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Hayami MF, Menju T, Ide T, Uchida T, Adachi Y. Growth of Floc Structure and Subsequence Compaction into Smaller Granules through Breakup and Rearrangement of Aluminum Flocs in a Constant Laminar Shear Flow. Gels 2024; 10:49. [PMID: 38247772 PMCID: PMC10815830 DOI: 10.3390/gels10010049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 01/01/2024] [Accepted: 01/03/2024] [Indexed: 01/23/2024] Open
Abstract
We have constructed an outer-cylinder-rotating Couette device for high-speed shear flow in laminar flow conditions and visualized the structure formation and subsequent rearrangement of PACl (flocculant made of aluminum hydroxide gel) and kaolinite flocs by visible light imaging. In a previous report, we analyzed the case of relatively low shear rate (G-value = 29 1/s) and confirmed that the flocculation process could be separated into two stages: a floc growth stage and a breakup/rearrangement stage. Once the large bulky flocs that reached the maximum size appeared, they rearranged and densified through structural fracture and rearrangement. In this report, this process was further investigated by conducting experiments under two different high shear rates (58 and 78 1/s) at which breakup and rearrangement became more pronounced, and three different aluminum kaolinite ratios (ALT ratios) that were over and under the optimum dosage (neutralization point by Zeta potential). Visualization results confirmed that, during the growth stage, the flocculation rate could be approximated by a scaling relationship between floc size and elapsed time, which depended on the ALT ratio. After reaching the maximum size, the floc rapidly became compact and dense following adsorption of the gel, incorporating fine fragments from erosion breakup. The over and under dosages created a lot of fragments of erosion breakup, but less so in the optimum dosage. In the optimum ALT ratio, fragments did not remain because they were incorporated into the flocs and densified, and the floc size was thought to be maintained. The floc circularity distribution peaked at around 0.6 and 1, suggesting that the flocs were spherical in shape due to erosion breakup.
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Affiliation(s)
- Mii Fukuda Hayami
- Infrastructure Systems Research and Development Center, Toshiba Infrastructure Systems & Solutions Corporation, 1, Toshiba, Fuchu 183-8511, Tokyo, Japan
| | - Takashi Menju
- Infrastructure Systems Research and Development Center, Toshiba Infrastructure Systems & Solutions Corporation, 1, Toshiba, Fuchu 183-8511, Tokyo, Japan
| | - Takeshi Ide
- Infrastructure Systems Research and Development Center, Toshiba Infrastructure Systems & Solutions Corporation, 1, Toshiba, Fuchu 183-8511, Tokyo, Japan
| | - Tatsuro Uchida
- Energy Systems Research and Development Center, Toshiba Energy Systems & Solutions Corporation, 1-20, Kansei, Tsurumi, Yokohama 230-0034, Kanagawa, Japan
| | - Yasuhisa Adachi
- Faculty of Life and Environmental Science, University of Tsukuba, 1-1-1, Tennodai, Tsukuba 305-8572, Ibaraki, Japan;
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Shan LL, Tan Z, Chen Y, Wang RS, Zhang M, Pang CL, Cui YH, Liao ZM, Ma HQ, Zhu ZB. Biodegradability enhancement of waste lubricating oil regeneration wastewater using electrocoagulation pretreatment. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:106421-106430. [PMID: 37728675 DOI: 10.1007/s11356-023-29841-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 09/07/2023] [Indexed: 09/21/2023]
Abstract
As a sustainable management of fossil fuel resources and ecological environment protection, recycling used lubricating oil has received widespread attention. However, large amounts of waste lubricating-oil regeneration wastewater (WLORW) are inevitably produced in the recycling process, and challenges are faced by traditional biological treatment of WLORW. Thus, this study investigated the effectiveness of electrocoagulation (EC) as pretreatment and its removal mechanism. The electrolysis parameters (current density, initial pH, and inter-electrode distance) were considered, and maximal 60.06% of oil removal was achieved at a current density of 15 mA/cm2, initial pH of 7, and an inter-electrode distance of 2 cm. The dispersed oil of WLORW was relatively easily removed, and most of the oil removal was contributed by emulsified oil within 5-10 μm. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that effective removal of the biorefractory organic compounds could contribute to the improvement of biodegradability of WLORW. Thus, the 5-day biochemical oxygen demand/chemical oxygen demand ratio (BOD5/COD) was significantly enhanced by 4.31 times, which highly benefits future biological treatment. The routes of WLORW removal could be concluded as charge neutralization, adsorption bridging, sweep flocculation, and air flotation. The results demonstrate that EC has potential as an effective pretreatment technology for WLORW biological treatment.
