RESULTS the next methanol relative longer affect the

RESULTS
AND DISCUSSION

Effect
of blocking with methanol solution

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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+ .

Figure
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.

Increasing
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.

Effect
of blocking carbonyl with glycol solution

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

Figure
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.

The
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.

Analysis
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

(c)

 

(a)

 

(b)

 

  

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.

CONCLUSION

The
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.

 

ACKNOWLEDGEMENT

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.