Synthesis of M. oleifera leaf extract capped magnetic nanoparticles for effective lead [Pb (II)] removal from solution: Kinetics, isotherm and reusability study

Extensive dependency on lead for different industrial purposes has caused large scale water contamination, human exposure and significant public health issues in many parts of the world. The present work is focused on biologically synthesized magnetic nanoadsorbents to remove Pb(II) from aqueous solution. The magnetic nanoparticles were fabricated from aqueous leaf extract of Moringa oleifera. Several methods such as scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX), particle size analyzer, magnetic property measurement system (MPMS), FTIR, BET surface area analyzer, and XRD were used to characterize the synthesized nanoparticles. Removal of lead was monitored by performing batch adsorption method. Study of temperature, pH, initial lead concentration and contact time were carried out to understand the extent of lead removal under various experimental states. Kinetic study deciphered that equilibrium adsorption corresponds more to pseudo-second order model than to first order model. The first order rate constant k(1) and second order rate constant k(2) were found to be -0.0682 min(-1) and 3.75 x 10(-3) g mg(-1) min(-1), respectively. Isotherm analysis revealed that the sorption of lead onto nanoadsorbent obeyed Freundlich adsorption isotherm. The maximum adsorption capacities were found to be 49.00, 54.69 and 64.97 mg.g(-1) at 30, 40 and 50 degrees C, respectively. The values of separation factor (R-L) were found to be 1.14 x 10(-3), 1.34 x 10(-3), and 1.73 x 10(-3) for 30, 40 and 50 degrees C, respectively. Thermodynamic study showed that the adsorptive separation of Pb(II) onto synthesized nanosorbent was spontaneous and feasible with enhanced randomness. Some thermodynamic parameters like Delta G degrees, Delta S degrees and Delta H degrees were deduced to observe the effect of temperature on sorption behavior. The synthesized nanomaterial performed efficiently and 94.08% removal of Pb(II) was achieved within 60 min of contact time. (C) 2020 Elsevier B.V. All rights reserved.