Efficient Treatment of PAH-Contaminated Water Using Magnetic-Modified Myriophyllum aquaticum Waste Biomass

To clarify the sorption mechanism and removal efficiency of PAHs by waste biomass-based magnetic sorbents, the sorption performance of magnetic Myriophyllum aquaticum biomass (MMaB) for PAHs was studied. The structural characteristics and magnetic properties of MMaB were measured by FTIR, SEM–EDS, XRD and VSM. Batch experiments were carried out to evaluate the effects of contact time, initial concentration and properties of PAHs, pH, ionic strength and temperature on PAH sorption. The results showed that the sorption of seven PAHs achieved equilibrium at approximately 4–6 h, which fit well to the pseudo-second-order kinetic model. The isotherms followed the Freundlich model and linear model well, indicating that the sorption process was controlled by chemisorption. The distribution parameter ( K d ) values were 91.3, 563.7, 1010.5, 2917.8, 2706.6, 9046.8 and 15969.0 L·kg −1 for naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, pyrene, and fluoranthene on MMaB, respectively, following the order of their hydrophobicity (e.g., K ow ). A positive correlation was obtained: log K d = 0.8091log K ow + 1.7034. Water chemical properties such as pH and ionic strength had no obvious effect on PAH removal. The spontaneity, feasibility and exothermic properties of PAH removal by MMaB were explained from thermodynamic point of view. The as-prepared MMaB sorbent underwent four consecutive sorption cycles and had good cycling performance. These studies indicate that MMaB has great potential as an easily-prepared, easy-to-operate and efficient biosorbent to remove PAHs from wastewater.