Abstract

MECHANISM OF ADSORPTION OF FERROUS IONS FROM WASTE WATER ON NATURAL ADSORBENTS

*Satish Patil, Jayesh Patil, Sameer Renukdas and Naseema Patel

ABSTRACT

Adsorption studies of Fe (II) ions on six different natural adsorbents were carried out by batch experiments. Different parameters such as initial dye concentration, adsorbent dose, pH, agitation time, agitation speed, particle size of adsorbent and temperature were studied. Freundlich and Langmuir isotherm models were used to test the equilibrium data. Both the isotherm models were found to be best fitted. The monolayer (maximum) adsorption capacities (qm) were found between 5.181 to 10.526 mg/g for adsorbents under study. The correlation coefficient R2 for second order adsorption model has very high values for all adsorbents (R2 = 0.999) and qe(the) values are consistent with qe(exp) showed that pseudo second order adsorption equation of Lagergren fit well with whole range of contact time. Intra particle diffusion plot showed boundary layer effect and larger intercepts indicates greater contribution of surface sorption in rate determining step. Adsorption was found to increase on increasing pH, increasing temperature, increasing agitation speed and decreasing particle size. Thermodynamic analysis showed negative values of ΔG indicating adsorption was favourable and spontaneous, small positive values of ΔH below 40 KJ/mole indicating endothermic physical adsorption and positive values of ΔS indicating increased disorder and randomness at the solid- solution interface of ferrous ions with biosorbents. Desorption studies showed that adsorption of ferrous ions on biosorbents involved an ion exchange mechanism. Adsorption capacity of Cinnamon plant leaf powder towards ferrous ions was found to be more than other adsorbents under study.

Keywords: Adsorption, mechanism, ferrous ions, isotherms, kinetic, thermodynamic.