SCIENCE OF THE TOTAL ENVIRONMENT
·
2019
·
IF 5.589
Dachao Lin,Zhongsen Yan,Xiaobin Tang,Jinlong Wang,Heng Liang,Guibai Li
Nanofiltration is routinely applied as an advanced water treatment technology after conventional water treatment. However, the residual coagulant after coagulation process may affect the nanofiltration process and to our best of knowledge, few studies focused on this phenomenon. To address such issues, ferric and aluminum ions were adopted as the model coagulant, and the influences of coagulant concentrations, coagulant conditioning time and fouling strategies on gypsum scaling were systematically investigated. The results indicated that coagulant conditioned on the membrane surface could improve membrane flux, enhance scaling, and increase the conductivity of permeate. The contents of coagulant accumulated on the membrane surface gradually increased with its increasing concentration in feed solution and extending conditioning time, resulting in severer scaling and flux decline. Interestingly, the formation of heterogeneous scaling layer will contribute to membrane fouling alleviation and prevent the further flux decline regardless of the ongoing increase of coagulant concentrations in the feed water as well as on the membrane surface. As a result, a critical value of coagulant concentrations in the feed water was obtained in present conditions. Furthermore, it's found that successive fouling strategy could lead to less gypsum scaling but severer flux decline, compared to simultaneous fouling strategy. Both the scaling quantity and scaling morphologies conferred significant influence on the flux decline. It is suggested that the concentrations of coagulant should be strictly controlled prior to nanofiltration process, especially with practical relevance for the applications of it in treating the water rich in calcium ions and sulfate anions.
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2021
·
IF 7.312
Yonghai Gan,Zhihao Hang,Bingdang Wu,Haojie Li,Wentao Zhang,Yeyang Sun,Runsheng Li,Shujuan Zhang
Basicity is an intrinsic factor of coagulants that plays important roles in turbidity removal. However, the effects of basicity on the coagulation performance of titanium (Ti) coagulants remain unclear. This knowledge gap is mainly due to the lack of highly polymerized Ti coagulants. In this study, we fabricated a series of Ti-based coagulants with basicity values in the range of 0–93% and evaluated their coagulation performance with simulated and real waters of low-turbidity. A positive correlation was observed between the basicity of the Ti coagulants and the coagulation performance, i.e., higher basicity led to higher turbidity removal, larger floc size, and faster settling rate. For the two titanium xerogel coagulants (TXC) of similar chemical structures, the one with a higher basicity (TXC-93%) worked better than the one of a lower basicity (TXC-78%). The advantage brought from the difference in basicity is of great significance in the purification of low-turbidity water. For the treatment of a surface river water, the required dosage of TXC-93% was about 1/2 to 1/3 of those of titanium tetrachloride (TiCl 4 ) and polytitanium tetrachloride (PTC-21%), and was comparable to that of a high-quality commercialized polyaluminum chloride (PAC-72%). The results here provide a useful technical guidance for the mass production and application of Ti coagulants.
研究领域:
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Journal of Environmental Sciences
·
2019
·
IF 3.556
Yuxiang Xue,Zhouzhou Liu,Aimin Li,Hu Yang
The applications of natural polymeric flocculants due to their green feature has been recently received much more attention. In this work, the combined usages of a cationic starch-based coagulant and polyaluminum chloride (PACl) were extensively evaluated for various addition sequences in the coagulation of both raw (surface water from the Jiuxiang River) and synthetic turbid water (two kaolin suspensions with different initial turbidities). Two typical cationic starch-based coagulants with different structures (St-G and St-E) were tried. In comparison to St-G, St-E and PACl used individually as well as St-G and St-E dosed after PACl, the combination of the starch-based coagulants fed before PACl showed higher turbidity removal efficiency, which featured not only less optimal doses of both inorganic and organic coagulants but also lower residual turbidity. On the basis of a detailed analysis of the particle size and its distribution in solution supernatants before and after coagulation by two starch-based coagulants and PACl, polymeric coagulants preferentially coagulate the small-sized colloids due to their distinct long-chain structures, but PACl preferentially coagulates the medium-sized ones. Thus, the medium-sized particles that were previously formed by the starch-based coagulants would be collectively and effectively removed by the subsequent addition of PACl. The addition sequence of the inorganic and organic coagulants in their combined usage is an important factor for improvement of the turbidity removal efficiency in practice.
