Zebene, Kiflie (PhD)Temechachew, Tigabu2018-12-252023-11-102018-12-252023-11-102017-10http://etd.aau.edu.et/handle/12345678/15291In 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)en-USEthiopian sandMethylene blue dyeadsorptionThesis