Adsorption kinetics and isotherms of methylene blue by geopolymers derived from common clay and rice husk ash
Maingi, F. M.
Mbuvi, H. M.
Ng’ang’a, M. M.
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With the onset of industrialization mankind has witnessed various environmental issues in the society. Industrialization has not only brought development and prosperity but eventually disturbed the ecosystem. It is currently estimated that 1.1 billion people in the world lack access to enhanced clean water supplies. Consequently, pursuance of sustainable materials and technologies for wastewater remediation is critical. Use of adsorbents for wastewater treatment is preferable due to their simplicity and cheap materials involved. Geopolymers are synthesized hydrothermally using alumina and silica which possesses amorphous surface for use as adsorbents. There is adequate information and reports in literature that indicate clay contain alumina and silica. Similarly, findings have shown that rice husk ash contains substantial amounts of silica. This work reports synthesis of geopolymers GP-1, GP-2 and GP-3 prepared by using different SiO2/Al2O3 ratios and consequently equilibrium and kinetics behaviour of adsorption of methylene blue. The geopolymers were characterized using FT-IR, EDS, XRD and SEM. Geopolymer adsorbents were subjected to methylene blue batch sorption experiments that indicated the adsorption of MB increased with increased Si/Al ratio in geopolymers. The adsorption isotherms were described by Langmuir, Freundlich, Temkin and Sips isotherms. Data for adsorption of MB onto geopolymers fitted best in Sips adsorption model. Kinetic studies showed that Pseudo -second order model were more suitable than the Pseudo- first order model in explaining the kinetics of adsorption