EFFECT electrolytic dialysis [12] methods have been developed. Nevertheless,


Kurniawati 2)*, Intan Lestari 3), Hermansyah Aziz 1),
Zulkarnain Chaidir 1), Rahmiana Zein 1)

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The effect of blocking agent on metals sorption has been
investigated. The functional groups
carboxyl and carbonyl modified with blocking agent (methanol 99 % and glycol)
in order to determine biosorption capacity of kelengkeng shell (Euphoria longan Lour) of Cu2+,
Pb2+, Zn2+ and Cd2+ ions. The chemical blocked
was invesitigated by using Fourier Transform Infrared (FTIR). Determination of
the possible reduction in metal uptake with the blocking of biosorbent was
performed in column method. The results
revealed in
blocking of carboxyl and carbonyl groups decreased of biosorption capacities of
heavy metals by Kelengkeng shell
is 36.86 %- 38.19 %, approximately. This proved the fact
that carboxyl and carbonyl groups in Kelengkeng
sheels played the main role on biosorption process of heavy metals.

Biosorption, Column method, Kelengkeng (Euphoria logan Lour) shell, Blocking




Important environmental
problems caused by heavy metal pollution due to its toxic effects on the
environment and accumulation throughout the food chain. The main sources of
heavy metal pollution are the mining industry, milling and surface finishing,
the use of various toxic metals such as Cu, Pb, Zn, and Cd into the environment
1-3. Heavy metal including cadmium, zinc, copper, and lead as sources of
anthrophogeny, mining, metal plating and other industries waste which are the
most common pollutants become an environmental problem of worldwide focus. All
sorts of methods including chemical precipitation or
coagulation 4, 5, 6, ion exchange 7 or adsorption 8–10, membrane
separation 11, and electrolytic dialysis 12 methods have been developed. Nevertheless,
the productiveness of the physical-chemical processes particularly the cost
effectiveness are edged. Hence, the low-cost alternative of research is more
likely needed of world wide 4, 13.

Nowadays, natural
materials and agricultural waste which are subjected by various low-cost
adsorbents have been proposed as an alternative to remove heavy metal ions from
aqueous solutions 14–16. Some biowaste of agriculture have been proved as
effective toxic heavy metals or dyes removal for instance Garcinia mangostana L. Fruit shell 4, Arenga pinnata Merr fruit shell 8, persimmon
peel 17, tomato waste 18, durian (Durio
zibethinus) 19, langsat fruit (Lansium
domesticum Corr) seed 20, water melon shell 21, lengkeng shell and seed
22, 25, etc. Most of biowaste of agriculture have been focused by
the researchers who are interested in the development of biosorbent with much
more selective and larger capacity in removing metal ions.

process in values ionic interactions, polar interaction and the combined
interaction between metal with biopolymers (macromolecules), as the source
functional group, which plays an important role in binding metal ion. The
functional group is available at macromolecules such as carboxyl group, amine,
hydroxyl, thiolate, phosphodiester, carbonyl and phosphate groups 23.

this study, kelengkeng (Euphoria longan Lour) shell which was an agricultural
product waste was used as a biosorbent to removal Cu2+, Pb2+,
Zn2+ and Cd2+ ions in water. The shell of kelengkeng was
characterized by FTIR spectroscopy to identity functional groups in the
molecules kelengkeng shell before and after modified with blocking agent. This
objective determined the role of carboxyl and carbonyl functional groups in
shell of kelengkeng on biosorption of Cu2+, Pb2+, Zn2+
and Cd2+  ions. The research was
determined effect of blocking agent in the in functional groups to sorption capacity
with column method.


