Utilization of a biosorbent based on Azadirachta indica (Neem) leaves for removal of water-soluble dyes

A biosorbent is developed from Azadirachta indica (Neem) leaves in the form of a finely ground dried powder (53-74 mu). The powder was used to remove three water-soluble dyes, viz., brilliant green, congo red and methylene blue from aqueous medium. The adsorptive interactions were tested under varying conditions of concentration of the dyes, amount of adsorbent, pH, and temperature. It was found that 670, 1000 and 2000 mg respectively of the powder could remove almost 100 % of the dyes from 1 L of water containing 10, 20 and 25 mg of brilliant green, congo red and methylene blue dyes, respectively. The interactions followed pseudo first order kinetics. The Langmuir monolayer adsorption capacity had values of 133.69, 72.38 and 8.76 g kg(-1) for brilliant green, congo red and methylene blue. The adsorption of brilliant green and methylene blue on neem leaf powder (NLP) was endothermic with mean Delta H values of 12.12 and 9.40 kJ mol(-1) respectively while that of congo red was exothermic with mean Delta H value of -12.75 kJ mol(-1).