Adsorption Behavior Of Vanadium(V)on Different Adsorbents

For soil heavy metal pollution poses a serious threat to the food production,the form conversion and accumulation of heavy metal pollutants in the soil are attracting the attention of scholars.Vanadium in the environment is brought into the animal in the form of diet and breathing,posing a threat to human health.Vanadium pollution do not immediately threatened ecosystems in the global range,but the vanadium precipitate and migration will gradually destroy the ecological environment.It will be very beneficial to control vanadium pollution and enact environmental standards that further study of migration and transformation mechanism of vanadium in soil environment.Which will guarantee more secure in the production of agricultural products.Batch sorption kinetics and isothermal characteristics of V(V)were investigated on yellow cinnamon soil,manual loessial soil,aeolian sandy soil,cultivated loessial soil,three natural soil colloids and modified sawdust biochar.Absorbent materials were characterized by the specific surface area(BET),atomic force microscopy(AFM),X-ray diffraction(XRD),electron scanning electron microscope(SEM)and fourier transform infrared spectroscopy(FTIR)to explore V(V)adsorption mechanism of different adsorption material.This study is to reveal different adsorbent's ability of V(V)on different adsorption material,to understand the behavior of V(V)in soil and provide a scientific basis for ecological restoration of biochar in environment.This study yielded the following major conclusions:(1)Hold ability of vanadium(V)in different soilsDue to the different physical and chemical properties of yellow cinnamon soil,manual loessial soil,aeolian sandy soil and cultivated loessial soil,such as organic matter content,specific surface area,particle size distribution and mineral composition,the adsorption of V(V)have larger different.The rapid adsorption time of V(V)in soils could complete in 60 min,120 min,120 min and 30 min,respectively.Dynamic data is most conformed to the secondary dynamic model.This shows that the adsorption of vanadium on soil is a dynamic adsorption process of complex chemical and physical adsorption.Freundlich isotherm can be well fitted of isothermal adsorption data.Shaanxi soil adsorption of V(V)are molecular layer adsorption.The maximum adsorption capacity of V(V)on yellow cinnamon soil,manual loessial soil,aeolian sandy soil and cultivated loessial soil were 1147.4 mg · kg-1,854.4mg·kg-1,748.6 mg·kg-1and 730.8 mg·kg-1.The maximum adsorption ability of V(V)on the four soils were stable at pH value of 4 to 8,and the adsorption capacity increased with theincrease of ionic strength.(2)Adsorption characteristics of vanadium(V)on different soil colloidsAFM micrographs showed cultivated loessial soil colloid have a larger particle diameter with 181.30 nm compared with aeolian soil colloid and old manured loessal soil colloid.XRD spectra revealed the presence of different minerals in natural soil colloids including biotite,kaolinite,calcite and quartz,which might contribute to sorption process.The sorption ability decreased with increase of colloidal particle size.The sorption was mainly attributed to complexation by active carboxylate and alcohol groups of colloidal components.Sorption kinetics and isotherms of V(V)onto natural soil colloids were best fitted with Pseudo-second-order and Freundlich models.Langmuir model indicated that sorption capacity of old manured loessal soil colloid and aeolian soil colloid was comparable(285.7and 238.1 mg g-1);however,cultivated loessial soil colloid exhibited the lowest sorption capacity(41.5 mg g-1)due to its larger particle diameter and aggregated shape.The maximum V(V)sorption capacity reached plateau values at a solution pH ranged between 5.0-9.0 for Old manured loessal soil colloid and aeolian soil colloid,and 6.0-8.0 for cultivated loessial soil colloid.Sorption capacity of V(V)onto natural soil colloids decreased with increasing IS.(3)Batch sorption of vanadium(V)on sawdust biochar modified by iron-soakedThe adsorption quantity of V(V)on the modified sawdust biochar is maximum at pH around 7.The adsorption process of vanadium on modified biochar be completed within 1hour and reach adsorption equilibrium within 24 hours.Adsorption kinetic conforms to the Pseudo-second-order equation.The maximum adsorption capacity of raw biochar was 1.9905 mg g-1.Therefore,the modified biochar was 17.231 mg g-1.It was 8.66 times than the raw carbon's adsorption capacity.Iron-soaked modified sawdust biochar can significantly increase the adsorption properties to V(V),change the element of biochar and reduces the porosity of biochar.The good adsorption performance of V(V)on the modified biochar is because of the electrostatic incorporation of the sawdust biochar modified by iron-soaked and the negative vanadium ion form.