{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,22]],"date-time":"2026-04-22T22:01:15Z","timestamp":1776895275198,"version":"3.51.2"},"reference-count":75,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2025,10,30]],"date-time":"2025-10-30T00:00:00Z","timestamp":1761782400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FCT\u2014Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia, I.P., within the scope of the project UID\/04292\/MARE\u2014Centro de Ci\u00eancias do Mar e do Ambiente","award":["UIDB\/50020\/2020"],"award-info":[{"award-number":["UIDB\/50020\/2020"]}]},{"name":"FCT\u2014Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia, I.P., within the scope of the project UID\/04292\/MARE\u2014Centro de Ci\u00eancias do Mar e do Ambiente","award":["UIDP\/50020\/2020"],"award-info":[{"award-number":["UIDP\/50020\/2020"]}]},{"name":"ALiCE","award":["LA\/P\/0045\/2020"],"award-info":[{"award-number":["LA\/P\/0045\/2020"]}]},{"name":"ARNET","award":["LA\/P\/0069\/2020"],"award-info":[{"award-number":["LA\/P\/0069\/2020"]}]},{"name":"CeFEMA","award":["UIDB\/04540\/2020"],"award-info":[{"award-number":["UIDB\/04540\/2020"]}]},{"name":"Mobilizing Agenda Sustainable Stone by Portugal","award":["02-C05-i01.02-2022.PC644943391-00000051"],"award-info":[{"award-number":["02-C05-i01.02-2022.PC644943391-00000051"]}]},{"DOI":"10.13039\/501100000780","name":"European Union","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100000780","id-type":"DOI","asserted-by":"crossref"}]},{"name":"FCT","award":["2022.10551.BD"],"award-info":[{"award-number":["2022.10551.BD"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Environments"],"abstract":"<jats:p>The limestone quarrying and processing industry generates huge amounts of waste, with limestone sludge being one of the most prevalent and challenging by-products. This study aims to evaluate the potential of limestone sludge as a sustainable secondary raw material for the mechanochemical synthesis of bioceramics, specifically hydroxyapatite (HA), for high-added-value applications in bone tissue engineering. High-energy milling is innovatively used as the processing route: dry sludge (functioning as the calcium source), a phosphate source, and water were milled with the aim of producing calcium phosphates (in particular, hydroxyapatite) via mechanosynthesis. The industrial sludge was thoroughly analyzed for chemical composition, heavy metals, and mineral phases to ensure suitability for biomedical applications. The mixture of reagents was tailored to comply with Ca\/P = 1.67 molar ratio. Milling was carried out at room temperature; the milling velocity was 600 rpm, and milling time ranged from 5 to 650 min. Characterization by XRD, Raman spectroscopy, and SEM confirmed the progressive transformation of calcite into hydroxyapatite through a metastable DCPD intermediate, following logarithmic reaction kinetics. The resulting powders are fine, homogeneous, and phase-pure, demonstrating that mechanosynthesis provides a low-cost and environmentally friendly pathway to convert limestone waste into functional bioceramic materials. This suggests that Moleanos sludge is a viable and sustainable source to produce tailored calcium phosphates and confirms mechanosynthesis as a cost-effective and reliable technology to activate the low-kinetics chemical reactions in the CaCO3-H3PO4\u2013H2O system. This work highlights a novel circular economy approach for the valorization of industrial limestone sludge, turning a difficult waste stream into a high-value, sustainable resource.<\/jats:p>","DOI":"10.3390\/environments12110405","type":"journal-article","created":{"date-parts":[[2025,10,30]],"date-time":"2025-10-30T03:44:39Z","timestamp":1761795879000},"page":"405","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Limestone Processing Sludge: From Waste to Sustainable Resource"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2552-8437","authenticated-orcid":false,"given":"Mafalda","family":"Guedes","sequence":"first","affiliation":[{"name":"UnIRE, Department of Mechanical Engineering, Instituto Superior de Engenharia de Lisboa, Instituto Polit\u00e9cnico de Lisboa, Rua Conselheiro Em\u00eddio Navarro 1, 1959-007 Lisboa, Portugal"},{"name":"CeFEMA-LaPMET, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-6359-9416","authenticated-orcid":false,"given":"Joana","family":"Carrasqueira","sequence":"additional","affiliation":[{"name":"MARE\u2014Marine and Environmental Sciences Centre, ARNET\u2014Aquatic Research Network, School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, 2520-614 Peniche, Portugal"}]},{"given":"Tom\u00e1s","family":"Seixas","sequence":"additional","affiliation":[{"name":"CeFEMA-LaPMET, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4167-5237","authenticated-orcid":false,"given":"Cl\u00e9lia","family":"Afonso","sequence":"additional","affiliation":[{"name":"MARE\u2014Marine and Environmental Sciences Centre, ARNET\u2014Aquatic Research Network, School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, 2520-614 Peniche, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8008-9839","authenticated-orcid":false,"given":"Maria Manuel","family":"Gil","sequence":"additional","affiliation":[{"name":"MARE\u2014Marine and Environmental Sciences Centre, ARNET\u2014Aquatic Research Network, School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, 2520-614 Peniche, Portugal"},{"name":"+ATLANTIC\u2014Associa\u00e7\u00e3o para um Laborat\u00f3rio Colaborativo do Atl\u00e2ntico, Rua do Conhecimento 4, 2520-614 Peniche, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7775-0614","authenticated-orcid":false,"given":"Raul","family":"Bernardino","sequence":"additional","affiliation":[{"name":"MARE\u2014Marine and Environmental Sciences Centre, ARNET\u2014Aquatic Research Network, School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, 2520-614 Peniche, Portugal"},{"name":"LSRE-LCM\u2014Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials, School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, 2520-614 Peniche, Portugal"},{"name":"ALiCE\u2014Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3960-9943","authenticated-orcid":false,"given":"Roberto","family":"Gamboa","sequence":"additional","affiliation":[{"name":"MARE\u2014Marine and Environmental Sciences Centre, ARNET\u2014Aquatic Research Network, School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, 2520-614 Peniche, Portugal"}]},{"given":"Susana","family":"Bernardino","sequence":"additional","affiliation":[{"name":"MARE\u2014Marine and Environmental Sciences Centre, ARNET\u2014Aquatic Research Network, School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, 2520-614 Peniche, Portugal"},{"name":"LSRE-LCM\u2014Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials, School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, 2520-614 Peniche, Portugal"},{"name":"ALiCE\u2014Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,30]]},"reference":[{"key":"ref_1","unstructured":"Oates, J.A.H. 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