PHYTOSORPTION OF COPPER, ZINC, CADMIUM AND SYNTHETIC AZO DYES BY PONTEDERIA CRASSIPES AND IPOMOEA AQUATICA: A COMPARATIVE TOLERANCE AND REMOVAL-EFFICIENCY STUDY

Abstract

Aquatic macrophytes that combine high pollutant tolerance with strong uptake efficiency are central to the practical deployment of phytoremediation, yet co-occurring heavy-metal and dye contamination in industrial effluent is rarely tested on the same species pair under comparable conditions. Pontederia crassipes and Ipomoea aquatica — the two best-performing macrophytes identified in a companion screening of sugar-mill effluent treatment — were evaluated for phytosorption of copper, zinc and cadmium (0.01–0.50%) over 8 days, and for the synthetic azo dyes Methyl Orange, Methyl Red (0.1%) and, for P. crassipes alone, Eriochrome Black T (0.02–0.05%), over 5 days. P. crassipes tolerated a substantially broader concentration range for all three metals (Cu up to 0.05%, Zn up to 0.20%, Cd up to 0.50%) than I. aquatica (Cu and Zn only to 0.01%, Cd to 0.05%), and achieved higher day-8 sorption at each species' best-tolerated concentration (Cu 71.5% vs 56.6%; Zn 80.7% vs 53.6%; Cd 94.0% vs 59.7%). For the azo dyes, both species removed the majority of Methyl Orange (>90% by day 5) but only moderately removed Methyl Red (26.9–34.6%); P. crassipes alone survived Eriochrome Black T exposure, removing 70.0–74.4% by day 5, while I. aquatica perished within 24 h at both concentrations. These results identify P. crassipes as the more broadly tolerant and efficient phytosorbent of the two species for mixed heavy-metal and azo-dye contamination, attributable to its rapid growth, fibrous root architecture and high biomass, supporting its use as a polishing agent for industrial effluents carrying co-occurring metal and dye loads.