Adsorption of Chromium (IV) by a Low Cost Adsorbent Prepared from Neem Leaves

The adsorption capacity of Neem Leaves powder (NLP) used as a low-cost adsorbent for the removal of Chromium (VI) from aqueous solutions was investigated. During the adsorption process, batch technique was used. The effects of initial metal ion concentration, adsorbent dose, temperature, pH and agitation/contact time on adsorption rate at constant solution pH of 6.4, under a constant temperature of 30°C were studied.The results were analyzed using three adsorption isotherm models; Freundlich, Langmuir and Temkin. Evaluating the correlation coefficients showed that Langmuir isotherm described the data more appropriately than the other isotherms. The adsorption capacity (qm) from Langmuir isotherm for Chromium (VI) was found to be 125.83mg g 1. The effectiveness of Neem Leave Powder (NLP) in the adsorption of the heavy metal (Chromium VI) from aqueous solution, kinetic studies showed that a pseudo second order model was more suitable than the pseudo first order model. It was concluded that Neem Leave Powder (NLP) can be used as an effective adsorbent for the removal of Chromium (VI) from aqueous solutions. The adsorption process was observed to be exothermic. The negative value of Gibb free energy indicates feasibility and spontaneity of the system while the negative values of the entropy and enthalpy indicate randomness and the exothermic nature of adsorption, respectively.