Single and binary adsorption of lead and cadmium ions in aqueous solutions and river water by butylamine functionalized vermiculite: performance and mechanism

Lead and cadmium are toxic to human, animal, and plant health; they enhance oxidative stress indirectly while simultaneously acting through other toxicodynamic mechanisms. In this study, pristine vermiculite (VER) was functionalized with butylamine (BUT) and a novel organoclay (BUT-VER) adsorbent material was produced for simultaneous removal of Pb(II) and Cd(II) in aquatic medium. The adsorbents were characterized by spectroscopic, microscopic, spectrometric, and potentiometric techniques. The adsorption affecting parameters, including pH, time, initial concentration, temperature, and co-existing cations were investigated and optimized. The kinetic data results were in better agreement with pseudo-second-order (PSO) model (R-2 > 0.992). Multiple isotherm models were used to study the adsorption system and results showed that adsorption was monolayer. The BUT-VER showed an improvement in adsorption capacity in a single system (Pb(II): from 134.2 to 160.6 mg g(-1)) and (Cd(II): from 51.1 to 58.9 mg g(-1)) while in binary system (Pb(II): from 107.3 to 114.5 mg g(-1)) and (Cd(II): from 33.7 to 39.7 mg g(-1)), respectively. Furthermore, BUT-VER was tested in real river water and removed efficiency of >99% was achieved in just 1 h. The dominant mechanisms were electrostatic attraction and complexation. BUT-VER was regenerated for five consecutive cycles and showed >90% removal efficiency. These findings suggest that the proposed inexpensive adsorbent has the potential for practical applications of toxic metals removal from water.