Biosorption of methylene blue from water by live Lemna minor

A number of green treatment technologies have been used for textile wastewater treatment, among which phytoremediation is a low cost, effective, and promising alternative — to conventional treatment techniques. The aim of this study was to investigate performance of Lemna minor (L. minor) for phytoremediation of Methylene Blue (MB). A Box–Behnken experimental design (BBD) was applied to study individual and combined effect of operating parameters on MB dye removal efficiency: MB dye concentration (x1: 5 – 25 mgL−1), amount of L. minor (x2: 1 – 5 g), and pH of the solution (x3: 4.5 – 9.0). Response surface analysis and response model were utilized to reveal the relationship between operating parameters and MB removal efficiency. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) analyses of L. minor samples were used to infer on the removal mechanism. The predicted optimum values were x1=15 mgL−1, x2=4.9 g, and x3=6.8, for the highest removal efficiency (98%) within 24 h. FTIR and SEM analyses indicated that the dye removal mechanism was mainly biosorption. Desorption experiments revealed that L. minor released only a small fraction of the sorbed dye. Consequently, in addition to being environmental friendly and cost effective, results of this study show that L. minor can be effectively used for MB dye removal from wastewaters while adding to the pertinent but limited literature by presenting its applicability in wider operating parameter ranges, maximization of removal efficiency through experimental design, and evidence that biosorption is a plausible mechanism. [Display omitted] •Lemna minor exhibited a promising performance in MB phytoremediation with 98.0%•L. minor uptake capacities pointed to saturation at MB concentration of 25 mg/L.•FTIR and SEM analyses revealed biosorption to be the main removal mechanism.•Response model accurately predicted methylene blue removal efficiency.