Enhance the adsorption behavior of methylene blue from wastewater by using ZnCl2 modified neem (Azadirachta indica) leaves powder

Many unwanted by-products containing several hazardous dyes are found in wastewater produced from the manufacturing units, such as printing, leather, paper, textiles, cosmetics, etc. Especial attention is given to overcome this problem, using different treatment methods and adsorbents. From the tree leaves of the neem (Azadirachta indica), an adsorbent was developed, characterized, and used for Methylene Blue (MB) elimination from wastewater. The area of the adsorbent surface, pore volume, and average pore width were found to be 58.6 m2/g, 0.106 cm3/g, and 13.8 Å, respectively. The adsorption behavior of MB using the modified powder of neem leaves was investigated under different experimental conditions. The adsorption capacities for MB by chemical modified adsorbent were found to be 370, 434, and 476 mg/g at 298, 313, and 328 K, respectively. The kinetic and isotherm calculated data obeyed the models of second-order kinetic and Langmuir, correspondingly. Constants of thermodynamics like ∆S°, ∆H°, and ∆G° were estimated. The positive values of ∆H° recommend that this adsorption is an endothermic process. The values of ∆G° are negative at the temperatures under investigation (298–328 K), indicating that this adsorption is a spontaneous process.