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
·
2021
·
IF 10.588
Gefei Ma,Hui Xu,Xiaofang Yang,Guangyu An,Qinxue Yang,Xi Wang,Dongsheng Wang
Natural organic matter (NOM) can tremendously influence the purification efficiency of the drinking water treatment process. Coagulation was the first and primary process of NOM removal in the drinking water treatment process. The interaction between coagulants and NOM molecules remains unclear. Three typical coagulants (Al 13 , FeCl 3, and AlCl 3 ) were used to investigate the effects on NOM removal. The measurement of NOM was conducted using 15 T Electrospray Ionization coupled Fourier-Transform-Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR MS). The coagulation process altered the mass peak numbers as well as relative intensity of the peaks which were positively correlated with TOC value. The lignin-like compound was the most abundant moiety in raw water. Al-based coagulants remove more unsaturated larger compounds (lower KMD and higher carbon number). Al 13 remove the unsaturated hydrocarbons preferably. FeCl 3 is more reactive with NOM molecules and removes more fully saturated compounds. These findings revealed the coagulation removal mechanism of NOM with different structural characteristics and advise the practical use of coagulants for various raw water with different NOM characteristics.
研究领域:
环境科学
·
分析化学
✓ 已验证
DOI
高影响因子
WATER RESEARCH
·
2021
·
IF 11.236
Yonghai Gan,Li Zhang,Shujuan Zhang
Coagulation is a conventional method in water treatment. In recent decades, with the rapid development of membrane filtration, the use of coagulation is facing some new challenges. How to minimize the membrane fouling became a leading-edge topic in the study of coagulation. Here, the performances of three types of titanium coagulants were evaluated in terms of both the coagulation removal of toxic micropollutants and the alleviation of membrane fouling. Three oxysalts and two antibiotics were taken as representatives of inorganic and organic micropollutants. As compared with titanium tetrachloride (TiCl 4 ) and polytitanium chloride (PTC), titanium xerogel (TXC) with a higher polymerization degree showed much better performances in direct coagulation removal of oxysalts and antibiotics and in pre-coagulation for mitigating membrane fouling in both coagulation-sedimentation-ultrafiltration (CSUF) and in-line coagulation-ultrafiltration (CUF) processes. In the CSUF system, the membrane permeate flux with TXC pre-coagulation (89.5%) was much higher than those of TiCl 4 (56.1%) and PTC (57.4%). After a 5 day continuous operation, the transmembrane pressure in the CUF system with TXC coagulation was increased only to 4.9 kPa, while those of PTC and TiCl 4 were 12.2 and 18.5 kPa, respectively. The results here demonstrate that TXC is a promising coagulant for pollutant removal and membrane fouling alleviation, due to the following merits: better floc properties, weaker pH-dependence, and higher resistance to coordination with organic pollutants. The observation shed new lights on the fabrication and application of coagulants in a wide variety of scenarios.
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
International Journal of Environmental Research and Public Health
·
2023
·Vol. 20
·期 4
·2793
·
IF 4.614
Jie He,Qixuan Song,Jian He
In order to address the growing problem of water pollution caused by the excessive discharge of contaminants and provide a better aquatic ecosystem for the public, increasing attention has been paid to the harmlessness and efficiency of coagulation. In this study, polyaluminum lanthanum silicate (PALS) was synthesized through co-polymerization as a novel coagulant to treat wastewater. FTIR, XRD, and SEM were used to analyze the morphology and structure of the material, which further confirmed that the PALS was successfully synthesized. The results indicated that PALS had a great performance in the treatment of a kaolin–humic acid suspension under the optimal synthesis conditions with Al/Si = 3, La/Si = 0.1, and basicity = 0.7. Compared with conventional coagulants, PALS exhibited a better performance at a low coagulant dose and could achieve a good removal effect for an ultraviolet wavelength less than 254 nm (UV254) (83.87%), residual turbidity (0.49 NTU), and dissolved organic carbon (DOC) (69.57%) at the optimal conditions. Additionally, the PALS showed a better effect on phosphate removal than other coagulants did, where the removal efficiency could reach 99.60%. Charge neutralization and adsorption bridging were the potential wastewater treatment mechanisms employed by the PALS, which showed varied contributions under different pH levels. The results indicated that PALS can be a promising coagulant in water treatment.Keywords:coagulant;water treatment;phosphate adsorption;polymer bridging
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2023
·
IF 8.6
Hailin Yu,Huili Zhang,Chunlong Sun,Wen Yuan,Hongliang Li,Wei Jiang,Long Dong,Yingjun Wang,Hongsheng Liu
The complexity of oily sewage from oilfields has risen with the advancement of polymer flooding technology, thereby increasing the treatment challenge. In this study, a composite coagulant, PVPAM-PPFS, was proposed, inspired by octopus tentacles, with PVP as the backbone. FTIR , 1 H NMR and Rg radius of gyration were used to characterize the functional groups and conformation of PVPAM-PPFS in aqueous environments. The composite coagulant exhibits facile dispersion in water. Upon hydrolysis of PVPAM-PPFS, numerous molecular chains resembling octopus tentacles are formed and confirmed through Atomic Force Microscopy (AFM). When applied to oily sewage in oilfields, PVPAM-PPFS demonstrates enhanced interaction with emulsified oil layers, capturing colloidal particles in water and thereby facilitating efficient separation of oil, water, and flocs. Lastly, the mechanism of PVPAM-PPFS was analyzed through a combination of coagulation experiments and detection of floc morphology. PVPAM-PPFS will better interact with colloidal particles in water through increased charge neutralization, bridging adsorption, and sweeping capabilities. Significantly, an enhanced crude oil recovery rate is observed from the recovered oil droplets following the disruption of the emulsion layer.
