Investigations on calcination and dehydration process, optimization of calcination technique, and quality evaluation of borax

Effect of heating rate on the dehydration process of borax was studied by using thermogravimetric analysis, and the optimal heating rate was determined. The calcined temperature, calcined time, and sample laying thickness were selected as influencing factors, with the dehydration rate, content of sodium tetraborate, fluffiness, and minimal inhibitory concentration as evaluation indices, the calcination process of borax was optimized by the method of analytic hierarchy process (AHP)-criteria importance through intercriteria correlation (CRITIC) combined with response surface test. The changes in microscopic morphology and compositional structure of borax before and after calcination were analyzed by scanning electron microscopy, infrared spectroscopy, and Raman spectroscopy. The anti-inflammatory activity of calcined borax was investigated by lipopolysaccharide (LPS)-induced RAW264.7 cell model. The antioxidant capacity of calcined borax was assessed by the scavenging rate of 2, 2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radical for furtherly evaluating the quality of calcined borax. The results showed that the optimal heating rate for the calcination of borax was 10 ℃·min^-1, and the optimized technical conditions were as follows: the calcined temperature was 293.31 ℃, calcined time was 47.44 min, and sample laying thickness was 0.54 cm. After calcination, the microscopic morphology and compositional structure of borax were all changed, and the in vitro anti-inflammatory and anti-oxidation capacities of calcined borax were enhanced compared to those of crude one. The established calcination technique of borax is stable and feasible, which can provide guidance for the industrial production of calcined borax.