Watermelon rind (WR) an agro waste was evaluated as an adsorbent for the removal of Cr 3+ ions from aqueous solution. Batch mode adsorption studies were performed by varying parameters such as pH, contact time, adsorbent dose and initial metal ion concentration. Maximum loading capacity of WR was found to be 172.6 mg g À1 for Cr 3+ ions at pH 3. Kinetic studies show that removal of Cr 3+ ions is rapid and follows a pseudosecond order model. Equilibrium data fit better with the Langmuir isotherm than the Freundlich isotherm. Thermodynamic parameters such as DG°, DH°and DS°were derived for the current system. The negative values of DG°show that the nature of sorption process is spontaneous. FTIR studies reveal that hydroxyl and carboxyl groups were responsible for uptake of metal ions. Successive desorption of Cr 3+ ions reveals that WR can be an economical sorbent for the removal of heavy metals from aqueous solution. The results conclude that watermelon rind an agro waste can effectively be used for the removal of chromium ions from aqueous solution.ª 2014 Production and hosting by Elsevier B.V. on behalf

The present study reports the feasibility of removing Pb 2+ ions from aqueous solution using watermelon rind (WR) as a low cost adsorbent. Fixed bed column studies were employed to study the removal efficiency of Pb 2+ ions by varying the column parameters such as flow rate, bed height and initial metal ion concentration. The results showed that breakthrough and exhaustion time increases with a decrease in flow rate, inlet concentration, and an increasing bed height. The breakthrough curves obtained were analyzed with Adams-Bohart, Thomas and Yoon-Nelson models. On comparison of the R 2 values, both the Thomas and Yoon-Nelson models were found to have a better fit than the Adams-Bohart model and these two models can be used to predict the adsorption of Pb 2+ ions in a fixed bed column. Desorption of Pb 2+ ions on WR was repeated for three cycles in 0.1 M HCl solution. The loading capacity of WR was compared with other adsorbents and was found to be high. These results show that watermelon rind, a non-hazardous agro waste, can be successfully employed for the elimination of Pb 2+ ions from aqueous solution.244 | Environ. Sci.: Water Res. Technol., 2015, 1, 244-250 This journal isThe majority of adsorption studies have been carried out in batch modes which are limited to a laboratory process and generally not applicable to most of the long term treatment processes. Continuous column studies are the most valuable and economical treatment processes used in practice for the removal of heavy metal ions from industrial effluents. Activated carbon is a commonly used sorbent for the removal of inorganic and organic pollutants from waste water. In spite of its effectiveness in the removal of pollutants, high activation cost limits its use as an economical adsorbent. Hence, the present study reports the use of a low cost adsorbent such as watermelon rind for the removal of Pb 2+ ions from aqueous solution.

The present study reports the feasibility of synthesis of palladium nanoparticles (Pd NPs) by watermelon rind. The aqueous extract prepared from watermelon rind, an agro waste, was evaluated as capping and reducing agent for biosynthesis of palladium nanoparticles. The formation of Pd NPs was visually monitored with change in color from pale yellow to dark brown and later monitored with UV-Vis spectroscopy. The synthesized Pd NPs were further characterized by XRD, FTIR, DLS, AFM and TEM techniques. The synthesized Pd NPs were employed in Suzuki coupling reaction as catalyst. The results reveal that watermelon rind, an agro waste, is capable of synthesizing spherical-shaped Pd NPs with catalytic activity.

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