Influence of Mechanical Activation on the Structure and Sorption Properties of Hydrolytic Lignin, Kaolin and Composites Based Thereon

An express method of solvent-free mechanochemistry using fine grinding in air for 3 and 6 minutes in a mill (0.94 kW; 26,000 rpm) is employed to targetedly change in the structure of kaolin and increase its sorption capacity. During the same process, kaolin is modified together with hydrolytic lignin to hydrophobize its surface and improve its sorption properties. The influence of mechanical activation on the structure and properties of kaolin, hydrolytic lignin and their composites based with different component ratios is studied using electron microscopy, X-ray diffraction, infrared spectroscopy, low-temperature nitrogen adsorption and UV absorption spectroscopy. The dense structure of kaolinite remains preserved, hydrogen bonds in hydrolytic lignin are ruptured and the number of carbonyl groups increases, and fragments of natural polymer are grafted to kaolinite. It has been found that an aggregation-agglomeration microstructure is formed in the composites. Kaolin, as well as the composite of kaolin and hydrolytic lignin with a mass ratio of 10 : 1, treated with a mechanical energy dose of 0.83 kJ · g, exhibited significant changes in structure and demonstrated relatively high sorption characteristics. The Brunauer-Emmett-Teller specific surface area of this sorbents is ~ 16 m · g, the adsorption of bovine serum albumin are 83.63 and 44.10 mg · g, respectively. Thus, the dry mechanical activation in air under ‘mild’ conditions makes it possible to increase the sorption of bovine serum albumin of kaolin by 104%.