Equilibrium kinetics thermodynamics and optimization studies for adsorption of cd ii and pb ii ions from aqueous solution using novel adsorbents

Abstract

Water is most indispensable and precious gift to human beings from nature but it is being polluted day by day with increasing urbanization and industrialization. Water pollution by heavy metals has received prevalent attention due to their high toxicity. Heavy metals such as lead, cadmium, mercury, arsenic, chromium are systemic toxicants and also classified as human carcinogens according to International Agency for Research and Cancer (IARC). Innovative, promising and cost effective methods are required for treatment of water contaminated with heavy metals as their accretion in living organism causes various diseases. In the present work, mesoporous material based on Gemini surfactant (C16-6-16) (G MCM-41), Pavo Cristatus feather (PCF), Punica Granatum (pomegranate) carpellary membrane (PGCM) and its chemically modified form with 2,4 dinitrophenylhydrazine (MPGCM) have been employed as adsorbents for removal of Cd(II) and Pb(II) ions from aqueous solution. Batch adsorption studies were conducted to study the influence of different factors such as initial metal ion concentration, contact time, temperature, pH, and adsorbent dose on uptake of Cd(II) and Pb(II) ions using G-MCM-41, PCF, PGCM and MPGCM as adsorbents. Different isotherm models such as Langmuir, Freundlich and Temkin were applied to evaluate the equilibrium data. The kinetics of adsorption study was investigated by using different kinetic models and for all the adsorbents used in current study, pseudo-second-order model was the best fit. The thermodynamic parameters were also determined to evaluate the spontaneous nature and heat change during the adsorption process. Response surface methodology (RSM) was also applied to optimize the adsorption variables. Using Design Expert® software, the experiments were designed for each adsorbent and the runs were randomized. To evaluate the reusability of the adsorbent, regeneration was achieved in a number of repeated cycles with a desorbing agent. Comparison of adsorbents was done in terms of efficiency, recycl