| Summary: | Urea coated with urea-acetaldehyde and zeolite powder was carry out to
produce slower release fertilizer, which can increase the effectiveness and
efficiency of urea fertilizer used and reduce environmental pollution. The aim of
this research was to study urea coating process with urea acetaldehyde and
zeolite as slow release fertilizer.
Urea was reacted with acetaldehyde at a temperature of ± 50 °C and pH 4
with sulfuric acid catalyst to become urea-acetaldehyde that had lower solubility
of the water than that of urea. Urea-acetaldehyde was mixed with zeolite and
coated to urea in a rotary drum to form granules. The variables studied were
mass ratio of urea with acetaldehyde urea and zeolite powder, and volume ratio
of water in coating material. Coated urea products will be analysis as slow
release fertilizer (SRF).
The results of this study obtained that the molecular weight of urea
acetaldehyde is 116.77 g/mol and solubility of urea acetaldehyde is 0.0814 g/mL.
Mass transfer coefficient of urea coated fertilizer ( kc ) for variations of mass urea
in coated urea ranged between 0.2035 � 0.2210 cm/s, and for variation of the
volume of water added in the coating material ranged from 0.163 � 0.2204 cm/s.
The average dissolution rate of coated urea in this study is 3 minute 10 second,
that rate is still too fast for slow release fertilizer standards but it still lower than
that of urea, i.e. 2 minute 45 second. The results of this study show that the mass
of urea and the volume of water in the coating material effect on the compressive
strength, thickness coatings and dissolution rate of coated urea products. Highest
mass fraction of the coating material will make thicker coatings, also greater
compressive strength and lower dissolution rate of coated urea products. The
greater of volume of water added is, the thicker the coatings, the greater the
compressive strength and the lower the dissolution rate of coated urea products
are.
Keywords : urea, urea acetaldehyde (UA), zeolite, urea coating, fertilizer, slow
release fertilizer (SRF), dissolution rate, thickness coatings.
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