{"title":"Novel coal fly ash–chitosan composite for highly efficient, cost-effective and stable removal of lead and chromium from industrial wastewater†","authors":"Khandgave Santosh Sopanrao and Inkollu Sreedhar","doi":"10.1039/D5EW00257E","DOIUrl":null,"url":null,"abstract":"<p >In the present study, a novel and economical adsorbent was synthesized from a coal fly ash–chitosan composite to remove Pb<small><sup>2+</sup></small> and Cr<small><sup>6+</sup></small> from aqueous solutions. The characterization of the adsorbent under optimal conditions revealed that it was mesoporous and rich in different functional groups, which enhanced its adsorption properties. The optimal conditions for the adsorption process were achieved at three levels. At the first level, the optimal conditions for fly ash calcination (300 °C for 2 h), H<small><sub>3</sub></small>PO<small><sub>4</sub></small> concentration (0.4 mol L<small><sup>−1</sup></small>), MFA–CS ratio (3 : 1), and effective morphology (nanopowder) for Pb<small><sup>2+</sup></small> and Cr<small><sup>6+</sup></small> removal were achieved. At the second level, response surface methodology achieved adsorption capacities of 339.27 mg g<small><sup>−1</sup></small> for Pb<small><sup>2+</sup></small> removal and 242.84 mg g<small><sup>−1</sup></small> for Cr<small><sup>6+</sup></small> removal under optimal conditions. The third level involved pH standardization, which further enhanced the adsorption capacities to 352.19 mg g<small><sup>−1</sup></small> for Pb<small><sup>2+</sup></small> removal and 265.13 mg g<small><sup>−1</sup></small> for Cr<small><sup>6+</sup></small> removal. These results were well fitted by the pseudo-second-order kinetic and Langmuir isotherm models, demonstrating that the adsorption progressed <em>via</em> monolayer chemisorption. Removal efficiencies of 86.78% and 67.09% were obtained for Pb<small><sup>2+</sup></small> and Cr<small><sup>6+</sup></small>, respectively, during their simultaneous removal. Thermodynamic studies confirmed the spontaneity of the adsorption process. The adsorbent demonstrated reusability, retaining its performance over 15 regeneration cycles. In column studies, maximum adsorption capacities of 255.61 mg g<small><sup>−1</sup></small> for Pb<small><sup>2+</sup></small> and 42.08 mg g<small><sup>−1</sup></small> for Cr<small><sup>6+</sup></small> were achieved, described well by the Thomas model. This cost-effective adsorbent, driven by ion exchange and surface complexation mechanisms, holds significant promise for wastewater treatment.</p>","PeriodicalId":75,"journal":{"name":"Environmental Science: Water Research & Technology","volume":" 8","pages":" 1977-2001"},"PeriodicalIF":3.1000,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ew/d5ew00257e?page=search","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Environmental Science: Water Research & Technology","FirstCategoryId":"93","ListUrlMain":"https://pubs.rsc.org/en/content/articlelanding/2025/ew/d5ew00257e","RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENGINEERING, ENVIRONMENTAL","Score":null,"Total":0}
引用次数: 0
Abstract
In the present study, a novel and economical adsorbent was synthesized from a coal fly ash–chitosan composite to remove Pb2+ and Cr6+ from aqueous solutions. The characterization of the adsorbent under optimal conditions revealed that it was mesoporous and rich in different functional groups, which enhanced its adsorption properties. The optimal conditions for the adsorption process were achieved at three levels. At the first level, the optimal conditions for fly ash calcination (300 °C for 2 h), H3PO4 concentration (0.4 mol L−1), MFA–CS ratio (3 : 1), and effective morphology (nanopowder) for Pb2+ and Cr6+ removal were achieved. At the second level, response surface methodology achieved adsorption capacities of 339.27 mg g−1 for Pb2+ removal and 242.84 mg g−1 for Cr6+ removal under optimal conditions. The third level involved pH standardization, which further enhanced the adsorption capacities to 352.19 mg g−1 for Pb2+ removal and 265.13 mg g−1 for Cr6+ removal. These results were well fitted by the pseudo-second-order kinetic and Langmuir isotherm models, demonstrating that the adsorption progressed via monolayer chemisorption. Removal efficiencies of 86.78% and 67.09% were obtained for Pb2+ and Cr6+, respectively, during their simultaneous removal. Thermodynamic studies confirmed the spontaneity of the adsorption process. The adsorbent demonstrated reusability, retaining its performance over 15 regeneration cycles. In column studies, maximum adsorption capacities of 255.61 mg g−1 for Pb2+ and 42.08 mg g−1 for Cr6+ were achieved, described well by the Thomas model. This cost-effective adsorbent, driven by ion exchange and surface complexation mechanisms, holds significant promise for wastewater treatment.
期刊介绍:
Environmental Science: Water Research & Technology seeks to showcase high quality research about fundamental science, innovative technologies, and management practices that promote sustainable water.