Red Mud-based Composite Particles Stabilize The Cadmium And Lead In The Soil

If not properly repaired,Heavy metal contaminated soils will directly or indirectly affect the environment such as water and the atmosphere,seriously threatening the health of animals,plants and humans.Compared with other common soil heavy metal pollutants,cadmium and lead heavy metals have strong toxicity.Therefore,it has important research significance for in-situ remediation of cadmium and lead contaminated soil.Red mud wass used as a common repair material due to its excellent heavy metal contaminated soil remediation performance.Red mud could be used for the repair of heavy metals because it contains more alkaline substances,and the eluate can form heavy hydroxides into hydroxide or carbonate precipitates.It acts to passivate the activity of heavy metals in the soil.In addition,the red mud is rich in iron-aluminum oxide.These iron-aluminum oxides could provide surface adsorption sites for heavy metals and reduce the absorption of heavy metals by plants.However,direct application of red mud into the soil will cause the soil pH to rise rapidly in a short period of time,changing the rational environment of the soil,and there was a risk of affecting the growth of plants and microorganisms in the soil,and even the types and quantities of plants and microorganisms in the soil may be large.The phenomenon of reduced amplitude.Hydroxyapatite exhibits excellent heavy metal exchange when removing heavy metals,and the removal performance often increases with the increase of pH.In this study,the prepared hydroxyapatite resin was coated on the surface of red mud particles to form a composite.The particles form a core-shell structure with a mutual benefit function.On the one hand,the hydroxyapatite resin can release the lye released by the red mud;on the other hand,the lye released by the red mud provides an alkaline environment suitable for the reaction of hydroxyapatite and heavy metals.It had been proved by experiments that this material not only has good repairing ability,but also had certain water retention and sustained release properties,and had a longer action time than red mud raw materials and red mud particles.This multifunctional material not only realizes the resource utilization of red mud,but also solves the environmental problems of soil heavy metal pollution.In this study,the sol-gel method was used to synthesize common hydroxyapatite.It was proved by experiments that the combination of red mud raw material and hydroxyapatite had a certain gain effect on the removal of heavy metal cadmium and lead.The hydroxyapatite resin was made into hydroxyapatite resin.It was found that when the degree of neutralization of acrylic acid was 75-85% and the dosage of hydroxyapatite was 2.0g,the water absorption performance of hydroxyapatite resin is about 160% of its own weight,water retention performance(50% of its own weight when placed for 10 days)and the removal performance of heavy metal cadmium and lead solution removal rate(removal rate of 60 to 65%)was the best.Experiments on the removal of heavy metal cadmium and lead solutions by red mud particles formed by different calcination temperatures(calcination at 400~1200 °C and temperature gradient at 100 °C)show that the red mud particles formed by calcination at 600 °C have better removal.Performance(removal rate of 80~82%),and sufficient mechanical strength.Wrapped on the surface of red mud particles by two different methods to form dry and wet red mud-based composite particles,and compared with red mud raw materials,red mud particles and hydroxyapatite,studied for cadmium(Cd)The feasibility of in-situ remediation of lead(Pb)heavy metal contaminated soil.Through experiments,it can be found that the wet red mud composite particles can effectively alleviate the red mud lye and have the best stabilizing properties of heavy metal cadmium and lead.When the mass ratio was 1%,the initial concentration of 72.6% ion exchange state could be obtained.Cadmium and 71.2% ion-exchanged lead were converted to other inactive states;when the mass ratio was 5%,the initial concentration of 82.6% of ion-exchanged cadmium and 79.2% of ion-exchanged lead were converted to other inactive states.