Kinetics and equilibrium studies for the removal of heavy metals in both single and binary systems using hydroxyapatite

S T Ramesh,N Rameshbabu,R Gandhimathi,P V Nidheesh,M Srikanth Kumar

doi:10.1007/s13201-012-0036-3

S T Ramesh, N Rameshbabu + Show 3 more

Open Access

https://doi.org/10.1007/s13201-012-0036-3

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Abstract

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-, pseudosecond-order 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.

Highlights

The heavy metals are of great concern because of their extreme toxicity even at low concentration and the tendency to accumulate in the food chain (Mohan and Singh 2002)
The results indicated that the adsorption kinetic data were best described by pseudosecond-order model
It is evident from the results of second-order model that the correlation coefficients for Cu and Zn are very high and the experimental and theoretical qe values are in good match. These results suggest that the adsorption of the Cu and Zn ions in single and binary system on HA follows the second-order type kinetic reaction

Summary

Introduction

The heavy metals are of great concern because of their extreme toxicity even at low concentration and the tendency to accumulate in the food chain (Mohan and Singh 2002). The removal of toxic heavy metals from industrial wastewaters is one of the most important issues of environmental remediation. Heavy metals such as Pb, Cd, Cu, Zn, Hg, Cr, and Ni are the main contaminants of surface water, groundwater, and soils. Heavy metal contamination of waters and soils is dangerous to the living organisms. Heavy metals are major pollutants in marine, ground, industrial and even treated wastewaters (Valdman et al 2001). The presence of toxic heavy metals in water has several problems with animals, plants and human being (Ozer and Pirincci 2006)

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