Synthesis and evaluation of novel nanocomposites for removal of zinc ions from aqueous solutions

Abstract Zn(II) contamination in aquatic systems poses significant risks to environmental safety and public health. In this study, BaCO3/BaAl2O4/C nanocomposites, denoted BA600 and BA800, were synthesized by a facile Pechini sol-gel route at 600 and 800 °C and evaluated for Zn(II) removal from aqueous solutions. Besides, XRD data evidenced the presence of crystalline BaCO3 and BaAl2O4 phases, and the average crystal size increased from 54 nm for BA600 to 66 nm for BA800. Morphological analyses showed that BA600 had a denser aggregated structure, whereas BA800 exhibited coarser and more uniform particles. Under the optimum conditions of pH 6, adsorbent dose 0.1 g, and 298 K, equilibrium was reached within 60 min for BA600 and 80 min for BA800. The maximum adsorption capacities were 124.38 mg/g for BA600 and 90.58 mg/g for BA800. Zn(II) adsorption followed the pseudo-second-order kinetic model and the Langmuir isotherm and was found to be spontaneous, exothermic, and predominantly chemical in nature. After five adsorption/desorption cycles, the removal efficiencies decreased from 79.62 to 69.76% for BA600 and from 56.31 to 44.57% for BA800, corresponding to retention of 87.62% and 79.15% of their initial performance, respectively. In real wastewater, the adsorption capacities reached 110.40 mg/g for BA600 and 77.60 mg/g for BA800. These findings demonstrate that BA600, in particular, is an efficient adsorbent for Zn(II) removal from aqueous media.