WATER RESEARCH
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2021
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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
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水处理工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Water Process Engineering
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2020
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IF 3.465
Chang Tian,Yan-Xia Zhao
Polytitanium coagulants have been recently developed and have received wide attention due to both strong coagulation capability and sludge recycling to produce valuable by-products, titanium dioxide (TiO 2 ). This study reports the performance of coagulation with emerging polytitanium salts, polytitanium chloride (PTC) and polytitanium sulfate (PTS), for the treatment of two common cyanobacteria ( Microcystis aeruginosa , MA and Microcystis wesenbergii , MW)-laden surface water, which has been barely reported. Of particular concern is the coagulant dosage and solution pH dependence of polytitanium coagulation, which are the main parameters influencing coagulation efficiency. The influence of basicity (B) of PTC and PTS on coagulation performance was simultaneously included. Results show the optimized B value of 1.5 with coagulant dosage of 30 mg/L and initial solution pH between 7–9 for both PTC and PTS coagulation, wherein obvious advantage of PTC was observed over PTS regardless of MA- or MW-laden surface water treatment. The PTC coagulation could achieve almost complete removal of algae (about 99.0 %) with synergic removal of organic matter with high-efficiency. Both PTC and PTS were more capable at alkaline solution pH conditions for turbidity and algae removal through sweep flocculation, while satisfied removal of the humic acid-representative organic matters was observed at acidic to neutral pH conditions by charge neutralization. Satisfied flocculation zones were determined according to synergic removal of algae, turbidity and organic matters, with most of the satisfied points distributed at solution pH 7–9 conditions. This study will provide theoretical basis and facilitate wide application of the polytitanium coagulation for algae-loaded surface water treatment.
研究领域:
环境工程
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水处理
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胶体与界面化学
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环境化学
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给排水科学与工程
✓ 已验证
DOI
高影响因子
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
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2023
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IF 5.2
Jun Guo,Xia Xu,Ruoying Yang,Yingang Xue,Liping Wang,Qiuya Zhang,Mingguo Peng,Xuefeng Liu
The combination of organic and inorganic coagulants is considered to be an effective strategy for Humic Acid (HA) removal. In this study, the performance of Titanium-based coagulants aided by Cationic-Polyacrylamide (CPAM) to HA molecules was compared. It was found that CPAM had a higher promotion effect in the TXC system. The reason for why CPAM was more suitable for the TXC system could be explained by analyzing Zeta potential , FTIR, and XPS . By comparing the coagulation mechanism of TiCl 4 (TC) and Poly-Titanium Chloride (PTC), we found that complexation was the main mechanism of TC and PTC in acidic and neutral environments. The C-O-Ti Bond was formed by complexing the Ti-OH with the C-OH and -COOH functional groups of HA molecules. Sweeping was the most important removal mechanism of TXC in the neutral and alkaline environment, and CPAM bridged floc through hydrogen bond force for enhancing the sweeping effect. In addition, the role of CPAM in TXC system was further demonstrated by Zeta potential analysis. Both TC and PTC were positively charged in the measured pH range, so the removal of Humic acid was limited by increasing zeta potential. In both neutral and alkaline environments, TXC kept a negative surface charge and CPAM significantly enhanced the adsorption of HA on the TXC floc surface. This study provided clues for the interaction mechanism between titanium salt coagulants and HA, and it also provided a reference for the application of TXC coagulant combined with CPAM flocculant for the removal of HA molecules.
研究领域:
环境科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
Surfaces and Interfaces
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2025
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IF 6.3
Heng Zhang,Xiaoyu Gao,Xiaoyu Xu,Yuxuan Li,Rongfu Xu,Yisheng Feng,Liming Feng
To prepare an environmentally friendly and corrosion-resistant chemical conversion film on a steel substrate, cerium salt, titanium salt, and the organic additives 2-mercaptobenzimidazole (2-MBI) and polyethylene glycol (PEG) were introduced into oxalic acid (OA) to form an oxalate composite chemical conversion film. The composite chemical conversion film is composed of large-sized FeC 2 O 4 ·2H 2 O rectangular crystal grains and long aspect ratio FeC 2 O 4 ·2H 2 O nanorods interspersed among the grains. A large number of nanoscales FeC 2 O 4 ·2H 2 O grains help to disperse the corrosion current, preventing localized corrosion, and the fitted polarization resistance reaches 7203.7ohm cm 2 . 2-MBI complexes with metal ions, participating in the formation of the double electric layer. Titanium salt participates in film formation in the form of titanium oxide, while PEG and OA enhance the bonding strength and density of the film-forming materials in the layer by coating titanium oxide, acting as dispersants and wetting agents. As Fe 2+ generated from corrosion at the interface between the steel substrate and the working liquid combines with oxalic acid to form insoluble ferrous oxalate, the carbon chain migrates outward to the surface of the conversion film. The stronger bond energies of C = O, C O-Fe, and Fe-O facilitate the inward movement of self-assembly behaviour, which significantly increases the carbon content on the film surface and reducing the surface energy in contact with air. After soaking in a 5 wt.% sodium chloride solution, sodium-containing compounds formed on the surface of the conversion film, hindering chloride corrosion. The large number of nanoscale ultrafine dihydrate ferrous oxalate grains in the film effectively suppresses localized corrosion. During the corrosion process, 2-MBI moves to the film surface through complexes formed with titanium oxide via Ti-N bonds, thereby obstructing the intrusion of corrosion liquid ions and enhancing the corrosion resistance of the film layer, endowing it with a certain degree of self-healing capability. Cerium salt participates in film formation as a non-stoichiometric compound with an ambiguous valence state, and the transformation of the cerium element's valence state is another reason for the self-healing property of the conversion film.
研究领域:
材料科学
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电化学
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表面工程
✓ 已验证
产品关联
DOI
高影响因子
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