Adsorption of Selected Metals Ions in Solution Using Nano-Bentonite Particles: Isotherms and Kinetics

Abstract

An inexpensive and easily obtainable Egyptian bentonite was applied for the elimination of metals from aqueous solution. A simple solvothermal technique was utilized to formulate nano-bentonite to keep the method cost low. The capability of nano-bentonite particles as adsorbents to remove copper, nickel and manganese ions was scrutinized under numerous conditions in batch methods. The metal ions adsorption was reliant on initial sorbent concentration, pH, contact time and adsorbent dosage. Batch experimentations were conducted at 30 °C and 300 rpm. The results showed that pH 9 for Cu2+ and pH 7 for Mn2+ and Ni2+ ions were the most appropriate values, whereas the maximum adsorbent capacity was at a dosage of 0.075 g, recording sorption efficiencies of 99%, 42.18%, and 17.82% for copper, nickel, and manganese, respectively. The percent metal removal approached equilibrium within 30 min for all examined metals, with cupper recording 99%, nickel 49.92% and manganese 21.31% removal, having a trend of Cu2+ > Ni2+ > Mn2+. Experimental isotherm records were analyzed by Langmuir and Freundlich models. Langmuir model showed higher R2 values of 0.97, 0.83 and 0.98 for copper, nickel and manganese, respectively, which fitted the equilibrium adsorption process better than the Freundlich model (R2 = 0.97, 0.65, and 0.98 for Cu2+, Ni2+ and Mn2+ ions, respectively). The monolayer adsorption capacity was 35.46 mg g−1, 9.91 mg g−1 and 9.99 mg g−1 for Cu2+, Mn2+ and Ni2+ ions, respectively. The kinetic records for the adsorption process conformed with pseudo-second-order rate equations. The study suggests that nano-bentonite can be efficiently used as an inexpensive material for metal ions elimination.