparation of New Poly Silicate Iron Coagulants and Their Coagulation Property on Micro-polluted Water

The sodium silicate, ferric chloride, ferrous sulfate, sodium chlorate and other common inorganic materials were used to synthesize two new poly silicate iron coagulants： Polysilicate Ferric Chloride （PFSiC） and Polymeric Ferric Silicate Sulfate （PFSiS）. Their coagulation effect on micro-polluted water was compared with the poly ferric choride （PFC） saled in the market. The results showed that turbidity, organic matter, total phosphorus, total nitrogen removal rate ofPFSiC, PFSiS coagulant were better than PFC on micro-polluted water treatment at the same dosage. The coagulation effect of PFSiC was the best. The surface morphology of three coagulants was observed by scanning electron microscopy （SEM）, and the coagulation mechanism was discussed preliminarily.

Ellagic Acid-induced Hypercoagulable State in Animals:a Potentially Useful Animal Hypercoagulable Model for Evaluation of Anticoagulants

Objective To establish and evaluate a hypercoagulable animal model for the assessment of anticoagulants. Methods Forty mice, thirty-two rats, and twenty-four rabbits were randomly and equally divided into control group (saline) and three ellagic acid (EA)-treated groups (low, middle, and high doses). In the mice, bleeding time (BT) was estimated with tail transaction, and clotting time (CT) with template method. Prothrombin time (PT) and the activated partial thromboplastin time (APTT) in rats and rabbits were measured by means of Quick's one-stage assay and modified APTT assay respectively. In addition, thrombin activity was estimated in rats with PT assay using a hemagglutination analyzer. The circulating platelet aggregates were de- tected in rabbits through platelet counting and presented as the circulating platelet aggregate ratio (CPAR). Results EA shortened BT and CT in mice, PT and APTT in rats, and increased thrombin activity and CPAR, all in a dose-dependent manner. EA also brought reduction of PT and APTT in rabbits in dose- and time-dependent manners. Conclusion EA could induce hypercoagulable state through activating coagulation system and platelets in mice, rats, and rabbits.

Heparin and other anticoagulants in amniotic fluid embolism(AFE):Literature review and concept of the therapy

Aim: The objective of this study is to review all the reported outcomes of heparin application in amniotic fluid embolism (AFE) so far and to find out why, when and how heparin or other anticoagulants should be used in AFE. Material and methods: We searched Medline (from 1969 to 2011), using two key words: 1) amniotic fluid embolism;2) amniotic fluid embolism and heparin. The search for the former produced 1127 replies, of which 208 were case reports of AFE. In response to the other key word, there were 94 articles. We looked through all the articles, selecting those relevant for our study. Results: In the years 1969-2011, 208 AFE cases were reported. Heparin (unfractionated heparin) or low molecular weight heparin (LMWH) was applied in 20 cases (9.6%), being the main drug in 11 cases (5.3%) and in 6 cases as a component of spectacular treatment of AFE (surgical treatment and extracorporal membrane oxygenation). In one of these cases anithrombin (AT) with LMWH was used. In one patient heparin therapy was considered to be unsuccessful and hence recombinant plasminogen activator (rt-PA) was instituted. All the patients survived. Conclusions: 1) The attempts to use heparin in AFE could be defined as promising, although the number of treated patients is too small for conclusion;2) The postulate to use heparin at the very onset of AFE (a bolus of 10,000 U followed by monitored intravenous infusion) has serious justification: one of the pathways of AFE is the target for heparin (coagulation pathway).

PREPARATION OF ASYMMETRIC POLYETHERKETONE FLAT AND HOLLOW FIBER MEMBRANES FOR GAS SEPARATION USING ACETIC ACID BASED COAGULANTS

Membranes for gas separation have developed significantly in the last twenty years,however,there is still a need for high temperature and chemically resistant membranes that exhibit good selectivity and gas permeability.Our study examines the fundamental properties of polyetherketone (PEK,a thermally stable and chemically resistant polymer) membranes prepared using concentrated sulphuric acid (98% H_2SO_4) as the solvent.Non-solvents used in the work included acetic acid,ethanol,methanol,glycerol,and water....

