Adsorption of Cr(III) on Areca Nut Fibers – An Environmentally Friendly Approach

Development of pollutant removal methodologies based on biosorption has become attractive due to many desirable characteristics. However, practical applications of biosorption have not been much attended to. On the other hand, the use of chromium and its compounds has been steadily increased in the ever-expanding industrial sector. Consequently, there is a necessity to remove chromium from the environment, especially from water bodies. The methodologies to be adopted for pollutant removal should not only be cost-effective and environmentally friendly but also be efficient. In this respect, the study reported herein is on the use of areca nut fibers (ARF), leading to an excellent Cr(III) removal of > 90% from 10 ppm solution under optimized conditions of biosorbent dosage, shaking time, settling time, and solution pH. However, adsorption characteristics of ARF, which are not desirable at higher Cr(III) concentrations, can be significantly strengthened by surface modification, which is feasible due to the fibrous nature of the biosorbent. This is evidenced by obtaining > 90% Cr(III) removal from 25 ppm solution with NaOH-treated ARF, which is approximately 130% increment as compared to the situation before any treatment. Adsorption of Cr(III) on ARF is a monolayer process, as determined by the validity of the Langmuir adsorption isotherm model. X-ray fluorescence spectroscopic studies confirm the biosorption of Cr(III) on the fibers, while Fourier transform infrared spectroscopic investigation indicates the presence of carboxylic acid groups in the biosorbent, which could be deprotonated during NaOH treatment, leading to stronger affinity toward positively charged Cr(III) species. Results of static experiments performed could be extended toward dynamic experiments and proto-type studies to apply ARF for industrial applications.