{"title":"KOH-activated lightweight expanded clay aggregate (LECA) for malachite green adsorption: activation mechanism and adsorption process assessment","authors":"F. Pishdadi-Aghdarreh, R. Norouzbeigi, E. Velayi","doi":"10.1007/s13762-024-06212-4","DOIUrl":null,"url":null,"abstract":"<div><p>Removing organic dyes soluble in water is of paramount importance for managing and protecting water resources. This study investigated the removal of malachite green (MG) by lightweight expanded clay aggregate (LECA) as a green adsorbent and improved its removal using KOH activation. Alkaline-activated LECA had a pore volume of 0.03 cm<sup>3</sup>/g and a specific surface area of 3.43 m<sup>2</sup>/g. The zeta potential of LECA was decreased with alkaline activation, which ranged between − 10.2 mV for raw LECA and − 24 mV for alkaline-activated LECA. The adsorption of MG on raw and alkaline-activated samples was studied in a batch process to determine the effects of initial dye concentration (10–350 mg/L), pH of the solution (2–10), contact time (5–400 min), and adsorption temperature (15–55 °C). The optimum conditions for MG adsorption were 180 min of contact time, 2.5 g/L of adsorbent, and a pH of 8. The maximum MG removal efficiency at optimal conditions was 56.2% and 90.6%, respectively, for raw and alkaline-activated LECA. Results showed that MG adsorption isotherm was well correlated using a linear Langmuir equation, with maximum adsorption capacities of 14.70 mg/g for raw and 43.10 mg/g for activated samples. Raw and KOH-activated samples were consistent with the pseudo-second-order model with R<sup>2</sup> > 0.99. The standard Gibbs free energies of MG uptake at 15, 25, 35, and 55 °C were negative. The values of ΔH° and ΔS° were 12.783 kJ/mol and 59 J/mol K, respectively. As a result, MG adsorption on KOH-activated LECA was endothermic and spontaneous.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":589,"journal":{"name":"International Journal of Environmental Science and Technology","volume":"22 7","pages":"5633 - 5654"},"PeriodicalIF":3.0000,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Environmental Science and Technology","FirstCategoryId":"93","ListUrlMain":"https://link.springer.com/article/10.1007/s13762-024-06212-4","RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Removing organic dyes soluble in water is of paramount importance for managing and protecting water resources. This study investigated the removal of malachite green (MG) by lightweight expanded clay aggregate (LECA) as a green adsorbent and improved its removal using KOH activation. Alkaline-activated LECA had a pore volume of 0.03 cm3/g and a specific surface area of 3.43 m2/g. The zeta potential of LECA was decreased with alkaline activation, which ranged between − 10.2 mV for raw LECA and − 24 mV for alkaline-activated LECA. The adsorption of MG on raw and alkaline-activated samples was studied in a batch process to determine the effects of initial dye concentration (10–350 mg/L), pH of the solution (2–10), contact time (5–400 min), and adsorption temperature (15–55 °C). The optimum conditions for MG adsorption were 180 min of contact time, 2.5 g/L of adsorbent, and a pH of 8. The maximum MG removal efficiency at optimal conditions was 56.2% and 90.6%, respectively, for raw and alkaline-activated LECA. Results showed that MG adsorption isotherm was well correlated using a linear Langmuir equation, with maximum adsorption capacities of 14.70 mg/g for raw and 43.10 mg/g for activated samples. Raw and KOH-activated samples were consistent with the pseudo-second-order model with R2 > 0.99. The standard Gibbs free energies of MG uptake at 15, 25, 35, and 55 °C were negative. The values of ΔH° and ΔS° were 12.783 kJ/mol and 59 J/mol K, respectively. As a result, MG adsorption on KOH-activated LECA was endothermic and spontaneous.
期刊介绍：
International Journal of Environmental Science and Technology (IJEST) is an international scholarly refereed research journal which aims to promote the theory and practice of environmental science and technology, innovation, engineering and management.
A broad outline of the journal''s scope includes: peer reviewed original research articles, case and technical reports, reviews and analyses papers, short communications and notes to the editor, in interdisciplinary information on the practice and status of research in environmental science and technology, both natural and man made.
The main aspects of research areas include, but are not exclusive to; environmental chemistry and biology, environments pollution control and abatement technology, transport and fate of pollutants in the environment, concentrations and dispersion of wastes in air, water, and soil, point and non-point sources pollution, heavy metals and organic compounds in the environment, atmospheric pollutants and trace gases, solid and hazardous waste management; soil biodegradation and bioremediation of contaminated sites; environmental impact assessment, industrial ecology, ecological and human risk assessment; improved energy management and auditing efficiency and environmental standards and criteria.
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