Minimization of Residual Aluminum in Drinking Water by Using Nontoxic Polysilicate Coagulants

Two kinds of complex polysilicate coagulants-polysilicate iron PSI and polysilicate ferric aluminum PSFA were prepared. The polymerization processes of PSI and PSFA were investigated under various conditions. Experimental results show that the molecular weight(M.W.) of polysilicic acid PS and the molar ratio of Fe 3+ to SiO 2 are two of the most important factors for preparing high effective coagulants PSI and PSFA. It is shown that PSI and PSFA are not only high effective, nontoxic and cheap coagulants, but also effective for decreasing the dosage of aluminum salt. The mechanism of coagulation of PSI and PSFA is also discussed in this paper.

The effects of coagulants on the structure of PBO materials

PBO materials possess super mechanical properties and high thermal and chemical resistance due to their special rigid-rod backbones with heterocyclie chemical structure and supermolecular microstrueture. But these structures may be affected by a series of preparing technologies, among which the coagulant is even more important. In this paper the chemical and microstrueture changes of PBO materials coagulated with different solvents were investigated. Analyses of molecular weight and chemical structure of PBO coagulated indicate that the heteroeyclie ring of PBO will experience cleavage in coagulation and in this stage water plays an important role. The final structure of PBO materials may involve several intermediate structures lying between benzoxazole a,d the open ring. Wide-angle X-ray diffraction （WAXD） 20 scans and scanning probe microscope （ SPM ） show that the microstrueture of PBO materials eoagulated in solvents with different properties will change a lot and those coagulants with the smaller rate of diffusion like methanol can cause more ordered molecule alignment containing fewer voids.

Removal of dispersant-stabilized carbon nanotubes by regular coagulants

Coagulation followed by sedimentation, as a conventional technique in the water treatment plant, can be the first line of defense against exposures of carbon nanotubes （CNTs） to aquatic organisms and human beings, which has been rarely documented. This study investigated the removal of dispersant-stabilized CNT suspensions by poly aluminum chloride （PAC1） and KAl（SO4）2-12H20 （alum）, with a focus on the effects of dispersant type, coagulant type and dosage. PAC1 performed better than alum in the removal of tannic acid-, humic acid-, and sodium dodecyl benzenesulfonate-stabilized CNTs, but worse for polyethylene glycol octylphenyl ether （TX100）-stabilized CNTs. Neither coagulant could effectively precipitate cetyltrimethyl ammonium bromide-stabilized CNTs. The removal by PACl first increased up to a plateau and then decreased with the continued increase of coagulant dosage. However, the removal rates leveled off but did not decrease after achieving their highest level with the continued addition of alum. The coagulation and flocculation of the CNT suspensions by PACl could be regulated mainly by the mechanism of adsorption charge neutralization, whereas the coagulation by alum mainly involved electrical double-layer compression.

Coagulation behavior and floc properties of compound bioflocculant–polyaluminum chloride dual-coagulants and polymeric aluminum in low temperature surface water treatment

This study was intended to compare coagulation behavior and floc properties of two dualcoagulants polyaluminum chloride–compound bioflocculant（PAC–CBF）（PAC dose first） and compound bioflocculant–polyaluminum chloride（CBF–PAC）（CBF dose first） with those of PAC alone in low temperature drinking water treatment. Results showed that dualcoagulants could improve DOC removal efficiency from 30% up to 34%. Moreover, CBF contributed to the increase of floc size and growth rate, especially those of PAC–CBF were almost twice bigger than those of PAC. However, dual-coagulants formed looser and weaker flocs with lower breakage factors in which fractal dimension of PAC–CBF flocs was low which indicates a looser floc structure. The floc recovery ability was in the following order：PAC–CBF 〉 PAC alone 〉 CBF–PAC. The flocculation mechanism of PAC was charge neutralization and enmeshment, meanwhile the negatively charged CBF added absorption and bridging effect.

