Immobilization cocodust biomass with
silica gel as adsorbent for Cd(II) and Pb(II) ions in solution
Tri Endah1, Buhani2, Suharso3
1SMAN 5 Metro, Jl. Wolter Monginsidi 22A Hadimulyo Metro 34111, Lampung, Indonesia 2,3FMIPA Universitas Lampung, Jl. Brojonegoro No 1, Bandar Lampung 35145, Indonesia
Abstract
It has been studied cocodust immobilization with silika gel as adsorbent of heavy metal Cd(II) and Pb(II) ions in solution using batch metode. Adsorbent material characterizations obtained were performed with using Scanning Electron Microscope (SEM)- Energy Dispersive X-ray Spectrophotometer (EDS) to observe surface morphology of adsorbent and element composition existed in material resulted from immobilization. Analisys of adsorbent material functional group was carried out with using IR and determination of Cd(II) and Pb(II) ions concentration was applied with using atomic adsorption spectrofotometer (AAS). Adsorbent characterization result by infrared spectrophotometer (IR) shows that functional group of OH, C=O, Si-O-Si, and C-H are exist on adsorbent. In addition, adsorbent characterizations by SEM-EDS proves the existency of Si, O, and C element on adsorbent. Adsorption process of Cd(II) and Pb(II) ions is optimum at pH 6 with contact time of 60 minutes. Adsorption process of Cd(II) and Pb(II) ions on cocodust biomass tends to follow second orde pseudo kinetic and Freundlich adsorption isoterm model with concentration of Cd(II) and Pb(II) ions adsorbed each 17.91 and 23.64 mg g-1.
Keywords adsorption, cocodust, heavy metal, immobilization
1.
Introduction
Heavy metals produced from the residue (waste) industry is one of the hazardous material is very disturbing life and the environment. Cadmium (Cd) and Lead (Pb) is a heavy metal that is produced from industrial waste. Cd and Pb metals in the body cause neurological disorders. Cd and Pb metals in the body can not be removed but will accumulate as chemically bonded. Threfore, be required to eliminate or decrease the concentration of heavy metals and reduce in the environment (Buhani et al., 2010).
Currently there are several techniques that can be used to separate heavy metals from industrial waste, among other ion exchange, addition of alkoxy (RO), chemical precipitation and adsorption (Riyahie et al., 2011; Selvaraj et al., 1997
)
. From some of these methods, themethod of adsorption is a technique that is widely used to reduce the concentration of metal so effective to minimize the entry of metals into the environment.
Cocodust have been used as adsorbent metal cocodust Ni2+and Zn2+(Fatemeh et al.,
2013), that is modified using acid solvent and neutralized with alkali. Cocodust have been used adsorption Cd(II) (Essient et al., 2011.). Adorption of Cd(II) from Aqueous Solution used carbon active from cocodust (Kadirvelu & Namasivayam, 2002).
thats washed using aquabidest 3 times. Then dried in an oven at 100ºC for 24 hours (Mehrasbi et al., 2009).
Immobilization of biomass cocodust
Biomass cocodust (in diameter 150-200 m)from 22A Hadimulyo metro, Province Lampung, Indonesia) was chemically modified in two step. Firstly, cocodust was activated by silica gel from TEOS. Immobilized by silica gel used a procedure Buhani, 2010. The observe surface morphology before and after immobilized using SEM analysis. Analysis of adsorbent material which interaction with metal ion, functional group was carried out using IR.
Adsorption process
Adsorbat solution made of Cd (NO3) .4H2O and Pb (NO3)2in a concentration of 1000
ppm as the mother liquor. Adsorption was performed using 20 mg of adsorbent and 50 mL of ion Cd(II) and Pb(II) with a variation of pH between 2-10 stirred using a shaker at 100 rotasion min-1 at a temperature of 25ºC. Kinetics adsorption was studied using first and
pseudo second order on the variation of the contact time between 0-90 minutes. Variations in the concentration of metal ions is used to determine the maximum absorption of between 0 -100 mg L-1. Isotherm adsorption Langmuir and Freundlich models can provide information
absorption that occurs in the general adsorbent.
3.
Results and discussion
Infrared spectra to identify the functional groups of cocodust biomass, silica gel and cocodust immobilization results are presented in Figure 1. The cluster functions contained in the adsorbent can be observed. There is a change in the absorption band cocodust immobilization. At a frequency of 462.92 cm-1 is indicated as vibration of Si-O-Si and at
794.67 cm-1indicate the presence of Si-O stretching vibration (Si-O-Si). The absorption at
964.41 cm-1is vibration Si-O on Si-OH. Strong absorption bend at a frequency of 1087.85
cm-1shows the stretching vibration of Si-O of the Si-O-Si. Ribbon at a frequency of 1635.64
cm-1is vibration asymmetry C = O is derived from silica. There are a few peaks that disappear
after immobilized, such as frequencies between 1200 1500 cm-1 that characterizes the
lignocellulose and overton between 1600 2000 cm-1. But there is also a peak at cocodust
immobilization obtained from pure cocodust ie at a frequency of 548, 08 cm-1 for Si-O
stretching vibration; 1527 cm-1there is a little lignin, and at a frequency of 2931.80 cm-1for
Figure 1. Functional groups of cocodust biomass, silica gel and cocodust immobilization.
