Preparation Of Magnetic Composites And The Adsorption Properties For Heavy Metals Of Wastewater

Heavy metal pollution problems continue to cause public concern in recent years,heavy metals in the natural environment can not be removed and will have a huge cumulative effect of human health.According to the practical application requirements of heavy metal removal,magnetic composite adsorbent was designed and fabricated for the adsorption of single solute wastewater and compound heavy metal wastewater.The main research contents are as follows.?1?Fe₃O₄ particles were prepared by coprecipitation method.KH-550 were grafted and further modified by PAA,PEI.The magnetic properties,functional groups,crystal structure,surface morphology were analyzed by means of VSM,FT-IR,XRD,SEM and BET.The results showed that the surface of the material has been modified by the active groups such as imino/amino group and carboxyl group.?2?The relationship between the reaction conditions and the adsorption capacity of Fe₃O₄@SiO₂?-NH₂/-COOH?on Cd²⁺,Pb²⁺,Cu²⁺adsorption was investigated.The results showed that the adsorption effect of the material was more effective when the pH value was 7⁹ and the strong acid system didn't conducive to the adsorption.The ion concentration and temperature increase were favorable to promote the effect of surface point and the heavy metal.When the amount of adsorbent was low,the amount of adsorption was higher.?3?The thermodynamic study was carried out by isothermal adsorption model:Langmuir model fitting results showed R²>0.97,Freundlich model fitting results showed R²>0.85;Langmuir model theory hypothesis was closer to Fe₃O₄@SiO₂?-NH₂/-COOH?on the true thermodynamics of heavy metals adsorption behavior,indicated that the material was mainly a uniform adsorption.The maximum adsorption capacity of Pb²⁺was 106.2 mg/g,the maximum adsorption capacity of Cd²⁺was 65.3 mg/g,and the maximum adsorption capacity of Cu²⁺was37.9 mg/g.Gibbs correlation function calculation showed that the adsorption process spontaneously proceed.?4?The relationship between the adsorption capacity of each heavy metal and the time was discussed,and several dynamic models were used to make the linear fitting.The results showed that the adsorption of the three ions mainly occurred within 0.5 h,and the adsorption capacity almost did not change anymore after 1.5 h.The quasi-first order kinetic model fitting results showed R²>0.3;the modified Elovich model fitting results showed R²>0.6;the quasi-second order kinetic model fitting results showed R²>0.99;the particle diffusion model fitting results showed R²>0.41.The adsorption behavior in a single solute solution was in good agreement with the quasi-second order kinetic theory,indicated that the active groups of the material were combined with heavy metals in the form of chemical bonds.?5?The adsorption performance of the magnetic adsorbent in the composite heavy metal ion solution was tested.The adsorption capacity of Pb²⁺was 37.3 mg/g,the adsorption capacity of Cd²⁺was 16.2 mg/g,and the adsorption capacity of Cu²⁺was 9.2 mg/g.The order of adsorption of each metal was Pb>Cd>Cu.The adsorption reaction in the composite wastewater was about 2 h.The results showed that the purification effect of Pb²⁺was the best with the removal rate more than90%.The applicability of the material to low concentration wastewater was higher.?6?Magnetic material had a good magnetic separation performance,it could be totally separated from wastewater within 5 minutes.The adsorption of Pb²⁺,Cd²⁺and Cu²⁺on the regenerated materials still had good adsorption effects,and the adsorption capacity of the regenerated materials were more than 90%of unregenerated materials.The magnetic materials had good stability under weak acid or weak alkaline conditions,but extreme acidic conditions could lead to adsorbent denaturation.