Environmental & Analytical Toxicology

Phenol being a priority pollutant, the purpose of the research is to find out the efficiency of the rice husk as adsorbent for removal of phenol from the wastewater. The characterization of rice husk is studied using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and Brunauer-Emmett-Teller analyzers. The percentage removal of phenol is obtained in batch experiments with variation of pH (3-9), contact period (60-300 min), adsorbent dosage (2-10 gm/L), phenol concentration (50-250 mg/L) and temperature (25-35°C). The results indicate that the phenol removal reaches up to 95%. The optimized values of adsorption process (pH=7, contact period=240 min, adsorbent dosage=6 gm/L, initial phenol level=50 mg/L and temperature=35°C) are used for testing of various kinetic, thermodynamic and isotherm models. The kinetic study indicates that the pseudo-second order kinetic model (r²=0.99873) is better than the first order kinetic model (r²=0.97984) and hence it supports chemisorptions. The Elovich and the Boyd models also favour chemisorptions. The Dubinin-Radushkevich model supports physisorption, however it is not effective as correlation coefficient (r²=0.73643) is low. The Reichenberg model suggests for film diffusion, while the Fick's model suggests for both and intraparticle diffusion taking 120 min each. The Smith and Furusawa model indicate faster movement of phenol from the bulk to the solid phase. The isotherm study indicates that Freundlich model favors most than Temkin and Langmuir models and hence it supports chemisorptions. The study of thermodynamic supports for spontaneous, endothermic and random process and also supports chemisorption. The novelty of this research is the elaborated analysis of numerous models, which perhaps has not been covered in any of such research work published before. The authors conclude that the rice husk is a low-cost and suitable adsorbent for the removal of phenol from the wastewater.