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].