{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T21:11:36Z","timestamp":1792789896539,"version":"4.5.0"},"reference-count":49,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,10,3]],"date-time":"2026-10-03T00:00:00Z","timestamp":1790985600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002855","name":"National Key Research and Development Program Foundation of China","doi-asserted-by":"publisher","award":["2022YFC3902702"],"award-info":[{"award-number":["2022YFC3902702"]}],"id":[{"id":"10.13039\/501100002855","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["52174257"],"award-info":[{"award-number":["52174257"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"award":["52174257"],"award-info":[{"award-number":["52174257"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Graduate Innovative Fund of Wuhan Institute of Technology","award":["CX2025142"],"award-info":[{"award-number":["CX2025142"]}],"id":[{"id":"https:\/\/ror.org\/04jcykh16","id-type":"ROR","asserted-by":"crossref"}]},{"award":["CX2025142"],"award-info":[{"award-number":["CX2025142"]}],"id":[{"id":"https:\/\/ror.org\/04jcykh16","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Fine calcium fluoride (CaF2) particles formed during fluoride removal processes often exhibit poor aggregation and separation behavior, especially in phosphogypsum (PG) leachate with high soluble fluoride concentrations. In this study, polyferric sulfate (PFS) was employed as a coagulation aid following CaO precipitation to enhance CaF2 aggregation and solid\u2013liquid separation, with particular focus on the underlying molecular mechanisms. Experimental results showed that the sequential addition of CaO followed by PFS significantly improved fluoride removal compared with CaO precipitation alone. Under optimal conditions, the sequential CaO\/PFS addition achieved a maximum fluoride removal efficiency of 94.1%, compared with 88.3% for the CaO-only system. Molecular dynamics simulations revealed that Fe-containing species promoted CaF2 aggregation through electrostatic attraction and bridging interactions involving OH\u2212, Ca2+, and F\u2212. Quantitative analyses based on radial distribution functions, coordination numbers, solubility parameters, and self-diffusion coefficients further demonstrated that pH, ion concentration, and dosing sequence strongly influenced aggregate formation, with sequential dosing showing superior performance over simultaneous addition. This work provides molecular-level insight into inorganic coagulation-assisted CaF2 aggregation and offers theoretical support and practical guidance for efficient fluoride removal and resource-oriented treatment of PG leachate.<\/jats:p>","DOI":"10.3390\/molecules31193524","type":"journal-article","created":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T10:02:27Z","timestamp":1791194547000},"page":"3524","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Efficient Removal of Fluoride from Phosphogypsum Leachate: Insights into Microscopic Mechanism of Polyferric Sulfate-Assisted Precipitation via Molecular Simulation"],"prefix":"10.3390","volume":"31","author":[{"given":"Wen","family":"Fang","sequence":"first","affiliation":[{"name":"Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China"},{"name":"School of Optoelectronic Materials & Technology, Jianghan University, Wuhan 430056, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"}]},{"given":"Zhiguo","family":"Zhang","sequence":"additional","affiliation":[{"name":"China Wuhuan Engineering Corporation Ltd., Wuhan 430072, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"resources","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7283-4034","authenticated-orcid":false,"given":"Yuefei","family":"Zhang","sequence":"additional","affiliation":[{"name":"Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China"},{"name":"School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, Wuhan 430205, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"given":"Jin","family":"Lv","sequence":"additional","affiliation":[{"name":"China Wuhuan Engineering Corporation Ltd., Wuhan 430072, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"}]},{"given":"Nan","family":"Yang","sequence":"additional","affiliation":[{"name":"China Wuhuan Engineering Corporation Ltd., Wuhan 430072, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Ruan","family":"Chi","sequence":"additional","affiliation":[{"name":"Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,10,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"478","DOI":"10.1007\/s10163-023-01849-8","article-title":"Role of polyacrylamide in the removal of soluble phosphorus and fluorine from phosphogypsum","volume":"26","author":"Liang","year":"2023","journal-title":"J. Mater. Cycles Waste Manag."