Preparation of multi-modified/carbonized/gelatinized starch and its de-risking effect on Cd(II) and hymexazol in wastewater

In this study, starch (S) was gelatinized and carbonized to prepare carbonized/gelatinized S (CGS) as the research material. Then, peat extract (Pe) and surfactants with different ratios were single- and multi-modified on CGS, respectively, to prepare Pe-modified CGS (Pe-CGS) and multi-modified CGS, respectively. The microscopic morphology of multi-modified CGS was studied using various testing methods. The de-risking effect on Cd(II) and hymexazol in wastewater was investigated, and the effects of temperature, pH, and ionic strength were compared. The spheroidal structure of S was destroyed after carbonization, and Pe and surfactants were modified on the surface and changed the surface properties of CGS. The adsorption processes of Cd(II) and hymexazol were suitable to be described by the Langmuir and Freundlich models, respectively. The maximum adsorption capacities (qm) of Cd(II) and adsorption capacity parameter (k) of hymexazol on different modified CGSs presented the peak value at BS/Pe-CGS. With the increase in the modification ratio of Pe, BS, and SDS, qm and k increased, which showed a high value at 100 % modification. Increases in temperature and pH were beneficial to Cd(II) adsorption but were not conducive to hymexazol adsorption. The adsorption amount decreased for Cd(II) and increased first and then reduced for hymexazol with the rise in ionic strength. The adsorption process exhibited spontaneity, endothermic behavior for Cd(II), exothermic behavior for hymexazol, and an entropy-increasing reaction. The adsorption amount of Cd(II) and hymexazol by multi-modified CGS maintained approximately 81 % of the original sample after three rounds of regeneration. •Multi-modified/carbonized/gelatinized starch has high pollutant adsorption capacity.•High temperature and pH promote Cd(II) adsorption and inhibit hymexazol adsorption.•Cd(II) and hymexazol adsorptions are spontaneous and an entropy-increasing process.•The adsorption amount can maintain 81 % of the raw material by tertiary regeneration.