Modelling and optimization of lead adsorption by CoFe2O4@CMC@HZSM-5 from aqueous solution using response surface methodology

A modified magnetic nano-biocomposite based on zeolite (CoFe2O4@CMC@HZSM-5) was synthesized and characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning electron microscopy, vibrating sample magnetometer, and Brunauer- Emmett-Teller tests. CoFe2O4@CMC@HZSM-5 was applied as an adsorbent for the efficient removal of Pb(II). Then, the applicability of the nano-biocomposite adsorbent was investigated for the lead removal. To determine the relationship between effective parameters on lead adsorption, the response surface methodology was applied. Maximum removal efficiency by CoFe2O4@CMC@ HZSM-5 under optimal conditions with a contact time of 300 min, pH = 5, Pb(II) concentration of 400 mg/L, and 0.4 g of the adsorbent (reactor volume = 200 mL) was 96% for synthetic and 75% for real samples, respectively. The adsorption of Pb(II) by CoFe2O4@CMC@HZSM-5 followed the Langmuir isotherm and pseudo-second-order kinetic models. According to the negative Delta H degrees values, the adsorption of Pb(II) onto CoFe2O4@CMC@HZSM-5 was exothermic and thermodynamics studies indicated that was not possible and spontaneous in nature. The magnetic nano-biocomposite adsorbent had good reusability and attained a high removal efficiency of 91% for Pb(II) after six consecutive adsorption cycles, thus can be recommended as a coefficient adsorbent for the removal of Pb(II) from contaminated water.