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"10449","DOI":"10.1007\/s13762-023-04783-2","article-title":"Application of phoshogypsum in soilization: A review","volume":"20","author":"Qi","year":"2023","journal-title":"Int. J. Environ. Sci. Technol."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Alfimova, N., Levickaya, K., Buhtiyarov, I.Y., Nikulin, I., Kozhukhova, M., and Strokova, V. (2025). Effect of Phosphogypsum Characteristics on the Properties of Phosphogypsum-Based Binders. J. Compos. Sci., 9.","DOI":"10.3390\/jcs9080413"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"4038444","DOI":"10.1155\/2022\/4038444","article-title":"Defluoridation of Water Using Aluminum Hydroxide Activated Carbon Biosorbents","volume":"2022","author":"Gebremariam","year":"2022","journal-title":"Adv. Mater. Sci. Eng."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"167975","DOI":"10.1016\/j.cej.2025.167975","article-title":"From hazardous waste to backfill materials: Deep stabilization of soluble fluoro-phosphorus in phosphogypsum flotation tailings via mechanochemical-geopolymer coupling technology","volume":"522","author":"Chen","year":"2025","journal-title":"Chem. Eng. J."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Lv, X., and Xiang, L. (2022). The Generation Process, Impurity Removal and High-Value Utilization of Phosphogypsum Material. Nanomaterials, 12.","DOI":"10.3390\/nano12173021"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"125899","DOI":"10.1016\/j.chemosphere.2020.125899","article-title":"Water defluorination using granular composite synthesized via hydrothermal treatment of polyaluminum chloride (PAC) sludge","volume":"247","author":"Cho","year":"2020","journal-title":"Chemosphere"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"620","DOI":"10.1039\/D1VA00039J","article-title":"Fluoride contamination, consequences and removal techniques in water: A review","volume":"1","author":"Ahmad","year":"2022","journal-title":"Environ. Sci. Adv."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"3018","DOI":"10.1007\/s11663-024-03151-w","article-title":"Study on Strengthening the Crystallization Process of Removing F and P from Phosphogypsum Produced by Dihydrate\u2013Hemihydrate Wet Process","volume":"55","author":"Yi","year":"2024","journal-title":"Metall. Mater. Trans. B"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Lang, Q., Liu, Y., Guo, G., and Zhang, Y. (2025). Electrochemical Characterization and Simulation of Ion Transport in Anion Exchange Membranes for Water Treatment Applications. Membranes, 15.","DOI":"10.3390\/membranes15040123"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"141544","DOI":"10.1016\/j.chemosphere.2024.141544","article-title":"Layer-by-layer assembled graphitic carbon nitride membranes for water treatment","volume":"353","author":"Joseph","year":"2024","journal-title":"Chemosphere"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1913","DOI":"10.1002\/cjoc.202400058","article-title":"Recent Advances in the Electrochemical Defluorinative Transformations of C\u2014F Bonds","volume":"42","author":"Wan","year":"2024","journal-title":"Chin. J. Chem."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"679","DOI":"10.1016\/j.chemosphere.2014.09.090","article-title":"Removal of fluoride and uranium by nanofiltration and reverse osmosis: A review","volume":"117","author":"Shen","year":"2014","journal-title":"Chemosphere"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"145535","DOI":"10.1016\/j.scitotenv.2021.145535","article-title":"Removal of fluoride from industrial wastewater by using different adsorbents: A review","volume":"773","author":"Wan","year":"2021","journal-title":"Sci. Total Environ."},{"key":"ref_15","unstructured":"Wambu, E.W., Frau, F., Machunda, R., Pasape, L., Barasa, S.S., and Ghiglieri, G. (2022). Water Defluoridation Methods Applied in Rural Areas Over the World, IntechOpen."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Sinharoy, A., Lee, G.-Y., and Chung, C.-M. (2024). Optimization of Calcium Fluoride Crystallization Process for Treatment of High-Concentration Fluoride-Containing Semiconductor Industry Wastewater. Int. J. Mol. Sci., 25.","DOI":"10.3390\/ijms25073960"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"107940","DOI":"10.1016\/j.mineng.2022.107940","article-title":"Study on the influence and mechanism of polyferric sulfate on COD removal and reuse of scheelite flotation wastewater","volume":"191","author":"Lu","year":"2023","journal-title":"Miner. Eng."