Optimization and Kinetic Study of Treating Dye-Contaminated Wastewater Using Bio-Composite Synthesized from Natural Waste

Abstract

The main objective of the present research project was to investigate the possibility of using low cost, eco-friendly, and easily available adsorbents, such as mint biomass and marble stone waste, for the removal of dyes, DRIM blue HS-RL and DRIM black ep-B, from wastewater using an efficient procedure, which is adsorption. Nine different combinations of these adsorbents were prepared with and without modification using sodium metasilicate and potassium ferricyanide. Spectroscopic analysis was carried out to investigate the λmax of the dyes. Adsorbent nanocomposites were characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and zeta (ζ) potential. Adsorption equilibrium studies were investigated by determining the adsorption at the following conditions: initial dye concentrations (5–50 ppm), adsorbent doses (0.005–0.5 g), contact times (15–240 min), temperatures (30–70 °C) and pH (5–10). Of all the nine adsorbents, MTPF showed the maximum adsorption capacity at 50 ppm initial dye concentration, 0.005 g dosage of adsorbent and 240 min contact time for both dyes. DRIM Blue HS-RL was adsorbed efficiently at 6 pH and temperature 60 °C and DRIM black ep-B was adsorbed at pH 5 and temperature 50 °C by MTPF (mint–tawera composite treated with potassium ferricyanide). Among the various adsorption isotherms (Langmuir, Dubinin–Radushkevich, Freundlich, Herkin–Jura, and Temkin isotherms), some adsorbent followed the Freundlich isotherm while the others followed the Langmuir isotherm. The best-fit model was decided based on their high R2 value and agreement between qe calculated from isotherms and those obtained experimentally. At equilibrium concentration, application of kinetic models (pseudo-first-order, and pseudo-second-order) revealed that the best-fit model was pseudo-second-order kinetic model for both dyes, as their R2 > 0.9, and qe calculated was close to qe obtained experimentally.