Influencing Factors In The Process Of Producing Boric Acid

Sulfuric acid acidification method was common nowadays in the producing of boric acid. But its purity can only up to reagent standard. So it is unappeasable to some occasion such as the requirement of nuclear industrial boric acid which was used in national defence technology. The objective of this thesis is to analyzing the current production technology of producing boric acid, and then ameliorating its industrial flow to get high purity boric acid.Some methods such as borax acidification by sulfuric acid or hydrochloric acid and recrystallization had been used to prepare high purity boric acid. Some influencing factors such as sulfuric acid composition and hydrochloric acid in the process of acidification, initial temperature of neutralization reaction, reacting time, reacting temperature, ratio of liquid-solid, stirring speed, crystallization temperature, drying temperature, and extraction rate were studied in this paper. Comparing with the two different acid leaching experiments, the method of hydrochloric acid acidification achieved better results. As the initial temperature was 90℃, pH value kept 3-4, leaching temperature retained at 95～100℃, the reaction was instantaneous. The crystallization temperature was 15℃, crystallization time was kept for 10h. After it dried at the temperature of 70℃, high purity boric acid (99.7%) was acquired.Effects of boric acid concentration, crystallization temperature, crystallization time, model of stirring paddle and stirring velocity on crystallization of boric acid were also studied. The optimal conditions were that the proportion of liquid-solid was 3:1, stirring speed was 80r/min with anchor paddle, crystallization time kept for 10h at 15℃. The high purity boric acid (99.9%) was acquired by hydrochloric acid acidification and then recrystallization.