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1016\/j.bej.2017.01.020","article-title":"Comparison of flocs characteristics using before and after composite coagulants under different coagulation mechanisms","volume":"121","author":"Wang","year":"2017","journal-title":"Biochem. Eng. J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"124771","DOI":"10.1016\/j.seppur.2023.124771","article-title":"Efficient purification of graphite industry wastewater by a combined neutralization-coagulation-flocculation process strategy: Performance of flocculant combinations and defluoridation mechanism","volume":"326","author":"Deng","year":"2023","journal-title":"Sep. Purif. Technol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"125920","DOI":"10.1016\/j.chemosphere.2020.125920","article-title":"Relationship between the structure of chitosan-based flocculants and their performances in the treatment of model azo dyeing wastewater","volume":"247","author":"Zheng","year":"2020","journal-title":"Chemosphere"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"134072","DOI":"10.1016\/j.colsurfa.2024.134072","article-title":"Evaluation an anionic polyacrylamide flocculant with microblock structure in the hematite wastewater treatment: Characterization and flocculation performance","volume":"693","author":"Zhu","year":"2024","journal-title":"Colloids Surf. Physicochem. Eng. Asp."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"13474","DOI":"10.1007\/s12274-023-6311-9","article-title":"Enhanced sampling in molecular dynamics simulations and their latest applications\u2014A review","volume":"16","author":"Shen","year":"2023","journal-title":"Nano Res."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"131159","DOI":"10.1016\/j.conbuildmat.2023.131159","article-title":"Investigation of asphalt oxidation kinetics aging mechanism using molecular dynamic simulation","volume":"377","author":"Liu","year":"2023","journal-title":"Constr. Build. Mater."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"129217","DOI":"10.1016\/j.fuel.2023.129217","article-title":"The investigation of flocculation and deposition of heavy components in the crude oil tank based on experiment and molecular simulation","volume":"353","author":"Wang","year":"2023","journal-title":"Fuel"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"125576","DOI":"10.1016\/j.colsurfa.2020.125576","article-title":"Understanding the flocculation mechanism of quartz and kaolinite with polyacrylamide in seawater: A molecular dynamics approach","volume":"608","author":"Quezada","year":"2021","journal-title":"Colloids Surf. Physicochem. Eng. Asp."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Shi, C., Guo, D., Li, Y., Zhang, Z., and Tang, L. (2021). Effect of the polymerized titanium ferric sulfate (PTFS) coagulant on sedimentation of coal slime water. Minerals, 1.","DOI":"10.3390\/min12010026"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"117151","DOI":"10.1063\/1.4936846","article-title":"Understanding flocculation mechanism of graphene oxide for organic dyes from water: Experimental and molecular dynamics simulation","volume":"5","author":"Liu","year":"2015","journal-title":"AIP Adv."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"20220327","DOI":"10.1515\/rams-2022-0327","article-title":"Poly-ferric sulphate as superior coagulant: A review on preparation methods and properties","volume":"62","author":"Mohamad","year":"2023","journal-title":"Rev. Adv. Mater. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2292","DOI":"10.1021\/acssuschemeng.6b02625","article-title":"Batch Preparation of High Basicity Polyferric Sulfate by Hydroxide Substitution from Bipolar Membrane Electrodialysis","volume":"3","author":"Zhang","year":"2017","journal-title":"ACS Sustain. Chem. Eng."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"459","DOI":"10.1016\/j.jhazmat.2007.11.108","article-title":"Polyferric sulphate: Preparation, characterisation and application in coagulation experiments","volume":"3","author":"Zouboulis","year":"2008","journal-title":"J. Hazard. Mater."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1016\/j.sbi.2021.11.011","article-title":"Recent progress in general force fields of small molecules","volume":"72","author":"He","year":"2022","journal-title":"Curr. Opin. Struct. Biol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"895","DOI":"10.1016\/j.molliq.2018.08.024","article-title":"Rotational and translational dynamics of the SPC\/E water model","volume":"275","author":"Meyer","year":"2019","journal-title":"J. Mol. Liq."},{"key":"ref_33","unstructured":"Frisch, M., Trucks, G., Schlegel, H., Scuseria, G., Robb, M., and Cheeseman, J.J.I.W. (2016). Gaussian 16 Rev. A. 03, Gaussian. GaussView 5.0."