An environmental-friendly approach for phytoremediation of zinc ion by Lemnaceae species: process behavior and characterization studies.

Abstract

Phytoremediation is a promising approach grounded in green and sustainable development principles for decontaminating water and soil. Among the studied duckweed species (Spirodela polyrhiza, Wolffia arrhizal, and Lemna minor), S. polyrhiza exhibited the highest zinc removal efficiency of 88.50% by day 7, followed by L. minor and W. arrhiza with removal efficiency of 78.69 and 38.59%, respectively. This study investigated the effects of environmental factors, including initial zinc ion concentration (50, 100, 150, 200, and 250 mg/L), solution pH (pH 5, 6, 7, and 8), and macrophytes mass (5, 10, 15, 20, and 25 g) on the phytoremediation of the zinc ion from synthetic wastewater by S. polyrhiza. The process effectively treated 500 mL of synthetic wastewater containing 100 ppm zinc ion and the process could be enhanced to achieve the removal efficiency of 90% by adjusting the solution pH to slightly acidic (pH 5) and increasing the mass of duckweed to its saturation point (20 g). Excessive zinc intake by duckweed led to chlorophyll reduction, negatively impacting the duckweed growth rate. Scanning electron microscopy (SEM) analysis revealed that the duckweed fronds' surface became uneven after the treatment, with the irregular small particles attached due to cellular damage. The energy dispersive X-ray (EDX) analysis confirmed the successful uptake and accumulation of zinc in the duckweed cells from the synthetic wastewater. In conclusion, duckweed-based phytoremediation demonstrates significant potential for removing zinc ion from wastewater, at low and moderate concentrations.