Chemical and Apparatus

All materials used in
this research included in an analytical reagent level. Deionized double
destilled water was performed in the experimental studies. The main solution
was prepared by Pb(NO3)2 , ZnCl2 , CuSO4,
Cd(NO3)2 (1000 mg/L) E-merck,  HNO3 65 %,  NNO3 1 % (v/v), metanol 99 %,
etanadiol (glycol), HCl pro analysis. The following apparatus was used: Colomn
glass size (1 id x 15) cm, Atomic Absorption Spectrophotometer (AAS, varian
AA240, America), FTIR (Perkin elmer, Frountier)

Preparation of biosorbent

Shell of kelengkeng was
used as a biosorbent for biosorption of Cu2+, Pb2+, Zn2+
and Cd2+  ions from an aqueous
solution. Shell of kelengkeng was found from the market of Padang city, West
Sumatera, Indonesia. Kelengkeng were washed with deionized water, air-dried for
7 days and grounded using crusher with particle size 106-425µm.

Blocking Biosobent
treatment procedures

treatment: The carboxyl group
was blocked with blocking agent such as methanol. Blocking process was
performed by shaking at room temperature, 8 g of the raw biosorbent in 100, 150
and 200 mL of 99,9% methanol and concentrated hydrochloric acid (HCl). HCl 0.1
M was produced for six hour and 200 rpm and then, the biosorbent was washed by
using deionized water, followed by the air-drying. The dried biosorbent was
ready to be used.

treatment: The carboxyl group of the biosorbent was blocked
with glycol blocking agent. Blocking was carried out by shaking, at room
temperature, 8 g of the raw biosorbent in 25, 50 and 75 mL of glycol (etanadiol)
and concentrated hydrochloric acid (HCl), given a final acidic concentration of
0.1 M HCl for 6 h at 200 rpm. Then the biosorbent was thoroughly washed with
deionized water and then air-dried. The biosorbent was dried and ready to used.

Sorption Experiments

The column sorption
experiments were experimented in a 1 cm (internal diameter) and 15 cm (length)
of glass column. In a column process, each blocking and unblocking biosorbent
was entered 0.5 g into the glass column, the standard solution was carried out
at pH 3 for sorption of Zn, Pb, Cu ions and Ph 5 for Cd ion in a glass column.
Atomic Absoprtion Spectrophotometer (AAS) was used to measure the concentration
of metals of the filtrate. To determine the amount of metals adsorbed by
Kelengkeng shell, the formula used is:



Q is the metal uptake
(mg/g), V is volume of solution (L), C0 and Ce is initial
and final concentration of metal in solution (mg/ L), M is mass of biosorbent


of blocking with methanol solution

Column biosorption method
was subjected before and after blocking biomaterial. It was addressed to
compare the efficiency of biosorption and then the active compounds
contribution existing in biomaterial 24. The
distribution of metal removal by raw of biomass and blocked biomass are
described in Fig. 1.

The biosorbent blocking
with methanol had a significant impact on heavy metals removal and determined
the surface change of carboxyl group in biosorbent.Fig.1 showed the blocking
with 100, 150, and 200 mL methanol 99.9
%, as blocking agent group carboxyl cause a decrease in absorption capacity.
The optimization volume for blocking is taken at a volume of 150 mL for Pb2+
and Cu2+ and for metals Cd2+  and Zn2+ were taken on a volume
of  200 mL, as in this volume give a
minimum uptake from 4.905
to 1.792 mg/g for Pb2+
, 7.513
to 5.051 mg/g for Cu2+
, 2.544 to 2.0 mg/g for Zn2+ and 4.64 to 3,955 mg/g for Cd2+ .

1. Effect of the volume blocking agent for  carboxyl groups to biosorption capacity of Cu2+,
Pb2+and Cd2+  400
mg/L, respectively,  Zn2+ 200
mg/L, by kelengkeng shell; particle size 250 mm,
mass 0.5 g, flow rate 2 mL/min.

the volume of the next methanol relative longer affect the absorption capacity
of kelengkeng shell. The decline in kelengkeng shell absorption is apparently
due esterification reaction of carboxyl to ester cause a reduction in the
number of active centers negatively changed surface of the kelengkeng shell. The
purpose of this study were determination of optimum conditions in biosorption
and function of carboxyl groups in the process of biosorption metal cations.

of blocking carbonyl with glycol solution

of the volume of glycol (1,2 ethanediol) of biosorption characteristic to heavy
metals sorption by kelengkeng shell shown in Fig. 2.

