Phytoremediation of tetracycline via the coontail Ceratophyllum demersum in antibiotics-contaminated water

This study investigated the phytoremediation of tetracycline (TC) for 21 days using the coontail Ceratophyllum demersum. Experiments were conducted at varying TC concentrations: 5, 10, 50, 75, 100, and 150 mg/L. Besides, the water quality of the hydroponic medium was monitored based on pH values, total dissolved solids (TDS), dissolved oxygen (DO), and water temperatures. The TC concentration that killed half of the plants (half-life) in 14 days was 50 mg/L. Removals of TC were 85.0%, 82.0%, 79.7%, 78.0%, 67.0%, and 60.0% for TC concentrations of 50, 40, 30, 20, 10, and 5 mg/L, respectively. On day 21, their respective residual TC concentrations were 7.5, 7.2, 6.1, 4.4, 3.3, and 2 mg/L. The coontail was characterized by analysis Fourier transform infrared (FTIR) spectroscopy. This work revealed that the presence of O–H, –CH2-, CC, CO, C–H, and O–Si–O groups in the plant tissues had enabled coontail to absorb TC from aqueous solution. Meanwhile, pH and TDS values increased alongside the TC concentrations. By contrast, the DO values decreased due to the bacterial decomposition of dead plants and depleted the oxygen in the water during phytoremediation. Our findings suggested that the coontail might be an appropriate phytoremediation agent for treating antibiotics-contaminated wastewater.