Biosorption of cadmium(II) from aqueous solution onto Hydrilla verticillata

Abstract

Biosorption is an effective method to remove heavy metals from wastewater. In this work, the biosorption of Cd(II) onto Hydrilla verticillata was examined in aqueous solution with parameters of initial pH, adsorbent dosage, contact time, initial Cd(II) concentration, temperature, and co-existing ion. Linear Langmuir and Freundlich models were applied to describe the equilibrium isotherms, and both of the two models were fitted well. The monolayer adsorption capacity of Cd(II) was found to be 50 mg/g at pH 6 and 20°C. Dubinin-Radushkevich isotherm model was also applied to the equilibrium data. The mean free energy of adsorption (11.18 kJ/mol) indicated that the adsorption of Cd(II) onto H. verticillata might be carried out via chemical ion-exchange mechanism. Thermodynamic parameters, including free energy (DG 0 ), enthalpy (DH 0 ), and entropy (DS 0 ) of adsorption, were also calculated. These results showed that the biosorption of Cd(II) onto H. verticillata was a feasible, spontaneous, and exothermic process in nature. Desorption experiments indicated that 0.01 mol/L EDTA and HNO 3 were efficient desorbents for the recovery of Cd(II) from biomass. IR spectrum analysis suggested that amido, hydroxyl, C=O and C-O could combine strongly with Cd(II). EDX spectrum analysis suggested that an ion exchange mechanism might be involved.

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

“…At dosage higher than 1.0 g, there were not enough biosorbate molecules for available binding sites. A similar result has been reported for biosorption of cadmium on to H. verticillata where the saturation level reached at dosage higher than 0.1 g (Huang et al, 2009).…”

“…There are four probabilities for the RLvalues. For favorable adsorption, 0 < RL<1 For unfavorable adsorption, RL > 1 For linear adsorption, RL= 1 For irreversible adsorption, RL= 0 (Huang et al, 2009).…”

“…Aquatic plants also are known to adsorb heavy metals from aqueous solutions (Huang et al, 2009;Chathuranga et al, 2012).…”

Enhanced biosorption of metal ions from wastewater by Fenton modified Hydrilla verticillata dried biomass

“…1. After Fenton modification of biomass and biosorption process, shift in different peaks was observed, suggesting the combination of functional groups and metal ions (Baral et al 2009;Huang et al 2010). SEM images of FMDBH are shown in Fig.…”

“…Therefore, in the present research work, H. verticillata plant was selected for the study because of its wide spread availability throughout the year and very fast growth rate (2.5 cm per day; Nigam et al 2013). Various literatures on biosorption of different metals utilizing H. verticillata as biosorbent suggest that these aquatic plants possess hydroxyl groups in their cellulosic matrix (Huang et al 2010;Li et al 2013;Naveen et al 2011). Modification or pre-treatment of biosorbent using Fenton's reagent technique can be used to oxidize these hydroxyl groups of cellulose into carboxyl groups by creating a weak cationic ion exchanger (Shukla and Pai 2005), which ultimately could enhance the metal removal efficiency up to many folds as compared to the other previous research studies (Nasernejad et al 2005;Kumar et al 2007;Li et al 2007;Singh et al 2007;King et al 2008;Mohammadi et al 2010;Liang et al 2011;Momcilovic et al 2011;Tay et al 2011;Zhang 2011;Verma et al 2013;Kumar 2014;Tasar et al 2014) without imposing much burden on the economy.…”