Efficient adsorption and recovery of Pb(II) from aqueous solution by a granular pH-sensitive chitosan-based semi-IPN hydrogel

摘要

A series of granular pH-sensitive semi-interpenetrating polymer network (semi-IPN) hydrogels based on chitosan (CTS), acrylic acid (AA) and gelatine (GE) were utilized for the adsorption and recycle of Pb(II) from aqueous solutions. The composite hydrogels have been characterized by FT-IR and TGA. The effects of contact time, pH value and initial Pb(II) concentration on the adsorption were investigated. Results indicated that the adsorption capacity of the hydrogel increased with increasing pH value and initial Pb(II) concentration, and a pH-sensitive adsorption characteristic was presented. The adsorption rate of the semi-IPN hydrogels on Pb(II) is fast with an adsorption rate constant of 14.9790mg/(gs), and adsorption equilibrium could be reached within 10min. The adsorption isotherms of the hydrogels for Pb(II) could be described well by the Langmuir equation, rather than the Freundlich equation. The as-prepared hydrogels showed good reusability with 0.05mol/l HNO _3 solutions as the desorbing agent and 0.1mol/l NaOH solutions as the regeneration agent, respectively.After five consecutive adsorption-desorption processes, the semi-IPN hydrogel with 20wt% GE may reach 85.26% of its initial adsorption capacity. In addition, the adsorbed Pb(II) can be quantitatively recovered by simply eluting the hydrogel with dilute HNO _3 solution, and a recovery ratio of 89.27% was reached for the semi-IPN hydrogel. The satisfactory adsorption amount is mainly derived from the chelating of functional groups (i.e. -COO - and -NH _2) with Pb(II) ions. The hydrogel adsorbents exhibited excellent affinity for Pb(II), and can be applied to treat wastewater containing heavy metal ion and simultaneously recover the valuable metal sources.