A comprehensive review of anionic azo dyes adsorption on surface-functionalised silicas
- 27 September 2022
- journal article
- review article
- Published by Springer Science and Business Media LLC in Environmental Science and Pollution Research
- Vol. 29 (51), 76565-76610
- https://doi.org/10.1007/s11356-022-23062-0
Abstract
Surface -functionalised silica networks are advanced adsorbents. They have been given much attention for treating wastewater using the adsorption technique due to the silanol reactivity, resulting in strong binding affinities towards many pollutants. This review discusses the removal of anionic azo dyes utilising various functional groups such as amines, surfactants, polymers, macrocyclic, and other chelating groups functionalised on silica’s surface. This review also reveals the steadily increasing interest in surface-functionalised silicas as adsorbents, emphasising the scholarly advancements in this field as a platform for future research. For that, adsorption capacities with different experimental conditions have been compared. The possible adsorption mechanisms, rate-limiting step, and factors affecting the anionic azo dye adsorption process have been comprehensively discussed. This review discloses that adsorbent characteristics such as porosity and functional groups, besides structural properties of an anionic azo dye, significantly affect adsorption. The adsorption process followed the Langmuir isotherm and pseudo-second-order models, with a predominantly spontaneous and endothermic nature. Multiple interactions, including electrostatic interaction, π-π interactions, and hydrogen bonding, are observed between dyes and functionalised silicas, indicating the adsorption process’s complexity. Regeneration and cost-economic analysis are also presented to provide a roadmap for sustainable improvements. Chemical and biological regeneration techniques restore > 80% of the spent functionalised silicas. There is a significant opportunity to improve their efficiencies and regenerability, resulting in surface-functionalised silicas being used commercially instead of only in the laboratory. Finally, future research has been proposed by identifying current research gaps, particularly concerning the application of functionalised silicas in wastewater treatment. Graphical abstractThis publication has 120 references indexed in Scilit:
- Primary–secondary amino silica nanoparticle: synthesis and dye removal from binary systemDesalination and Water Treatment, 2013
- Amine-functionalized silica nanoparticle: Preparation, characterization and anionic dye removal abilityDesalination, 2011
- Amine-Functionalized Titanosilicates Prepared by the Sol−Gel Process as Adsorbents of the Azo-Dye Orange IIIndustrial & Engineering Chemistry Research, 2010
- Removal of azo and anthraquinone reactive dyes from industrial wastewaters using MgO nanoparticlesJournal of Hazardous Materials, 2009
- Characteristics, Chemical Modification Processes as well as the Application of Silica and its Modified FormsCritical Reviews in Analytical Chemistry, 2009
- Effect of structural properties of acid dyes on their adsorption behaviour from aqueous solutions by amine modified silicaJournal of Hazardous Materials, 2009
- Environmentally stable adsorbent of tetrahedral silica and non-tetrahedral alumina for removal and recovery of malachite green dye from aqueous solutionJournal of Hazardous Materials, 2008
- Determination of the hydroxyl group content in silica by thermogravimetry and a comparison with 1H MAS NMR resultsThermochimica Acta, 2001
- The surface chemistry of amorphous silica. Zhuravlev modelColloids and Surfaces A: Physicochemical and Engineering Aspects, 2000
- Pseudo-second order model for sorption processesProcess Biochemistry, 1999