title: Acid-base treated vermiculite as high performance adsorbent: Insights into the mechanism of cationic dyes adsorption, regeneration, recyclability and stability studies.
abstract: Additional treatment with NaOH of acid activated vermiculite results in even higher increase in the adsorption capacity in comparison to samples modified only in acidic solution (first step of activation) with respect to raw material. Optimization of treatment conditions and adsorption capacity for two cationic dyes (methylene blue (MB) and astrazon red (AR)), also as binary mixture, was evaluated. The capacity, based on column studies, increased from 48 ± 2 to 203 ± 4 mg g-1in the case of methylene blue and from 51 ± 1 to 127 ± 2 mg g-1in the case of astrazon red on starting and acid-base treated material, respectively. It was shown that adsorption mechanism changes for both cationic dyes after NaOH treatment and it results in decrease of adsorption rate. In binary mixtures methylene blue is bound stronger by adsorbent and astrazon red may be removed in initial stage of adsorption. Extensive studies on desorption/regeneration process proved high efficiency in recyclable use of all materials. Although cation exchange capacity decreases due to acid treatment, after base treatment exchange properties are used more efficiently. On the other hand, increased specific surface area has less significant contribution into the adsorption potential of studied materials. Obtained adsorbents worked efficiently in 7 adsorption-regeneration cycles and loss of adsorption capacity was observed only in two first cycles.
authors.affiliation: REQUIMTE, LAQV, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua Dr. António Bernardino de Almeida 431, 4200-072, Porto, Portugal. Electronic address: stawor@gmail.com.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Stawiński
authors.affiliation: Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060, Kraków, Poland. Electronic address: wegrzyn@chemia.uj.edu.pl.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Węgrzyn
authors.affiliation: Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060, Kraków, Poland. Electronic address: tom_91@o2.pl.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Dańko
authors.affiliation: REQUIMTE, LAQV, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua Dr. António Bernardino de Almeida 431, 4200-072, Porto, Portugal. Electronic address: omf@isep.ipp.pt.
authors.forename: Olga
authors.initials: O
authors.lastname: Freitas
authors.affiliation: REQUIMTE, LAQV, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua Dr. António Bernardino de Almeida 431, 4200-072, Porto, Portugal. Electronic address: saf@isep.ipp.pt.
authors.forename: Sónia
authors.initials: S
authors.lastname: Figueiredo
authors.affiliation: Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060, Kraków, Poland. Electronic address: chmielar@chemia.uj.edu.pl.
authors.forename: Lucjan
authors.initials: L
authors.lastname: Chmielarz
mesh_terms: D000143:Acids / Q000737:chemistry*; D000327:Adsorption; D000468:Alkalies / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry*; D002412:Cations / Q000737:chemistry* / Q000378:metabolism*; D004396:Coloring Agents / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D008751:Methylene Blue / Q000032:analysis
chemical_list: D000143:Acids; D000468:Alkalies; D000538:Aluminum Silicates; D002412:Cations; D004396:Coloring Agents; C003760:vermiculite; D008751:Methylene Blue
keywords: Acid treatment; Adsorption; Base treatment; Cationic dyes; Regeneration; Vermiculite