Study On Adsorption And Removal Of Heavy Metals By Coated Iron Sand And Its Practical Application Effectiveness

With the development of China’s social economy,various types of pollution have appeared in drinking water sources in some cities and towns,among which micro-pollution by heavy metals has become a prominent problem in the field of water source protection.At the same time,China’s urban water supply industry is generally facing the challenge of the improvement of drinking water quality standards.The existing conventional water treatment technology is difficult to meet the practical requirements.Considering that the conventional process filter is responsible for the interception and removal of most pollutants,it has a broad application prospect for the modification of filter materials to strengthen the filtration and removal of heavy metal pollutants in water.The surface of quartz sand was modified with ferric nitrate.By scanning electron microscope observation,specific surface area determination and X-ray diffraction identification,the surface characteristics of quartz sand before and after modification were compared and analyzed.The characterization results showed that the specific surface area of the coated iron sand was increased significantly,which was 5.07 times that of the original sand.After modification,the roughness of quartz sand is increased,and the surface composition is hematite and goethite.The wastewater containing Mn(Ⅱ),Pb(Ⅱ)and Sb(Ⅲ)was taken as the treatment object to investigate the effect of the amount of iron sand added and the p H value of the solution on the adsorption of heavy metals.The adsorption process of heavy metals was analyzed by adsorption isotherm and adsorption kinetics experiment.Results show that the coated iron ore of four kinds of heavy metal removal rate as the additive quantity.p H value are increase with the development of IOCS can better fit Langmuir adsorption heavy metal isothermal adsorption equation and dynamic model of the secondary to the Mn(Ⅱ),Pb(Ⅱ),Sb(Ⅲ)the saturated adsorption capacity were 0.197 mg/g and 0.448 mg/g and 2.403 mg/g,showing the coated iron ore in the treatment of heavy metals in terms of high performance.The adsorption process of the complex to heavy metals was investigated,and it was found that the Langmuir model and quasi-second-order kinetic model could be well fitted.The saturated adsorption capacity of Pb(Ⅱ)and Sb(Ⅲ)was increased by25.4% and 14.3%,respectively,while that of Mn(Ⅱ)was decreased by 15.2%,which may be caused by different stability constants of metal-Fullitic acid complex conditions.Through infrared spectrum characterization,complex adsorption of heavy metals,carboxyl and hydroxyl groups on the surface of the peak presents different degree reduced.Dynamic experiments were carried out at different filtration rates.With the increase of filtration rate,the filtration cycle of quartz sand and iron sand coated filter column were decreased to some degree,but under the same filtration rate,the filtration cycle of iron sand coated filter column was greater than that of sand filter column,and the increase of water head loss was less than that of sand filter column..In the study on the removal of heavy metals,it was found that the filtering effect of the iron-coated sand filter column was obviously better than that of the sand filter column,and the filtering period was longer.The average removal rate of Mn,Pb and Sb was 69.7%,93.9% and 96.8%,higher than 20.0%,58.1% and 30.7% of quartz sand in 24 hours working time.When the two filter columns were backrinsed with clean water,the removal of suspended matter could be recovered basically,but the recovery effect of heavy metal and organic matter removal was not ideal,and the recovery of iron-coated sand filter column was better than that of quartz sand.