Influence Of FNP Zeta Potential On The Removal Of Heavy Metals

Nowadays,water pollution caused by heavy metals has aroused widespread concern among people.Developing inexpensive and highly efficient heavy metal purification materials and optimizing the water treatment process are of great significance for water recycling.The effect of zeta potential of?FNP?on adsorption efficiency of three heavy metal ions,Pb???,Cd???and Ni???,had been investigated in this thesis.The experimental results showed that the surface zeta potential of FNP can be used as a parameter to evaluate the FNP adsorption performance,it may be used as a FNP reference index of the removal capacity of heavy metal ions from contaminated water.Under the condition of pH=7,298 K,C_?FNP?=0.003 g/mL and Coductivity 2?s·cm^-1,FNP with different zeta potentials might be prepared by controlling^-ratio in the FNP synthesis.All prepared FNP materials were well characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,FTIR,and specific surface area.The adsorption ability of FNPs with different zeta potentials towards common heavy metal ions Pb???,Cd???and Ni???were studied.The effect of solution pH,initial heavy metal ions concentration,and competitive adsorption on the adsorption were checked carefully.A preliminary discussion was made on the adsorption mechanism.FNP could be regenerated in the presence of 5%PEM or 1mol/L HCl solutions.In this experiment,the zeta potential was selected as the physical parameter to check the surface properties of the FNP.The removal efficiency of Pb???,Cd???and Ni???by FNP increased with the increase of zeta potential,while its zeta potential decreased after adsorption.The FNP with-52.8 mV ZP has a superior spherical structure,large specific surface area and high charge density.Its removal efficiency for Pb???,Cd???and Ni???was 93.0%,97.1%and 64.9%,respectively.Higher initial heavy metal concentration and solution pH both favored the enhancement of adsorption capacity.Under the coexistence of Pb???,Cd???and Ni???,the adsorption capacity of FNP for coexisting ions were in an order of Pb???,Cd???and Ni???.Adsorption isotherm experiments showed the adsorption process was in accordance with an endothermic reaction.The adsorption equilibrium of FNP at 303.15 K could be well described by Langmuir isotherm equation with q_max value of 502.9 mg/g for Pb???,155.1 mg/g for Cd???and 87.5 mg/g for Ni???.The pseudo second-order equation could best fit the adsorption process,indicating the adsorption process is controlled by chemical mechanisms.Zeta potential analysis showed the pH_pzc moved to the alkaline direction,which indicates the release of H⁺during the adsorption process,The Fourier transform infrared spectroscopy?FTIR?and X-ray photoelectron spectroscopy?XPS?analysis revealed that Pb???,Cd???and Ni???may form inner-sphere complex on FNP surface.FNP adsorbent can be regenerated readily by treating with 5%PEM or 1mol/L HCl solutions.FNP zeta potential value increased from 17.8 to 50.6 and 48.6,respectively.The comparison of regeneration experiment results shows that the removal efficiency of heavy metals onto FNP treated by 5%PEM solution is the best.After 5 rounds,the removal efficiency of Pb???,Cd???and Ni???were basically maintained at 90.0%,87.0%and 60.5%,respectively,which demonstrated that the removal performance towards the heavy metal ions by the regenerated FNP was still excellent.