Removal of heavy metal ions (Pb ²⁺ and Ni ²⁺ ) from aqueous solution using nonwovens produced from lignocellulosic milkweed fibers

Batch-adsorption technique was employed to evaluate the adsorption capacity of the nonwovens produced from lignocellulosic milkweed fibers for the removal of heavy metal ions, i.e. Pb ²⁺ and Ni ²⁺ , from aqueous solutions. The impact of controllable factors such as solution pH, initial concentration, contact time and operating temperature on the adsorption quantity of Pb ²⁺ and Ni ²⁺ was investigated using Atomic Absorption Spectrophotometer. The kinetic and isotherm of the adsorption process were also modeled. The milkweed fibers demonstrated superior performance for the removal of Pb ²⁺ ions from wastewater over Ni ²⁺ ions. The results demonstrated that the equilibrium concentration of heavy metal ions in solution varies with solution pH and the least equilibrium concentration is observed at pH = 6, regardless of ion type. The results also revealed that the removal percentage of Ni ²⁺ ions reached the value of 65.58% at contact time of 60 min while Pb ²⁺ ions removal percentage was as high as 96.16% at contact time of 90 min. It was concluded that an increase in operating temperature from 26 to 45°C causes to slight decrease of the removal percentage for both Pb ²⁺ and Ni ²⁺ ions by ∼5.7% and ∼9.5%, respectively. The adsorption behavior of milkweed fibers toward Pb ²⁺ and Ni ²⁺ ions followed Freundlich and Langmuir isotherm models, respectively. Moreover, pseudo-second order model was the best to describe the adsorption kinetics of both metal ions.