Chemical Precipitation removal of Boron in Synthetic Wastewater using Microwave Heating

Objectives : The objective of this study is to investigate the potential for the removal of boron(B) from synthetic wastewater through chemical precipitation using microwave heating to identify the optimal conditions for the removal of boron.Methods : Synthetic wastewater was prepared using boric acid(H3BO3) and distilled water. The range of variables that exert an influence on boron removal included the initial pH 3-13, the calcium hydroxide(Ca(OH)2) dosage of 0.5-10 g per 30 mL(17–333 g/L), and the boron concentration of 100-1,500 mg/L. A face-centered design in response surface method was employed to identify the optimal conditions for boron removal in a continuous scale and to ascertain the interaction of the factors.Results and Discussion : In discontinuous conditions, the maximum removal efficiency was observed at initial pH 3, Ca(OH)2 of 2 g, and the boron concentration of 1,500 mg/L. As the pH value decreased, the removal of boron increased. The greatest removal efficiency was observed when the dosage of Ca(OH)2 was 2-5 g. It was also found that the higher the concentration of boron, the greater the removal efficiency. In the continuous scale, the optimal conditions for boron removal were identified as initial pH 3.3, the dosage of 6.2 g Ca(OH)2, and the boron concentration of 1,500 mg/L, with the removal efficiency of 93%. All independent variables exerted a statistically significant influence on chemical precipitation removal(p<0.05). In comparison to pH(p=0.047), boron concentration(p<0.001) and Ca(OH)2 dosage(p<0.001) demonstrated a more pronounced impact on boron removal. The interaction between boron concentration and Ca(OH)2 dosage was also identified as statistically significant(p<0.001).Conclusion : Chemical precipitation using microwave heating was effective in removal of boron from wastewater, and the optimal conditions in continuous scale through response surface analysis were initial pH 3.3, boron concentration 1,500 mg/L, and Ca(OH)2 dosage 6.2 g(207 g/L).