Application Mechanism Of Nanotechnology In Rice Husk Resource Utilization And Reduction Of Heavy Metal Uptake By Plants

With the development of science and technology,nanotechnology is increasingly used in the environmental field.Nanotechnology brings new directions and challenges to the disposal of agricultural waste and soil pollution.On the one hand,this study explored the application and mechanism of nanotechnology in rice husk resource utilization,and synthesized nano silver?Ag?and nano silicon dioxide?SiO₂?by using rice husk.On the other hand,nanomesoporous SiO₂,titanium dioxide?TiO₂?,zinc sulfide?ZnS?and molybdenum disulfide?MoS₂?are used as soil heavy metal repairing agents to explore the effect of nanomaterials on plant heavy metal absorption and plant growth.The main research results are as follows:?1?Using rice husk to biosynthesis nano Ag,the approached optimized conditions for Ag nanoparticles?AgNPs?formation:volume ratio of rice husk to silver nitrate,reaction temperature,pH and reaction time is 9:1,80°C,9 and 2 h.Under this reaction condition,the produced silver nanocomposite were predominantly spherical in shape,with a size range between 20-40 nm.Hydrodynamic diameter is 66.9 nm,and zeta potential is-17.5mV with a negative charge.?2?To understand the the mechanism of AgNPs formation by rice husk extracts,gas chromatography-massspectrometry?GC-MS?analysis was performed on reaction suspension before and after reaction.Totally 340 low molecular weight metabolites were find in rice husk extracts,include sugar,amino acid,fatty acid,organic acid and so on.49metabolites were almost not detectable in suspension at the end of the reaction,this indicates that these compounds have been participated in the forming of Ag ions to AgNPs,either act as reducing or stabilizing agent.?3?The antioxidant capacity of biosynthesis AgNPs by rice husk almost equal to the commercial pure AgNPs.SiO₂ nanoparticle that synthesis by the rice husk residues had good adsorption properties for chromium?Cr?,cuprum?Cu?and cadmium?Cd?.Especially for Cr,which was reduced by 50.25%?P<0.05?.As for the adsorption capacity of Cr,synthesis is comparable with a commercial mesoporous SiO₂ nanoparticle?CSN?.?4?Results showed that SiO₂ and TiO₂ nano materials had no impact on photosynthetic pigment contents in cucumber leaves.Both metal sulfide nano materials ZnS and MoS₂ inhibited photosynthetic pigment content.Exposure to nano ZnS significantly decreased carotenoid?Car?content by 9.19%?P<0.05?,exposure to MoS2nano materials significantly decreased chlorophyll b?Chl b?content by 11.33%?P<0.05?.?5?MoS₂ nano materials significantly?P<0.05?decreased the content of zinc?Zn?,cuprum?Cu?,nickel?Ni?,chromium?Cr?,plumbum?Pb?,arsenic?As?and cadmium?Cd?in cucumber roots.Four types of nano materials generally had similar pattern on reducing heavy metals bioaccumulation in above-ground cucumber tissue.Two metal sulfides?ZnS and MoS₂?had better performance in reducing the heavy metal uptake in cucumber plants compared to SiO₂ and TiO₂.?6?TiO₂ and MoS₂ nano materials disturbed the accumulation of a number of nutrients including silicon?Si?,magnesium?Mg?,iron?Fe?,kalium?K?and manganese?Mn?in cucumber root.K accumulation in leaves decreased by 8.97%-17.02%?P<0.05?when exposed to SiO₂,TiO₂ and MoS₂.Exposure to TiO₂,ZnS and MoS2 resulted in the significant decrease of leaf natrium?Na?accumulation by 31.08%-56.40%?P<0.05?.The interfered sodium and potassium uptake in leaf may negatively impact plant further growth.