Removal of Boron Using Ettringite Synthesized from Industrial By-products

• Main Authors: Chang-Sheng Chen, 陳昶昇
• Other Authors: Jhy-Chern Liu
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/6s8ga7

碩士 === 國立臺灣科技大學 === 化學工程系 === 105 === The treatment of wastewater containing boron by adsorption through synthesized ettringite was investigated in this study. Ettringite was synthesized using industrial by-products (basic oxygen furnace slag and flue gas desulfurization gypsum) and an addition of pure aluminum sulfate at a molar ratio ([Ca]:[Al]:[SO4]) of 3:2:3 under pHe of 12.02 and 25℃. The synthesized ettringite was characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) to ensure the quality and composition. Kinetic study indicated that boron adsorption reached equilibrium after 30 minutes and followed pseudo-second-order kinetic model. Equilibrium adsorption study (C0=5-50 mg B/L) showed that the reaction was affected by pH and experimental results were better fitted with Langmuir isotherm. The removal of boron seemed to be independent of ionic strength through the range of 0-0.05 M of NaNO3. Thermodynamic analysis revealed that the adsorption process by ettringite was spontaneous and exothermic. The value of standard Gibbs free energy change became less negative with an increase of temperature, implying that the reaction was less favorable with increasing temperature. The magnitude of change of standard enthalpy ("∆H°=" 127.65 kJ/mol) suggests a chemisorption mechanism. Evidence from XRD and FESEM indicated an adsorption process without precipitation reaction involved. The results of this study showed it is feasible to synthesize adsorbent from industrial by-products for the removal of boron from wastewater.