研究领域:
环境科学
·
化学工程
✓ 已验证
DOI
高影响因子
RSC Advances
·
2017
·Vol. 7
·期 67
·42329-42338
·
IF 3.108
Zhaoyang Su,Xing Li,Yanling Yang,Yiran Fan
Much attention has been paid to coagulation as a pretreatment for controlling membrane fouling. Until now, however, there has been no literature available on the application of Zr-based coagulants in the coagulation–ultrafiltration process. The aim of this work is therefore to investigate the coagulation behavior of ZrOCl2 and its influence on membrane fouling, in comparison with that of the commonly used Al-based coagulants, Al2(SO4)3 and PACl. Floc formation kinetics were studied via ‘a turbidity fluctuation technique’ (PDA measurement). A variation in the pH and temperature of raw water was also considered in order to test the performance of the three targeted coagulants. The results indicated that the best coagulation efficiency was achieved with the Zr coagulant, under neutral pH conditions and at a room temperature of 25 °C. This coagulant resulted in minimum turbidity (0.72 NTU) and the lowest concentration of the supernatant at UV254 (0.005 cm−1); the corresponding values for Al2(SO4)3 were 2.79 NTU and 0.011 cm−1, respectively, while those for PACl being 6.78 NTU and 0.015 cm−1. The flocs obtained by the addition of this Zr coagulant were larger in size and had superior strength, recovery potential and settleability. In addition, membrane fouling was apparently alleviated through use of the Zr coagulant, especially in terms of the irreversible fouling, followed by PACl and Al2(SO4)3. The superior removal efficiency of low-medium MW HA may be a plausible explanation for this phenomenon. Particularly, this work describes a novel Zr coagulant as an important potential candidate for application to the coagulation–ultrafiltration process in the future.
研究领域:
环境工程
·
水处理技术
✓ 已验证
产品关联
DOI
高影响因子
SCIENCE OF THE TOTAL ENVIRONMENT
·
2022
·
IF 10.753
Pan Hu,Kexin Su,Yibei Sun,Pengwei Li,Jun Cai,Hu Yang
Microplastic (MP) pollution has increasingly become an enormous global challenge due to the ubiquity and uncertain environmental performance, especially for nano- and micro- sized MPs. In this work, the performance and mechanisms in coagulation of 100 nm–5.0 μm sized polystyrene particles using an etherified starch-based coagulant (St-CTA) assisted by polysilicic acid (PSA) were systematically studied on the basis of the changes in MPs removal rates under various pH levels and in the presence of different coexisting inorganic and organic substances, zeta potentials of supernatants, and floc properties. St-CTA in conjunction with PSA had a high performance in coagulation of nano- and micro- sized MPs from water with a lower optimal dose and larger and compacter flocs. Besides, the MPs removal rate can be improved in acidic and coexisting salt conditions. The efficient performance in removal of MPs by this enhanced coagulation was owing to the synergic effect, that is, the effective aggregation of MPs through the charge neutralization of St-CTA followed by the efficient netting-bridging effect of PSA. The effectiveness of this enhanced coagulation was further confirmed by removal of two other typical nano-sized MPs, such as poly(methyl methacrylate) and poly(vinyl chloride), from different water sources including tap water , river water, and sludge supernatant from a sewage treatment plant. This work provided a novel enhanced coagulation technique that can effectively remove nano- and micro- sized MPs from water.
