Removal of rhodamine 6G from synthetic effluents using Clitoria fairchildiana pods as low-cost biosorbent.

Many organic dye pollutants have been identified in rivers and lakes around the world, and concern is growing with them as they cause serious changes in the ecological balance of aquatic environments. One of these dyes is rhodamine R6G, which is very water-soluble and has a high corrosive power. Therefore, Clitoria fairchildiana (CF) pods were used as a biosorbent to remove R6G from synthetic dye effluents. CF was characterized by infrared spectroscopy, thermogravimetric analysis, x-ray diffraction, elemental analysis, Boehm titration, and zero charge point measurements. The influence of various factors, such as solution pH, contact time, adsorbent mass, and concentration of R6G, was studied using batch equilibrium experiments. The optimum contact time to reach equilibrium was found to be 15 min, while the optimum adsorbent dose was 8 g L-1. The maximum adsorption capacity of CF (73.84 mg g-1) was observed at pH 6.4 and 298.15 K. Adsorption kinetics followed a pseudo-second-order law, and the isotherm could be best fitted with a Liu model. The obtained thermodynamic parameters indicate that the adsorption of R6G is spontaneous and enthalpy-driven. We thus conclude that CF is an efficient, green, and readily available biosorbent for dye removal from wastewater.