Effects of cross-linking with sodium trimetaphosphate on structural and adsorptive properties of porous wheat starches

In this study, effect of cross-linking with 4% sodium trimetaphosphate on the structural and adsorptive properties of porous wheat starches was investigated. The results showed that the cross-linked porous starches (CLPS) exhibited lower solubility, swelling power and ordered structure but higher thermal stability compared with the corresponding porous starches (PS). Cross-linking led to the formation of more dense holes on the surfaces of PS, as observed by SEM. XPS results demonstrated that phosphate groups were bound to the -OH groups on starches by covalent bonds (C-O-P). Adsorption experiments manifested that the CLPS exhibited higher adsorption capacities for water, oil and methylene blue compared to the corresponding PS. Furthermore, the isothermal data of the CLPS fitted the Langmuir isotherm model well compared to Freundich and Tempkin models, and the adsorption was exothermic and favorable. These results suggest that cross-linking modification can improve the thermal stability and adsorptive properties of PS.