Adsorption properties and mechanisms of potassium nickel hexacyanoterrate/carboxymethyl konjac glucomannan gel microspheres for Cs⁺

Potassium nickel hexacyanoterrate/carboxymethyl konjac glucomannan gel microspheres (KNiFC/CKGM) biomass adsorbent was synthesized by the sol-gel method via composite with KNiFC, using CKGM as the substrate material, which was prepared by carboxymethylation modification of konjac glucomannan (KGM). The KNiFC/CKGM adsorbent was used to remove Cs⁺ in wastewater. Batch adsorption experiments such as pH value, contact time, initial Cs⁺ concentration, temperature and competing ions were investigated to analyze the adsorption properties of KNiFC/CKGM, and the adsorption process was studied by kinetic and thermodynamic analysis. The corresponding adsorption mechanisms were also analyzed by FTIR, SEM, EDX, XPS and XRD. Under the adsorption condition that the temperature is 298.15 K, the adsorption dosage is 1 gL^-1, adsorption time is 18 h and initial Cs⁺ concentration is 20 mgL^-1, the removal rate of the adsorbent material can reach 94.8%. The experimental results show that the adsorption data is well fitted with in line Freundlich isotherm model (R²=0.985) and pseudo-second-order kinetics model (R²=0.999). In the range of 288.15-328.15 K, there is a positive correlation between temperature and the Cs⁺ adsorption quantity. And the adsorption progress is a spontaneous endothermic reaction. The results of FTIR, SEM and XPS demonstrate that the KNiFC is loaded well on CKGM, and KNiFC/CKGM can keep the complete structure during adsorption experiments. EDX and XRD results show that adsorption of KNiFC/CKGM to Cs⁺ on adsorbents is mainly due to ion exchange between K⁺ and Cs⁺.