Cellulose-based hyperbranched polyvinylamine adsorbent for efficient and rapid removal of Cr (VI)

1 1 Non-standard abbreviations: ABM = Allyl bromide; AIBN = 2,2′-Azobis(2-methylpropionitrile); PVAm = Polyvinylamine; H-PVAm = Hyperbranched polyvinylamine; L-PVAm = Linear polyvinylamine; H-PEI = Hyperbranched polyethylenimine; DPO = Dipentaerythritol; DPHAE = Dipentaerythritol Hexaallyl Ether; ECH = Epichlorohydrin; MCC = Microcrystalline cellulose; NVF = N-vinylformamide; PNVF = Poly(N-vinylformamide); H-PVAm-MCC= Hyperbranched polyvinylamine-modified cellulose-based adsorbent; L-PVAm-MCC = Linear polyvinylamine-modified cellulose-based adsorbent; H-PEI-MCC = Hyperbranched polyethylenimine- functionalized cellulose-based adsorbent; Abstract The development of natural polymer-based materials for the efficient and rapid removal of hexavalent chromium (Cr (VI)) from water remains a persistent global challenge. In this study, hyperbranched polyvinylamine (H-PVAm 1 ) was prepared via copolymerization and hydrolysis using N-vinylformamide (NVF) and the branching agent dipentaerythritol hexaallyl ether (DPHAE, 1 wt% relative to NVF) as raw materials. Subsequently, using epichlorohydrin (ECH) as the crosslinking agent, H-PVAm 1 was grafted onto the surface of microcrystalline cellulose (MCC) to obtain the functionalized cellulose adsorbent H-PVAm 1 -MCC. Benefiting from the high primary amine content and three-dimensional branched structure of H-PVAm 1 , H-PVAm 1 -MCC exhibited high primary amine density (19.06 mmol/g), high specific surface area (13.5 m²/g), and good salt resistance. The maximum adsorbed amount of H-PVAm 1 -MCC for Cr (Ⅵ) reached 538 mg/g, which was higher than that of most reported amine-modified cellulose-based adsorbents. Moreover, H-PVAm 1 -MCC exhibited rapid Cr (VI) adsorption kinetics, even at low concentrations (1 ppm). Within 2 min of adsorption, the residual Cr (VI) concentration satisfied the WHO drinking water guideline (≤0.05 ppm). Even in the presence of coexisting ions, H-PVAm 1 -MCC maintained a high Cr (VI) removal rate. Moreover, H-PVAm 1 -MCC exhibited good stability, maintaining 90% adsorbed amount after eight adsorption-desorption cycles. This study provides a strategy for the further development of cellulose-based Cr (VI) adsorbents.