},{"key":"ref_34","unstructured":"Lu, T. (2026, August 01). Sobtop Version [1.0(dev3.1)]. Available online: http:\/\/sobereva.com\/soft\/Sobtop."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"580","DOI":"10.1002\/jcc.22885","article-title":"Multiwfn: A multifunctional wavefunction analyzer","volume":"33","author":"Lu","year":"2012","journal-title":"J. Comput. Chem."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"112708","DOI":"10.1016\/j.cam.2019.112708","article-title":"An efficient Dai\u2013Liao type conjugate gradient method by reformulating the CG parameter in the search direction equation","volume":"371","author":"Lotfi","year":"2020","journal-title":"J. Comput. Appl. Math."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"120116","DOI":"10.1016\/j.molliq.2022.120116","article-title":"Effects of thermostats\/barostats on physical properties of liquids by molecular dynamics simulations","volume":"365","author":"Ke","year":"2022","journal-title":"J. Mol. Liq."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.physleta.2005.04.046","article-title":"A Parrinello\u2013Rahman approach to vortex lattices","volume":"341","author":"Carretero","year":"2005","journal-title":"Phys. Lett. A"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"154","DOI":"10.3390\/i5040154","article-title":"Complexity and Convergence of Electrostatic and van der Waals Energies within PME and Cutoff Methods","volume":"5","author":"Zhan","year":"2004","journal-title":"Int. J. Mol. Sci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.softx.2015.06.001","article-title":"GROMACS: High performance molecular simulations through multi-level parallelism from laptops to supercomputers","volume":"1","author":"Abraham","year":"2015","journal-title":"SoftwareX"},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Zhang, J., Yang, C., Niu, F., Gao, S., and Dong, J. (2021). Molecular Dynamics Study on the Leaching of Zinc-Bearing Dust Sludge by Choline Chloride-Malonic Acid. Minerals, 11.","DOI":"10.3390\/min11101080"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"164502","DOI":"10.1063\/1.4933208","article-title":"A molecular dynamics simulations study on the relations between dynamical heterogeneity, structural relaxation, and self-diffusion in viscous liquids","volume":"143","author":"Henritzi","year":"2015","journal-title":"J. Chem. Phys."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1016\/S0927-7757(00)00602-6","article-title":"Hydrolysis characteristic of polyferric sulfate coagulant and its optimal condition of preparation","volume":"182","author":"Cheng","year":"2001","journal-title":"Colloids Surf. A Physicochem. Eng. Asp."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/j.hydromet.2018.07.011","article-title":"Encapsulation of scorodite using crystalline polyferric sulfate precipitated from the Fe(II)-SO42\u2212-O2-H2O system","volume":"180","author":"Ke","year":"2018","journal-title":"Hydrometallurgy"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"100202","DOI":"10.1016\/j.ceja.2021.100202","article-title":"Analysis of synthesis structures and flocculation stability of a polyphosphate ferric sulfate solid","volume":"9","author":"Zhou","year":"2022","journal-title":"Chem. Eng. J. Adv."},{"key":"ref_46","unstructured":"(1996). Integrated Wastewater Discharge Standard (Standard No. GB 8978-1996)."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"147537","DOI":"10.1016\/j.jclepro.2026.147537","article-title":"Optimized crystallization and thermal treatment for high-purity calcium fluoride recovery from fluoride-containing wastewater","volume":"541","author":"Kim","year":"2026","journal-title":"J. Clean. Prod."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Sar, S., Samuelsson, C., Engstr\u00f6m, F., and \u00d6kvist, L.S. (2020). Experimental study on the dissolution behavior of calcium fluoride. Metals, 10.","DOI":"10.3390\/met10080988"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"118741","DOI":"10.1016\/j.molliq.2022.118741","article-title":"Influence of external electric field on polymerization of Fe (III) flocculant in water: A reactive molecular dynamics and experiment study","volume":"352","author":"Han","year":"2022","journal-title":"J. Mol. Liq."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/19\/3524\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T10:03:01Z","timestamp":1791194581000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/19\/3524"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,10,3]]},"references-count":49,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2026,10]]}},"alternative-id":["molecules31193524"],"URL":"https:\/\/doi.org\/10.3390\/molecules31193524","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,10,3]]}}}