Cocodust biomass surface morphology before and after diimobilisasi observed using SEM, as shown in Figure 2. In Figure 2b shows that the biomass cocodust after immobilized with silica gel looks more stable. Silica gel chosen as the supporting matrix because it has a large surface and side active as silanol (-SiOH) and siloxane (Si-O-Si) which can chemical bonding with functional groups contained in cocodust, the abundance of silica with a seemingly SEM image look lighter or brighter.
(a) (b)
Figure 2. SEM image: (a) cocodust active, and (b) cocodust imobilization.
Effect of pH
In this study the influence of pH studied by varying pH and adsorbent interactions of metal ions in the range of 2-10 and shown in Figure 3 with a concentration of 100 mg / L at a temperature of 25ºC. Increased binding of metal ions affected by the increase of H+ions on
the surface of the adsorbent. Adsorption of Cd(II) and Pb(II) ions optimum at pH 6, the pH is a balance between the number of H+ions and metal ions resulting in competition maximum,
so that the data obtained adsorption of metal bound to the adsorbent perfectly Cd(II) and Pb(II) ions respectively 14.57 and 14.03 mg g-1. At pH 2 solution resulting in competition
between H+excess ions with the metal ions in solution. Charged metal ions is less reactive
than the H+ions are bemuatan +1 so that the seizure of the H+ions and metal ions in solution
Pb(II) 3 125 0.282 111.550 0.0530 0.963
From the results of the average constant (k1) and qe than shown in Table 1 shows the
pseudo first order models are not appropriate for immobilization cocodust adsorption process, so it is used second pseudo order kinetic model. The equation for the second pseudo order kinetics follow
= + , (1)
whereqeis the adsorption capacity, and k2constants second order that can produce slop and
intercept, it can be shown in equation 1. The value of the equationk2and qe are shown in
Table 1. From the results seen that the adsorption models kinetika followed pseudo second order.
Isoterm adsorption
Base on according to corelation cooficient value C/n to C Langmuir isoterm adsorption in equation 2 was gotten regresion in Cd(II) and Pb(II) ions 0.804; dan 0.92. Energy value < 0 (Table 2), shown spontanious adsorption. Value of k to show adsorption affinity adsorbent. The more increasing of k adsorbent affinities of biosorbent great. Adsorption to Pb(II)>Cd(II) ions, it becauses of Pb(II) ions is a intermediet metal and radius Pb(II) more Cd(II) ions. So, according to HSAB theory that OH-is a hard base. That Pb(II) ion, it is easier to bond OH-than
Cd(II).
Table 2. Comparation Langmuir and Freundlich isoterm adsorption models at Cd(II) and
Pb(II) ions to Cocodustbiomass imobilisation.
Langmuir Isoterm Adsorption
qe
(mg/g) b R2
nm
(mol/g x 10-4) K(103) E(kJ/mol)
Cd(II) 11.70 2.04 0.80 10.40 4.79 -20.99
Pb(II) 12.80 0.55 0.92 6.25 29.09 -25.46
Freundlich Isoterm Adsorption
k(intersep) R2 n (1/slope)
Cd(II) 0.20 0.94 1.94
Pb(II) 0.59 0.98 2.08
Pb(II) ions adsorption following Freundlich isoterm adsorption. It is because of shaped multy layer from adsorbat moleculs at surface, it is heterogen. The result of compare Langmuir and Freundlich isoterm adsorption it showed at Table 2.
4.
Conclusion and remarks
The results showed that immobilizationcocodustvery well be used as an adsorbent. Cocodust adsorption kinetics of the modified metal ion Cd (II) and Pb (II) followed pseudo second order with rate constant (k2) each by 8.4722 and 111.55 g mg-1 min-1. And the
isotherm models were used tend to follow the pattern of Freundlich adsorption, which indicates the maximum adsorption capacity of ion Cd(II) and Pb(II) at 17.91 and 23.64 mg g-1at a temperature of 25C. Cocodust adsorption properties of immobilization occurs in
physically.
Acknowledgment
I would thanks to goverment of provincy scholarship, Prof. Sutopo Hadi, Ph.D., Andi Setiawan, Ph.D., and Prof. Wasinton, Ph.D., thanks to discuss.
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