| As China’s annual chromium is widely used in the chemical industry,dye production,wood preservation,leather tanning,chrome plating,various alloy manufacturing,and many other products and applications,chromium pollution in water and soil is becoming more and more serious,jeopardizing environmental movements.Plants and other living organisms and human health.With the development of nano-iron(n ZVI),people have a new way of thinking about heavy metal pollution in water and soil.By using traditional liquid phase reduction method,biochar(BC)and sodium carboxymethyl cellulose(CMC-Na)were added during the preparation of nano-iron to obtain biochar-supported sodium carboxymethyl cellulose stabilized nanometer.Iron(BC-n ZVI-CMC),SEM,XRD and FT-IR were used to characterize BC-n ZVI-CMC materials,and the removal effect and mechanism of hexavalent chromium in BC-n ZVI-CMC materials were investigated.The ferrous sulfate passivated soil chromium "return to yellow" factor and the passivationeffect of BC-n ZVI-CMC material on heavy metal chromium in soil.The SEM,XRD and FT-IR characterization methods show that the nano-iron particles are more evenly dispersed in the surface of the biochar,which indicates that the biochar acts as a carrier to improve the agglomeration of the nano-iron.At the same time,the nano-iron is CMC is coated on the surface of biochar,indicating that CMC plays a good role in protecting the air in the BC-n ZVI system.In the particle size distribution analysis of nano-iron particles,the particle size of more than200 nano-iron particles was randomly calculated,and the particle size of nano-iron was mainly between 40-160 nm.The minimum particle size of nano-iron was 30 nm,and the average particle size was 90 nm.Among them,the particles between 0-100 nm accounted for 57.28%,indicating that the prepared nano-iron particles conform to the nano-scale.The XRD pattern of BC-n ZVI-CMC shows that a main peak appears at 2? =44.75°.Compared with the PDF standard card,the obtained nano-iron is nano-element zero-valent iron.The passivation of hexavalent chromium in water by BC-n ZVI-CMC material shows that the removal rate of hexavalent chromium increases with the increase of the dosage of four stabilized nano-irons.The removal rate of hexavalent chromium by four biochar-loaded stabilized nano-irons decreases with increasing p H.Antioxidant experiments showed that BC-n ZVI-CMC showed a trend of decreasing first,then increasing and then stabilizing with the increase ofthe proportion of nano-iron,indicating that the amount of nano-iron is within a certain range,with the loading of nano-iron on biochar.The increase in the amount of agglomeration increased,and the removal efficiency of stabilized nano-iron to hexavalent chromium was reduced.The removal rate of hexavalent chromium in solution by fresh CMC-Na only reached 15.23%,indicating that CMC is in BC-n ZVI-CMC.The role played by the system is mainly to encapsulate nano-iron.Adsorption kinetics,adsorption isotherms,FT-IR and XPS indicate that the adsorption of hexavalent chromium by BC-n ZVI-CMC material is mainly chemical adsorption of ion exchange and chelation reaction,and the trivalent chromium formed by the reaction is hydrogen.A relatively stable state such as an oxide or a Fe(III)/Cr(III)complex exists on the surface of the biochar.In the study of soil chrome "return to yellow",it is concluded that as the soil temperature increases and the organic matter content increases,the content of total chromium and hexavalent chromium is gradually reduced.The p H changes to the soil to extract total chromium and hexavalent.The effect of chromium content is not obvious.The changes of soil chromium-Eh diagram,temperature and organic matter change on total chrome and hexavalent chromium in splp leaching from soil can be seen.The trend of U-shaped change is presented,which comprehensively shows that the buffering performance of the soil itself has a relatively large effect on the total chromiumleaching from the soil,and has a leading effect on the content of chromium leaching from the soil.The passivation of soil chromium by BC-n ZVI-CMC indicates that under the four carbon-iron ratios and dosages,the BC-n ZVI-CMC material will make the soil chromium more stable towards the stable forms OX,OM and RS.State transitions,therefore,BC-n ZVI-CMC materials are highly likely to be a class of passivating materials that have long-lasting properties for soil chromium. |
