Abstract
South African coal fly ash (SACFA) was used to effectively remove phenol, 2-nitrophenol and 4-nitrophenol from wastewater. The rate of adsorption follows first-order kinetics before attaining equilibrium with the sorption rate (Kad) obtained being the  highest for 4-nitrophenol (p-nitrophenol) (7.0 x 10.3/h), followed by phenol (1.2 x 10.3/h) and 2-nitrophenol (o-nitrophenol) (1.0 x 10.3/h). Batch studies were performed to evaluate the adsorption process, and it was found that the Freundlich isothermeffectively fits the experimental data for the adsorbates better than the Langmuir model, with the fly ash having the highest adsorption capacity of 6.51 X 10-2 mg/g for 4-nitrophenol, 6.00 x 10-2 mg/g for 2-nitrophenol and 6.31 x10-2 mg/g for phenol. The fly ash was found to adsorb 90.2% of phenol, 88.9% of 2-nitrophenol and 92.6% of 4-nitrophenol at an initialconcentration of 20 mg/.. The desorption studies suggested that the desorption of 4-nitrophenol was the most difficult of the three adsorbates to be desorbed. The desorption efficiency was 17.9% for phenol, 18.8% for 2-nitrophenol and 10.2% for 4-nitrophenol. This work proved that SACFA can be used as an efficient adsorbent material for removal of phenol from water and wastewater.
Highlights
Wastewaters containing phenolic compounds are a serious environmental problem, and these waters cannot be released into the environment without treatment
The N2 adsorption gave the specific surface area (SBET) and pore volume for the fly ash used in this analysis as 1.279 m2/g and 0.001437 cm3/g, respectively
These results are comparable with those reported by Viraraghavan and Alfaro (1998) where the specific surface area (SSA) of the fly ash they used in adsorbing
Summary
Wastewaters containing phenolic compounds are a serious environmental problem, and these waters cannot be released into the environment without treatment. Several different adsorbent solids such as activated carbon (Garcia-Araya et al, 2003; Nouri et al, 2002), silica (Hanna et al, 2002), glass powder (Atun, 1992), polymeric resins (Wagner and Schultz, 2001; Abburi, 2003), fly ash (Akgerman and Zardkoohi, 1996; Kao et al, 2000; Sarkar et al, 2005; Sarkar and Acharya, 2006; Srivastava et al, 2006; Viraraghavan and Alfaro, 1998), peat (Allen, 1987; Viraraghavan and Alfaro, 1998), kaolinite (Barhoumi et al, 2003) and zeolites (Koh and Dixon, 2001; Sismanoglu and Pura, 2001) have all been proposed to remove phenolic pollutants from wastewater. An expensive material, so many of the other alternatives suggested become very attractive from a cost point of view In this regard fly ash is a very attractive option, because it is cheap, widely available and has good mechanical stability for handling purposes and employment in adsorption columns
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