Preparation Of Modified Floating Bead Material And Its Removal Of Heavy Metals From Soil

With the continuous improvement of the level of economic development in China,the intensification of pollution caused by industrialization and urban development,and the application of agricultural chemicals,these human activities lead to the content of heavy metals in soil exceeding the standard value of soil environment and the ability of soil purification,which directly destroys the soil environment.Remediation materials as adsorbents and improvers are widely used in the treatment of soil heavy metal pollution.In order to remove heavy metals from soil quickly and conveniently,flyash beads were selected as the main floating material and nano-zero-valent iron as the main adsorbing material for heavy metals.A new floating soil remediation agent,nano-iron loaded on flyash beads,was prepared,using a scanning electron microscope,X-ray diffraction and X-ray photoelectron spectrometer characterization methods such As the nature of the drift beads nano iron with different forms of heavy metals(Pb,Cd,for example,cationic form anion form in the As,for example)adsorption effect.The main experimental results are as follows:(1)Put flyash beads with 25%sulfuric acid acidification FeS04·7H2O control drift beads with iron quality ratio of 7:1 in inert gas under the condition of reducing iron nanoparticles preparation have to drift beads can be load as flyash bead-nzvi,FB-NZVI for short.By means of SEM,EDX,XRD and XPS,it is proved that the nano-zero-valent iron has been successfully loaded on the bleaching beads and is dispersed evenly without agglomeration.(2)The successfully prepared flyash bead loaded nano-iron materials can adsorb Pb and Cd in the form of cationic heavy metals as follows:48,01mg/g and 9,27mg/g,respectively.Through Langmuir model analysis,the theoretical maximum adsorption capacity was 54.55 mg/g and 10.44 mg/g,respectively.The adsorption mechanism of FB-NZVI on Pb is probably that the zero-valent iron reduced with Pb2+ to form the hydroxide precipitation of Pb0 and Pb.The adsorption mechanism of Cd is precipitation and adsorption with nano-iron.(3)The FB-NZVI adsorption capacity of the anionic heavy metal As can reach:4.2 mg/g.Through Langmuir model analysis,the theoretical maximum adsorption capacity was 5.5 mg/g.The pH range of As removal by FB-NZVI is wider,and the best effect is when the pH is 7.The adsorption mechanism of FB-NZVI may be that zero-valent iron reacts with As to form a reductive reaction,which complexes with iron oxides and then adsorbs and removes As.(3)The FB-NZVI can effectively remove Pb and Cd contents in the contaminated soil and reduce the bioavailability of heavy metals,and can rapidly remove 255mg/kg Pb and 2.57mg/kg Cd pollution within 4 weeks.The FB-NZVI can effectively remove the As content in the contaminated soil and remove the As pollution of 11.8mg/kg within 4 weeks.In practical soil remediation application,it is suggested that 2.5%FB-NZVI is the most suitable material.