Comparative adsorption of Pb(II) on phosphoric acid- and sulfuric acid-modified lignocellulose-based cornstalk in aqueous solutions

The purpose of this study was to compare and analyze the effects of phosphorylated (PCS) and sulfonated cornstalk (SCS) on the removal efficiency of cationic Pb(II) ions from aqueous solutions. The pHpzc of cornstalk (CS) was 7.31, while those in SCS and PCS were lower at 4.17 and 2.25, respectively, confirming that acidic functional groups were attached to the surfaces of SCS and PCS. The maximum adsorption capacity of Pb(II) occurred in the order of PCS (182.76 mg/g) > SCS (114.36 mg/g) > CS (34.87 mg/g). The adsorption of Pb(II) onto SCS and PCS was close to chemisorption, and the adsorption efficiency increased in proportion to an increase in temperature. According to Fourier-transform infrared spectroscopy and Brunauer-Emmett-Teller analysis, sulfonation or phosphorylation of cornstalk help increased the number of carboxyl groups and porosity of the adsorbents, which facilitated the adsorbents to adsorb lead in aqueous solution. In summary, when CS was sulfonated and phosphorylated, the removal efficiency of Pb(II) from aqueous solutions was improved by 3.28 and 5.24 times, respectively.