| Summary: | Humic acid (HA) has been immobilized through cross linking in
carboxymethyl cellulose (CMC) using crosslink agent of N,N
methylenbisacrilamide and its application as planting media mixture of Capsicum
annum. L. Humic acid was extracted from peat soil of Rawa Pening, while CMC
was synthesized from cellulose isolated from bagasse.
Humic acid from the peat soil of Rawa Pening was extracted by soaking in
0.1 M NaOH solution (ratio of soil and NaOH, 1:10 (b/v)) and followed by
acidication using HCl solution to pH@1. Cellulose as raw material for CMC was
isolated by refluxing the bagasse at 100oC for 3 hours in 100 mL NaOH solution
in various concentrations (5.0 %. 7.5 %, 10.0 % and 15.0 % (w/v)). Cellulose as
residue was purified by bleaching method using 5% (v/v) NaOCl solution. The
synthesis of CMC was done by reacting the isolated cellulose with sodium
chloroacetic (SCA) at 70oC. The immobilization of HA on CMC was carried out
through cross linking of AH on CMC obtained from the reaction of 5 g cellulose
and 2 g SCA in water medium at temperature 70oC by using MBA.
The results of the characterization with FTIR indicated that there was
similarity between the spectra of technical cellulose (Sigma) and those of
cellulose obtained from process of extraction using 5% (w/v) NaOH. The water
absorption ability test showed that CMC obtained from the reaction of 5 g
cellulose and 2 g SCA possessed the highest absorption of water, i.e. as much as
80.15 mL/g. FTIR spectra indicated that COOH group has already been released
from its interaction with impurities after one step purification using the mixture of
HCl and HF solution. Humic acid capability to absorb water was not as good as
CMC. Indication of the presence of cross linking among CMC, MBA, and HA
could be found in the FTIR spectra, i.e. by the decreasing of absorption intensity
at 3300-2900 cm-1 for O-H stretching. Capability to absorb water was the highest
for the immobilization product of CMC and HA at weight ratio 5:1, i.e. as much
14.39 mL/g. Cation exchangable capacity (CEC) test indicated that the increase of
HA portion could increase the CEC of CMC-HA. The use of the immobilization
product of AH on CMC in planting media of chili was able to minimize the need
of fertilizer to 50%.
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