Phytoremediation of Congo red and methyl orange dye-contaminated water with the coontail Ceratophyllum demersum aquatic plant

Abstract

This study investigated phytoremediation of Congo red (CR) and methyl orange (MO) dye-contaminated water samples with Ceratophyllum demersum L. (coontail). Phytotoxicity assessments were also conducted to clarify the effects of dye concentrations on the growth and half-life of the plant. Based on the results, the 100 mg/L dye killed half of the plant (half-life) within 27 days. Increased dye concentration and exposure period also led to elevated toxicity in the plants. The results indicated that the dyes negatively affected plant growth. Conversely, incorporating NPK nutrients contributed to the plants overcoming toxicity and enhanced their growth. Furthermore, the MO dye exhibited fewer negative effects on the plant than the CR dye. Nevertheless, the phytoremediation process applied was successful. A 20 g of the coontail plant (dye solution volume = 5 L, initial pH = 7.0, initial dye level = 25 mg/L) dye removal percentages 100 % and 98 % CR and MO dyes during 15 days of exposure, respectively. FTIR data revealed that the various functional groups on the plant surface enabled coontail to absorb dyes from aqueous solutions, including carboxyl and carbonyl groups. Comparisons of control (without dye) and exposed (25 mg/L of initial dye concentration) coontail FESEM images demonstrated considerably altered morphological properties during phytoremediation of the dyes. These changes indicated effective loading of the dye onto the surfaces of the coontail samples. The uptake of dyes by coontail follows the Michaelis-Menten kinetics, indicating that adsorption occurs through a limited number of active sites on the plant's surface. Consequently, coontail is a notably efficient plant, applicable in eradicating dye-contaminated wastewater.