Synthesis of zeolite LTA using an agro-industrial residue as the SiO ₂ precursor and evaluating its effectiveness in the removal of copper ions from water

This paper deals with the synthesis and characterization of zeolite type A (ZA) using an agro-industrial residue such as barley husk as ecological and nonexpensive silica (SiO ₂ ) precursor. The amorphous silica phase was achieved by pyrolysis and then was used to form a synthetic gel in a typical hydrothermal procedure where the carbonaceous phase was removed by calcination afterwards. The characterization of prepared materials by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy techniques was carried out. ZA was evaluated in the removal of copper ions from water by atomic absorption spectrophotometry. Also, kinetic studies by using pseudo-first-order (PFO) and pseudo-second-order models were carried out to evaluate the performance of ZA. The PFO model showed a better approximation for ZA data. Finally, thermodynamic equilibrium was well represented by Langmuir and Freundlich models achieving a maximum adsorption capacity of 143.9 mg g ^–1 .