Purification and characterization of Brine Lake salt of Afdera and Dobi
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Date
2019-06
Authors
Journal Title
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Publisher
Addis Ababa University
Abstract
Improving the quality of salt using physic-chemical treatment process is an important issue
for industrial and health benefit of the society. This study was performed to purify and
characterize the brine lake salt of Afdera and Dobi. The salt samples were dried in an oven
and the moisture content was determined. The levels of metal and heavy metal impurities
were determined using FAAS after wet digestion using HNO3. The concentration of Cd
contents were not detected; however, the mean concentrations of other dissolved metals in
the sample of Afdera in ppm were 296 for Ca, 818.9 for Mg, 0.1145 for Cu, 0.0144 for Pb,
0.0175 for Zn, and 2.0554 for Fe. For salt sample from Dobi the metals concentrations in
ppm were 635.7 for Ca, 666.3 for Mg, 0.0472 for Cu, 0.0139 for Pb, 0.0139 for Zn, and
2.6342 for Fe. The percentage contents of sample from Afdera were 96.6 for NaCl, 1.09 for
Loss of mass, 1.05 for matter insoluble, 1.08 for SO4, 1.60 for alkalinity, 7.8 for pH.
Similarly,the contents of sample from Dobi were 91.21 for NaCl, 1.25 for Loss of mass, 1.75
for matter insoluble, 8.12 for SO4, 1.80 for alkalinity, and 7.9 for pH. The crude salt
samples were treated by using NaOH, Na2CO3, and BaCl2 to reduce Ca
2+
, Mg
2+,
and SO4
2-
.
Using CCD with face centered statistical experimental design, interaction effects of process
variable, optimum operating conditions and the optimum purity of salt that can be achieved
at these condtions were determined. The selected operating conditions for salt sample of
Afdera were 38.23
0
C of reaction temperature, 2.65g of NaOH, and 2.69g of Na2CO3, 0.235g
of BaCl2 and 50.26min of reaction time, With an optimum salt purity of 99.63 %.Similarly,
the selected operating conditions for salt sample of Dobi were 25
0
C of temperature, 2.97g of
NaOH, and 3g of Na2CO3, 5.29g of BaCl2 and 27.58min of reaction time with an optimum
salt purity of 99.68 %.The model adequacy was checked by analysis of variance.Based on
the analysis for salt sample of Afdera, the correlation coefficients, R-Squared (R
2
),adjusted
R-Squared and predicted R-Squared havea value of 0.9997 , 0.9966, and 0.8105
respectively. For salt sample of Dobi,R-Squared (R
2
), adjusted R-Squared and predicted R-
Squared have a value of 0.9997,0.9970 and 0.8047 respectively.After purification the NaCl
content of salt of Afdera and Dobi were enhanced to 99.65% and 99.60% respectively.
Description
Keywords
purification, crude salt, bio-toxicity, sample digestion, heavy metals, impurities Sodium Chloride, Loss of Mass, Matter Insoluble, Sulphate, Alkalinity