High adsorption of fulvic acid by amino modified styrene-type macroporous resin and evaluation of its mechanism

Amino-modified HPD 100 styrene-type macroporous resin (M-HPD 100) was successfully synthesized by the atom transfer radical polymerization process. The modified resin showed excellent performance in the degradation of fulvic acid (FA). FA removal was pH, temperature and flow velocity dependent. The adsorption data could be well interpreted by the Freundlich model. The maximum adsorption efficiency for M-HPD 100 obtained from the Freundlich model was 92.5% at 298 K, which was 37% higher than that of unmodified styrene-type macroporous resin (HPD 100). The adsorption process could be described by the pseudo-second-order kinetic model. The intra-particle diffusion and film diffusion were believed to be the rate-limiting process for both adsorbents. Thermodynamic parameters suggested it was a multi-layer physicochemical process. More importantly, although limited improvements were seen, the results of this study suggested that the surface of resin can be modified with functional groups to enhance the adsorption of FA from aqueous solution and may give other advantages; for example, despite the interference of the pore diffusion coefficient and other substances, M-HPD 100 has excellent regeneration capacity, and the adsorption and desorption efficiency was 74% and 64.28% respectively after six regenerations, which proved it has engineering application value.