Cu(II) ions removal from aqueous solution by synthesized Phragmites australis/emeraldine base biocomposite

Abstract

The influence of in situ synthesized biocomposite consisted of Phragmites australis (Pha) -common reed and emeraldine base (Emb) on the removal of copper ion from aqueous media is discussed. The biocomposites were prepared with two different ratios of common reed/aniline (samples Pha/Emb1 and Pha/Emb2, respectively. Physicochemical parameters such as initial copper ion concentration, composite dosage and contact time between the composites and Cu(II) ions in aqueous solution were studied. An assessment of the equilibrium and the kinetics of sorption of copper ions has been made. Removal efficiency of 99.6 % was achieved with Pha/Emb1 and 91.9 % with Pha/Emb2, respectively. The experimental results were fitted to the isotherms of Langmuir, Freundlich, Temkin and DubininRadushkevich. It was established that the Langmuir isotherm is more suitable for the case of emeraldine base and for composite Pha/Emb1, while the Dubinin-Radushkevich isotherm is more suitable for the case of Pha/Emb2 (with higher content of common reed). The influence of the plant quantity in the biocomposite is important for the mechanism of Cu 2+ removal. Physical adsorption and ion exchange are dominant in the case of Pha/Emb1, and Emb, while in the case of Pha/Emb2 the chemical interaction is predominant. The kinetics of Cu(II) adsorption onto biocomposites followed pseudo-second-order model. IntroductionThe industrial wastewaters in most cases contain metal ions which can be removed by chemical or physicochemical processes. Because of their hazard impact on the environment and the high cost of the used methods, it needs to develop new, cost-effective and efficient methods for industrial wastewater treatment. The most widely used methods for metal ions removal from aqueous medium is precipitation, adsorption and ion exchange, because of their effectiveness, low cost and possibility of metal recovery.Increasing attention to the biosorbents such as rice hulls, raw pomegranate peel, peanut shells, sphagnum moss peat, tree fern, as well as dried activated sludge, is paid because they are widely spread, not expensive raw materials.1-6 Also, there are various polymeric substances which can capture various ions, as a result of the complexation reactions. Such materials are chitosan, 7,8 polythioamide, 9 polypyrrole, 10 polyaniline, 11 etc. These polymers can be used either separately or as composites -the combination of different polymers 12,13,15 or combination of the polymer with some adsorbents. [14][15][16] One of the widely used polymeric substance is polyaniline, which conductive properties and complexing ability are well-known. The polyaniline can be found in one of three idealized oxidation states -leucoemeraldine, emeraldine, and (per)nigraniline. The emeraldine form of polyaniline exists as emeraldine salt and emeraldine base. The deprotonated nonconducting emeraldine base has more free electron pairs in its structure in comparison with protonated conducting emeraldine salt, which contribute to its better complexation ability. 17-19The co...