Abstract
Raw and modified bentonite has been used to develop effective sorbents to remove phosphate from aqueous solution. Acid thermoactivation, Rewoquate, Irasoft, calcium, Fe and Al were employed to treat the bentonite. Results show that samples adsorption capacity for phosphate is in the order of, unmodified bentonite = acid thermoactivation < Rewoquate < calcium ≅ Irasoft < Fe < Al ≅ Fe-Al. The phosphate adsorption with Fe-Al-bentonite (FAB) modification was more than 99% and the phosphate removal reached the peak value in the initial 30 min. The phosphate adsorption of FAB was pH independent in the range of 2–10. The common coexisting ions in wastewater have no effect on the phosphate adsorption. The phosphate adsorption results were very well fitted in the Freundlich and Langmuir isotherm model and the maximum adsorption capacity was 8.33 mg P/g at pH 6.5 for 1 hour, which was better than similar modified bentonite with low time and Fe-Al consumption. FAB was characterized by scanning electron microscopy, X-ray diffraction, X-ray fluorescence and Fourier transform infrared. Therefore, the results confirm that FAB is a selective phosphate sorbent and environmentally friendly for its potential application for phosphate removal from wastewater.
Highlights
Removal and recovery of phosphorus compounds from wastewater has an important role in managing environmental and economic concerns, such as eutrophication of surface waters and depletion of phosphorus resources
Results show that the phosphate adsorption of different modified bentonites is in the order of: raw sorbent 1⁄4 acidthermoactivation < Rewoquate < calcium ≅ Irasoft < Fe < Al ≅ Fe-Al
Contact time between a solution containing Al-Fe as the modifiers and bentonite is one of the physical parameters that may affect the adsorption of phosphate, but the results show that this parameter had negligible effect on phosphate adsorption
Summary
Removal and recovery of phosphorus compounds from wastewater has an important role in managing environmental and economic concerns, such as eutrophication of surface waters and depletion of phosphorus resources. Several techniques have been widely investigated for phosphorus removal from wastewater including chemical precipitation, and physical and biological processes (Clark et al ; de-Bashan & Bashan ; Mulkerrins et al ). Among these methods, phosphate removal from aqueous solutions by adsorption has recently been given more. Clays are low-cost and available minerals that, due to their individual properties, are used as general sorbents in water and wastewater treatments Several studies used bentonite as a phosphate sorbent from water and wastewater, but this study investigated different methods for bentonite modification and optimized preparation. After selection of best modification process and parameters, their structures and mineralogy were thoroughly characterized
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