Isotherm Study for the Biosorption of Cd (II) from Aqueous Solution by the Aquatic Weed: Ceratophyllum demersum

D L S M Jayarathne,S S Iqbal,S Ariharan,M Thayaparan

doi:10.4038/jepsl.v4i2.7859

Abstract

Owing to various anthropogenic activities our environment is being polluted especially by discharging effluents containing heavy metals. Heavy metals are non degradable and persist for a long time in the environment. Hence they pose potential risk on the environment. Cadmium is a toxic element and cause severe damages to both animals and plants. Biosorption which is a process that utilizes dead or living biomass to sequester heavy metals is currently gaining considerable important as an alternative low cost and eco-friendly technology to remove heavy metals from aquatic media. In this study, three aquatic plants such as Eichhornia crassipes, Ceratophyllum demersum and Salvinia mullets were screened for the biosorption of cadmium and the plant biomass was analyzed for Cd using Atomic Absorption Spectrometer. Ceratophyllum demersum was selected and batch experiments were carried out to examine the influence of biosorbent dosage, initial concentration of metal ion and contact time on the cadmium (II) ion adsorption. Sorption data was analyzed using linear and nonlinear regression methods of Langmuir and Freundlich isotherm models. Desorption experiment was also carried out. Biosorption of cadmium by Ceratophyllum demersum was very rapid (20 minutes) at pH 5 and at room temperature. Adsorption capacity of Ceratophyllum demersum for cadmium increased with increasing concentration of Cd ions. The nonlinear adsorption isotherm of Langmuir model did not fit well with the sorption data (high χ2 = 4.58). Although three linear forms (I, II and V) of Langmuir isotherm model supported the sorption data (R2=0.9316, 0.9124 and 0.912), however the separation factor, RL, was less than zero and also maximum adsorption capacity, qm were very low in all five linear forms. Both linear and nonlinear forms of Freundlich adsorption isotherm model exhibited a better fit with high correlation R2=0.92 and low χ2 = 1.95 respectively, which indicates a multilayer adsorption. Desorption experiments indicated that 0.1M EDTA, 0.1M HCl and 0.1M HNO3 were efficient desorbents for recovery of Cd (II) from the loaded biomass. Journal of Environmental Professionals Sri Lanka: 2015 Vol. 4 No. 2: 10-24

Highlights

The discharge of heavy metals into aquatic systems has become a serious problem of concern all over the world
Biomass was separated from the metal solution by filtering through a filter paper and filtrate was subjected to residual Cd determination by Atomic Absorption Spectrophotometer (AAS)
Screening of Biosorbents Ceratophyllum demersum adsorbed maximum cadmium from the aqueous solution, and it was selected as the best biosorbent (Figure 1)

Summary

Introduction

The discharge of heavy metals into aquatic systems has become a serious problem of concern all over the world. Biosorption has been recognized as an effective alternate method for removing heavy metals from aqueous solutions. Aquatic plants are known to adsorb heavy metals from aqueous solutions (Huang et al, 2009; Chathuranga et al, 2012).

Results

Conclusion