Continuous dye adsorption and desorption on an invasive macrophyte ( Salvinia minima )

Abstract

The continuous adsorption-desorption of methylene blue (MB) on an invasive macrophyte, Salvinia minima, was investigated in fixed-bed columns. The effects of bed depth (h) (9.30, 18.70, and 28 cm), inlet dye concentration (C₀) (51 ± 1.20, 154 ± 2.00, and 250 ± 1.50 mg L⁻¹), and flow rate (Q) (7 and 14 mL min⁻¹) on dye removal and breakthrough curves were assessed. Thomas, modified dose-response (MDR) and bed depth service time (BDST) models were fitted to the experimental data. Desorption and regeneration studies were also performed. The breakthrough time was affected by h, C₀, and Q. The dynamic bed capacity at the breakthrough point (q_b) increased with increasing h but decreased with increasing C₀ and Q. Dynamic bed capacities (q_e) from 318 to 322 mg g⁻¹ were achieved at h = 28 cm, C₀ = 154 ± 2.0, or 250 ± 1.50 mg L⁻¹, independently of the Q value. High MB removals were also observed (75–78%). FTIR analysis revealed that hydroxyl and carboxyl groups could be involved in dye adsorption. MDR and BDST models were both successfully used to predict the breakthrough curves of MB adsorption onto S. minima. A high regeneration efficiency (> 87%) was obtained after three adsorption-desorption cycles. These results confirm that the use of S. minima biomass could be a very efficient and eco-friendly alternative for MB adsorption in continuous mode.

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