4.6. Effect of pH of dye solution on dye removal
To remove methylene blue pollutants from the dyeing effluent, Methylene
blue aqueous solution (10 ppm) was first prepared. Then take 100 ml of
it as a sample and measure its pH using transcellular paper. And then
using dilute acid chloride (HCl) to acidify the pH and by using (KOH) to
alkaline the pH of solutions. They were then examined to obtain the
optimum pH. After reaching the desired pH, add 1 ml of oxygenated water
and finally add 0.1 gr of nanocomposite metal-organic framework
(NiFe2O4@SiO2@HKUST-1)
at 30% by weight as adsorbent. It was subjected to ultrasonic mixing
for better mixing. every 10 minutes take a sample and centrifuge the
sample, then, using a spectrophotometer, the wavelength was measured and
then the removal efficiency was calculated.
Fig (18): Graph showing the effect of pH on the removal of methylene
blue dye
The results showed that the dye removal on the metal organic framework
would be different at different pHs. This difference is due to the
charge of dye ions and the degradation properties by changing the pH of
the solution. Decrease of pH from alkaline to acidic, methylene blue dye
removal increased because at acidic pH the concentration of
H+ and in the alkaline pH concentration of OH
increased in the solution and increasing the concentration of these ions
increases or decreases the removal efficiency of the dye. Results in Fig
(18) shown, acidic pH increased methylene blue dye removal efficiency
due to increased H+ concentration and the presence of
hydrogen peroxide (H2O2) in solution. In
the alkaline pH range, the Fe (Ⅲ) in the environment, it precipitates
(Fe(OH)3) and decomposes
H2O2 into water and oxygen. In addition,
the formation of iron (2) complexes at higher pH reduces its
concentration in the environment, in contrast, the re-production of Fe
(Ⅱ) is prevented by the reaction of (Fe3+) and
(H2O2) at more acidic pHs so acidic pH
is considered as the optimum pH [64-69].