Valorization of aquatic weed Salvinia minima to value-added eco-friendly biosorbent: preferential removal of dye and heavy metal

We explore the use of Salvinia minima (water spangles), tropical aquatic floating plant, biomass as a potential biosorbent for preferential removal of the cationic dyes viz Methylene blue (MB), Crystal violet (CV) and Bismark brown (BB), and heavy metal ions (Pb²⁺, Zn²⁺, and Ni²⁺) in a batch adsorption process. The influence of different adsorption parameters such as adsorbent dose, solution pH, contact time, initial dye concentration, and temperature were examined, and the optimal experimental conditions were determined. The experimental data fitted well with the pseudo-second-order kinetic model, which revealed the adsorption mechanism to be predominantly chemisorption. The equilibrium isotherm was followed by Freundlich isotherm, multilayer adsorption model. The dye removal efficiencies were obtained to be 99.4, 99.1, and 96.5% for CV, MB, BB, and 98.56, 95.69, and 92.99% for Pb²⁺, Zn²⁺, and Ni²⁺, respectively, at 10 mg L⁻¹ initial dye and heavy metal ion concentration. The maximum adsorption capacity for the dyes CV, MB, BB is 94.13, 150.98, and 228.81 mg g⁻¹, and for heavy metal ions Pb²⁺, Zn²⁺, and Ni²⁺ is 174.32, 232.43, 171.40 mg g⁻¹ was obtained. Overall the biosorbent proved to be a potent economical alternative for wastewater treatment containing dyes and heavy metal ions effluent. Graphical abstract: Salvinia minima leaf biomass was used as a biosorbent for efficient and preferential adsorption studies of dyes and heavy metal ions from an aqueous medium.[Figure not available: see fulltext.].