Fast and Highly Efficient Adsorption Removal of Toxic Pb(II) by a Reusable Porous Semi-IPN Hydrogel Based on Alginate and Poly(Vinyl Alcohol)

Abstract

A porous semi-interpenetrating network (semi-IPN) hydrogel adsorbent with excellent adsorption properties and removal efficiency towards Pb(II) was prepared by a facile grafting polymerization reaction in aqueous medium using natural biopolymer sodium alginate (SA) as the main chains, sodium acrylate (NaA) as the monomers, and poly(vinyl alcohol) (PVA) as the semi-IPN component. FTIR, TGA and SEM analyses confirm that NaA monomers were grafted onto the macromolecular chains of SA, and PVA chains were interpenetrated and entangled with the crosslinked network. The incorporation of PVA facilitates to form pores on the surface of hydrogel adsorbent. The semi-IPN hydrogel containing 2 wt% of PVA exhibits high adsorption capacity and fast adsorption rate for Pb(II). The best adsorption capacity reaches 784.97 mg/g, and the optimal removal rate reaches 98.39% (adsorbent dosage, 2 g/L). In addition, the incorporation of PVA improved the gel strength of hydrogel, and the storage modulus of hydrogel increased by 19.4% after incorporating 2 wt% of PVA. The increase of gel strength facilitates to improve the reusability of hydrogel. After 5 times of regeneration, the adsorption capacity of SA-g-PNaA decreased by 23.2%, while the adsorption capacity of semi-IPN hydrogel only decreased by 10.8%. The adsorption kinetics of the hydrogel in the initial stage (the moment when the adsorbent contacts solution) and the second stage are fitted by segmentation. It is intriguing that the adsorption kinetics fits well with both pseudo-second-order kinetic model and pseudo-first-order model before 60 s, while only fits well with pseudo-second-order adsorption model in the whole adsorption process. The chemical complexing adsorption mainly contribute to the efficient capturing of Pb(II).

Polysaccharide-Based Composite Hydrogels as Sustainable Materials for Removal of Pollutants from Wastewater

“…that present effective chelating sites or ion-exchange groups. Among the HMIs, the most scrutinized have been Cu(II) [ 43 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ], Ni(II) [ 76 , 78 , 81 ], Cd(II) [ 42 , 44 , 76 , 79 , 82 ], Pb(II) [ 79 , 80 , 82 , 83 , 84 ], and Hg(II) [ 84 , 85 ].…”

“…Pb(II) ions were successfully removed from aqueous solutions by adsorption on reusable porous semi-IPN hydrogels based on poly(vinyl alcohol) (PVA) entrapped in a matrix consisting of PAA grafted onto ALG [ 83 ]. At the optimum PVA content in the composite sorbent (i.e., 2 wt.%) the maximum Pb(II) sorbed amount was 787.4 mg/g sorbent (at sorbent dose = 2 g/L, pH = 5, and 303 K) ( Table 3 ).…”

“…At the optimum PVA content in the composite sorbent (i.e., 2 wt.%) the maximum Pb(II) sorbed amount was 787.4 mg/g sorbent (at sorbent dose = 2 g/L, pH = 5, and 303 K) ( Table 3 ). The semi-IPN hydrogel exhibited a better reusability compared with the control hydrogel without PVA, and about 90% of Pb(II) sorption performance recovery after five sorption/desorption cycles was found [ 83 ]. In another work, Ma et al investigated the removal of Pb(II), Cu(II), and Cd(II) from individual and multicomponent systems by DN hydrogels obtained from lignin extracted from rice husk and PAAm [ 82 ].…”

Construction and Ion Transport-Related Applications of the Hydrogel-Based Membrane with 3D Nanochannels

“…Therefore, adjusting the gel network structure can improve the adsorption efficiency. A semi-interpenetrating network was prepared by introducing linear polyvinyl alcohol (PVA) into the copolymer crosslinking of sodium alginate-grafted-sodium polyacrylate (SA-g-PNaA) [ 98 ]. The formation of this structure was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), which showed the movement of PVA characteristic absorption peak, indicating hydrogen bond interaction between the polymer network and PVA.…”

“…Reprinted with permission from Ref. [ 98 ]. ( c ) Schematic diagram of Ti 3 C 2 Tx MXene coated vertical channel reduced graphene oxide (A-RGO) hydrogel.…”