Abstract

In the present investigation, Azadirachta indica (neem) leaf powder is used as an adsorbent for the removal of chromium from aqueous solutions. The equilibrium studies are systematically carried out in a batch process, covering various process parameters that include agitation time, adsorbent size and dosage, initial chromium concentration, volume of aqueous solution and pH of the aqueous solution. Adsorption behavior is found to follow Freundlich and Langmuir isotherms. The adsorption mechanism is described by a pseudo second order kinetics. 

Key words: Adsorption, neem, chromium, kinetics.

Abbreviation

Nomenclature: b = Langmuir constant, g^-1; C_{o =} Initial concentration of chromium (VI) in aqueous solution, mg/L; C_t = Concentration of chromium (VI) in aqueous solution after time t min, mg / L; C_e = Equilibrium concentration of chromium (VI) in aqueous solution, mgL; d_p  = Adsorbent size, mm; k_f = Freundlich constant, mg/g; K_ad = Lagergren first order rate constant, min^-1; K   =  Second order rate constant, g.mg^-1.min^-1  ;K_L =  Langmuir constant, mg/g; m  =  Amount of adsorbent taken per 1 L of aqueous solution, g/L; n =   Freundlich constant, dimensionless; q_{t   =} Amount of Cr(VI) adsorbed per unit mass of adsorbent at t min, (C_o-C_t)/m, mg/g; q_e =Amount of Cr (VI) adsorbed per unit mass of adsorbent at equilibrium,(C_o-C_e)/m, mg/g; q_m   =  Maximum amount of Cr (VI) adsorbed per unit mass of adsorbent, mg/g; R = Correlation coefficient; R_L =   Separation factor, 1/ (1+bC_e­); t  =  Agitation time, h; V = Volume of the aqueous solution, ml; w = Adsorbent dosage, g.