Novel low-cost adsorbent based on economically modified bentonite for lead(II) removal from aqueous solutions

Abstract

Some metals are toxic and considered hazardous pollutants due to their stability in the environment. Current technologies involve materials which can be difficult to synthesize, are high-cost, or are themselves potentially toxic. In this study, the potential of modified Algerian bentonite as low-cost adsorbent for Pb(II) removal from aqueous solutions was evaluated. Sodium homoionic clay (SHC), calcium homoionic clay (CHC), and acid-activated clay (HC10) were prepared through the treatment of a natural Algerian bentonite (ANC) by sodium, calcium, and sulfuric acid solutions, respectively. The adsorbent materials were characterized by X-ray diffraction, chemical analyses, Fourier transform infrared (FTIR) spectra, and nitrogen sorption at 77 K. Parameters affecting metal uptake, including contact time and lead(II) concentration, pH values, and mass of adsorbents, were evaluated. The results obtained allowed us to conclude that the kinetic data was better represented by the pseudo second-order model. Langmuir, Freundlich, and Temkin models were fitted to experimental isotherms. The Langmuir model shows a better representation of the isotherm data for Pb ions for all systems. This work suggested that the modified clay may be promising candidates for the removal of lead ions from aqueous solutions. The largest adsorption capacity of 82.85 mg/g is observed for sodium homoionic clay. The three adsorbents also showed a high efficiency in the lead(II) adsorption from much diluted solutions. Indeed, all lead(II) ions were removed from much diluted solutions of 5 mg/L; lead can form a Lpb2-type complex with layered silicate of bentonite.