Alkali Treatment of ZSM-5 Molecular Sieve and Its Adsorptive Performance of Pb2+ from Aqueous Solution

The alkali treatment of zeolite molecular sieve and its adsorptive performance toward Pb²⁺ ion from aqueous solution were investigated. The results showed that alkali solution treatment could enhance adsorb Pb²⁺ from aqueous solution effectively. Zeolite treated with 0.50 mol/L NaOH solution exhibits the highest adsorption capacity. Adsorption kinetics and isotherm of Pb²⁺ uptake using alkali modified zeolite molecular could be satisfactorily described with pseudo second-order kinetics model and Langmuir model, respectively. The maximum adsorption capacity calculated by Langmuir model at 30 ℃was 54.64 mg/g, about 0.60 times higher than the original material. When the adsorbent dosage was greater than 1.0 g/L with 20 mg/L Pb²⁺ initial concentration, the adsorption removal efficiency was higher than 98.5%. Common cations could affect the adsorption process, and the effect sequence was Cu²⁺>Na⁺≈ K⁺>Mg²⁺. Besides, IR, BET and XRD analysis were employed to characterize the materials, and it was found that the increase of average pore diameter and the decrease of Si/Al ratio were the main reasons of the increase of adsorption capacity after the alkali treatment.