A two-step way to synthesize nano inner-modified aluminum trihydroxide

This paper devotes to synthesize a new-style nano inner-modified aluminum trihydroxide (IMATH) flame retardant by carbonation in a rotating packed bed (RPB) reactor and hydrothermal modification. Sodium aluminate (SA) solution was carbonated in RPB reactor to yield nano aluminum trihydroxide (ATH) gels, which subsequently reacted with oxalic acid at the optimum hydrothermal conditions of 1 h and 160 °C to form nano IMATH powders. Factors affecting the explosive nucleation in the carbonation process and the properties of ATH product such as temperature, terminal pH, high gravity level, SA concentration, liquid flux and G/L ratio were mainly studied to achieve the required nano ATH gels, and the hydrothermal modification process was also researched. The as-synthesized nano IMATH was characterized by FESEM, XRD, BET, TG-DSC, FTIR and compared with nano ATH. Experimental results show that nano IMATH starts thermal decomposition at 350 °C and has a weight loss of 51%, both higher than nano ATH. In addition, nano IMATH inherits many characters of nano ATH such as crystal phase, endothermic enthalpy and particle morphology. It is confirmed that carbonation parameters have significant influences on the properties of ATH gels, and therefore further affect the properties of IMATH.