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Abstract:The present study deals with the application of Watermelon Shell, an agricultural waste, for the adsorptive removal of Cu(II) from its aqueous solutions. This paper incorporates the effects of time, dose, temperature, concentration, particle size, agitation speed and pH. Analytical techniques have been employed to find pore properties and characteristics of adsorbent materials. Batch kinetic and isotherm studies have also been performed to understand the ability of the adsorbents. The adsorption behavior of the Cu(II) has been studied using Freundlich, Langmuir and Tempkin adsorption isotherm models. The monolayer adsorption capacity determined from the Langmuir adsorption equation has been found as 111.1 mg/g. Kinetic measurements suggest the involvement of pseudo-second-order kinetics in adsorptions and is controlled by a particle diffusion process. Adsorption of Cu(II) on adsorbents was found to increase on decreasing initial concentration, increasing pH up to 8, increasing temperature, increasing agitation speed and decreasing particle size. Overall, the present findings suggest that watermelon outer shell is environmentally friendly, efficient and low-cost biosorbent which is useful for the removal of Cu(II) from aqueous media.

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Removal of heavy metals is very important with respect to environmental considerations. This study investigated the sorption of copper (Cu) and zinc (Zn) in single and binary aqueous systems onto laboratory prepared hydroxyapatite (HA) surfaces. Batch experiments were carried out using synthetic HA at 30°C. Parameters that influence the adsorption such as contact time, adsorbent dosage and pH of solution were investigated. The maximum adsorption was found at contact time of 12 and 9 h, HA dosage of 0.4 and 0.7 g/l and pH of 6 and 8 for Cu and Zn, respectively, in single system. Adsorption kinetics data were analyzed using the pseudofirst-, pseudosecondorder and intraparticle diffusion models. The results indicated that the adsorption kinetic data were best described by pseudosecond-order model. Langmuir and Freundlich isotherm models were applied to analyze adsorption data, and Langmuir isotherm was found to be applicable to this adsorption system, in terms of relatively high regression values. The removal capacity of HA was found to be 125 mg of Cu/g, 30.3 mg of Zn/g in single system and 50 mg of Cu/g, 15.16 mg of Zn/g in binary system. The results indicated that the HA used in this work proved to be effective material for removing Cu and Zn from aqueous solutions.

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