Coagulation indices and fibrinogen degradation products as predictive biomarkers for tumor-node-metastasis staging and metastasis in gastric cancer

BACKGROUND Gastric cancer(GC)is a prevalent malignancy with a substantial health burden and high mortality rate,despite advances in prevention,early detection,and treatment.Compared with the global average,Asia,notably China,reports disproportionately high GC incidences.The disease often progresses asymptoma-tically in the early stages,leading to delayed diagnosis and compromised out-comes.Thus,it is crucial to identify early diagnostic biomarkers and enhance treatment strategies to improve patient outcomes and reduce mortality.METHODS Retrospectively analyzed the clinical data of 148 patients with GC treated at the Civil Aviation Shanghai Hospital between December 2022 and December 2023.The associations of coagulation indices-partial thromboplastin time(APTT),prothrombin time(PT),thrombin time(TT),fibrinogen,fibrinogen degradation products(FDP),fasting blood glucose,and D-dimer(D-D)with TNM stage and distant metastasis were examined.RESULTS Prolongation of APTT,PT,and TT was significantly correlated with the GC TNM stage.Hence,abnormal coagulation system activation was closely related to disease progression.Elevated FDP and D-D were significantly associated with distant metastasis in GC(P<0.05),suggesting that increased fibrinolytic activity contributes to increased metastatic risk.CONCLUSION Our Results reveal coagulation indices,FDPs as GC biomarkers,reflecting abnormal coagulation/fibrinolysis,aiding disease progression,metastasis prediction,and helping clinicians assess thrombotic risk for early intervention and personalized treatment plans.

Removal characteristics of microplastics by Fe-based coagulants during drinking water treatment

Microplastics have caused great concern worldwide recently due to their ubiquitous presence within the marine environment. Up to now, most attention has been paid to their sources,distributions, measurement methods, and especially their eco-toxicological effects. With microplastics being increasingly detected in freshwater, it is urgently necessary to evaluate their behaviors during coagulation and ultrafiltration(UF) processes. Herein, the removal behavior of polyethylene(PE), which is easily suspended in water and is the main component of microplastics, was investigated with commonly used Fe-based salts. Results showed that although higher removal efficiency was induced for smaller PE particles, low PE removal efficiency(below 15%) was observed using the traditional coagulation process, and was little influenced by water characteristics. In comparison to solution pH, PAM addition played a more important role in increasing the removal efficiency, especially anionic PAM at high dosage(with efficiency up to 90.9%). The main reason was ascribed to the dense floc formation and high adsorption ability because of the positively charged Fe-based flocs under neutral conditions. For ultrafiltration, although PE particles could be completely rejected,slight membrane fouling was caused owing to their large particle size. The membrane flux decreased after coagulation; however, the membrane fouling was less severe than that induced by flocs alone due to the heterogeneous nature of the cake layer caused by PE, even at high dosages of Fe-based salts. Based on the behavior exhibited during coagulation and ultrafiltration, we believe these findings will have potential application in drinking water treatment.

Optimisation of chemical purification conditions for direct application of solid metal salt coagulants:Treatment of peatland-derived diffuse runoff

The drainage of peatland areas for peat extraction, agriculture or bioenergy requires affordable, simple and reliable treatment methods that can purify waters rich in particulates and dissolved organic carbon. This work focused on the optimisation of chemical purification process for the direct dosage of solid metal salt coagulants. It investigated process requirements of solid coagulants and the influence of water quality, temperature and process parameters on their performance. This is the first attempt to provide information on specific process requirements of solid coagulants. Three solid inorganic coagulants were evaluated： aluminium sulphate, ferric sulphate and ferric aluminium sulphate. Pre-dissolved aiuminium and ferric sulphate were also tested with the objective of identifying the effects of in-line coagulant dissolution on purification performance. It was determined that the pre-dissolution of the coagulants had a significant effect on coagulant performance and process requirements. Highest purification levels achieved by solid coagulants, even at 30% higher dosages, were generally lower （5%-30%） than those achieved by pre-dissolved coagulants. Furthermore, the mixing requirements of coagulants pre-dissolved prior to addition differed substantially from those of solid coagulants. The pH of the water samples being purified had a major influence on coagulant dosage and purification efficiency. Ferric sulphate （70 mg/L） was found to be the best performing solid coagulant achieving the following load removals： suspended solids （59%-88%）, total organic carbon （56%-62%）, total phosphorus （87%-90%）, phosphate phosphorus （85%-92%） and total nitrogen （33%-44%）. The results show that the use of solid coagulants is a viable option for the treatment of peatland-derived runoff water if solid coagulant-specific process requirements, such as mixing and settling time, are considered.

