Fourier Transform Infrared Spectroscopic Analysis of Fruit Peels before and after the Adsorption of Heavy Metal Ions from Aqueous Solution

Abstract

For orange peel (OP), lemon peel (LP), and banana peel (BP) as adsorbents for removal of heavy metal ions such as Cu2+, Ni2+, Cd2+, Pb2+, and Zn2+ from aqueous solution, a simple FT-IR technique was used and discussed to study the variation in functional groups upon modification. Metal−carbon bond formation was witnessed by FT-IR during metal ion adsorption. All of these adsorbents were characterized by FT-IR, BET, and SEM. The presence of carboxylic and hydroxyl groups was confirmed by FT-IR. The FT-IR spectrum of lemon peel cellulose (LPC) showed well resolved peaks for carboxylic acid and hydroxyl groups compared to LP indicating the appreciable contents of carboxylic acid and hydroxyl groups in LPC. The widely used Langmuir adsorption isotherms were used to describe the adsorption equilibrium process. The adsorption capacity of the metal ions such as Cu2+ and Ni2+ was found to be more than those of other metal ions. Upon comparison of the adsorbents, surface modified LPC (LPCACS) was found to show enhanced adsorption activity. A comparative study of adsorption was carried out with commercially available activated carbon (AC) also from which it was inferred that the order of the adsorption capacity is as follows: LPCACS > LPC > AC > LP > OP > BP.

Characterization of biochars produced from oil palm and rice husks and their adsorption capacities for heavy metals

“…1 Zeta potential of the EFBB and RHB measured at different pHs groups because its outer orbital electrons are completely filled-hence the decreased adsorption of Zn by the biochars. Pb has the fewest electrons in its outermost valence shell among the heavy metals studied; thus, it can bind with functional groups with donor sites better than Cu and Zn (Thirumavalavan et al 2011). The result of this study is in agreement with the result of Zhua et al (2012) who reported that metals adsorption onto xanthate-modified magnetic chitosan followed the order of Pb(II) [ Cu(II) [ Zn(II).…”

“…The absorption of Pb was highest for both biochars, followed by Cu and Zn. This can be explained by the fact that both Pb and Cu can easily react with functional groups containing unshared pairs of electrons such as those in O, N, P, and S. Additionally, Pb and Cu have a greater affinity for carboxyl groups than does Zn (Thirumavalavan et al 2011). Hence, Pb and Cu can easily coordinate with both the carboxyl and hydroxyl groups of the biochars, as the functional groups have valence shell electrons in the outer orbital.…”

“…2 Concentrations of heavy metals remaining in a buffer solution at pHs of 2 through 9, b non-buffer solution at pHs 2 through 9, c solution containing supernatant of the EFBB and Millipore Ò water at pHs 7.8 through 10.3, d solution containing supernatant of the RHB and Millipore Ò water at pHs 7.3 through 9, after equilibration Fig. 3 The amounts of Zn, Cu, and Pb adsorbed by the EFBB and RHB from solutions buffered at different pHs heavy metal adsorption (Thirumavalavan et al 2011). The weak band of C:C and -C:N triple bonds or accumulated -C=C=C-and -N=C=O double bonds at 2,000-2,500 cm -1 also shifted after adsorption of heavy metals, indicating their involvement in the adsorption process.…”

“…Other functional groups that showed shifting in their peaks before and after heavy metal adsorption were the COO-groups at 1,576.2 cm -1 , the CH 2 -group at 1,369 cm -1 (Chun et al 2004), and the C-O ester of alcohols, carboxylic acid groups and carboxylic acids between 1,020 and 1,300 cm -1 (Stuart 1996;Abdel-Ghani et al 2007). The appearance of new peaks approximately 1,011-1,020 cm -1 after adsorption of heavy metals may be due to the C-O ester stretching, and its appearance is significant in the heavy metals adsorption process (Thirumavalavan et al 2011). The shift in the 424 cm -1 band is due to a metal-hydrogen bond (Stuart 1996).…”

Applications of Bio-waste Materials as Green Synthesis of Nanoparticles and Water Purification

“…The maximum absorption ability according to the Langmuirmodel was 3.18 mmol/g (658 mg/g), which was reported very high for other biosorbents and similar to some ion interchange resins. Besides these, several other researchers also examined citrus husks or lemon husks as adsorbents for varied aquatic Contaminants elimination [60].…”