Studies on removal of malachite green from aqueous solution by sorption method using water hyacinth - Eichornia crassipes roots

Dye containing waste water can cause serious water pollution problems by hindering light penetration and photo synthesis and toxicity from heavy metals associated with dyes. In this research study, batch experiments were conducted using thermally activated Eichornia crassipes roots as an adsorbent for the removal a basic dye, malachite green, from aqueous solutions. Effect of operating variables i.e. pH, sorbent dosage, dye concentration and contact time was studied in an agitated batch adsorber. Results showed that maximum dye uptake was observed at an optimum pH 7 .There was no significant difference in dye concentration remaining when the pH increased from 5-10. Dye removal was influenced by initial dye concentration and the sorption process followed first order kinetics. Among the three isotherms tested Redlich Peterson and Langmuir isotherms fitted reasonably well to the data. The negative value of the free energy change indicates the spontaneous nature of biosorption. From the above findings, it was observed that the biosorption process obeyed the first order adsorption kinetics. The negative value of the free energy change calculated indicates the spontaneous nature of the sorption and confirms the affinity between the sorbent and the dye cations.