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Precipitation as the main mechanism for Cd(II), Pb(II) and Zn(II) removal from aqueous solutions using natural and activated forms of red mud

This finding raise doubt about the effectiveness of the traditional adsorption isotherms and kinetics models to describe trace metals removal using RM, contributing with new insights for future researches involving these hazardous materials. | Environmental Advances 4 2021 100056 Contents lists available at ScienceDirect Environmental Advances journal homepage www.elsevier.com locate envadv Precipitation as the main mechanism for Cd II Pb II and Zn II removal from aqueous solutions using natural and activated forms of red mud Fabiano Tomazini da Conceição a Mariana Scicia Gabriel da Silva a Amauri Antonio Menegário b Maria Lucia Pereira Antunes c Guillermo Rafael Beltran Navarro a Alexandre Martins Fernandes a Caetano Dorea d Rodrigo Braga Moruzzi a a Instituto de Geociências e Ciências Exatas UNESP - Universidade Estadual Paulista 1 Avenida 24-A n 1515 C. P. 178 CEP 13506-900 Bela Vista Rio Claro São Paulo Brazil b Centro de Estudos Ambientais UNESP - Universidade Estadual Paulista Rio Claro Brazil c Instituto de Ciência e Tecnologia UNESP - Universidade Estadual Paulista Sorocaba Brazil d Department of Civil Engineering University of Victoria Victoria Canada a r t i c l e i n f o a b s t r a c t Keywords The red mud RM has been used as an alternative low-cost adsorbent to remove trace elements with the ad- Brazilian red mud sorption onto sodalite surface described as the main removal mechanism for trace elements. However recent Trace elements studies have shown that precipitation might be of great importance for some trace metals removal using natural Sequential extraction and thermal activated RM. Therefore the aim of this study was to identify the main mechanism responsible for Kinetics modelling Cd II Pb II and Zn II removal from aqueous solutions using natural and activated forms of RM based on se- quential extractions and a precipitation kinetic model was developed. Results showed that the carbonate fraction was responsible for the highest trace elements removal ca. 85 with the minerals assemblages precipitated otavite CdCO3 cerussite - PbCO3 smithsonite - ZnCO3 and anglesite - PbSO4 . The kinetic model showed that the mineral precipitation was limit due to the HCO3 consumption during the .