{"title":"Exploring the influence of aquatic phosphate on Fe floc dynamics in water treatment","authors":"","doi":"10.1016/j.watres.2024.122146","DOIUrl":null,"url":null,"abstract":"<div><p>The formation of flocs is crucial in the coagulation process of water treatment. However, the nature of ligand exchange on the surface of primary nanoparticles (PNPs) during floc formation requires further investigation to enhance our understanding of the coagulation mechanism. Phosphate (P) is a ubiquitous nutrient ion in aquatic surface water, in this study, the impact of P on floc growth under different pH conditions were investigated. The results revealed that floc growth patterns depended on both P dosage and pH. The mode of ligand exchange between P and in-situ formed ferric hydroxide within a pH range of 5 to 10 was further explored, and remarkable disparities in pH changes induced by P addition were observed. At lower pH levels, OH<sup>−</sup> release occurred relatively slowly, stabilizing with continued P addition. At neutral pH, OH<sup>−</sup> release was comparatively higher with P addition, while under alkaline conditions, both the quantity of OH<sup>−</sup> and its release rate decreased. It was deduced that <img>Fe–OH<sub>2</sub><sup>1/2+</sup> sites function as \"active sites,\" while <img>Fe–OH<sup>1/2−</sup> sites act as \"inert sites\" on the surface of PNPs formed during flocculation. These sites are crucial in the interconnections between flocs formed during coagulation and in floc growth. Analyses of Fe PNPs by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), with and without P addition, revealed that the introduction of P inhibits or interferes with the self-crystallization of Fe PNPs through chemical coordination reactions. The results offer deeper insights into the coagulation mechanism and the transformation of Fe flocs in raw waters containing P during water treatment practices.</p></div>","PeriodicalId":443,"journal":{"name":"Water Research","volume":null,"pages":null},"PeriodicalIF":11.4000,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Water Research","FirstCategoryId":"93","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0043135424010455","RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, ENVIRONMENTAL","Score":null,"Total":0}
引用次数: 0
Abstract
The formation of flocs is crucial in the coagulation process of water treatment. However, the nature of ligand exchange on the surface of primary nanoparticles (PNPs) during floc formation requires further investigation to enhance our understanding of the coagulation mechanism. Phosphate (P) is a ubiquitous nutrient ion in aquatic surface water, in this study, the impact of P on floc growth under different pH conditions were investigated. The results revealed that floc growth patterns depended on both P dosage and pH. The mode of ligand exchange between P and in-situ formed ferric hydroxide within a pH range of 5 to 10 was further explored, and remarkable disparities in pH changes induced by P addition were observed. At lower pH levels, OH− release occurred relatively slowly, stabilizing with continued P addition. At neutral pH, OH− release was comparatively higher with P addition, while under alkaline conditions, both the quantity of OH− and its release rate decreased. It was deduced that Fe–OH21/2+ sites function as "active sites," while Fe–OH1/2− sites act as "inert sites" on the surface of PNPs formed during flocculation. These sites are crucial in the interconnections between flocs formed during coagulation and in floc growth. Analyses of Fe PNPs by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), with and without P addition, revealed that the introduction of P inhibits or interferes with the self-crystallization of Fe PNPs through chemical coordination reactions. The results offer deeper insights into the coagulation mechanism and the transformation of Fe flocs in raw waters containing P during water treatment practices.
期刊介绍：
Water Research, along with its open access companion journal Water Research X, serves as a platform for publishing original research papers covering various aspects of the science and technology related to the anthropogenic water cycle, water quality, and its management worldwide. The audience targeted by the journal comprises biologists, chemical engineers, chemists, civil engineers, environmental engineers, limnologists, and microbiologists. The scope of the journal include:
•Treatment processes for water and wastewaters (municipal, agricultural, industrial, and on-site treatment), including resource recovery and residuals management;
•Urban hydrology including sewer systems, stormwater management, and green infrastructure;
•Drinking water treatment and distribution;
•Potable and non-potable water reuse;
•Sanitation, public health, and risk assessment;
•Anaerobic digestion, solid and hazardous waste management, including source characterization and the effects and control of leachates and gaseous emissions;
•Contaminants (chemical, microbial, anthropogenic particles such as nanoparticles or microplastics) and related water quality sensing, monitoring, fate, and assessment;
•Anthropogenic impacts on inland, tidal, coastal and urban waters, focusing on surface and ground waters, and point and non-point sources of pollution;
•Environmental restoration, linked to surface water, groundwater and groundwater remediation;
•Analysis of the interfaces between sediments and water, and between water and atmosphere, focusing specifically on anthropogenic impacts;
•Mathematical modelling, systems analysis, machine learning, and beneficial use of big data related to the anthropogenic water cycle;
•Socio-economic, policy, and regulations studies.
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