Adsorption of dye crystal violet onto surface-modified Eichhornia crassipes

Eichhornia charcoal is modified with sodium dodecyl sulfate (SDS) is an anionic surfactant being employed as an adsorbent for the removal of dye crystal violet from aqueous solutions. Morphology and surface of the adsorbent were characterized by elemental analysis, Boehm titrations, point of zero charge measurements, Brunauer, Emmett, Teller, scanning electron microscope, FTIR and XRD techniques. Batch adsorption experiments were conducted to evaluate the effect of contact time, pH, initial dye concentration, temperature, adsorbent dose, and salt (NaCl) concentration. Adsorption mechanism of the dye for the adsorbent has been monitored through different kinetics and adsorption isotherm models. Positive value of change in entropy (∆S) and change in enthalpy (∆H) insinuated that adsorption process occurs with increase in randomness and endothermic, whereas negative values of free energy change (∆G) signifies the spontaneous nature of the present system. It was alluded that kinetics followed a pseudo-second-order equation. On the basis of the Langmuir analysis, the maximum adsorption capacity was determined as 116.3 mg of dye per gram of adsorbent. Therefore, Eichhornia crassipes, a waste, modified by anionic surfactant was suitable to be used as an effective adsorbent for cationic dye removal.