Production and Characterization of Silica Gel For Textile Wastewater Treatment (Methylene Blue Dye)
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Date
2017-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
AAU
Abstract
In the world, different pollutants from industries released every day to the soil and ground water
without treatment. This will lead to different health problems to both human beings and animals.
According to pure earth non-profit environmental organization, because of pollution more than
200 million peoples was affected. In some of the world’s most polluted places babies are born with
birth defects, children have lost 30 to 40 IQ points, and life expectance may be as low as 45 because
of cancer and other diseases. In Ethiopia most textile factories are located nearby water bodies and
they discharge their colour effluent to canals, rivers, lakes and streams without treatment. Those
effluents have the capacity to cause an adverse effect on all forms of livings. Among those dyes
discharging MB dye without treatment can affect human life and aquatic life. To protect human
life as well as aquatic life the product silica gel (SiO
2
) was successfully prepared from sodium
silicate solution and sulphuric acid by sol-gel process to treat dye house waste. The obtained dry
silica gel is characterized by using X-ray diffraction (XRD) and Fourier transform infrared
spectroscopy (FTIR). The variables pH of silicic acid sol and pH of quenching water was studied
by using design expert 7.0.0 software. A 2 Factorial model was adopted in order to represent the
results in the form of three-dimensional surfaces. The results showed that the pH of silicic acid sol
effect is more significant than pH of quenching water. We obtained gels with a good adsorption
capacity of MB dye 48.84 mg/g at pH of silicic acid sol 3 and pH of quenching water is acidic (4).
The adsorption experiments were conducted at different particle size, wide range of pH, adsorbent
dosage, temperature, initial concentration, and contact time to adsorb MB dye efficiently. It was
observed that around 78.8 % removal efficiency of MB day was achieved after 15 min, at solution
pH around 10.06 and 25
O
C temperature using 0.02 g weight of dose of silica gel with particle size
≤ 100 μm and intial concentration of 20 mg/L of 50 ml dye solution. Different adsorption isotherm
models, adsorption kinetics and adsorption thermodynamics are carried out to determine the
maximum adsorption capacity, to identify feasibility and favourability of using silica gel for
adsorption of MB dye. Langmuir maximum adsorption capacity Q
m
is 58.45 mg/g, at 25
O
C and
pH 10.06 and 0.02 weight of adsorbent dose. The R
L
value (0.185 at 25
O
C) indicates that the
adsorption of MB dye on silica gel is favourable. From Freundlich isotherm model parameters,
value of 1/n = 0.6452 while 1/n = 1.55 indicating that the sorption of MB dye on silica gel is
favourable. The negative ∆G
O
values (-1067.82 to -1959.0 J/mol) indicates that the adsorption is
favourable and spontaneous at these temperatures. The positive value of ∆S
O
(39.45 J/mol.K)
Description
Keywords
Ethiopian sand, Methylene blue dye, adsorption