Sorption of organic dyes by layered double magnesium and aluminum hydroxide

The sorption of organic dyes was studied by the methods of X-ray phase analysis, spectrophotometry, and infrared spectroscopy, using methylene orange (MO) and methylene blue (MB) as a case study, by layered double hydroxide (LDH) of magnesium and aluminum with a specific surface area of ~ 200 m2/g, obtained by the low saturation method. It has been shown that the sorption capacity of layered double hydroxide in the case of a solution of MO reaches 82%, and for a solution of MB it is 15%. It has been experimentally established that the sorption of dyes does not lead to structural changes in LDH, as evidenced by the absence of any significant changes in the X-ray diffraction pattern of the samples before and after sorption. An assumption has been made that the sorption of dyes occurs on the surface of the sample (physical sorption). The theory of physical sorption is supported by the large specific surface area of the layered double hydroxide. Possible reasons for different sorption capacities for MO and MB solutions have been analyzed.