Heavy Metal Adsorption by Crude Coniferous Barks: A Modelling Study

Abstract

Equilibria and mechanisms involved in the adsorption process of metal ions (Cr3+, Cu2+, Ni2+, Pb2+ and Zn2+) from aqueous solutions using coniferous barks as biosorbent substrate were investigated. Crude barks were used in this study since previous experiments showed a decreasing uptake for chemically treated barks in the considered granulometry. In our experimental conditions, the maximum binding capacity of barks followed the decreasing order Cr3+ > Cu2+ > Pb2+ > Ni2+ > Zn2+ whereas their general binding affinity decreased as: Pb2+ > Cr3+ > Ni2+ > Zn2+ > Cu2+. Adsorption isotherms at the optimal physicochemical conditions were established and the adsorption phenomenon was described by the non-competitive Langmuir adsorption model which fitted well the experimental data. An evaluation of adsorption capability was carried out using model parameters which were graphically determined. Models for removal of cations have been discussed; they represent efficient tools for predicting the behaviour of the biosorbents in metal ion adsorption systems.

Bark, a suitable biosorbent for the removal of uranium from wastewater – From laboratory to industry

“…With a q max of 1.16 meq.g -1 (138 mgU.g -1 ) and a b value of 6.1 L.meq -1 , barks proved to easily adsorb uranium. In similar experimental conditions (Martin-Dupont et al, 2002), the uranium adsorption capability of Douglas fir barks appears to be at least five times that of lead, a common heavy metal with a charge similar to UO 2 2+ and a mass of 207 g.mol -1 (270 g.mol -1 for UO 2 2+ ). With q max = 1.4 meq.g -1 (166 mgU.g -1 ) and b = 4.1 L.meq -1 , the data obtained in our laboratory experimental conditions with Amberlite IR120, a common synthetic cation exchange resin, are similar.…”

“…The ability of barks to remove heavy metal ions from polluted solutions (Al-Asheh et al, 1998;Gaballah et al, 1997;Gloaguen et al, 1997;Seki et al, 1997;Aoyama et al, 1993;Deshkar et al, 1990;Kumar et al, 1980;Randall et al, 1974) and the impact of various operating factors on this phenomenon (Deshkar et al, 1990) are well documented. In one of our precedent papers, these interactions were modeled using a Langmuir isotherm (Martin-Dupont et al, 2002) and adsorbent performances were improved using chemical modification by attachment of anionic functions (Martin-Dupont et al, 2004). This article aims to demonstrate the high stability of coniferous barks that should be considered not only as an additional biosorbent but also as an adsorption resin from a biological origin.…”

Heavy metals removal in aqueous environments using bark as a biosorbent

“…With temperature increase, the adsorption of metals increases, although the effect of temperature is small in the 4-25°C range (Martin-Dupont et al 2002). Ghodbane et al (2008) showed that maximum cadmium (II) uptake capacity of Eucalyptus bark increased from 14.53 to 16.47 mg/g when the temperature increased from 20 to 50°C.…”

“…Third, the metal speciation in solution is pH dependent, and at higher pH values, metal hydroxide complexes and precipitates can be formed (Naja et al 2009). Metal adsorption onto bark normally occurs under slightly acidic conditions and within the first minutes of contact time (Martin-Dupont et al 2002).…”

“…Metal-related factors are sorption type, i.e., non-competitive sorption or competitive sorption, polarizability, cation hydration enthalpy and number of unpaired electrons (Martin-Dupont et al 2002).…”