Oxidized Cross-Linked Guar Gum with Hydrophobic Groups: Structure, Properties and Removal of Reactive Blue-XBR in Simulated Water

Abstract

The objective of this research was to investigate the effect of cross-linking and oxidation on the structure of guar gum (GG) in heterogeneous phase system and ultimately to achieve the functional improvement of GG. The experimental results indicated that the crystalline structure of GG particles was not an amorphous structure, and the cross-linking occurred unevenly on GG. The surface of oxidized cross-linked guar gum (OCLGG) particles was severely eroded by the oxidant. Cross-linking was different from oxidation in the destruction manner and uniformity. Oxidation of hydrogen peroxide led to the breakage of GG molecular chains and its reduction in viscosity. The cross-linking and oxidization reduced the freeze–thaw stability and swelling power of GG, but increased its viscosity stability and retrogradation. They also obviously changed the thermal stability of GG and moved the peak of DSC curve of both cross-linked guar gum (CLGG) and OCLGG to the right. As a result, the peak temperature and melting enthalpy of GG were altered considerably. The reactive blue-XBR in the simulated waste water could be well removed by OCLGG. The novelty of the work lies in dimethyldichlorosilane being first used for GG cross-linking and a modification combinations such as cross-linking and oxidation with the function of chain scission.