Determination of adsorption characteristics of synthetic NaX nanoparticles

Zeolite nanoparticles were synthesized by means of a hydrothermal method and the sorption performances were tested in batch experiments using single and binary components of Pb²⁺, Ni²⁺and Cu²⁺ synthetic solutions. Fast adsorption was observed and the majority of sorption occurred within the first 5 min for each case of metal cations. Percentage metal removal increased with the adsorbent dosage and it was adversely affected by the initial metal concentrations. XRD, FTIR-ATR and XPS analyses revealed that the removal of metal ions occurred mainly on the basis of ion-exchange. Equilibrium sorption data were best described by Sips isotherm model and the maximum attainable metal amount on the NaX were estimated as 1.23, 1.76 and 2.20 mmol/g for the Pb²⁺, Ni²⁺, and Cu²⁺ cations, respectively. A single step desorption process conducted in NaCl solution seemed to be practically applicable for regeneration and after three adsorption/desorption cycles, 79, 76 and 48% of initial sorption capacity of NaX were preserved for lead, nickel and copper ions, respectively. Single isotherm parameters used for the prediction of binary equilibrium data were satisfactory. Binary sorption experiments for Pb²⁺-Ni²⁺, Pb²⁺-Cu²⁺ and Ni²⁺-Cu²⁺ couples reflected that the presence of secondary ions decreased the uptake of the primary one. Lead exhibited greater inhibition of the sorption of nickel and copper, demonstrating the stronger affinity of NaX for Pb²⁺. Extended Freundlich model best described all the three binary metal systems. Adsorption experiments carried out in real wastewater demonstrated that NaX nanoparticle has a high affinity for all the cations except copper.