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Affiliation(s)
- Li-Li Shan
- School of Civil Engineering and Architecture, East China Jiao Tong University, Nanchang, 330013, China
- Jiangxi JDL Environmental Protection Co., Ltd, Nanchang, 330199, China
- School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Zhao Tan
- School of Civil Engineering and Architecture, East China Jiao Tong University, Nanchang, 330013, China
| | - Yu Chen
- School of Civil Engineering and Architecture, East China Jiao Tong University, Nanchang, 330013, China
| | - Ruo-Shan Wang
- School of Civil Engineering and Architecture, East China Jiao Tong University, Nanchang, 330013, China
| | - Meng Zhang
- Jiangxi Academy of Environmental Sciences, Nanchang, 330039, China
| | - Chang-Long Pang
- Jiangxi ZXDH Environmental Protection Industry Tecnology Institute Co., Ltd, Nanchang, 330000, China
| | - Yu-Hong Cui
- School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Zhi-Min Liao
- Jiangxi JDL Environmental Protection Co., Ltd, Nanchang, 330199, China
| | - Hong-Qiang Ma
- School of Civil Engineering and Architecture, East China Jiao Tong University, Nanchang, 330013, China
| | - Ze-Bing Zhu
- School of Civil Engineering and Architecture, East China Jiao Tong University, Nanchang, 330013, China.
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Ghazali MEB, Adachi Y. Container size effects on the validity for the concept of sedimentation turbulence studied using coagulated suspension of Na-montmorillonite in the semi-dilute regime. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Tunable Dewatering Behavior of Montmorillonite Suspension by Adjusting Solution pH and Electrolyte Concentration. MINERALS 2020. [DOI: 10.3390/min10040293] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Montmorillonite is always a troublemaker for the dewatering in coal processing since its existence can decrease the rates of sedimentation and filtration of coal slurry. To eliminate the adverse effect of montmorillonite, adjusting the slurry pH and adding electrolytes are always the key methods. However, the underlying mechanism still needs to be further studied. The dewatering of Na-montmorillonite (Na-Mt) suspensions has been studied as a function of NaCl concentration (10−3, 10−2, and 10−1 M) at different pH values (6.0, 7.7, 8.1, 9.2). The point of zero charge of edge surface of Na-Mt (pHPZC,edge) appeared at the pH value of 6.8. The sedimentation and rheology experiments described the coagulation and flow behaviors of Na-Mt suspensions, respectively. The Na-Mt suspension coagulated spontaneously at low salt concentration with the pH ~ 6.0. For the pH > pHPZC,edge, the height of the sediment bed reduced and apparent viscosity increased with the increase of the electrolyte concentration. The filtration properties were evaluated on the basis of Darcy’s law. The obtained result clearly demonstrated that the filtration rate was accelerated with the increase of pH and electrolyte concentration. The modes of particle association and its effect on filtration performance were discussed. Moreover, a comparison with related results from the literature was performed. At pH ~ 6 and low electrolyte concentration, the positively charged Edge surfaces and negatively charged Face surfaces coagulate rapidly to form a sealed structure by electrostatic attraction. Furthermore, inside this sealed structure, the water molecules cannot be removed in the filtration process easily. However, by increasing the electrolyte concentration at pH > pHPZC,edge, the gradually formed Face/Face structure increases the filtration rate sharply because of the inhibiting effect of the electric double layer (EDL) and the osmotic expansion. Therefore, adjusting solution conditions of the aqueous suspension to tune the particle coagulation behavior is one of the effective methods to solve the problem of montmorillonite dewatering.
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