Coagulation behaviors and in-situ flocs characteristics of composite coagulants in cyanide-containing wastewater:Role of cationic polyelectrolyte

In this paper, composite coagulants （PFS, PFSC05, PFSC1 and PFSC5）, prepared by mixing polyferric sulfate （PFS） and cationic polyelectrolyte （CP） coagulants with different weight percent （Wv） of CP （Wp = 0%, 0.5%, 1% and 5%, respectively）, were adopted to treat cyanide-containing wastewater. PFSC5 exhibited superior coagulation performances at optimal conditions： the removal of total cyanide （TCN） and chemical oxygen demand （COD） was 95%-97% and 50%-55%, respectively. The effects of CP on the properties and structure of flocs were investigated by laser diffraction instrument and small-angle laser light scattering （SALLS）, respectively. The results show that the flocs of PFSC5 have higher growth rate, higher strength factor and lower recovery factor than other flocs. They are also much denser and more uniform owing to the higher fractal dimension （DO and less microflocs （10-100μm）. Furthermore, the dense structure of the PFSC5 flocs can be restored after shear and is more resistant to hydraulic conditions. Particularly, detailed morphology evolution of the flocs was in-situ detected by on-line particle imaging. Due to strong ionic strength in wastewater, the CP in PFSC5 plays a significant role of adsorption, while the main mechanism of CP is electrostatic patch aggregation during the PFSC05 systems.

Efficacy of two chemical coagulants and three different filtration media on removal of Aspergillus flavus from surface water

Aquatic fungi are common in various aqueous environments and play potentially crucial roles in nutrient and carbon cycling as well as interacting with other organisms. Species of Aspergillus are the most common fungi that occur in water. The present study was undertaken to elucidate the efficacy of two coagulants, aluminum sulfate and ferric chloride, used at different concentrations to treat drinking water, in removing Aspergillusflavus, as well as testing three different filtration media： sand, activated carbon, and ceramic granules, for their removal of fungi from water. The results revealed that both coagulants were effective in removing fungi and decreasing the turbidity of drinking water, and turbidity decreased with increasing coagulant concentration. Also, at the highest concentration of the coagulants, A. flavus was decreased by 99.6% in the treated water. Among ceramic granules, activated carbon, and sand used as media for water filtration, the sand and activated carbon filters were more effective in removing A.flavus than ceramic granules while simultaneously decreasing the turbidity levels in the test water samples. Post-treatment total organic carbon （TOC） and total nitrogen （TN） concentrations in the experimental water did not decrease; on the contrary, TN concentrations increased with the increasing dosage of coagulants. The filtration process had no effect in reducing TOC and TN in tested water.

Utilization of plant-based natural coagulants as future alternatives towards sustainable water clarification

Rapid industrial developments coupled with surging population growth have complicated issues dealing with water scarcity as the quest for clean and sanitized water intensifies globally. Existing flesh water supplies could be contaminated with organic, inorganic and biological matters that have potential harm to the society. Turbidity in general is a measure of water cloudiness induced by such colloidal and suspended matters and is also one of the major criteria in raw water monitoring to meet the stipulated water quality guidelines. Turbidity reduction is often accomplished using chemical coagulants such as alum. The use of alum is widely associated with potential development of health issues and generation of voluminous sludge. Natural coagulants that are available in abundance can certainly be considered in addressing the drawbacks associated with the use of chemical coagulants. Twenty one types of plant-based natural coagulants categorized as fruit waste and others are identified and presented collectively with their research summary in this review. The barriers and prospects of commercialization of natural coagulants in near future are also discussed.