2. Effect of the volume blocking agent for carbonyl functional group to
biosorption capacity of Cu2+, Pb2+and Cd2+ 400
mg/L, respectively,  Zn2+ 200
mg/L, by kelengkeng shell; particle size 250 mm,
mass 0.5 g, flow rate 2 mL/min.

absorption capacity for kelengkeng shell unblock on biosorption Pb2+
cation about 4.905
mg/g, and 1.6396
mg/g after kelengkeng shell treated with 50 ml glycol as blocked carbonyl
groups. The results shows that, the carbonyl group in kelengkeng shell plays a
large the biosorption process metal cations.

of Fourier Transform Infrared (FTIR)

FTIR which is one of
important anlytical techniques detects the characteristic of vibration in
functional groups existing on the surface of adsorbent. Moreover, it describes
possible functional group and binding mechanism related to the interaction
between metal ions 10, 20. The FTIR spectra of kelengkeng shell, after and
before blocking with methanol and glycol are shown in Fig. 3








Figure 3: FTIR spectra of
kelengkeng shell before blocking (a), Glycol blocking (b), and Methanol
blocking (c).

The FTIR spectrum of
biobsorbent was confirmed by a broad peak at 3422 cm-1. It indicates
the existence of macromolecular association (cellulose and pectin),  the presence of carbonyl and OH groups 24.
The stretching vibration of hydroxyl group is shown a large range of
frequencies as the confirmation of the exixtence hydroxyl bond in carboxylic
acid group. Symmetric and asymmetric CH stretching vibration of aliphatic acid
was indicated in the band at 2924 cm-1. Symmetric stretching
vibration of CH2 due to CH bonds of aliphatic acids was indicated at
peak 2854 cm-1. The peak of cellulose confirmed as finger print
region at 1000-1200 cm-1. The carboxyl groups band is shown at 1647
cm-1 and 1736 cm-1. The functional group of –COO- in
pectin was confrimed at 1373 cm-1.

The similar structures of
blocking biosorbent and unblocking biosorbent was confrimed by the similar
spectral profile. Nevertheless, by zooming in the spectra, some differences
were more like to be clearly identified.

The modification of
carboxyl groups with the blocking treatment was confirmed by FTIR spectra. The
difference between bonding energy related to the modification of carboxyl and
carbonyl groups in cellulose chains was identified as shift in wavenumber at
1636 cm-1.


low-cost biosorbent, particularly kelengkel shell with capacity 7.513 mg/g,
showed the good performence for the absorption of heavy metals. Ion of Cu2+,
Pb2+, Zn2+ and Cd2+ sorption by kelengkeng
shell blocking was higher compared to blocked methanol of kelengkeng shell which
decrease from 4.905 to 1.79 mg/g Pb2+, 7.513 to 5.051 mg/g Cu2+,
2.544 to 2.0 mg/g Zn2+, and 4.64 to 3.95 mg/g Cd2+.
Moreover, the metal ions sorption by using blocked glycol of kelengkeng shell
are namely decrease from 4.905 to 1.6396 mg/g Pb2+, 7.513 to 4.885
mg/g Cu2+, 2.544 to 1.9604 mg/g Zn2+, and 4.64 to 3.854
mg/g Cd2+. Based on the research result, carboxyl and carbonyl group
in Kelengkeng shell play an important role in the process of biosorption Cu2+,
Pb2+, Zn2+ and Cd2+. So, the
blocking agent decreases the adsorption capacity of Kelengkeng shell.



The special thank is
given to Directorate General of Higher Education, Ministry of Education and
Culture of the Replubic of Indonesia for giving financial support of this
research stated in the letter assignment number: 492/UN35.2/PG/2017.