Removal of lead ions and bisphenol S using β-cyclodextrin modified peanut shell from solution

ABSTRACT In this study, peanut shell was modified using β-cyclodextrin (β-CD) and citric acid to improve the adsorption capacity for removal of lead ion (Pb 2+ ) and bisphenol S (BPS) from solution in batch mode. Scanning electron microscopy, Fourier-transform infrared spectroscopy, elemental analysis, X-ray fluorescence analysis, specific surface area analysis, thermogravimetric analysis, etc were used to characterize the adsorbent before and after modification. The results showed that the adsorbent was successfully modified. The adsorption results of Pb 2+ and BPS on β-CD-PS indicated that acidic conditions were not conducive to the adsorption of Pb 2+ , the adsorption of BPS basically remained unchanged at pH 2~7, and alkaline conditions were not conducive to the adsorption. The presence of salt had a negative effect on Pb 2+ , but had no effect on the adsorption of BPS. The Langmuir and Koble–Corrigan models could predict the equilibrium adsorption process of Pb 2+ while Temkin and Koble–Corrigan models could describe the equilibrium adsorption process of BPS. The adsorption quantity from experiments is 89.6 mg·g –1 for Pb 2+ and 16.2 mg·g –1 for BPS at 293 K, respectively. The adsorption process of Pb 2+ was consistent with the pseudo-first-order and Elovich models, indicating the presence of ion-exchange in the adsorption process; the adsorption of BPS was consistent with the pseudo-second-order model, indicating that chemisorption was the main rate-controlling step. Thermodynamic studies indicated that the adsorption of Pb 2+ was a spontaneous and endothermic reaction with increasing entropy, while the adsorption of BPS was a spontaneous and exothermic reaction with decreasing entropy. 0.1 mol·L –1 HNO 3 could desorb and regenerate the β-CD-PS adsorbed Pb 2+ for three times, and 75% C 2 H 5 OH had a better desorption and regeneration effect for BPS loaded β-CD-PS. β-CD-PS can effectively remove the lead ion and BPS from mixtures and the study can provide the basis for the effective utilization of peanut shell in environmental remediation.