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF ENVIRONMENTAL MANAGEMENT
·
2025
·
IF 8.4
Ruohan Xia,Wancen Liu,Long D. Nghiem,Dingge Cao,Guoxue Li,Wenhai Luo
Biogas slurry from anaerobic digestion of organic wastes can be a potential biofertilizer for agricultural irrigation, which however, is challenged by suspended solids and contaminants. Thus, this study synthesized a composite coagulant and optimized its performance to advance biogas slurry treatment. A natural-synthetic polymer, chitosan (CTS), was modified by 2-methacryloxyethyltrimethyl ammonium chloride (DMC) via graft copolymerization and then combined with polyferric sulfate (PFS) to formulate the composite CTS-g(DMC)-PFS coagulant. Results show that CTS-g(DMC)-PFS exhibited stronger electrical neutralization and adsorption bridging to destabilize and aggregate colloidal particles, thus, exhibiting higher removal of suspended solids, heavy metals, and antibiotics over individual and pristine coagulants. Graft copolymerization of CTS with DMC at the mass ratio of 1:9 maximized its water solubility. Further blending this mixture with PFS at the mass ratio of 1:2 effectively improved the coagulation of biogas slurry, particularly for the removal of antibiotics and heavy metals (e.g. enrofloxacin and Cu). Moreover, CTS-g(DMC)-PFS produced dense and compact flocs for effective sedimentation. Detailed characterization attributed such improvement to the hydrolysis of cationic quaternary ammonium groups on grafted monomers and further coordinative effects between CTS-g(DMC) and Fe to enhance molecular chains and positive charges in CTS-g(DMC)-PFS to facilitate particle aggregation, contaminant adsorption, and then floc sedimentation.
研究领域:
环境科学
·
农业科学
·
材料化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMOSPHERE
·
2017
·
IF 4.208
Xu Chen,Yong Sik Ok,Dinesh Mohan,Charles U. Pittman,Xiaomin Dou
The increasingly wide use of semiconductor nanocrystals inevitably leads to their release into aquatic environment. The aggregation behaviors of 3-mercaptopropionic acid-capped CdSe/CdS core-shell quantum dots (MPA-QDs) under various water chemistry conditions were examined and their removal using Fe 3+ and Al 3+ coagulants was evaluated. Cationic species rather than concentrations affected the stability of MPA-QDs. Adding 2 mM Ca 2+ led to a much larger ζ-potential decrease and particle size increase than adding 150 mM K + at each tested solution pH. This indicated that complexation and depletion of surface-bound carboxyl groups by divalent Ca 2+ has a more pronounced effect than compression of the electrical double layer by high concentrations of monovalent K + . The presence of humic acid increased the stability of MPA-QDs, which might increase negative surface charging via overcoating or bind to the surface of MPA-QDs. The nanoparticles exhibited similar aggregation kinetics patterns in tap water and seawater, but varying patterns in the lake water because of the co-existence of 2.3 mM total of Ca 2+ and Mg 2+ . MPA-QDs (5 mg L −1 ) were readily coagulated by 2.4 mM Al 3+ or 1.2 mM Fe 3+ in tap water. Al 3+ and Fe 3+ can bind with carboxyl groups of the surface capping ligands, neutralize the negative charges on the surface of MPA-QDs and decrease the electrostatic repulsion forces to induce MPA-QDs aggregation. In addition, MPA-QDs could be bound with and wrapped into the flocs of hydrolysis products of coagulants. The results reported here could help broaden our understanding of the impacts and remediation of water-dispersed core-shell QD nanoparticles.
研究领域:
环境科学
·
纳米生物学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
·
2016
·Vol. 24
·期 2
·1757-1768
·
IF 2.76
Zhao Yanxia,Sun Yangyang,Tian Chang,Gao Baoyu,Wang Yan,Shon Hokyong,Yang Yanzhao
Titanium-based coagulation is expected to achieve both efficient water purification and sludge recycling. This study is the first attempt to use titanium tetrachloride (TiCl 4 ) for silver nanoparticle (AgNP)-humic acid composite contaminant removal in a coagulation-ultrafiltration (C-UF) process, where characterization of flocs and membrane fouling under varied coagulant dose, initial solution pH, and AgNP concentration conditions are the main contents. Results suggested that the TiCl 4 achieved high AgNP removal in the form of silver nanoparticle through adsorption and sweep flocculation and simultaneously exerted additional 68.2 % higher dissolved organic carbon removal than Al 2 (SO 4 ) 3 . The TiCl 4 produced larger and stronger flocs but with weaker recoverability and less compact degree than did Al 2 (SO 4 ) 3 . Floc properties were independent of AgNP concentration except floc fractal dimension, which was negatively correlated with AgNP concentration. The TiCl 4 precoagulation caused less membrane fouling within wider pH range than Al 2 (SO 4 ) 3 did in the C-UF process. Incorporation of AgNPs during the TiCl 4 pretreatment process facilitated the mitigation of membrane fouling, which was, however, negligibly influenced by AgNP concentration in the case of Al 2 (SO 4 ) 3 .
研究领域:
环境工程
·
水处理技术
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）