Biosorption of Cu (II) and Pb (II) ions using acid modified Senna tora pods with a focus on isotherms and kinetics studies

The removal of heavy metals by biosorption method using agricultural waste and plant materials has become a powerful technology that is been explored for the treatment of domestic and industrial waste water due to its easy operating requirements and low cost. This work reports the application of Senna tora pods for the elimination of heavy metals (Cu and Pb ions) by biosorption in batch system. The effects of pH, contact time, dosage and initial concentration were evaluated. The kinetic and isotherms models for the Cu(II)/Pb(II) biosorption were tested basically by the pseudo-first-order and pseudo-second order kinetic models. Langmuir, Freundlich and Temkin isotherms models have also been used to fit equilibrium adsorption data. The monolayer sorption capacity (q_L) of Cu(II) was found to be 0.791 mg/g while that of Pb(II) was 0.51 mg/g.The low Langmuir constant (K_L) values suggests that the adsorption process was largely due to physisorption mechanism. The adsorption kinetics follow a pseudo-first-order model for Cu(II) and pseudo-second-order model for Pb(II), and the equilibrium data is suitably fitted by the Langmuir models than the Freundlich due to the high R² values of 0.989 and 0.97 for Cu(II) and Pb(II) ions respectively. Consequently, there exists a closeness of the calculated sorption capacity (qcal) to the experimental sorption capacity (qex). In conclusion, the study generally showed that Senna tora pods is a potential and efficient adsorbent that could be explore for the bioremediation of heavy metal contaminated industrial wastewater.