Abstract
Pozzolan-based eco-adsorbents were synthesized by geopolymerization with addition of hydrogen peroxide (H2O2) with mass ratios 0% (GP0) and 1% (GP1) and the products used to sorb cationic methylene blue (MB) dye from water. The chemical composition, textural properties, mineral composition, surface functional groups, as well as morphology and internal structure of these samples were determined by the X-ray fluorescence, adsorption of nitrogen by the B.E.T (Bruamer Emmet Teller) method, X-ray diffraction, Fourier Transformed Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. The effects of contact time, dye initial concentration, adsorbent dosage, pH and temperature were examined and are herein reported. Incorporation of 1% H2O2 increased the specific surface area from 4.344 to 5.610 m2/g representing ~29% increase in surface area. This translated to an increase in the MB adsorption capacity by 15 orders of magnitude from 24.4 to 366.2 mg/g for GP0 and GP1, respectively. The adsorption rates of methylene blue onto the two geopolymers were best described by the pseudo-second order kinetic model. The adsorption equilibrium data were best described by the Sips and Freundlich isotherms models for GP0 and GP1, respectively. Thermodynamically, it was determined that the adsorption of methylene blue onto GP0 and GP1 is a physical and endothermic process. The results show that incorporation of a low amount of hydrogen peroxide into pozzolan-based geopolymers increases their adsorption capacity for methylene blue dye stupendously while preserving the surface chemistry.
Highlights
The problem of environmental pollution is still a topical issue because many industrial activities continue to generate various traditional and emerging pollutants, likely to create significant nuisance such as the destruction of aquatic fauna and flora [1]
The development the pozzolan-based eco-adsorbents was done by geopolymerization using hydrogen peroxide as a blowing agent with mass ratios 0 and 1%, labeled GP0 and GP1 respectively, in order to modify the textural properties and to evaluate their performance in removing the basic dye methylene blue in aqueous solution
The increase in surface area resulted to an increase in adsorption capacity by 15 orders of magnitude from 24.4 to 366.2 mg/g for GP0 and GP1, respectively
Summary
The problem of environmental pollution is still a topical issue because many industrial activities continue to generate various traditional and emerging pollutants, likely to create significant nuisance such as the destruction of aquatic fauna and flora [1]. Industrial effluents are among the major sources of environmental pollution These pollutants have the capacity to bioaccumulate along the food chain and accumulate in certain organs of the human body [2]. Faced by increasingly restrictive regulations, industries must obligatorily treat their effluents before discharging into the environment. To fight against this environmental issue, research in identification and elimination of water pollutants, such as methylene blue, directly involved in the appearance of imbalances in ecosystems like photosynthesis inhibition, under oxygenation, bioaccumulation or inducing serious disorders that can harm health such respiratory problems or even lead to death, both in animals and humans, is ever increasing [3]
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